No More Learning

We do not mean to advocate this as the only proper basis for
the temperance campaign, because the physiological and economic aspects
are of sufficient importance to keep up the campaign at twice the
present intensity. [23] But it is desirable to have the eugenic aspect of
the matter clearly understood, and to point out that in checking the
production of defectives in the United States, eugenics will do its
share, and a big share, toward the solution of the drink problem, which
is at the same time being attacked along other and equally praiseworthy
lines by other people.

A number of other substances are sometimes credited with being racial
poisons.

The poison of _Spirochaete pallida_, the microorganism which causes
syphilis, has been widely credited with a directly noxious effect on the
germ-plasm, and the statement has been made that this effect can be
transmitted for several generations. On the other hand, healthy children
are reported as being born to cured syphilitics. Further evidence is
needed, taking care to eliminate cases of infection from the parents. If
the alleged deterioration really occurs, it will still remain to be
determined if the effect is permanent or an induction, that is, a change
in the germ-cells which does not permanently alter the nature of the
inherited traits, and which would disappear in a few generations under
favorable conditions.

The case against lead is similar. Sir Thomas Oliver, in his _Diseases of
Occupation_, sums up the evidence as follows:

"Rennert has attempted to express in statistical terms the varying
degrees of gravity in the prognosis of cases in which at the moment of
conception both parents are the subjects of lead poisoning, also when
one alone is affected. The malign influence of lead is reflected upon
the fetus and upon the continuation of the pregnancy 94 times out of 100
when both parents have been working in lead, 92 times when the mother
alone is affected, and 63 times when it is the father alone who has
worked in lead. Taking seven healthy women who were married to lead
workers, and in whom there was a total of 32 pregnancies, Lewin (Berlin)
tells us that the results were as follows: 11 miscarriages, one
stillbirth, 8 children died within the first year after their birth,
four in the second year, five in the third year and one subsequent to
this, leaving only two children out of 32 pregnancies as likely to live
to manhood. In cases where women have had a series of miscarriages so
long as their husbands worked in lead, a change of industrial
occupation on the part of the husband restores to the wives normal
child-bearing powers. " The data of Constantin Paul, published as long
ago as 1860, indicated that lead exercised an injurious effect through
the male as well as the female parent. This sort of evidence is
certainly weak, in that it fails to take into account the possible
effects of environment; and one would do well to keep an open mind on
the subject. In a recent series of careful experiments at the University
of Wisconsin, Leon J. Cole has treated male rabbits with lead. He
reports: "The 'leaded' males have produced as many or more offspring
than normal fathers, but their young have averaged smaller in size and
are of lowered vitality, so that larger numbers of them die off at an
early age than is the case with those from untreated fathers. "

[Illustration: EFFECT OF LEAD AS A "RACIAL POISON"

FIG. 7. --That lead poisoning can affect the germ plasm of
rabbits is indicated by experiments conducted by Leon J. Cole at the
University of Wisconsin. With reference to the above illustration,
Professor Cole writes: "Each of the photographs shows two young from the
same litter, in all cases the mother being a normal (nonpoisoned)
albino. In each of the litters the white young is from an albino father
which received the lead treatment, while the pigmented offspring is from
a normal, homozygous, pigmented male. While these are, it is true,
selected individuals, they represent what tend to be average, rather
than extreme, conditions. The albino male was considerably larger than
the pigmented male; nevertheless his young average distinctly smaller in
size. Note also the brighter expression of the pigmented young. "]

There is, then, a suspicion that lead is a racial poison, but no
evidence as yet as to whether the effect is permanent or in the nature
of an induction.

This concludes the short list of substances for which there has been any
plausible case made out, as racial poisons. Gonorrhea, malaria, arsenic,
tobacco, and numerous other substances have been mentioned from time to
time, and even ardently contended by propagandists to be racial poisons,
but in the case of none of them, so far as we know, is there any
evidence to support the claim. And as has been shown, in the case of the
three chief so-called racial poisons, alcohol, syphilis and lead, the
evidence is not great. We are thus in a position to state that, from the
eugenists' point of view, the _origination_ of degeneracy, by some
direct action of the germ-plasm, is a contingency that hardly needs to
be reckoned with. Even in case the evidence were much stronger than it
is, the damage done may only be a physiological or chemical induction,
the effects of which will wear off in a few generations; rather than a
radical change in the hereditary constituents of the germ-plasm. The
germ-plasm is so carefully isolated and guarded that it is almost
impossible to injure it, except by treatment so severe as to kill it
altogether; and the degeneracy with which eugenists are called on to
deal is a degeneracy which is running along from generation to
generation and which, when once stopped by the cessation of
reproduction, is in little danger of being originated anew through some
racial poison.

