Now if the degree of resemblance between the
prevalence
of
myopia in parents and that in children be directly measured, and if it
be found that when the parent has eye trouble the child also has it,
then it seems that a general knowledge of heredity should lead to the
belief that the difficulty lies there, and that an environmental cause
for the poor vision of the school child was being sought, when it was
all the time due almost entirely to heredity.
myopia in parents and that in children be directly measured, and if it
be found that when the parent has eye trouble the child also has it,
then it seems that a general knowledge of heredity should lead to the
belief that the difficulty lies there, and that an environmental cause
for the poor vision of the school child was being sought, when it was
all the time due almost entirely to heredity.
Applied Eugenics by Roswell H. Johnson and Paul Popenoe
Heredity!
Heredity!
There is just one heredity in all the world that is ours--we are
children of God, and there is nothing in the whole big world that we
cannot do in His service with it. "
It is probably not beyond the truth to say that in this statement Jacob
Riis voiced the opinion of a majority of the social workers of this
country, and likewise a majority of the people who are faithfully and
with much self-sacrifice supporting charities, uplift movements, reform
legislation, and philanthropic attempts at social betterment in many
directions. They suppose that they are at the same time making the race
better by making the conditions better in which people live.
It is widely supposed that, although nature may have distributed some
handicaps at birth, they can be removed if the body is properly warmed
and fed and the mind properly exercised. It is further widely supposed
that this improvement in the condition of the individual will result in
his production of better infants, and that thus the race, gaining a
little momentum in each generation, will gradually move on toward
ultimate perfection.
There is no lack of efforts to improve the race, by this method of
direct change of the environment. It involves two assumptions, which are
sometimes made explicitly, sometimes merely taken for granted. These
are:
1. That changes in a man's surroundings, or, to use the more technical
biological term, in his nurture, will change the nature that he has
inherited.
2. That such changes will further be transmitted to his children.
Any one who proposes methods of race betterment, as we do in the present
book, must meet these two popular beliefs. We shall therefore examine
the first of them in this chapter, and the second in Chapter II.
Galton adopted and popularized Shakespere's antithesis of _nature_ and
_nurture_ to describe a man's inheritance and his surroundings, the two
terms including everything that can pertain to a human being. The words
are not wholly suitable, particularly since nature has two distinct
meanings,--human nature and external nature. The first is the only one
considered by Galton. Further, nurture is capable of subdivision into
those environmental influences which do not undergo much change,--e. g. ,
soil and climate,--and those forces of civilization and education which
might better be described as culture. The evolutionist has really to
deal with the three factors of germ-plasm, physical surroundings and
culture. But Galton's phrase is so widely current that we shall continue
to use it, with the implications that have just been outlined.
The antithesis of nature and nurture is not a new one; it was met long
ago by biologists and settled by them to their own satisfaction. The
whole body of experimental and observational evidence in biology tends
to show that the characters which the individual inherits from his
ancestors remain remarkably constant in all ordinary conditions to which
they may be subjected. Their constancy is roughly proportionate to the
place of the animal in the scale of evolution; lower forms are more
easily changed by outside influence, but as one ascends to the higher
forms, which are more differentiated, it is found more and more
difficult to effect any change in them. Their characters are more
definitely fixed at birth. [1]
It is with the highest of all forms, Man, that we have now to deal. The
student in biology is not likely to doubt that the differences in men
are due much more to inherited nature than to any influences brought to
bear after birth, even though these latter influences include such
powerful ones as nutrition and education within ordinary limits.
But the biological evidence does not lend itself readily to summary
treatment, and we shall therefore examine the question by statistical
methods. [2] These have the further advantage of being more easily
understood; for facts which can be measured and expressed in numbers are
facts whose import the reader can usually decide for himself: he is
perfectly able to determine, without any special training, whether twice
two does or does not make four. One further preliminary remark: the
problem of nature vs. nurture can not be solved in general terms; a
moment's thought will show that it can be understood only by examining
one trait at a time. The problem is to decide whether the differences
between the people met in everyday life are due more to inheritance or
to outside influences, and these differences must naturally be examined
separately; they can not be lumped together.
To ask whether nature in general contributes more to a man than nurture
is futile; but it is not at all futile to ask whether the differences in
a given human trait are more affected by differences in nature than by
differences in nurture. It is easy to see that a verdict may be
sometimes given to one side, sometimes to the other. Albinism in
animals, for instance, is a trait which is known to be inherited, and
which is very slightly affected by differences of climate, food supply,
etc. On the other hand, there are factors which, although having
inherited bases, owe their expression almost wholly to outside
influences. Professor Morgan, for example, has found a strain of fruit
flies whose offspring in cold weather are usually born with
supernumerary legs. In hot weather they are practically normal. If this
strain were bred only in the tropics, the abnormality would probably not
be noticed; on the other hand, if it were bred only in cold regions, it
would be set down as one characterized by duplication of limbs. The
heredity factor would be the same in each case, the difference in
appearance being due merely to temperature.
Mere inspection does not always tell whether some feature of an
individual is more affected by changes in heredity or changes in
surroundings. On seeing a swarthy man, one may suppose that he comes of
a swarthy race, or that he is a fair-skinned man who has lived long in
the desert. In the one case the swarthiness would be inheritable, in the
other not. Which explanation is correct, can only be told by examining a
number of such individuals under critical conditions, or by an
examination of the ancestry. A man from a dark-skinned race would become
little darker by living under the desert sun, while a white man would
take on a good deal of tan.
The limited effect of nurture in changing nature is in some fields a
matter of common observation. The man who works in the gymnasium knows
that exercise increases the strength of a given group of muscles for a
while, but not indefinitely. There comes a time when the limit of a
man's hereditary potentiality is reached, and no amount of exercise will
add another millimeter to the circumference of his arm. Similarly the
handball or tennis player some day reaches his highest point, as do
runners or race horses. A trainer could bring Arthur Duffy in a few
years to the point of running a hundred yards in 9-3/5 seconds, but no
amount of training after that could clip off another fifth of a second.
A parallel case is found in the students who take a college examination.
Half a dozen of them may have devoted the same amount of time to it--may
have crammed to the limit--but they will still receive widely different
marks. These commonplace cases show that nurture has seemingly some
power to mold the individual, by giving his inborn possibilities a
chance to express themselves, but that nature says the first and last
word. Francis Galton, the father of eugenics, hit on an ingenious and
more convincing illustration by studying the history of twins. [3]
There are, everyday observation shows, two kinds of twins--ordinary
twins and the so-called identical twins. Ordinary twins are merely
brothers, or sisters, or brother and sister, who happen to be born two
at a time, because two ova have developed simultaneously. The fact that
they were born at the same time does not make them alike--they differ
quite as widely from each other as ordinary brothers and sisters do.
Identical twins have their origin in a different phenomenon--they are
believed to be halves of the same egg-cell, in which two growing-points
appeared at a very early embryonic stage, each of these developing into
a separate individual. As would be expected, these identical twins are
always of the same sex, and extremely like each other, so that sometimes
their own mother can not tell them apart. This likeness extends to all
sorts of traits:--they have lost their milk teeth on the same day in one
case, they even fell ill on the same day with the same disease, even
though they were in different cities.
Now Galton reasoned that if environment really changes the inborn
character, then these identical twins, who start life as halves of the
same whole, ought to become more unlike if they were brought up apart;
and as they grew older and moved into different spheres of activity,
they ought to become measurably dissimilar. On the other hand, ordinary
twins, who start dissimilar, ought to become more alike when brought up
in the same family, on the same diet, among the same friends, with the
same education. If the course of years shows that identical twins remain
as like as ever and ordinary twins as unlike as ever, regardless of
changes in conditions, then environment will have failed to demonstrate
that it has any great power to modify one's inborn nature in these
traits.
With this view, Galton collected the history of eighty pairs of
identical twins, thirty-five cases being accompanied by very full
details, which showed that the twins were really as nearly identical, in
childhood, as one could expect to find. On this point, Galton's
inquiries were careful, and the replies satisfactory. They are not,
however, as he remarks, much varied in character. "When the twins are
children, they are usually distinguished by ribbons tied around the
wrist or neck; nevertheless the one is sometimes fed, physicked, and
whipped by mistake for the other, and the description of these little
domestic catastrophes was usually given by the mother, in a phraseology,
that is sometimes touching by reason of its seriousness. I have one case
in which a doubt remains whether the children were not changed in their
bath, and the presumed A is not really B, and _vice versa_. In another
case, an artist was engaged on the portraits of twins who were between
three and four years of age; he had to lay aside his work for three
weeks, and, on resuming it, could not tell to which child the respective
likeness he had in hand belonged. The mistakes become less numerous on
the part of the mother during the boyhood and girlhood of the twins, but
are almost as frequent as before on the part of strangers. I have many
instances of tutors being unable to distinguish their twin pupils. Two
girls used regularly to impose on their music teacher when one of them
wanted a whole holiday; they had their lessons at separate hours, and
the one girl sacrificed herself to receive two lessons on the same day,
while the other one enjoyed herself from morning to evening. Here is a
brief and comprehensive account: 'Exactly alike in all, their
schoolmasters could never tell them apart; at dancing parties they
constantly changed partners without discovery; their close resemblance
is scarcely diminished by age. "
[Illustration: FOUR BABY GIRLS AT ONCE
FIG. 1. --These quadruplet daughters were born to Mr. and Mrs.
F. M. Keys, Hollis, Okla. , on July 4, 1915, and were seven months old
when the photograph was taken. Up to that time they had never had any
other nourishment than their mother's milk. Their weights at birth were
as follows (reading from left to right): Roberta, 4 pounds; Mona, 4-1/2
pounds; Mary, 4-1/4 pounds; Leota, 3-3/4 pounds. When photographed,
Roberta weighed 16 pounds and each of the others weighed 16-1/4. Their
aunt vouches for the fact that the care of the four is less trouble than
a single baby often makes. The mother has had no previous plural births,
although she has borne four children prior to these. Her own mother had
but two children, a son and a daughter, and there is no record of twins
on the mother's side. The father of the quadruplets is one of twelve
children, among whom is one pair of twins. It is known that twinning is
largely due to inheritance, and it would seem that the appearance of
these quadruplets is due to the hereditary influence of the father
rather than the mother. If this is the case, then the four girls must
all have come from one egg-cell, which split up at an early stage. Note
the uniform shape of the mouth, and the ears, set unusually low on the
head. ]
"The following is a typical schoolboy anecdote:
"'Two twins were fond of playing tricks, and complaints were frequently
made; but the boys would never own which was the guilty one, and the
complainants were never certain which of the two it was. One head master
used to say he would never flog the innocent for the guilty, and the
other used to flog them both. '
"No less than nine anecdotes have reached me of a twin seeing his or her
reflection in the looking-glass, and addressing it in the belief that it
was the other twin in person.