Through these facts, the problem of race betterment is not only
immensely simplified, but it is clearly shown to be more a matter for
treatment by the biologist, acting through eugenics, than for the
optimistic improver of the environment.

There is another way in which it is widely believed that some such
result as a direct influence of the germ-plasm can be produced: that is
through the imaginary process known as maternal impression, prenatal
influence, etc. Belief in maternal impressions is no novelty. In the
book of Genesis[24] Jacob is described as making use of it to get the
better of his tricky father-in-law. Some animal breeders still profess
faith in it as a part of their methods of breeding: if they want a black
calf, for instance, they will keep a white cow in a black stall, and
express perfect confidence that her offspring will resemble midnight
darkness. It is easy to see that this method, if it "works," would be a
potent instrument for eugenics. And it is being recommended for that
reason. Says a recent writer, who professes on the cover of her book to
give a "complete and intelligent summary of all the principles of
eugenics":

"Too much emphasis can not be placed upon the necessity of young people
making the proper choice of mates in marriage; yet if the production of
superior children were dependent upon that one factor, the outlook would
be most discouraging to prospective fathers and mothers, for weak traits
of character are to be found in all. But when young people learn that by
a conscious endeavor to train themselves, they are thereby training
their unborn children, they can feel that there is some hope and joy in
parentage; that it is something to which they can look forward with
delight and even rapture; then they will be inspired to work hard to
attain the best and highest that there is in them, leading the lives
that will not only be a blessing to themselves, but to their succeeding
generation. "

The author of this quotation has no difficulty in finding supporters.
Many physicians and surgeons, who are supposed to be trained in
scientific methods of thought, will indorse what she says. The author of
one of the most recent and in many respects admirable books on the care
of babies, is almost contemptuous in her disdain for those who think
otherwise:

"Science wrangles over the rival importance of heredity and environment,
but we women know what effects prenatal influence works on children. "
"The woman who frets brings forth a nervous child. The woman who rebels
generally bears a morbid child. " "Self-control, cheerfulness and love
for the little life breathing in unison with your own will practically
insure you a child of normal physique and nerves. "

Such statements, backed up by a great array of writers and speakers whom
the layman supposes to be scientific, and who think themselves
scientific, can not fail to influence strongly an immense number of
fathers and mothers. If they are truly scientific statements, their
general acceptance must be a great good.

But think of the misplaced effort if these widespread statements are
false!

Is there, or is there not, a short cut to race betterment? Everyone
interested in the welfare of the race must feel the necessity of getting
at the truth in the case; and the truth can be found only by rigorously
scientific thought.

Let us turn to the observed facts. This sample is taken from the health
department of a popular magazine, quite recently issued:

"Since birth my body has been covered with scales strikingly resembling
the surface of a fish. My parents and I have expended considerable money
on remedies and specialists without deriving any permanent benefit. I
bathe my entire body with hot water daily, using the best quality of
soap. The scales fall off continually. My brother, who is younger than
myself, is afflicted with the same trouble, but in a lesser degree. My
sister, the third member of the family, has been troubled only on the
knees and abdomen. My mother has always been quite nervous and
susceptible to any unusual mental impression. She believes that she
marked me by craving fish, and preferring to clean them herself. During
the prenatal life of my brother, she worried much lest she might mark
him in the same way. In the case of my sister she tried to control her
mind. "[25]

Another is taken from a little publication which is devoted to
eugenics. [26] As a "horrible example" the editor gives the case of Jesse
Pomeroy, a murderer whom older readers will remember. His father, it
appears, worked in a meat market. Before the birth of Jesse, his mother
went daily to the shop to carry a luncheon to her husband, and her eyes
naturally fell upon the bloody carcases hung about the walls.
Inevitably, the sight of such things would produce bloody thoughts in
the mind of the unborn child!

These are extreme cases; we quote from a medieval medical writer another
case that carries the principle to its logical conclusion: A woman saw a
Negro,--at that time a rarity in Europe. She immediately had a sickening
suspicion that her child would be born with a black skin. To obviate the
danger, she had a happy inspiration--she hastened home and washed her
body all over with warm water. When the child appeared, his skin was
found to be normally white--except between the fingers and toes, where
it was black. His mother had failed to wash herself thoroughly in those
places!

Of course, few of the cases now credited are as gross as this, but the
principle involved remains the same.

We will take a hypothetical case of a common sort for the sake of
clearness: the mother receives a wound on the arm; when her child is
born it is found to have a scar of some sort at about the same place on
the corresponding arm. Few mothers would fail to see the result of a
maternal impression here. But how could this mark have been transmitted?
This is not a question of the transmission of acquired characters
through the germ-plasm, or anything of that sort, for the child was
already formed when the mother was injured. One is obliged, therefore,
to believe that the injury was in some way transmitted through the
placenta, the only connection between the mother and the unborn child;
and that it was then reproduced in some way in the child.

Here is a situation which, examined in the cold light of reason, puts a
heavy enough strain on the credulity. Such an influence can reach the
embryo only through the blood of the mother. Is it conceivable to any
rational human being, that a scar, or what not, on the mother's body can
be dissolved in her blood, pass through the placenta into the child's
circulation, and then gather itself together into a definite scar on the
infant's arm?

There is just as much reason to expect the child to grow to resemble the
cow on whose milk it is fed after birth, as to expect it to grow to
resemble its mother, because of prenatal influence, as the term is
customarily used, for once development has begun, the child draws
nothing more than nourishment from its mother.

Of course we are accustomed to the pious rejoinder that man must not
expect to understand all the mysteries of life; and to hear vague talk
about the wonder of wireless telegraphy. But wireless telegraphy is
something very definite and tangible--there is little mystery about it.
Waves of a given frequency are sent off, and caught by an instrument
attuned to the same frequency. How any rational person can support a
belief in maternal impressions by such an analogy, if he knows anything
about anatomy and physiology, passes comprehension.

Now we are far from declaring that a reason can be found for everything
that happens. Science does not refuse belief in an observed fact merely
because it is unexplainable. But let us examine this case of maternal
impressions a little further. What can be learned of the time element?

Immediately arises the significant fact that most of the marks,
deformities and other effects which are credited to prenatal influence
must on this hypothesis take place at a comparatively late period in the
antenatal life of the child. The mother is frightened by a dog; the
child is born with a dog-face. If it be asked when her fright occurred,
it is usually found that it was not earlier than the third month, more
likely somewhere near the sixth.

But it ought to be well known that the development of all the main parts
of the body has been completed at the end of the second month. At that
time, the mother rarely does more than suspect the coming of the child,
and events which she believes to "mark" the child, usually occur after
the fourth or fifth month, when the child is substantially formed, and
it is impossible that many of the effects supposed to occur could
actually occur. Indeed, it is now believed that most errors of
development, such as lead to the production of great physical defects,
are due to some cause within the embryo itself, and that most of them
take place in the first three or four weeks, when the mother is by no
means likely to influence the course of embryological development by her
mental attitude toward it, for the very good reason that she knows
nothing about it.

Unless she is immured or isolated from the world, nearly every expectant
mother sees many sights of the kind that, according to popular
tradition, cause "marks. " Why is it that results are so few? Why is it
that women doctors and nurses, who are constantly exposed to unpleasant
sights, have children that do not differ from those of other mothers?

Darwin, who knew how to think scientifically, saw that this is the
logical line of proof or disproof. When Sir Joseph Hooker, the botanist
and geologist who was his closest friend, wrote of a supposed case of
maternal impression, one of his kinswomen having insisted that a mole
which appeared on her child was the effect of fright upon herself for
having, before the birth of the child, blotted with sepia a copy of
Turner's _Liber Studiorum_ that had been lent her with special
injunctions to be careful, Darwin[27] replied: "I should be very much
obliged, if at any future or leisure time you could tell me on what you
ground your doubtful belief in imagination of a mother affecting her
offspring. I have attended to the several statements scattered about,
but do not believe in more than accidental coincidences. W. Hunter told
my father, then in a lying-in hospital, that in many thousand cases he
had asked the mother, before her confinement, whether anything had
affected her imagination, and recorded the answers; and absolutely not
one case came right, though, when the child was anything remarkable,
they afterwards made the cap to fit. "

Any doctor who has handled many maternity cases can call to mind
instances where every condition was present to perfection, for the
production of maternal impression, on the time-honored lines. None
occurred. Most mothers can, if they give the matter careful
consideration, duplicate this experience from their own. Why is it that
results are so rare?

That Darwin gave the true explanation of a great many of the alleged
cases is perfectly clear to us. When the child is born with any peculiar
characteristic, the mother hunts for some experience in the preceding
months that might explain it. If she succeeds in finding any experience
of her own at all resembling in its effects the effect which the infant
shows, she considers she has proved causation, has established a good
case of prenatal influence.

It is not causation; it is coincidence.

If the prospective mother plays or sings a great deal, with the idea of
giving her child a musical endowment, and the child actually turns out
to have musical talent, the mother at once recalls her yearning that
such might be the case; her assiduous practice which she hoped would be
of benefit to her child. She immediately decides that it did benefit
him, and she becomes a convinced witness to the belief in prenatal
culture. Has she not herself demonstrated it?

She has not. But if she would examine the child's heredity, she would
probably find a taste for music running in the germ-plasm. Her study and
practice had not the slightest effect on this hereditary disposition; it
is equally certain that the child would have been born with a taste for
music if its mother had devoted eight hours a day for nine months to
cultivating thoughts of hatred for the musical profession and repugnance
for everything that possesses rhythm or harmony.