"Children are usually quick in distinguishing between their parent and
his or her twin; but I have two cases to the contrary. Thus, the
daughter of a twin says:
"'Such was the marvelous similarity of their features, voice, manner,
etc. , that I remember, as a child, being very much puzzled, and I think,
had my aunt lived much with us, I should have ended by thinking I had
two mothers! '
"In the other case, a father who was a twin, remarks of himself and his
brother:
"'We were extremely alike, and are so at this moment, so much so that
our children up to five and six years old did not know us apart. '
"Among my thirty-five detailed cases of close similarity, there are no
less than seven in which both twins suffered from some special ailment
or had some exceptional peculiarity. Both twins are apt to sicken at the
same time in no less than nine out of the thirty-five cases. Either
their illnesses, to which I refer, were non-contagious, or, if
contagious, the twins caught them simultaneously; they did not catch
them the one from the other. "
Similarity in association of ideas, in tastes and habits was equally
close. In short, their resemblances were not superficial, but extremely
intimate, both in mind and body, while they were young; they were reared
almost exactly alike up to their early manhood and womanhood.
Then they separated into different walks of life. Did this change of the
environment alter their inborn character? For the detailed evidence,
one should consult Galton's own account; we give only his conclusions:
In many cases the resemblance of body and mind continued unaltered up to
old age, notwithstanding very different conditions of life; in others a
severe disease was sufficient to account for some change noticed. Other
dissimilarity that developed, Galton had reason to believe, was due to
the development of inborn characters that appeared late in life. He
therefore felt justified in broadly concluding "that the only
circumstance, within the range of those by which persons of similar
conditions of life are affected, that is capable of producing a marked
effect on the character of adults, is illness or some accident which
causes physical infirmity. The twins who closely resembled each other in
childhood and early youth, and were reared under not very dissimilar
conditions, either grow unlike through the development of natural [that
is, inherited] characteristics which had lain dormant at first, or else
they continue their lives, keeping time like two watches, hardly to be
thrown out of accord except by some physical jar. "
Here was a distinct failure of nurture to modify the inborn nature. We
next consider the ordinary twins who were unlike from the start. Galton
had twenty such cases, given with much detail. "It is a fact," he
observes, "that extreme dissimilarity, such as existed between Jacob and
Esau, is a no less marked peculiarity of twins of the same sex than
extreme similarity. " The character of the evidence as a whole may be
fairly conveyed by a few quotations:
(1) One parent says: "They have had _exactly the same nurture_ from
their birth up to the present time; they are both perfectly healthy and
strong, yet they are otherwise as dissimilar as two boys could be,
physically, mentally, and in their emotional nature. "
(2) "I can answer most decidedly that the twins have been perfectly
dissimilar in character, habits, and likeness from the moment of their
birth to the present time, though they were nursed by the same woman,
went to school together, and were never separated until the age of
thirteen. "
(3) "They have never been separated, never the least differently treated
in food, clothing, or education; both teethed at the same time, both had
measles, whooping cough, and scarlatina at the same time, and neither
has had any other serious illness. Both are and have been exceedingly
healthy, and have good abilities; yet they differ as much from each
other in mental cast as any one of my family differs from another. "
(4) "Very dissimilar in mind and body; the one is quiet, retiring, and
slow but sure; good-tempered, but disposed to be sulky when
provoked;--the other is quick, vivacious, forward, acquiring easily and
forgetting soon; quick-tempered and choleric, but quickly forgiving and
forgetting. They have been educated together and never separated. "
(5) "They were never alike either in mind or body, and their
dissimilarity increases daily. The external influences have been
identical; they have never been separated. "
(6) "The two sisters are very different in ability and disposition. The
one is retiring, but firm and determined; she has no taste for music or
drawing. The other is of an active, excitable temperament; she displays
an unusual amount of quickness and talent, and is passionately fond of
music and drawing. From infancy, they have been rarely separated even at
school, and as children visiting their friends, they always went
together. "
And so on. Not a single case was found in which originally dissimilar
characters became assimilated, although submitted to exactly the same
influences. Reviewing the evidence in his usual cautious way, Galton
declared, "There is no escape from the conclusion that nature prevails
enormously over nurture, when the differences of nurture do not exceed
what is commonly to be found among persons of the same rank in society
and in the same country. "
This kind of evidence was a good start for eugenics but as the science
grew, it outgrew such evidence. It no longer wanted to be told, no
matter how minute the details, that "nature prevails enormously over
nurture. " It wanted to know exactly how much. It refused to be satisfied
with the statement that a certain quantity was large; it demanded that
it be measured or weighed. So Galton, Karl Pearson and other
mathematicians devised means of doing this, and then Professor Edward L.
Thorndike of Columbia University took up Galton's problem again, with
more refined methods.
The tool used by Professor Thorndike was the coefficient of correlation,
which shows the amount of resemblance or association between any two
things that are capable of measurement, and is expressed in the form of
a decimal fraction somewhere between 0 and the unit 1. Zero shows that
there is no constant resemblance at all between the two things
concerned,--that they are wholly independent of each other, while 1
shows that they are completely dependent on each other, a condition that
rarely exists, of course. [4] For instance, the correlation between the
right and left femur in man's legs is . 98.
Professor Thorndike found in the New York City schools fifty pairs of
twins of about the same age and measured the closeness of their
resemblance in eight physical characters, and also in six mental
characters, the latter being measured by the proficiency with which the
subjects performed various tests. Then children of the same age and sex,
picked at random from the same schools, were measured in the same way.
It was thus possible to tell how much more alike twins were than
ordinary children in the same environment. [5]
[Illustration: THE EFFECT OF NURTURE IN CHANGING NATURE
FIG. 2. --Corn of a single variety (Leaming Dent) grown in two
plots: at the left spaced far apart in hills, at the right crowded. The
former grows to its full potential height, the latter is stunted. The
size differences in the two plots are due to differences in environment,
the heredity in both cases being the same. Plants are much more
susceptible to nutritional influences on size than are mammals, but to a
less degree nutrition has a similar effect on man. Photograph from A. F.
Blakeslee. ]
"If now these resemblances are due to the fact that the two members of
any twin pair are treated alike at home, have the same parental models,
attend the same school and are subject in general to closely similar
environmental conditions, then (1) twins should, up to the age of
leaving home, grow more and more alike, and in our measurements the
twins 13 and 14 years old should be much more alike than those 9 and 10
years old. Again (2) if similarity in training is the cause of
similarity in mental traits, ordinary fraternal pairs not over four or
five years apart in age should show a resemblance somewhat nearly as
great as twin pairs, for the home and school condition of a pair of the
former will not be much less similar than those of a pair of the latter.
Again, (3) if training is the cause, twins should show greater
resemblance in the case of traits much subject to training, such as
ability in addition or multiplication, than in traits less subject to
training, such as quickness in marking off the A's on a sheet of printed
capitals, or in writing the opposites of words. "
The data were elaborately analyzed from many points of view. They showed
(1) that the twins 12-14 years old were not any more alike than the
twins 9-11 years old, although they ought to have been, if environment
has great power to mold the character during these so-called "plastic
years of childhood. " They showed (2) that the resemblance between twins
was two or three times as great as between ordinary children of the same
age and sex, brought up under similar environment. There seems to be no
reason, except heredity, why twins should be more alike. The data showed
(3) that the twins were no more alike in traits subject to much training
than in traits subject to little or no training. Their achievement in
these traits was determined by their heredity; training did not
measurably alter these hereditary potentialities.
"The facts," Professor Thorndike wrote, "are easily, simply and
completely explained by one simple hypothesis; namely, that the nature
of the germ-cells--the conditions of conception--cause whatever
similarities and differences exist in the original natures of men, that
these conditions influence mind and body equally, and that in life the
differences in modification of mind and body produced by such
differences as obtain between the environments of present-day New York
City public school children are slight. "
"The inferences," he says, "with respect to the enormous importance of
original nature in determining the behavior and achievements of any man
in comparison with his fellows of the same period of civilization and
conditions of life are obvious. All theories of human life must accept
as a first principle the fact that human beings at birth differ
enormously in mental capacities and that these differences are largely
due to similar differences in their ancestry. All attempts to change
human nature must accept as their most important condition the limits
set by original nature to each individual. "
Meantime other investigators, principally followers of Karl Pearson in
England, were working out correlation coefficients in other lines of
research for hundreds of different traits. As we show in more detail in
Chapter IV, it was found, no matter what physical or mental trait was
measured, that the coefficient of correlation between parent and child
was a little less than . 5 and that the coefficient between brother and
brother, or sister and sister, or brother and sister, was a little more
than . 5. On the average of many cases the mean "nature" value, the
coefficient of direct heredity, was placed at . 51. This gave another
means of measuring nurture, for it was also possible to measure the
relation between any trait in the child and some factor in the
environment. A specific instance will make this clearer.
Groups of school children usually show an appalling percentage of
short-sightedness. Now suppose it is suggested that this is because they
are allowed to learn to read at too early an age. One can find out the
age at which any given child did learn to read, and work out the
coefficient of correlation between this age and the child's amount of
myopia. If the relation between them is very close--say . 7 or . 8--it
will be evident that the earlier a child learns to read, the more
short-sighted he is as he grows older. This will not prove a relation of
cause and effect, but it will at least create a great suspicion. If on
the contrary the correlation is very slight, it will be evident that
early reading has little to do with the prevalance of defective vision
among school children. If investigators similarly work out all the other
correlations that can be suggested, finding whether there is any
regular relation between myopia and overcrowding, long hours of study,
general economic conditions at home, general physical or moral
conditions of parents, the time the child spends out of doors, etc. , and
if no important relation is found between these various factors and
myopia, it will be evident that no factor of the environment which one
can think of as likely to cause the trouble really accounts for the poor
eyesight of school children.
[Illustration: HEIGHT IN CORN AND MEN
FIG. 3. --An unusually short and an unusually tall man,
photographed beside extreme varieties of corn which, like the men, owe
their differences in height indisputably to heredity rather than to
environment. No imaginable environmental differences could reverse the
positions of these two men, or of these two varieties of corn, the
heredity in each case being what it is. The large one might be stunted,
but the small one could not be made much larger. Photograph from A. F.
Blakeslee. ]
This has actually been done,[6] and none of the conditions enumerated
has been found to be closely related to myopia in school children.
Correlations between fifteen environmental conditions and the goodness
of children's eyesight were measured, and only in one case was the
correlation as high as . 1. The mean of these correlations was about
. 04--an absolutely negligible quantity when compared with the common
heredity coefficient of . 51.
Does this prove that the myopia is rather due to heredity? It would, by
a process of exclusion, if every conceivable environmental factor had
been measured and found wanting. That point in the investigation can
never be reached, but a tremendously strong suspicion is at least
justified.
Now if the degree of resemblance between the prevalence of
myopia in parents and that in children be directly measured, and if it
be found that when the parent has eye trouble the child also has it,
then it seems that a general knowledge of heredity should lead to the
belief that the difficulty lies there, and that an environmental cause
for the poor vision of the school child was being sought, when it was
all the time due almost entirely to heredity. This final step has not
yet been completed in an adequate way,[7] but the evidence, partly
analogical, gives every reason to believe in the soundness of the
conclusion stated, that in most cases the schoolboy must wear glasses
because of his heredity, not because of overstudy or any neglect on the
part of his parents to care for his eyes properly during his childhood.
[Illustration: WHY MEN GROW SHORT OR TALL
FIG. 4. --Pedigree charts of the two men shown in the preceding
illustration. Squares represent men and circles women; figures
underlined denote measurement in stocking feet. It is obvious from a
comparison of the ancestry of the two men that the short one comes from
a predominantly short family, while the tall one gains his height
likewise from heredity. The shortest individual in the right-hand chart
would have been accounted tall in the family represented on the left.
After A. F. Blakeslee. ]
The extent to which the intelligence of school children is dependent on
defective physique and unfavorable home environment is an important
practical question, which David Heron of London attacked by the methods
we have outlined. He wanted to find out whether the healthy children
were the most intelligent. One is constantly hearing stories of how the
intelligence of school children has been improved by some treatment
which improved their general health, but these stories are rarely
presented in such a way as to contribute evidence of scientific value.
It was desirable to know what exact measurement would show. The
intelligence of all the children in fourteen schools was measured in its
correlation with weight and height, conditions of clothing and teeth,
state of nutrition, cleanliness, good hearing, and the condition of the
cervical glands, tonsils and adenoids. It could not be found that mental
capacity was closely related to any of the characters dealt with. [8] The
particular set of characters measured was taken because it happened to
be furnished by data collected for another purpose; the various items
are suggestive rather than directly conclusive. Here again, the
correlation in most cases was less than . 1, as compared with the general
heredity correlation of . 5.
The investigation need not be limited to problems of bad breeding.
Eugenics, as its name shows, is primarily interested in "good breeding;"
it is particularly worth while, therefore, to examine the relations
between heredity and environment in the production of mental and moral
superiority.
If success in life--the kind of success that is due to great mental and
moral superiority--is due to the opportunities a man has, then it ought
to be pretty evenly distributed among all persons who have had favorable
opportunities, provided a large enough number of persons be taken to
allow the laws of probability full play. England offers a good field to
investigate this point, because Oxford and Cambridge, her two great
universities, turn out most of the eminent men of the country, or at
least have done so until recently. If nothing more is necessary to
ensure a youth's success than to give him a first-class education and
the chance to associate with superior people, then the prizes of life
ought to be pretty evenly distributed among the graduates of the two
universities, during a period of a century or two.
This is not the case. When we look at the history of England, as Galton
did nearly half a century ago, we find success in life to an unexpected
degree a family affair. The distinguished father is likely to have a
distinguished son, while the son of two "nobodies" has a very small
chance of becoming distinguished. To cite one concrete case, Galton
found[9] that the son of a distinguished judge had about one chance in
four of becoming himself distinguished, while the son of a man picked
out at random from the population had about one chance in 4,000 of
becoming similarly distinguished.
The objection at once occurs that perhaps social opportunities might
play the predominant part; that the son of an obscure man never gets a
chance, while the son of the prominent man is pushed forward regardless
of his inherent abilities. This, as Galton argued at length, can not be
true of men of really eminent attainments. The true genius, he thought,
frequently succeeds in rising despite great obstacles, while no amount
of family pull will succeed in making a mediocrity into a genius,
although it may land him in some high and very comfortable official
position. Galton found a good illustration in the papacy, where during
many centuries it was the custom for a pope to adopt one of his nephews
as a son, and push him forward in every way. If opportunity were all
that is required, these adopted sons ought to have reached eminence as
often as a real son would have done; but statistics show that they
reached eminence only as often as would be expected for nephews of great
men, whose chance is notably less, of course, than that of sons of great
men, in whom the intensity of heredity is much greater.
Transfer the inquiry to America, and it becomes even more conclusive,
for this is supposed to be the country of equal opportunities, where it
is a popular tradition that every boy has a chance to become president.
Success may be in some degree a family affair in caste-ridden England;
is it possible that the past history of the United States should show
the same state of affairs?
Galton found that about half of the great men of England had
distinguished close relatives. If the great men of America have fewer
distinguished close relatives, environment will be able to make out a
plausible case: it will be evident that in this continent of boundless
opportunities the boy with ambition and energy gets to the top, and that
this ambition and energy do not depend on the kind of family he comes
from.
Frederick Adams Woods has made precisely this investigation. [10] The
first step was to find out how many eminent men there are in American
history. Biographical dictionaries list about 3,500, and this number
provides a sufficiently unbiased standard from which to work. Now, Dr.
Woods says, if we suppose the average person to have as many as twenty
close relatives--as near as an uncle or a grandson--then computation
shows that only one person in 500 in the United States has a chance to
be a near relative of one of the 3,500 eminent men--provided it is
purely a matter of chance. As a fact, the 3,500 eminent men listed by
the biographical dictionaries are related to each other not as one in
500, but as one in five. If the more celebrated men alone be considered,
it is found that the percentage increases so that about one in three of
them has a close relative who is also distinguished. This ratio
increases to more than one in two when the families of the forty-six
Americans in the Hall of Fame are made the basis of study. If all the
eminent relations of those in the Hall of Fame are counted, they average
more than one apiece. Therefore, they are from five hundred to a
thousand times as much related to distinguished people as the ordinary
mortal is.
To look at it from another point of view, something like 1% of the
population of the country is as likely to produce a man of genius as is
all the rest of the population put together,--the other 99%.
This might still be due in some degree to family influence, to the
prestige of a famous name, or to educational advantages afforded the
sons of successful men. Dr. Woods' study of the royal families of Europe
is more decisive. [11]
In the latter group, the environment must be admitted--on the whole--to
be uniformly favorable. It has varied, naturally, in each case, but
speaking broadly it is certain that all the members of this group have
had the advantage of a good education, of unusual care and attention. If
such things affect achievement, then the achievements of this class
ought to be pretty generally distributed among the whole class. If
opportunity is the cause of a man's success, then most of the members of
this class ought to have succeeded, because to every one of royal blood,
the door of opportunity usually stands open. One would expect the heir
to the throne to show a better record than his younger brothers,
however, because his opportunity to distinguish himself is naturally
greater. This last point will be discussed first.
Dr. Woods divided all the individuals in his study into ten classes for
intellectuality and ten for morality, those most deficient in the
qualities being put in class 1, while the men and women of preeminent
intellectual and moral worth were put in class 10. Now if preeminent
intellect and morality were at all linked with the better chances that
an inheritor of succession has, then heirs to the throne ought to be
more plentiful in the higher grades than in the lower. Actual count
shows this not to be the case. A slightly larger percentage of
inheritors is rather to be found in the lower grades. The younger sons
have made just as good a showing as the sons who succeeded to power; as
one would expect if intellect and morality are due largely to heredity,
but as one would not expect if intellect and morality are due largely to
outward circumstances.
Are "conditions of turmoil, stress and adversity" strong forces in the
production of great men, as has often been claimed? There is no evidence
from facts to support that view. In the case of a few great commanders,
the times seemed particularly favorable. Napoleon, for example, could
hardly have been Napoleon had it not been for the French revolution. But
in general there have been wars going on during the whole period of
modern European history; there have always been opportunities for a
royal hero to make his appearance; but often the country has called for
many years in vain. Circumstances were powerless to produce a great man
and the nation had to wait until heredity produced him. Spain has for
several centuries been calling for genius in leadership in some lines;
but in vain. England could not get an able man from the Stuart line,
despite her need, and had to wait for William of Orange, who was a
descendant of a man of genius, William the Silent. "Italy had to wait
fifty years in bondage for her deliverers, Cavour, Garibaldi and Victor
Emmanuel. "
"The upshot of it all," Dr. Woods decides, "is that, as regards
intellectual life, environment is a totally inadequate explanation. If
it explains certain characters in certain instances, it always fails to
explain many more, while heredity not only explains all, or at least
90%, of the intellectual side of character in practically every
instance, but does so best when questions of environment are left out of
discussion. "
Despite the good environment almost uniformly present, the geniuses in
royalty are not scattered over the surface of the pedigree chart, but
form isolated little groups of closely related individuals. One centers
in Frederick the Great, another in Queen Isabella of Spain, a third in
William the Silent, and a fourth in Gustavus Adolphus. Furthermore, the
royal personages who are conspicuously low in intellect and morality are
similarly grouped. Careful study of the circumstances shows nothing in
the environment that would produce this grouping of genius, while it is
exactly what a knowledge of heredity leads one to expect.
In the next place, do the superior members of royalty have
proportionately more superior individuals among their close relatives,
as was found to be the case among the Americans in the Hall of Fame? A
count shows at once that they do. The first six grades all have about an
equal number of eminent relatives, but grade 7 has more while grade 8
has more than grade 7, and the geniuses of grade 10 have the highest
proportion of nearer relatives of their own character. Surely it cannot
be supposed that a relative of a king in grade 8 has on the average a
much less favorable environment than a relative of a king in grade 10.
Is it not fair, then, to assume that this relative's greater endowment
in the latter case is due to heredity?
Conditions are the same, whether males or females be considered. The
royal families of Europe offer a test case because for them the
environment is nearly uniformly favorable. A study of them shows great
mental and moral differences between them, and critical evidence
indicates that these differences are largely due to differences in
heredity. Differences of opportunity do not appear to be largely
responsible for the achievements of the individuals.
But, it is sometimes objected, opportunity certainly is responsible for
the appearance of much talent that would otherwise never appear. Take
the great increase in the number of scientific men in Germany during the
last half century, for example. It can not be pretended that this is due
to an increased birth-rate of such talent; it means that the growth of
an appreciation of scientific work has produced an increased amount of
scientific talent. J. McKeen Cattell has argued this point most
carefully in his study of the families of one thousand American men of
science (_Popular Science Monthly_, May, 1915). "A Darwin born in China
in 1809," he says, "could not have become a Darwin, nor could a Lincoln
born here on the same day have become a Lincoln had there been no Civil
War. If the two infants had been exchanged there would have been no
Darwin in America and no Lincoln in England. " And so he continues,
urging that in the production of scientific men, at least, education is
more important than eugenics.
This line of argument contains a great deal of obvious truth, but is
subject to a somewhat obvious objection, if it is pushed too far. It is
certainly true that the exact field in which a man's activities will
find play is largely determined by his surroundings and education. Young
men in the United States are now becoming lawyers or men of science, who
would have become ministers had they been born a century or two ago. But
this environmental influence seems to us a minor one, for the man who is
highly gifted in some one line is usually, as all the work of
differential psychology shows, gifted more than the average in many
other lines. Opportunity decides in just what field his life work shall
lie; but he would be able to make a success in a number of fields.