It necessarily follows, then, that attempts to influence the inherent
nature of the child, physically or mentally, through "prenatal culture,"
are doomed to disappointment. The child develops along the lines of the
potentialities which existed in the two germ-cells that united to become
its origin. The course of its development can not be changed in any
specific way by any corresponding act or attitude of its mother, good
hygiene alone need be her concern.

It must necessarily follow that attempts to improve the race on a large
scale, by the general adoption of prenatal culture as an instrument of
eugenics, are useless.

Indeed, the logical implication of the teaching is the reverse of
eugenic. It would give a woman reason to think she might marry a man
whose heredity was most objectionable, and yet, by prenatal culture,
save her children from paying the inevitable penalty of this weak
heritage. The world has long shuddered over the future of the girl who
marries a man to reform him; but think what it means to the future of
the race if a superior girl, armed with correspondence school lessons in
prenatal culture, marries a man to reform his children!

Those who practice this doctrine are doomed to disillusion. The time
they spend on prenatal culture is not cultivating the child; it is
merely perpetuating a fallacy. Not only is their time thus spent
wasted, but worse, for they might have employed it in ways that really
would have benefited the child--in open-air exercise, for instance.

To recapitulate, the facts are:

(1) That there is, before birth, no connection between mother and child,
by which impressions on the mother's mind or body could be transmitted
to the child's mind or body.

(2) That in most cases the marks or defects whose origin is attributed
to maternal impression, must necessarily have been complete long before
the incident occurred which the mother, after the child's birth,
ascribes as the cause.

(3) That these phenomena usually do not occur when they are, and by
hypothesis ought to be, expected. The explanations are found after the
event, and that is regarded as causation which is really coincidence.

Pre-natal care as a euthenic measure is of course not only legitimate
but urgent. The embryo derives its entire nourishment from the mother;
and its development depends wholly on its supply of nourishment.
Anything which affects the supply of nourishment will affect the embryo
in a general, not a particular way. If the mother's mental and physical
condition be good, the supply of nourishment to the embryo is likely to
be good, and development will be normal. If, on the other hand, the
mother is constantly harassed by fear or hatred, her physical health
will suffer, she will be unable properly to nourish her developing
offspring, and it may be its poor physical condition when born,
indicates this.

Further, if the mother experiences a great mental or physical shock, it
may so upset her health that her child is not properly nourished, its
development is arrested, mentally as well as physically, and it is born
defective. H. H. Goddard, for example, tells[28] of a high-grade
imbecile in the Training School at Vineland, N. J. "Nancy belongs to a
thoroughly normal, respectable family. There is nothing to account for
the condition unless one accepts the mother's theory. While it sounds
somewhat like the discarded theory of maternal impression, yet it is not
impossible that the fright and shock which the mother received may have
interfered with the nutrition of the unborn child and resulted in the
mental defect. The story in brief is as follows. Shortly before this
child was born, the mother was compelled to take care of a sister-in-law
who was in a similar condition and very ill with convulsions. Our
child's mother was many times frightened severely as her sister-in-law
was quite out of her mind. "

It is easily understandable that any event which makes such an
impression on the mother as to affect her health, might so disturb the
normal functioning of her body that her child would be badly nourished,
or even poisoned. Such facts undoubtedly form the basis on which the
airy fabric of prenatal culture was reared by those who lived before the
days of scientific biology.

Thus, it is easy enough to see the real explanation of such cases as
those mentioned near the beginning of this discussion. The mothers who
fret and rebel over their maternity, she found, are likely to bear
neurotic children. It is obvious (1) that mothers who fret and rebel are
quite likely themselves to be neurotic in constitution, and the child
naturally gets its heredity from them: (2) that constant fretting and
rebellion would so affect the mother's health that her child would not
be properly nourished.

When, however, she goes on to draw the inference that "self-control,
cheerfulness and love . . . will practically insure you a child normal in
physique and nerves," we are obliged to stop. We know that what she says
is not true. If the child's heredity is bad, neither self-control,
cheerfulness, love, nor anything else known to science, can make that
heredity good.

At first thought, one may wish it were otherwise. There is something
inspiring in the idea of a mother overcoming the effect of heredity by
the sheer force of her own will-power. But perhaps in the long run it is
as well; for there are advantages on the other side. It should be a
satisfaction to mothers to know that their children will not be marked
or injured by untoward events in the antenatal days; that if the
child's heredity can not be changed for the better, neither can it be
changed for the worse.

The prenatal culturists and maternal-impressionists are trying to place
on her a responsibility which she need not bear. Obviously, it is the
mother who is most nearly concerned with the bogy of maternal
impressions, and it should make for her peace of mind to know that it is
nothing more than a bogy. It is important for the expectant mother to
keep herself in as nearly perfect condition as possible, both physically
and mentally. Her bodily mechanism will then run smoothly, and the child
will get from her blood the nourishment needed for its development.
Beyond that there is nothing the mother can do to influence the
development of her child.

There is another and somewhat similar fallacy which deserves a passing
word, although it is of more concern to the livestock breeder than to
the eugenist. It is called telegony and is, briefly, this: that
conception by a female results in a definite modification of her
germ-plasm from the influence of the male, and that this modification
will be shown in the offspring she may subsequently bear to a second
male. The only case where it is often invoked in the human race is in
miscegenation. A white woman has been married to a Negro, for instance,
and has borne one or more mulatto offspring. Subsequently, she mates
with a white man; but her children by him, instead of being pure white,
it is alleged, will be also mulattoes. The idea of telegony, the
persistent influence of the first mating, may be invoked to explain this
discrepancy.

It is a pure myth. There is no good evidence[29] to support it, and
there is abundant evidence to contradict it. Telegony is still believed
by many animal breeders, but it has no place in science. In such a case
as the one quoted, the explanation is undoubtedly that the supposed
father is not the real one; and this explanation will dispose of all
other cases of telegony which can not be explained, as in most instances
they can be, by the mixed ancestry of the offspring and the innate
tendency of all living things to vary.

Now to sum up this long chapter. We started with a consideration of the
germ-plasm, the physical basis of life; pointing out that it is
continuous from generation to generation, and potentially immortal; that
it is carefully isolated and guarded in the body, so that it is not
likely to be injured by any ordinary means.

One of the logical results of this continuity of the germ-plasm is that
modifications of the body of the parent, or acquired characters, can
hardly be transferred to the germ-plasm and become a part of the
inheritance. Further the experimental evidence upholds this position,
and the inheritance of acquired body characters may be disregarded by
eugenics, which is therefore obliged to concern itself solely with the
material already in existence in the germ-plasm, except as that material
may be changed by variation which can neither be predicted nor
controlled.

The evidence that the germ-plasm can be permanently modified does not
warrant the belief; and such results, if they exist at all, are not
large enough or uniform enough to concern the eugenist.

Pre-natal culture and telegony were found to be mere delusions. There is
no justification for hoping to influence the race for good through the
action of any kind of external influences; and there is not much danger
of influencing it for ill through these external influences. The
situation must be faced squarely then: if the race is to be improved, it
must be by the use of the material already in existence; by endeavor to
change the birth-and death-rates so as to alter the relative proportions
of the amounts of good and bad germ-plasm in the race. This is the only
road by which the goal of eugenics can be reached.




CHAPTER III

DIFFERENCES AMONG MEN


While Mr. Jefferson, when he wrote into the Declaration of Independence
his belief in the self-evidence of the truth that all men are created
equal, may have been thinking of legal rights merely, he was expressing
an opinion common among philosophers of his time. J. J. Rousseau it was
who made the idea popular, and it met with widespread acceptance for
many years. It is not surprising, therefore, that the phrase has long
been a favorite with the demagogue and the utopian. Even now the
doctrine is by no means dead. The American educational system is based
largely on this dogma, and much of the political system seems to be
grounded on it. It can be seen in the tenets of labor unions, in the
practice of many philanthropies--traces may be found almost anywhere one
turns, in fact.

Common enough as applied to mental qualities, the theory of human
equality is even more widely held of "moral" qualities. Men are
considered to be equally responsible for their conduct, and failure to
conform to the accepted code in this respect brings punishment.
It is
sometimes conceded that men have had differing opportunities to learn
the principles of morality; but given equal opportunities, it is almost
universally held that failure to follow the principles indicates not
inability but unwillingness. In short, public opinion rarely admits that
men may differ in their inherent capacity to act morally.

In view of its almost universal and unquestioned, although half
unconscious, acceptance as part of the structure of society, it becomes
of the utmost importance that this doctrine of human equality should be
examined by scientific methods.

Fortunately this can be done with ease. Methods of mental and physical
measurement that have been evolved during the last few decades offer
results that admit of no refutation, and they can be applied in hundreds
of different places.

[Illustration: DISTRIBUTION OF 10-YEAR-OLD SCHOOL CHILDREN

FIG. 8. --The graph shows that 10-year-old children in
Connecticut (1903) are to be found in every grade, from the first to the
eighth. The greatest number is in the fourth grade, and the number who
are advanced is just about the same as the number who are retarded. ]

It will not be worth while to spend any time demonstrating that all
individuals differ, at birth and during their subsequent life,
physically. The fact is patent to all. It carries with it as a necessary
corollary mental differences, since the brain is part of the body;
nevertheless, we shall demonstrate these mental differences
independently.