Darwin born in America would probably not have become the Darwin we
know, but it is not to be supposed that he would have died a "mute,
inglorious Milton": it is not likely that he would have failed to make
his mark in some line of human activity. Dr. Cattell's argument, then,
while admissible, can not properly be urged against the fact that
ability is mainly dependent on inheritance.
We need not stop with the conclusion that equality of training or
opportunity is unable to level the inborn differences between men. We
can go even farther, and produce evidence to show that equality of
training _increases the differences_ in results achieved.
This evidence is obtained by measuring the effects of equal amounts of
exercise of a function upon individual differences in respect to
efficiency in it. Suppose one should pick out, at random, eight
children, and let them do problems in multiplication for 10 minutes.
After a number of such trials, the three best might average 39 correct
solutions in the 10 minutes, and the three poorest might average 25
examples. Then let them continue the work, until each one of them has
done 700 examples. Here is equality in training; does it lead to uniform
results?
Dr. Starch made the actual test which we have outlined and found that
the three best pupils gained on the average 45 in the course of doing
700 examples; while the three poorest gained only 26 in the same course
of time.
Similar tests have been made of school children in a number of
instances, and have shown that equality of training fails to bring about
equality of performance. All improve to some extent; but those who are
naturally better than their comrades usually become better still, when
conditions for all are the same. E. L. Thorndike gives[12] the following
tabular statement of a test he conducted:
THE EFFECT OF EQUAL AMOUNTS OF PRACTICE UPON INDIVIDUAL DIFFERENCES
IN THE MENTAL MULTIPLICATION OF A THREE-PLACE BY A THREE-PLACE
NUMBER
Amount done Percentage of
per unit of correct figures
time in answers
Hours of Practice
|
| First 5 Examples First 5 Examples
| | |
| | Last 5 or 10 | Last 5 or 10
| | Examples | Examples
| | | | |
| | | Gain | | Gain
Initial highest five individuals 5. 1 85 147 61 70 78 18
" next five " 5. 1 56 107 51 68 78 10
" " six " 5. 3 46 68 22 74 82 8
" " six " 5. 4 38 46 8 58 70 12
" " five " 5. 2 31 57 26 47 67 20
" " one individual 5. 2 19 32 13 100 82 -18
Similar results have been obtained by half a dozen other experimenters,
using the tests of mental multiplication, addition, marking A's on a
printed sheet of capitals, and the like. It would be a mistake to
conclude too much from experiments of such restricted scope; but they
all agree in showing that if every child were given an equal training,
the differences in these traits would nevertheless be very great.
And although we do not wish to strain the application of these results
too far, we are at least justified in saying that they strongly indicate
that inborn mediocrity can not be made into a high grade of talent by
training. Not every boy has a chance to distinguish himself, even if he
receives a good education.
We are driven back to the same old conclusion, that it is primarily
inborn nature which causes the achievements of men and women to be what
they are. Good environment, opportunity, training, will give good
heredity a chance to express itself; but they can not produce greatness
from bad heredity.
These conclusions are familiar to scientific sociologists, but they have
not yet had the influence on social service and practical attempts at
reform which they deserve. Many popular writers continue to confuse
cause and effect, as for example H. Addington Bruce, who contributed an
article to the _Century Magazine_, not long ago, on "The Boy Who Goes
Wrong. " After alleging that the boy who goes wrong does so because he is
not properly brought up, Mr. Bruce quotes with approval the following
passage from Paul Dubois, "the eminent Swiss physician and philosopher:
"If you have the happiness to be a well-living man, take care not to
attribute the credit of it to yourself. Remember the favorable
conditions in which you have lived, surrounded by the relatives who
loved you and set you a good example; do not forget the close friends
who have taken you by the hand and led you away from the quagmires of
evil; keep a grateful remembrance for all the teachers who have
influenced you, the kind and intelligent school-master, the devoted
pastor; realize all these multiple influences which have made you what
you are. Then you will remember that such and such a culprit has not in
his sad life met with these favorable conditions; that he had a drunken
father or a foolish mother, and that he has lived without affection,
exposed to all kinds of temptation. You will then take pity upon this
disinherited man, whose mind has been nourished upon malformed mental
images, begetting evil sentiments such as immoderate desire or social
hatred. "
Mr. Bruce indorses this kind of talk when he concludes, "The blame for
the boy who goes wrong does not rest with the boy himself, or yet with
his remote ancestors. It rests squarely with the parents who, through
ignorance or neglect, have failed to mold him aright in the plastic days
of childhood. "
Where is the evidence of the existence of these plastic days of
childhood? If they exist, why do not ordinary brothers become as much
alike as identical twins? How long are we to be asked to believe, on
blind faith, that the child is putty, of which the educator can make
either mediocrity or genius, depending on his skill? What does the
environmentalist _know_ about these "plastic days"? If a boy has a
drunken father or foolish mother, does it not suggest that there is
something wrong with his pedigree? With such an ancestry, we do not
expect him to turn out brilliantly, no matter in what home he is brought
up. If a boy has the kind of parents who bring him up well; if he is,
as Dr. Dubois says, surrounded by relatives who love him and set him a
good example, we at once have ground for a suspicion that he comes of a
pretty good family, a stock characterized by a high standard of
intellectuality and morality, and it would surprise us if such a boy did
not turn out well. But he turns out well because what's bred in the bone
will show in him, if it gets any kind of a chance. It is his nature, not
his nurture, that is mainly responsible for his character.
CHAPTER II
MODIFICATION OF THE GERM-PLASM
Every living creature was at some stage of its life nothing more than a
single cell. It is generally known that human beings result from the
union of an egg-cell and a sperm-cell, but it is not so universally
understood that these germ-cells are part of a continuous stream of
germ-plasm which has been in existence ever since the appearance of life
on the globe, and which is destined to continue in existence as long as
life remains on the globe.
The corollaries of this fact are of great importance. Some of them will
be considered in this chapter.
Early investigators tended naturally to look on the germ-cells as a
product of the body. Being supposedly products of the body, it was
natural to think that they would in some measure reproduce the character
of the body which created them; and Darwin elaborated an ingenious
hypothesis to explain how the various characters could be represented in
the germ-cell. The idea held by him, in common with most other thinkers
of his period, is still held more or less unconsciously by those who
have not given particular attention to the subject. Generation is
conceived as a direct chain: the body produces the germ-cell which
produces another body which in turn produces another germ-cell, and so
on.
But a generation ago this idea fell under suspicion. August Weismann,
professor of zoology in the University of Freiburg, Germany, made
himself the champion of the new idea, about 1885, and developed it so
effectively that it is now a part of the creed of nearly every
biologist.
Weismann caused a general abandonment of the idea that the germ-cell is
produced by the body in each generation, and popularized the conception
of the germ-cell as a product of a stream of undifferentiated
germ-plasm, not only continuous but (potentially at least) immortal.
The body does not produce the germ-cells, he pointed out; instead, the
germ-cells produce the body.
The basis of this theory can best be understood by a brief consideration
of the reproduction of very simple organisms.
"Death is the end of life," is the belief of many other persons than the
Lotus Eaters. It is commonly supposed that everything which lives must
eventually die. But study of a one-celled animal, an Infusorian, for
example, reveals that when it reaches a certain age it pinches in two,
and each half becomes an Infusorian in all appearance identical with the
original cell. Has the parent cell then died? It may rather be said to
survive, in two parts. Each of these daughter cells will in turn go
through the same process of reproduction by simple fission, and the
process will be continued in their descendants. The Infusorian can be
called potentially immortal, because of this method of reproduction.
The immortality, as Weismann pointed out, is not of the kind attributed
by the Greeks to their gods, who could not die because no wound could
destroy them. On the contrary, the Infusorian is extremely fragile, and
is dying by millions at every instant; but if circumstances are
favorable, it _can_ live on; it is not inevitably doomed to die sooner
or later, as is Man. "It dies from accident often, from old age never. "
Now the single-celled Infusorian is in many respects comparable with the
single-celled germ of the higher animals. The analogy has often been
carried too far; yet it remains indisputable that the germ-cells of men
reproduce in the same way--by simple fission--as the Infusorian and
other one-celled animals and plants, and that they are organized on much
the same plan. Given favorable circumstances, the germ-cell should be
expected to be equally immortal. Does it ever find these favorable
circumstances?
The investigations of microscopists indicate that it does--that
evolution has provided it with these favorable circumstances, in the
bodies of the higher animals. Let us recall in outline the early history
of the fertilized germ-cell, the _zygote_ formed by the union of ovum
and spermatozoon. These two unite to form a single cell, which is
essentially the same, physiologically, as other germ-cells. It divides
in two similar cells; these each divide; the resulting cells again
divide, and so the process continues, until the whole body--a fully
developed man,--has been produced by division and redivision of the one
zygote.
But the germ-cell is obviously different from most of the cells that
make up the finished product, the body. The latter are highly
differentiated and specialized for different functions--blood cells,
nerve cells, bone cells, muscle cells, and so on, each a single cell but
each adapted to do a certain work, for which the original,
undifferentiated germ-cell was wholly unfit. It is evident that
differentiation began to take place at some point in the series of
divisions, that is to say, in the development of the embryo.
Th. Boveri, studying the development of a threadworm, made the
interesting discovery that this differentiation began at the first
division. Of the two daughter-cells produced from the zygote, one
continued dividing at a very slow rate, and without showing any
specialization. Its "line of descent" produced only germ-cells. The
products of division of the other daughter-cell began to differentiate,
and soon formed all the necessary kinds of cells to make up the body of
the mature worm. In this body, the cells from the first daughter-cell
mentioned were inclosed, still undifferentiated: they formed the
germ-cells of the next generation, and after maturity were ready to be
ejected from the body, and to form new threadworms.
Imagine this process taking place through generation after generation of
threadworms, and one will realize that the germ-plasm was passed on
directly from one generation to the next; that in each generation it
gave rise to body-plasm, but that it did not at any time lose its
identity or continuity, a part of the germ-plasm being always set aside,
undifferentiated, to be handed on to the next generation.
In the light of this example, one can better understand the definition
of germ-plasm as "that part of the substance of the parents which does
not die with them, but perpetuates itself in their offspring. " By
bringing his imagination into play, the reader will realize that there
is no limit to the backward continuity of this germ-plasm in the
threadworm. Granted that each species has arisen by evolution from some
other, this germ-cell which is observed in the body of the threadworm,
must be regarded as part of what may well be called a stream of
germ-plasm, that reaches back to the beginning of life in the world. It
will be equally evident that these is no foreordained limit to the
forward extension of the stream. It will continue in some branch, as
long as there are any threadworms or descendants of threadworms in the
world.