We present in Fig. 8 a graph from E. L. Thorndike, showing the number of
10-year-old children in Connecticut (1903) in each school grade. If the
children are all intellectually equal, all the 10-year-olds ought to be
in the same grade, or near it. Numerous explanations of their wide
distribution suggest themselves; as a working hypothesis one might adopt
the suggestion that it is because the children actually differ in innate
ability to the extent here indicated. This hypothesis can be tested by
a variety of mental measurements. S. A. Courtis' investigation of the
arithmetical abilities of the children in the schools of New York City
will be a good beginning. He measured the achievements of pupils in
responding to eight tests, which were believed to give a fair idea of
the pupil's capacity for solving simple arithmetical problems. The
results were, on the average, similar to the result he got in a certain
eighth-grade class, whose record is shown in Fig. 9. It is evident that
some of the children were good in arithmetic, some were poor in it; the
bulk of them were neither good nor bad but half way between, or, in
statistical language, mediocre.

[Illustration: VARIATION IN ABILITY

FIG. 9. --Diagram to show the standing of children in a single
class in a New York City school, in respect to their ability in
arithmetic. There are wide divergences in the scores they made. ]

The literature of experimental psychology and anthropology is crammed
with such examples as the above. No matter what trait of the individual
be chosen, results are analogous. If one takes the simplest traits, to
eliminate the most chances for confusion, one finds the same conditions
every time. Whether it be speed in marking off all the A's in a printed
sheet of capitals, or in putting together the pieces of a puzzle, or in
giving a reaction to some certain stimulus, or in making associations
between ideas, or drawing figures, or memory for various things, or
giving the opposites of words, or discrimination of lifted weights, or
success in any one of hundreds of other mental tests, the conclusion is
the same. There are wide differences in the abilities of individuals, no
two being alike, either mentally or physically, at birth or any time
thereafter.

[Illustration: ORIGIN OF A NORMAL PROBABILITY CURVE

FIG. 10. --When deviations in all directions are equally
probable, as in the case of shots fired at a target by an expert
marksman, the "frequencies" will arrange themselves in the manner shown
by the bullets in compartments above. A line drawn along the tops of
these columns would be a "normal probability curve. " Diagram by C. H.
Popenoe. ]

Whenever a large enough number of individuals is tested, these
differences arrange themselves in the same general form. It is the form
assumed by the distribution of any differences that are governed
absolutely by chance.

Suppose an expert marksman shoots a thousand times at the center of a
certain picket in a picket fence, and that there is no wind or any
other source of constant error that would distort his aim. In the long
run, the greatest number of his shots would be in the picket aimed at,
and of his misses there would be just as many on one side as on the
other, just as many above as below the center. Now if all the shots, as
they struck the fence, could drop into a box below, which had a
compartment for each picket, it would be found at the end of his
practice that the compartments were filled up unequally, most bullets
being in that representing the middle picket and least in the outside
ones. The intermediate compartments would have intermediate numbers of
bullets. The whole scheme is shown in Fig. 11. If a line be drawn to
connect the tops of all the columns of bullets, it will make a rough
curve or graph, which represents a typical chance distribution. It will
be evident to anyone that the distribution was really governed by
"chance," i. e. , a multiplicity of causes too complex to permit detailed
analysis. The imaginary sharp-shooter was an expert, and he was trying
to hit the same spot with each shot. The deviation from the center is
bound to be the same on all sides.

[Illustration: FIG. 11. --The "Chance" or "Probability" Form of
Distribution. ]

Now suppose a series of measurements of a thousand children be taken in,
let us say, the ability to do 18 problems in subtraction in 10 minutes.
A few of them finish only one problem in that time; a few more do two,
more still are able to complete three, and so on up. The great bulk of
the children get through from 8 to 12 problems in the allotted time; a
few finish the whole task. Now if we make a column for all those who did
one problem, another column beside it for all those who did two, and so
on up for those who did three, four and on to eighteen, a line drawn
over the tops of the columns make a curve like the above from
Thorndike.

Comparing this curve with the one formed by the marksman's spent
bullets, one can not help being struck by the similarity. If the first
represented a distribution governed purely by chance, it is evident that
the children's ability seems to be distributed in accordance with a
similar law.

With the limited number of categories used in this example, it would not
be possible to get a smooth curve, but only a kind of step pyramid. With
an increase in the number of categories, the steps become smaller. With
a hundred problems to work out, instead of 18, the curve would be
something like this:

[Illustration: FIG. 12. --Probability curve with increased
number of steps. ]

And with an infinite number, the steps would disappear altogether,
leaving a perfectly smooth, flowing line, unmarred by a single step or
break. It would be an absolutely _continuous_ distribution.