The reader may well express doubt as to whether what has been
demonstrated for the threadworm can be demonstrated for the higher
animals, including man. It must be admitted that in many of these
animals conditions are too unfavorable, and the process of embryology
too complicated, or too difficult to observe, to permit as distinct a
demonstration of this continuity of the germ-plasm, wherever it is
sought. But it has been demonstrated in a great many animals; no facts
which impair the theory have been discovered; and biologists therefore
feel perfectly justified in generalizing and declaring the continuity of
germ-plasm to be a law of the world of living things.
There is just one heredity in all the world that is ours--we are
children of God, and there is nothing in the whole big world that we
cannot do in His service with it. "
It is probably not beyond the truth to say that in this statement Jacob
Riis voiced the opinion of a majority of the social workers of this
country, and likewise a majority of the people who are faithfully and
with much self-sacrifice supporting charities, uplift movements, reform
legislation, and philanthropic attempts at social betterment in many
directions. They suppose that they are at the same time making the race
better by making the conditions better in which people live.
It is widely supposed that, although nature may have distributed some
handicaps at birth, they can be removed if the body is properly warmed
and fed and the mind properly exercised. It is further widely supposed
that this improvement in the condition of the individual will result in
his production of better infants, and that thus the race, gaining a
little momentum in each generation, will gradually move on toward
ultimate perfection.
There is no lack of efforts to improve the race, by this method of
direct change of the environment. It involves two assumptions, which are
sometimes made explicitly, sometimes merely taken for granted. These
are:
1. That changes in a man's surroundings, or, to use the more technical
biological term, in his nurture, will change the nature that he has
inherited.
2. That such changes will further be transmitted to his children.
Any one who proposes methods of race betterment, as we do in the present
book, must meet these two popular beliefs. We shall therefore examine
the first of them in this chapter, and the second in Chapter II.
Galton adopted and popularized Shakespere's antithesis of _nature_ and
_nurture_ to describe a man's inheritance and his surroundings, the two
terms including everything that can pertain to a human being. The words
are not wholly suitable, particularly since nature has two distinct
meanings,--human nature and external nature. The first is the only one
considered by Galton. Further, nurture is capable of subdivision into
those environmental influences which do not undergo much change,--e. g. ,
soil and climate,--and those forces of civilization and education which
might better be described as culture. The evolutionist has really to
deal with the three factors of germ-plasm, physical surroundings and
culture. But Galton's phrase is so widely current that we shall continue
to use it, with the implications that have just been outlined.
The antithesis of nature and nurture is not a new one; it was met long
ago by biologists and settled by them to their own satisfaction. The
whole body of experimental and observational evidence in biology tends
to show that the characters which the individual inherits from his
ancestors remain remarkably constant in all ordinary conditions to which
they may be subjected. Their constancy is roughly proportionate to the
place of the animal in the scale of evolution; lower forms are more
easily changed by outside influence, but as one ascends to the higher
forms, which are more differentiated, it is found more and more
difficult to effect any change in them. Their characters are more
definitely fixed at birth. [1]
It is with the highest of all forms, Man, that we have now to deal. The
student in biology is not likely to doubt that the differences in men
are due much more to inherited nature than to any influences brought to
bear after birth, even though these latter influences include such
powerful ones as nutrition and education within ordinary limits.
But the biological evidence does not lend itself readily to summary
treatment, and we shall therefore examine the question by statistical
methods. [2] These have the further advantage of being more easily
understood; for facts which can be measured and expressed in numbers are
facts whose import the reader can usually decide for himself: he is
perfectly able to determine, without any special training, whether twice
two does or does not make four. One further preliminary remark: the
problem of nature vs. nurture can not be solved in general terms; a
moment's thought will show that it can be understood only by examining
one trait at a time. The problem is to decide whether the differences
between the people met in everyday life are due more to inheritance or
to outside influences, and these differences must naturally be examined
separately; they can not be lumped together.
To ask whether nature in general contributes more to a man than nurture
is futile; but it is not at all futile to ask whether the differences in
a given human trait are more affected by differences in nature than by
differences in nurture. It is easy to see that a verdict may be
sometimes given to one side, sometimes to the other. Albinism in
animals, for instance, is a trait which is known to be inherited, and
which is very slightly affected by differences of climate, food supply,
etc. On the other hand, there are factors which, although having
inherited bases, owe their expression almost wholly to outside
influences. Professor Morgan, for example, has found a strain of fruit
flies whose offspring in cold weather are usually born with
supernumerary legs. In hot weather they are practically normal. If this
strain were bred only in the tropics, the abnormality would probably not
be noticed; on the other hand, if it were bred only in cold regions, it
would be set down as one characterized by duplication of limbs. The
heredity factor would be the same in each case, the difference in
appearance being due merely to temperature.
Mere inspection does not always tell whether some feature of an
individual is more affected by changes in heredity or changes in
surroundings. On seeing a swarthy man, one may suppose that he comes of
a swarthy race, or that he is a fair-skinned man who has lived long in
the desert. In the one case the swarthiness would be inheritable, in the
other not. Which explanation is correct, can only be told by examining a
number of such individuals under critical conditions, or by an
examination of the ancestry. A man from a dark-skinned race would become
little darker by living under the desert sun, while a white man would
take on a good deal of tan.
The limited effect of nurture in changing nature is in some fields a
matter of common observation. The man who works in the gymnasium knows
that exercise increases the strength of a given group of muscles for a
while, but not indefinitely. There comes a time when the limit of a
man's hereditary potentiality is reached, and no amount of exercise will
add another millimeter to the circumference of his arm. Similarly the
handball or tennis player some day reaches his highest point, as do
runners or race horses. A trainer could bring Arthur Duffy in a few
years to the point of running a hundred yards in 9-3/5 seconds, but no
amount of training after that could clip off another fifth of a second.
A parallel case is found in the students who take a college examination.
Half a dozen of them may have devoted the same amount of time to it--may
have crammed to the limit--but they will still receive widely different
marks. These commonplace cases show that nurture has seemingly some
power to mold the individual, by giving his inborn possibilities a
chance to express themselves, but that nature says the first and last
word. Francis Galton, the father of eugenics, hit on an ingenious and
more convincing illustration by studying the history of twins. [3]
There are, everyday observation shows, two kinds of twins--ordinary
twins and the so-called identical twins. Ordinary twins are merely
brothers, or sisters, or brother and sister, who happen to be born two
at a time, because two ova have developed simultaneously. The fact that
they were born at the same time does not make them alike--they differ
quite as widely from each other as ordinary brothers and sisters do.
Identical twins have their origin in a different phenomenon--they are
believed to be halves of the same egg-cell, in which two growing-points
appeared at a very early embryonic stage, each of these developing into
a separate individual. As would be expected, these identical twins are
always of the same sex, and extremely like each other, so that sometimes
their own mother can not tell them apart. This likeness extends to all
sorts of traits:--they have lost their milk teeth on the same day in one
case, they even fell ill on the same day with the same disease, even
though they were in different cities.
Now Galton reasoned that if environment really changes the inborn
character, then these identical twins, who start life as halves of the
same whole, ought to become more unlike if they were brought up apart;
and as they grew older and moved into different spheres of activity,
they ought to become measurably dissimilar. On the other hand, ordinary
twins, who start dissimilar, ought to become more alike when brought up
in the same family, on the same diet, among the same friends, with the
same education. If the course of years shows that identical twins remain
as like as ever and ordinary twins as unlike as ever, regardless of
changes in conditions, then environment will have failed to demonstrate
that it has any great power to modify one's inborn nature in these
traits.
With this view, Galton collected the history of eighty pairs of
identical twins, thirty-five cases being accompanied by very full
details, which showed that the twins were really as nearly identical, in
childhood, as one could expect to find. On this point, Galton's
inquiries were careful, and the replies satisfactory. They are not,
however, as he remarks, much varied in character. "When the twins are
children, they are usually distinguished by ribbons tied around the
wrist or neck; nevertheless the one is sometimes fed, physicked, and
whipped by mistake for the other, and the description of these little
domestic catastrophes was usually given by the mother, in a phraseology,
that is sometimes touching by reason of its seriousness. I have one case
in which a doubt remains whether the children were not changed in their
bath, and the presumed A is not really B, and _vice versa_. In another
case, an artist was engaged on the portraits of twins who were between
three and four years of age; he had to lay aside his work for three
weeks, and, on resuming it, could not tell to which child the respective
likeness he had in hand belonged. The mistakes become less numerous on
the part of the mother during the boyhood and girlhood of the twins, but
are almost as frequent as before on the part of strangers. I have many
instances of tutors being unable to distinguish their twin pupils. Two
girls used regularly to impose on their music teacher when one of them
wanted a whole holiday; they had their lessons at separate hours, and
the one girl sacrificed herself to receive two lessons on the same day,
while the other one enjoyed herself from morning to evening. Here is a
brief and comprehensive account: 'Exactly alike in all, their
schoolmasters could never tell them apart; at dancing parties they
constantly changed partners without discovery; their close resemblance
is scarcely diminished by age. "
[Illustration: FOUR BABY GIRLS AT ONCE
FIG. 1. --These quadruplet daughters were born to Mr. and Mrs.
F. M. Keys, Hollis, Okla. , on July 4, 1915, and were seven months old
when the photograph was taken. Up to that time they had never had any
other nourishment than their mother's milk. Their weights at birth were
as follows (reading from left to right): Roberta, 4 pounds; Mona, 4-1/2
pounds; Mary, 4-1/4 pounds; Leota, 3-3/4 pounds. When photographed,
Roberta weighed 16 pounds and each of the others weighed 16-1/4. Their
aunt vouches for the fact that the care of the four is less trouble than
a single baby often makes. The mother has had no previous plural births,
although she has borne four children prior to these. Her own mother had
but two children, a son and a daughter, and there is no record of twins
on the mother's side. The father of the quadruplets is one of twelve
children, among whom is one pair of twins. It is known that twinning is
largely due to inheritance, and it would seem that the appearance of
these quadruplets is due to the hereditary influence of the father
rather than the mother. If this is the case, then the four girls must
all have come from one egg-cell, which split up at an early stage. Note
the uniform shape of the mouth, and the ears, set unusually low on the
head. ]
"The following is a typical schoolboy anecdote:
"'Two twins were fond of playing tricks, and complaints were frequently
made; but the boys would never own which was the guilty one, and the
complainants were never certain which of the two it was. One head master
used to say he would never flog the innocent for the guilty, and the
other used to flog them both. '
"No less than nine anecdotes have reached me of a twin seeing his or her
reflection in the looking-glass, and addressing it in the belief that it
was the other twin in person.
"Children are usually quick in distinguishing between their parent and
his or her twin; but I have two cases to the contrary. Thus, the
daughter of a twin says:
"'Such was the marvelous similarity of their features, voice, manner,
etc. , that I remember, as a child, being very much puzzled, and I think,
had my aunt lived much with us, I should have ended by thinking I had
two mothers! '
"In the other case, a father who was a twin, remarks of himself and his
brother:
"'We were extremely alike, and are so at this moment, so much so that
our children up to five and six years old did not know us apart. '
"Among my thirty-five detailed cases of close similarity, there are no
less than seven in which both twins suffered from some special ailment
or had some exceptional peculiarity. Both twins are apt to sicken at the
same time in no less than nine out of the thirty-five cases. Either
their illnesses, to which I refer, were non-contagious, or, if
contagious, the twins caught them simultaneously; they did not catch
them the one from the other. "
Similarity in association of ideas, in tastes and habits was equally
close. In short, their resemblances were not superficial, but extremely
intimate, both in mind and body, while they were young; they were reared
almost exactly alike up to their early manhood and womanhood.
Then they separated into different walks of life. Did this change of the
environment alter their inborn character? For the detailed evidence,
one should consult Galton's own account; we give only his conclusions:
In many cases the resemblance of body and mind continued unaltered up to
old age, notwithstanding very different conditions of life; in others a
severe disease was sufficient to account for some change noticed. Other
dissimilarity that developed, Galton had reason to believe, was due to
the development of inborn characters that appeared late in life. He
therefore felt justified in broadly concluding "that the only
circumstance, within the range of those by which persons of similar
conditions of life are affected, that is capable of producing a marked
effect on the character of adults, is illness or some accident which
causes physical infirmity. The twins who closely resembled each other in
childhood and early youth, and were reared under not very dissimilar
conditions, either grow unlike through the development of natural [that
is, inherited] characteristics which had lain dormant at first, or else
they continue their lives, keeping time like two watches, hardly to be
thrown out of accord except by some physical jar. "
Here was a distinct failure of nurture to modify the inborn nature. We
next consider the ordinary twins who were unlike from the start. Galton
had twenty such cases, given with much detail. "It is a fact," he
observes, "that extreme dissimilarity, such as existed between Jacob and
Esau, is a no less marked peculiarity of twins of the same sex than
extreme similarity. " The character of the evidence as a whole may be
fairly conveyed by a few quotations:
(1) One parent says: "They have had _exactly the same nurture_ from
their birth up to the present time; they are both perfectly healthy and
strong, yet they are otherwise as dissimilar as two boys could be,
physically, mentally, and in their emotional nature. "
(2) "I can answer most decidedly that the twins have been perfectly
dissimilar in character, habits, and likeness from the moment of their
birth to the present time, though they were nursed by the same woman,
went to school together, and were never separated until the age of
thirteen. "
(3) "They have never been separated, never the least differently treated
in food, clothing, or education; both teethed at the same time, both had
measles, whooping cough, and scarlatina at the same time, and neither
has had any other serious illness. Both are and have been exceedingly
healthy, and have good abilities; yet they differ as much from each
other in mental cast as any one of my family differs from another. "
(4) "Very dissimilar in mind and body; the one is quiet, retiring, and
slow but sure; good-tempered, but disposed to be sulky when
provoked;--the other is quick, vivacious, forward, acquiring easily and
forgetting soon; quick-tempered and choleric, but quickly forgiving and
forgetting. They have been educated together and never separated. "
(5) "They were never alike either in mind or body, and their
dissimilarity increases daily. The external influences have been
identical; they have never been separated. "
(6) "The two sisters are very different in ability and disposition. The
one is retiring, but firm and determined; she has no taste for music or
drawing. The other is of an active, excitable temperament; she displays
an unusual amount of quickness and talent, and is passionately fond of
music and drawing. From infancy, they have been rarely separated even at
school, and as children visiting their friends, they always went
together. "
And so on. Not a single case was found in which originally dissimilar
characters became assimilated, although submitted to exactly the same
influences. Reviewing the evidence in his usual cautious way, Galton
declared, "There is no escape from the conclusion that nature prevails
enormously over nurture, when the differences of nurture do not exceed
what is commonly to be found among persons of the same rank in society
and in the same country. "
This kind of evidence was a good start for eugenics but as the science
grew, it outgrew such evidence. It no longer wanted to be told, no
matter how minute the details, that "nature prevails enormously over
nurture. " It wanted to know exactly how much. It refused to be satisfied
with the statement that a certain quantity was large; it demanded that
it be measured or weighed. So Galton, Karl Pearson and other
mathematicians devised means of doing this, and then Professor Edward L.
Thorndike of Columbia University took up Galton's problem again, with
more refined methods.
The tool used by Professor Thorndike was the coefficient of correlation,
which shows the amount of resemblance or association between any two
things that are capable of measurement, and is expressed in the form of
a decimal fraction somewhere between 0 and the unit 1. Zero shows that
there is no constant resemblance at all between the two things
concerned,--that they are wholly independent of each other, while 1
shows that they are completely dependent on each other, a condition that
rarely exists, of course. [4] For instance, the correlation between the
right and left femur in man's legs is . 98.
Professor Thorndike found in the New York City schools fifty pairs of
twins of about the same age and measured the closeness of their
resemblance in eight physical characters, and also in six mental
characters, the latter being measured by the proficiency with which the
subjects performed various tests. Then children of the same age and sex,
picked at random from the same schools, were measured in the same way.
It was thus possible to tell how much more alike twins were than
ordinary children in the same environment. [5]
[Illustration: THE EFFECT OF NURTURE IN CHANGING NATURE
FIG. 2. --Corn of a single variety (Leaming Dent) grown in two
plots: at the left spaced far apart in hills, at the right crowded. The
former grows to its full potential height, the latter is stunted. The
size differences in the two plots are due to differences in environment,
the heredity in both cases being the same. Plants are much more
susceptible to nutritional influences on size than are mammals, but to a
less degree nutrition has a similar effect on man. Photograph from A. F.
Blakeslee. ]
"If now these resemblances are due to the fact that the two members of
any twin pair are treated alike at home, have the same parental models,
attend the same school and are subject in general to closely similar
environmental conditions, then (1) twins should, up to the age of
leaving home, grow more and more alike, and in our measurements the
twins 13 and 14 years old should be much more alike than those 9 and 10
years old. Again (2) if similarity in training is the cause of
similarity in mental traits, ordinary fraternal pairs not over four or
five years apart in age should show a resemblance somewhat nearly as
great as twin pairs, for the home and school condition of a pair of the
former will not be much less similar than those of a pair of the latter.
Again, (3) if training is the cause, twins should show greater
resemblance in the case of traits much subject to training, such as
ability in addition or multiplication, than in traits less subject to
training, such as quickness in marking off the A's on a sheet of printed
capitals, or in writing the opposites of words. "
The data were elaborately analyzed from many points of view. They showed
(1) that the twins 12-14 years old were not any more alike than the
twins 9-11 years old, although they ought to have been, if environment
has great power to mold the character during these so-called "plastic
years of childhood. " They showed (2) that the resemblance between twins
was two or three times as great as between ordinary children of the same
age and sex, brought up under similar environment. There seems to be no
reason, except heredity, why twins should be more alike. The data showed
(3) that the twins were no more alike in traits subject to much training
than in traits subject to little or no training. Their achievement in
these traits was determined by their heredity; training did not
measurably alter these hereditary potentialities.
"The facts," Professor Thorndike wrote, "are easily, simply and
completely explained by one simple hypothesis; namely, that the nature
of the germ-cells--the conditions of conception--cause whatever
similarities and differences exist in the original natures of men, that
these conditions influence mind and body equally, and that in life the
differences in modification of mind and body produced by such
differences as obtain between the environments of present-day New York
City public school children are slight. "
"The inferences," he says, "with respect to the enormous importance of
original nature in determining the behavior and achievements of any man
in comparison with his fellows of the same period of civilization and
conditions of life are obvious. All theories of human life must accept
as a first principle the fact that human beings at birth differ
enormously in mental capacities and that these differences are largely
due to similar differences in their ancestry. All attempts to change
human nature must accept as their most important condition the limits
set by original nature to each individual. "
Meantime other investigators, principally followers of Karl Pearson in
England, were working out correlation coefficients in other lines of
research for hundreds of different traits. As we show in more detail in
Chapter IV, it was found, no matter what physical or mental trait was
measured, that the coefficient of correlation between parent and child
was a little less than . 5 and that the coefficient between brother and
brother, or sister and sister, or brother and sister, was a little more
than . 5. On the average of many cases the mean "nature" value, the
coefficient of direct heredity, was placed at . 51. This gave another
means of measuring nurture, for it was also possible to measure the
relation between any trait in the child and some factor in the
environment. A specific instance will make this clearer.
Groups of school children usually show an appalling percentage of
short-sightedness. Now suppose it is suggested that this is because they
are allowed to learn to read at too early an age. One can find out the
age at which any given child did learn to read, and work out the
coefficient of correlation between this age and the child's amount of
myopia. If the relation between them is very close--say . 7 or . 8--it
will be evident that the earlier a child learns to read, the more
short-sighted he is as he grows older. This will not prove a relation of
cause and effect, but it will at least create a great suspicion. If on
the contrary the correlation is very slight, it will be evident that
early reading has little to do with the prevalance of defective vision
among school children. If investigators similarly work out all the other
correlations that can be suggested, finding whether there is any
regular relation between myopia and overcrowding, long hours of study,
general economic conditions at home, general physical or moral
conditions of parents, the time the child spends out of doors, etc. , and
if no important relation is found between these various factors and
myopia, it will be evident that no factor of the environment which one
can think of as likely to cause the trouble really accounts for the poor
eyesight of school children.
[Illustration: HEIGHT IN CORN AND MEN
FIG. 3. --An unusually short and an unusually tall man,
photographed beside extreme varieties of corn which, like the men, owe
their differences in height indisputably to heredity rather than to
environment. No imaginable environmental differences could reverse the
positions of these two men, or of these two varieties of corn, the
heredity in each case being what it is. The large one might be stunted,
but the small one could not be made much larger. Photograph from A. F.
Blakeslee. ]
This has actually been done,[6] and none of the conditions enumerated
has been found to be closely related to myopia in school children.
Correlations between fifteen environmental conditions and the goodness
of children's eyesight were measured, and only in one case was the
correlation as high as . 1. The mean of these correlations was about
. 04--an absolutely negligible quantity when compared with the common
heredity coefficient of . 51.
Does this prove that the myopia is rather due to heredity? It would, by
a process of exclusion, if every conceivable environmental factor had
been measured and found wanting. That point in the investigation can
never be reached, but a tremendously strong suspicion is at least
justified.
Now if the degree of resemblance between the prevalence of
myopia in parents and that in children be directly measured, and if it
be found that when the parent has eye trouble the child also has it,
then it seems that a general knowledge of heredity should lead to the
belief that the difficulty lies there, and that an environmental cause
for the poor vision of the school child was being sought, when it was
all the time due almost entirely to heredity. This final step has not
yet been completed in an adequate way,[7] but the evidence, partly
analogical, gives every reason to believe in the soundness of the
conclusion stated, that in most cases the schoolboy must wear glasses
because of his heredity, not because of overstudy or any neglect on the
part of his parents to care for his eyes properly during his childhood.