If then, the results of all the tests that have been made on all mental
traits be studied, it will be found that human mental ability as shown
in at least 95% of all the traits that have been measured, is
distributed throughout the race in various degrees, in accordance with
the law of chance, and that if one could measure all the members of the
species and plot a curve for these measurements, in any trait, he would
get this smooth, continuous curve. In other words, human beings are not
sharply divided into classes, but the differences between them shade off
into each other, although between the best and the worst, in any
respect, there is a great gulf.

If this statement applies to simple traits, such as memory for numbers,
it must also apply to combinations of simple traits in complex mental
processes. For practical purposes, we are therefore justified in saying
that in respect of any mental quality,--ability, industry, efficiency,
persistence, attentiveness, neatness, honesty, anything you like,--in
any large group of people, such as the white inhabitants of the United
States, some individuals will be found who show the character in
question in a very low degree, some who show it in a very high degree;
and there will be found every possible degree in between.

[Illustration: NORMAL VARIABILITY CURVE FOLLOWING LAW OF CHANCE

FIG. 13. --The above photograph (from A. F. Blakeslee), shows
beans rolling down an inclined plane and accumulating in compartments at
the base which are closed in front by glass. The exposure was long
enough to cause the moving beans to appear as caterpillar-like objects
hopping along the board. Assuming that the irregularity of shape of the
beans is such that each may make jumps toward the right or toward the
left, in rolling down the board, the laws of chance lead to the
expectation that in very few cases will these jumps all be in the same
direction, as is demonstrated by the few beans collected in the
compartments at the extreme right and left. Rather the beans will tend
to jump in both right and left directions, the most probable condition
being that in which the beans make an equal number of jumps to the right
and left, as is shown by the large number accumulated in the central
compartment. If the board be tilted to one side, the curve of beans
would be altered by this one-sided influence. In like fashion a series
of factors--either of environment or of heredity--if acting equally in
both favorable and unfavorable directions, will cause a group of men to
form a similar variability curve, when classified according to their
relative height. ]

The consequences of this for race progress are significant. Is it
desired to eliminate feeble-mindedness? Then it must be borne in mind
that there is no sharp distinction between feeble-mindedness and the
normal mind. One can not divide sheep from goats, saying "A is
feeble-minded. B is normal. C is feeble-minded. D is normal," and so on.
If one took a scale of a hundred numbers, letting 1 stand for an idiot
and 100 for a genius, one would find individuals corresponding to every
single number on the scale. The only course possible would be a somewhat
arbitrary one; say to consider every individual corresponding to a grade
under seven as feeble-minded. It would have to be recognized that those
graded eight were not much better than those graded seven, but the
drawing of the line at seven would be justified on the ground that it
had to be drawn somewhere, and seven seemed to be the most satisfactory
point.

In practice of course, students of retardation test children by
standardized scales. Testing a hundred 10-year-old children, the
examiner might find a number who were able to do only those tests which
are passed by a normal six-year-old child. He might properly decide to
put all who thus showed four years of retardation, in the class of
feeble-minded; and he might justifiably decide that those who tested
seven years (i. e. , three years mental retardation) or less would, for
the present, be given the benefit of the doubt, and classed among the
possibly normal. Such a procedure, in dealing with intelligence, is
necessary and justifiable, but its adoption must not blind students, as
it often does, to the fact that the distinction made is an arbitrary
one, and that there is no more a hard and fast line of demarcation
between imbeciles and normals than there is between "rich men" and "poor
men. "

[Illustration: CADETS ARRANGED TO SHOW NORMAL CURVE OF VARIABILITY

FIG. 14. --The above company of students at Connecticut
Agricultural College was grouped according to height and photographed by
A. F. Blakeslee. The height of each rank, and the number of men of that
height, is shown by the figures underneath the photograph. The company
constitutes what is technically known as a "population" grouped in
"arrays of variates"; the middle rank gives the median height of the
population; the tallest array (5 ft. , 8 in. ) is the mode. If a line be
drawn connecting the upper ends of the rows, the resulting geometric
figure will be a "scheme of distribution of variates" or more briefly a
"variability curve," such as was shown in several preceding figures. The
arrangement of homogeneous objects of any kind in such form as this is
the first step in the study of variation by modern statistical methods,
and on such study much of the progress of genetics depends. ]

[Illustration: FIG. 15. --Height is one of the stock examples of
a continuous character--one of which all grades can be found. As will be
seen from the above diagram, every height from considerably under five
feet to considerably over six feet can be found in the army, but extreme
deviations are relatively rare in proportion to the amount of deviation.
The vertical columns represent the total number of individuals of a
given height in inches. From Davenport. ]

If a group of soldiers be measured as the children were measured for
arithmetical ability, their height will be distributed in this same
curve of probability. Fig. 14 shows the cadets of Connecticut
Agricultural College; it is obvious that a line drawn along the tops
of the files would again make the step-pyramid shown in Figures 10, 11
and 13. If a larger number were taken, the steps would disappear and
give place to a smooth curve; the fact is well shown in a graph for the
heights of recruits to the American Army (Fig. 15).