[Illustration: WHY MEN GROW SHORT OR TALL
FIG. 4. --Pedigree charts of the two men shown in the preceding
illustration. Squares represent men and circles women; figures
underlined denote measurement in stocking feet. It is obvious from a
comparison of the ancestry of the two men that the short one comes from
a predominantly short family, while the tall one gains his height
likewise from heredity. The shortest individual in the right-hand chart
would have been accounted tall in the family represented on the left.
After A. F. Blakeslee. ]
The extent to which the intelligence of school children is dependent on
defective physique and unfavorable home environment is an important
practical question, which David Heron of London attacked by the methods
we have outlined. He wanted to find out whether the healthy children
were the most intelligent. One is constantly hearing stories of how the
intelligence of school children has been improved by some treatment
which improved their general health, but these stories are rarely
presented in such a way as to contribute evidence of scientific value.
It was desirable to know what exact measurement would show. The
intelligence of all the children in fourteen schools was measured in its
correlation with weight and height, conditions of clothing and teeth,
state of nutrition, cleanliness, good hearing, and the condition of the
cervical glands, tonsils and adenoids. It could not be found that mental
capacity was closely related to any of the characters dealt with. [8] The
particular set of characters measured was taken because it happened to
be furnished by data collected for another purpose; the various items
are suggestive rather than directly conclusive. Here again, the
correlation in most cases was less than . 1, as compared with the general
heredity correlation of . 5.
The investigation need not be limited to problems of bad breeding.
Eugenics, as its name shows, is primarily interested in "good breeding;"
it is particularly worth while, therefore, to examine the relations
between heredity and environment in the production of mental and moral
superiority.
If success in life--the kind of success that is due to great mental and
moral superiority--is due to the opportunities a man has, then it ought
to be pretty evenly distributed among all persons who have had favorable
opportunities, provided a large enough number of persons be taken to
allow the laws of probability full play. England offers a good field to
investigate this point, because Oxford and Cambridge, her two great
universities, turn out most of the eminent men of the country, or at
least have done so until recently. If nothing more is necessary to
ensure a youth's success than to give him a first-class education and
the chance to associate with superior people, then the prizes of life
ought to be pretty evenly distributed among the graduates of the two
universities, during a period of a century or two.
This is not the case. When we look at the history of England, as Galton
did nearly half a century ago, we find success in life to an unexpected
degree a family affair. The distinguished father is likely to have a
distinguished son, while the son of two "nobodies" has a very small
chance of becoming distinguished. To cite one concrete case, Galton
found[9] that the son of a distinguished judge had about one chance in
four of becoming himself distinguished, while the son of a man picked
out at random from the population had about one chance in 4,000 of
becoming similarly distinguished.
The objection at once occurs that perhaps social opportunities might
play the predominant part; that the son of an obscure man never gets a
chance, while the son of the prominent man is pushed forward regardless
of his inherent abilities. This, as Galton argued at length, can not be
true of men of really eminent attainments. The true genius, he thought,
frequently succeeds in rising despite great obstacles, while no amount
of family pull will succeed in making a mediocrity into a genius,
although it may land him in some high and very comfortable official
position. Galton found a good illustration in the papacy, where during
many centuries it was the custom for a pope to adopt one of his nephews
as a son, and push him forward in every way. If opportunity were all
that is required, these adopted sons ought to have reached eminence as
often as a real son would have done; but statistics show that they
reached eminence only as often as would be expected for nephews of great
men, whose chance is notably less, of course, than that of sons of great
men, in whom the intensity of heredity is much greater.
Transfer the inquiry to America, and it becomes even more conclusive,
for this is supposed to be the country of equal opportunities, where it
is a popular tradition that every boy has a chance to become president.
Success may be in some degree a family affair in caste-ridden England;
is it possible that the past history of the United States should show
the same state of affairs?
Galton found that about half of the great men of England had
distinguished close relatives. If the great men of America have fewer
distinguished close relatives, environment will be able to make out a
plausible case: it will be evident that in this continent of boundless
opportunities the boy with ambition and energy gets to the top, and that
this ambition and energy do not depend on the kind of family he comes
from.
Frederick Adams Woods has made precisely this investigation. [10] The
first step was to find out how many eminent men there are in American
history. Biographical dictionaries list about 3,500, and this number
provides a sufficiently unbiased standard from which to work. Now, Dr.
Woods says, if we suppose the average person to have as many as twenty
close relatives--as near as an uncle or a grandson--then computation
shows that only one person in 500 in the United States has a chance to
be a near relative of one of the 3,500 eminent men--provided it is
purely a matter of chance. As a fact, the 3,500 eminent men listed by
the biographical dictionaries are related to each other not as one in
500, but as one in five. If the more celebrated men alone be considered,
it is found that the percentage increases so that about one in three of
them has a close relative who is also distinguished. This ratio
increases to more than one in two when the families of the forty-six
Americans in the Hall of Fame are made the basis of study. If all the
eminent relations of those in the Hall of Fame are counted, they average
more than one apiece. Therefore, they are from five hundred to a
thousand times as much related to distinguished people as the ordinary
mortal is.
To look at it from another point of view, something like 1% of the
population of the country is as likely to produce a man of genius as is
all the rest of the population put together,--the other 99%.
This might still be due in some degree to family influence, to the
prestige of a famous name, or to educational advantages afforded the
sons of successful men. Dr. Woods' study of the royal families of Europe
is more decisive. [11]
In the latter group, the environment must be admitted--on the whole--to
be uniformly favorable. It has varied, naturally, in each case, but
speaking broadly it is certain that all the members of this group have
had the advantage of a good education, of unusual care and attention. If
such things affect achievement, then the achievements of this class
ought to be pretty generally distributed among the whole class. If
opportunity is the cause of a man's success, then most of the members of
this class ought to have succeeded, because to every one of royal blood,
the door of opportunity usually stands open. One would expect the heir
to the throne to show a better record than his younger brothers,
however, because his opportunity to distinguish himself is naturally
greater. This last point will be discussed first.
Dr. Woods divided all the individuals in his study into ten classes for
intellectuality and ten for morality, those most deficient in the
qualities being put in class 1, while the men and women of preeminent
intellectual and moral worth were put in class 10. Now if preeminent
intellect and morality were at all linked with the better chances that
an inheritor of succession has, then heirs to the throne ought to be
more plentiful in the higher grades than in the lower. Actual count
shows this not to be the case. A slightly larger percentage of
inheritors is rather to be found in the lower grades. The younger sons
have made just as good a showing as the sons who succeeded to power; as
one would expect if intellect and morality are due largely to heredity,
but as one would not expect if intellect and morality are due largely to
outward circumstances.
Are "conditions of turmoil, stress and adversity" strong forces in the
production of great men, as has often been claimed? There is no evidence
from facts to support that view. In the case of a few great commanders,
the times seemed particularly favorable. Napoleon, for example, could
hardly have been Napoleon had it not been for the French revolution. But
in general there have been wars going on during the whole period of
modern European history; there have always been opportunities for a
royal hero to make his appearance; but often the country has called for
many years in vain. Circumstances were powerless to produce a great man
and the nation had to wait until heredity produced him. Spain has for
several centuries been calling for genius in leadership in some lines;
but in vain. England could not get an able man from the Stuart line,
despite her need, and had to wait for William of Orange, who was a
descendant of a man of genius, William the Silent. "Italy had to wait
fifty years in bondage for her deliverers, Cavour, Garibaldi and Victor
Emmanuel. "
"The upshot of it all," Dr. Woods decides, "is that, as regards
intellectual life, environment is a totally inadequate explanation. If
it explains certain characters in certain instances, it always fails to
explain many more, while heredity not only explains all, or at least
90%, of the intellectual side of character in practically every
instance, but does so best when questions of environment are left out of
discussion. "
Despite the good environment almost uniformly present, the geniuses in
royalty are not scattered over the surface of the pedigree chart, but
form isolated little groups of closely related individuals. One centers
in Frederick the Great, another in Queen Isabella of Spain, a third in
William the Silent, and a fourth in Gustavus Adolphus. Furthermore, the
royal personages who are conspicuously low in intellect and morality are
similarly grouped. Careful study of the circumstances shows nothing in
the environment that would produce this grouping of genius, while it is
exactly what a knowledge of heredity leads one to expect.
In the next place, do the superior members of royalty have
proportionately more superior individuals among their close relatives,
as was found to be the case among the Americans in the Hall of Fame? A
count shows at once that they do. The first six grades all have about an
equal number of eminent relatives, but grade 7 has more while grade 8
has more than grade 7, and the geniuses of grade 10 have the highest
proportion of nearer relatives of their own character. Surely it cannot
be supposed that a relative of a king in grade 8 has on the average a
much less favorable environment than a relative of a king in grade 10.
Is it not fair, then, to assume that this relative's greater endowment
in the latter case is due to heredity?
Conditions are the same, whether males or females be considered. The
royal families of Europe offer a test case because for them the
environment is nearly uniformly favorable. A study of them shows great
mental and moral differences between them, and critical evidence
indicates that these differences are largely due to differences in
heredity. Differences of opportunity do not appear to be largely
responsible for the achievements of the individuals.
But, it is sometimes objected, opportunity certainly is responsible for
the appearance of much talent that would otherwise never appear. Take
the great increase in the number of scientific men in Germany during the
last half century, for example. It can not be pretended that this is due
to an increased birth-rate of such talent; it means that the growth of
an appreciation of scientific work has produced an increased amount of
scientific talent. J. McKeen Cattell has argued this point most
carefully in his study of the families of one thousand American men of
science (_Popular Science Monthly_, May, 1915). "A Darwin born in China
in 1809," he says, "could not have become a Darwin, nor could a Lincoln
born here on the same day have become a Lincoln had there been no Civil
War. If the two infants had been exchanged there would have been no
Darwin in America and no Lincoln in England. " And so he continues,
urging that in the production of scientific men, at least, education is
more important than eugenics.
This line of argument contains a great deal of obvious truth, but is
subject to a somewhat obvious objection, if it is pushed too far. It is
certainly true that the exact field in which a man's activities will
find play is largely determined by his surroundings and education. Young
men in the United States are now becoming lawyers or men of science, who
would have become ministers had they been born a century or two ago. But
this environmental influence seems to us a minor one, for the man who is
highly gifted in some one line is usually, as all the work of
differential psychology shows, gifted more than the average in many
other lines. Opportunity decides in just what field his life work shall
lie; but he would be able to make a success in a number of fields.
Darwin born in America would probably not have become the Darwin we
know, but it is not to be supposed that he would have died a "mute,
inglorious Milton": it is not likely that he would have failed to make
his mark in some line of human activity. Dr. Cattell's argument, then,
while admissible, can not properly be urged against the fact that
ability is mainly dependent on inheritance.
We need not stop with the conclusion that equality of training or
opportunity is unable to level the inborn differences between men. We
can go even farther, and produce evidence to show that equality of
training _increases the differences_ in results achieved.
This evidence is obtained by measuring the effects of equal amounts of
exercise of a function upon individual differences in respect to
efficiency in it. Suppose one should pick out, at random, eight
children, and let them do problems in multiplication for 10 minutes.
After a number of such trials, the three best might average 39 correct
solutions in the 10 minutes, and the three poorest might average 25
examples. Then let them continue the work, until each one of them has
done 700 examples. Here is equality in training; does it lead to uniform
results?
Dr. Starch made the actual test which we have outlined and found that
the three best pupils gained on the average 45 in the course of doing
700 examples; while the three poorest gained only 26 in the same course
of time.
Similar tests have been made of school children in a number of
instances, and have shown that equality of training fails to bring about
equality of performance. All improve to some extent; but those who are
naturally better than their comrades usually become better still, when
conditions for all are the same. E. L. Thorndike gives[12] the following
tabular statement of a test he conducted:
THE EFFECT OF EQUAL AMOUNTS OF PRACTICE UPON INDIVIDUAL DIFFERENCES
IN THE MENTAL MULTIPLICATION OF A THREE-PLACE BY A THREE-PLACE
NUMBER
Amount done Percentage of
per unit of correct figures
time in answers
Hours of Practice
|
| First 5 Examples First 5 Examples
| | |
| | Last 5 or 10 | Last 5 or 10
| | Examples | Examples
| | | | |
| | | Gain | | Gain
Initial highest five individuals 5. 1 85 147 61 70 78 18
" next five " 5. 1 56 107 51 68 78 10
" " six " 5. 3 46 68 22 74 82 8
" " six " 5. 4 38 46 8 58 70 12
" " five " 5. 2 31 57 26 47 67 20
" " one individual 5. 2 19 32 13 100 82 -18
Similar results have been obtained by half a dozen other experimenters,
using the tests of mental multiplication, addition, marking A's on a
printed sheet of capitals, and the like. It would be a mistake to
conclude too much from experiments of such restricted scope; but they
all agree in showing that if every child were given an equal training,
the differences in these traits would nevertheless be very great.
And although we do not wish to strain the application of these results
too far, we are at least justified in saying that they strongly indicate
that inborn mediocrity can not be made into a high grade of talent by
training. Not every boy has a chance to distinguish himself, even if he
receives a good education.
We are driven back to the same old conclusion, that it is primarily
inborn nature which causes the achievements of men and women to be what
they are. Good environment, opportunity, training, will give good
heredity a chance to express itself; but they can not produce greatness
from bad heredity.
These conclusions are familiar to scientific sociologists, but they have
not yet had the influence on social service and practical attempts at
reform which they deserve. Many popular writers continue to confuse
cause and effect, as for example H. Addington Bruce, who contributed an
article to the _Century Magazine_, not long ago, on "The Boy Who Goes
Wrong. " After alleging that the boy who goes wrong does so because he is
not properly brought up, Mr. Bruce quotes with approval the following
passage from Paul Dubois, "the eminent Swiss physician and philosopher:
"If you have the happiness to be a well-living man, take care not to
attribute the credit of it to yourself. Remember the favorable
conditions in which you have lived, surrounded by the relatives who
loved you and set you a good example; do not forget the close friends
who have taken you by the hand and led you away from the quagmires of
evil; keep a grateful remembrance for all the teachers who have
influenced you, the kind and intelligent school-master, the devoted
pastor; realize all these multiple influences which have made you what
you are. Then you will remember that such and such a culprit has not in
his sad life met with these favorable conditions; that he had a drunken
father or a foolish mother, and that he has lived without affection,
exposed to all kinds of temptation. You will then take pity upon this
disinherited man, whose mind has been nourished upon malformed mental
images, begetting evil sentiments such as immoderate desire or social
hatred. "
Mr. Bruce indorses this kind of talk when he concludes, "The blame for
the boy who goes wrong does not rest with the boy himself, or yet with
his remote ancestors. It rests squarely with the parents who, through
ignorance or neglect, have failed to mold him aright in the plastic days
of childhood. "
Where is the evidence of the existence of these plastic days of
childhood? If they exist, why do not ordinary brothers become as much
alike as identical twins? How long are we to be asked to believe, on
blind faith, that the child is putty, of which the educator can make
either mediocrity or genius, depending on his skill? What does the
environmentalist _know_ about these "plastic days"? If a boy has a
drunken father or foolish mother, does it not suggest that there is
something wrong with his pedigree? With such an ancestry, we do not
expect him to turn out brilliantly, no matter in what home he is brought
up. If a boy has the kind of parents who bring him up well; if he is,
as Dr. Dubois says, surrounded by relatives who love him and set him a
good example, we at once have ground for a suspicion that he comes of a
pretty good family, a stock characterized by a high standard of
intellectuality and morality, and it would surprise us if such a boy did
not turn out well. But he turns out well because what's bred in the bone
will show in him, if it gets any kind of a chance. It is his nature, not
his nurture, that is mainly responsible for his character.
CHAPTER II
MODIFICATION OF THE GERM-PLASM
Every living creature was at some stage of its life nothing more than a
single cell. It is generally known that human beings result from the
union of an egg-cell and a sperm-cell, but it is not so universally
understood that these germ-cells are part of a continuous stream of
germ-plasm which has been in existence ever since the appearance of life
on the globe, and which is destined to continue in existence as long as
life remains on the globe.
The corollaries of this fact are of great importance. Some of them will
be considered in this chapter.
Early investigators tended naturally to look on the germ-cells as a
product of the body. Being supposedly products of the body, it was
natural to think that they would in some measure reproduce the character
of the body which created them; and Darwin elaborated an ingenious
hypothesis to explain how the various characters could be represented in
the germ-cell. The idea held by him, in common with most other thinkers
of his period, is still held more or less unconsciously by those who
have not given particular attention to the subject. Generation is
conceived as a direct chain: the body produces the germ-cell which
produces another body which in turn produces another germ-cell, and so
on.
But a generation ago this idea fell under suspicion. August Weismann,
professor of zoology in the University of Freiburg, Germany, made
himself the champion of the new idea, about 1885, and developed it so
effectively that it is now a part of the creed of nearly every
biologist.
Weismann caused a general abandonment of the idea that the germ-cell is
produced by the body in each generation, and popularized the conception
of the germ-cell as a product of a stream of undifferentiated
germ-plasm, not only continuous but (potentially at least) immortal.
The body does not produce the germ-cells, he pointed out; instead, the
germ-cells produce the body.
The basis of this theory can best be understood by a brief consideration
of the reproduction of very simple organisms.
"Death is the end of life," is the belief of many other persons than the
Lotus Eaters. It is commonly supposed that everything which lives must
eventually die. But study of a one-celled animal, an Infusorian, for
example, reveals that when it reaches a certain age it pinches in two,
and each half becomes an Infusorian in all appearance identical with the
original cell. Has the parent cell then died? It may rather be said to
survive, in two parts. Each of these daughter cells will in turn go
through the same process of reproduction by simple fission, and the
process will be continued in their descendants. The Infusorian can be
called potentially immortal, because of this method of reproduction.
The immortality, as Weismann pointed out, is not of the kind attributed
by the Greeks to their gods, who could not die because no wound could
destroy them. On the contrary, the Infusorian is extremely fragile, and
is dying by millions at every instant; but if circumstances are
favorable, it _can_ live on; it is not inevitably doomed to die sooner
or later, as is Man. "It dies from accident often, from old age never. "
Now the single-celled Infusorian is in many respects comparable with the
single-celled germ of the higher animals. The analogy has often been
carried too far; yet it remains indisputable that the germ-cells of men
reproduce in the same way--by simple fission--as the Infusorian and
other one-celled animals and plants, and that they are organized on much
the same plan. Given favorable circumstances, the germ-cell should be
expected to be equally immortal. Does it ever find these favorable
circumstances?
The investigations of microscopists indicate that it does--that
evolution has provided it with these favorable circumstances, in the
bodies of the higher animals. Let us recall in outline the early history
of the fertilized germ-cell, the _zygote_ formed by the union of ovum
and spermatozoon. These two unite to form a single cell, which is
essentially the same, physiologically, as other germ-cells. It divides
in two similar cells; these each divide; the resulting cells again
divide, and so the process continues, until the whole body--a fully
developed man,--has been produced by division and redivision of the one
zygote.
But the germ-cell is obviously different from most of the cells that
make up the finished product, the body. The latter are highly
differentiated and specialized for different functions--blood cells,
nerve cells, bone cells, muscle cells, and so on, each a single cell but
each adapted to do a certain work, for which the original,
undifferentiated germ-cell was wholly unfit. It is evident that
differentiation began to take place at some point in the series of
divisions, that is to say, in the development of the embryo.
Th. Boveri, studying the development of a threadworm, made the
interesting discovery that this differentiation began at the first
division. Of the two daughter-cells produced from the zygote, one
continued dividing at a very slow rate, and without showing any
specialization. Its "line of descent" produced only germ-cells. The
products of division of the other daughter-cell began to differentiate,
and soon formed all the necessary kinds of cells to make up the body of
the mature worm. In this body, the cells from the first daughter-cell
mentioned were inclosed, still undifferentiated: they formed the
germ-cells of the next generation, and after maturity were ready to be
ejected from the body, and to form new threadworms.
Imagine this process taking place through generation after generation of
threadworms, and one will realize that the germ-plasm was passed on
directly from one generation to the next; that in each generation it
gave rise to body-plasm, but that it did not at any time lose its
identity or continuity, a part of the germ-plasm being always set aside,
undifferentiated, to be handed on to the next generation.
In the light of this example, one can better understand the definition
of germ-plasm as "that part of the substance of the parents which does
not die with them, but perpetuates itself in their offspring. " By
bringing his imagination into play, the reader will realize that there
is no limit to the backward continuity of this germ-plasm in the
threadworm. Granted that each species has arisen by evolution from some
other, this germ-cell which is observed in the body of the threadworm,
must be regarded as part of what may well be called a stream of
germ-plasm, that reaches back to the beginning of life in the world. It
will be equally evident that these is no foreordained limit to the
forward extension of the stream. It will continue in some branch, as
long as there are any threadworms or descendants of threadworms in the
world.
The reader may well express doubt as to whether what has been
demonstrated for the threadworm can be demonstrated for the higher
animals, including man. It must be admitted that in many of these
animals conditions are too unfavorable, and the process of embryology
too complicated, or too difficult to observe, to permit as distinct a
demonstration of this continuity of the germ-plasm, wherever it is
sought. But it has been demonstrated in a great many animals; no facts
which impair the theory have been discovered; and biologists therefore
feel perfectly justified in generalizing and declaring the continuity of
germ-plasm to be a law of the world of living things.