The investigation in this direction need not be pursued any farther. For
the purpose of eugenics, it is sufficient to recognize that great
differences exist between men, and women, not only in respect of
physical traits, but equally in respect of mental ability.

This conclusion might easily have been reached from a study of the facts
in Chapter I, but it seemed worth while to take time to present the fact
in a more concrete form as the result of actual measurements. The
evidence allows no doubt about the existence of considerable mental and
physical differences between men.

The question naturally arises, "What is the cause of these differences? "

The study of twins showed that the differences could not be due to
differences in training or home surroundings. If the reader will think
back over the facts set forth in the first chapter, he will see clearly
that the fundamental differences in men can not be due to anything that
happens after they are born; and the facts presented in the second
chapter showed that these differences can not be due in an important
degree to any influences acting on the child prior to birth.




CHAPTER IV

THE INHERITANCE OF MENTAL CAPACITIES


We have come to the climax of the eugenist's preliminary argument; if
the main differences between human beings are not due to anything in the
environment or training, either of this or previous generations, there
can be but one explanation for them.

They must be due to the ancestry of the individual--that is, they must
be matters of heredity in the ordinary sense, coupled with the
fortuitous variations which accompany heredity throughout the organic
world.

We need not limit ourselves, however, to the argument by exclusion, for
it is not difficult to present direct evidence that the differences
between men are actually inherited by children from parents. The
problem, formally stated, is to measure the amount by which the likeness
of individuals of like ancestry surpasses the likeness of individuals of
different ancestry. After subtraction of the necessary amount for the
greater likeness in training, that the individuals of like ancestry will
have, whatever amount is left will necessarily, represent the actual
inheritance of the child from its ancestors--parents, grandparents, and
so on.

Obviously, the subtraction for environmental effects is the point at
which a mistake is most probable. We may safely start, therefore, with a
problem in which no subtraction whatever need be made for this cause.
Eye color is a stock example, and a good one, for it is not conceivable
that home environment or training would cause a change in the color of
brothers' eyes.

The correlation[30] between brothers, or sisters, or brothers and
sisters--briefly, the fraternal resemblance--for eye-color was found by
Karl Pearson, using the method described in Chapter I, to be . 52. We are
in no danger of contradiction if we state with positiveness that this
figure represents the influence of ancestry, or direct inheritance, in
respect to this particular trait.

Suppose the resemblance between brothers be measured for stature--it
is . 51; for cephalic index, that is, the ratio of width of skull to length
of skull--it is . 49; for hair color--it is . 59. In all of these points,
it will be admitted that no home training, or any other influence except
heredity, can conceivably play an important part. We could go on with a
long list of such measurements, which biometrists have made; and if they
were all summed up it would be found that the fraternal correlation in
these traits as to the heritability of which there can be no dispute, is
about . 52. Here is a good measure, albeit a technical one, of the
influence of heredity from the near ancestry. It is possible, too, to
measure the direct correlation between a trait in parent and the same
trait in offspring; the average of many cases where only heredity can be
thought to have had any effect in producing the result, is . 49. By the
two methods of measurement, therefore, quite comparable results are
obtained.

So much work has been done in this subject that we have no hesitation in
affirming . 5 to represent approximately the average intensity of
heredity for physical characters in man. If any well-marked physical
character be measured, in which training and environment can not be
assumed to have had any part, it will be found, in a large enough number
of subjects, that the resemblance, measured on a scale from 0 to 1, is
just about one-half of unity. Of course, perfect identity with the
parents is not to be expected, because the child must inherit from both
parents, who in turn each inherited from two parents, and so on.

So far, it may be said, we have had plain sailing because we have
carefully chosen traits in which we were not obliged to make any
subtraction whatever for the influence of training. But it is evident
that not all traits fall in that class.

This is the point at which the inheritance of mental traits has been
most often questioned. Probably no one will care to dispute the
inheritance of such physical traits as eye-color. But in considering the
mind, a certain school of popular pseudo-psychological writers question
the reality of mental inheritance, and allege that the proofs which the
geneticist offers are worthless because they do not make account of the
similarity in environment or training. Of course, it is admitted that
some sort of a mental groundwork must be inherited, but extremists
allege that this is little more than a clean slate on which the
environment, particularly during the early years of childhood, writes
its autograph.

We must grant that the analysis of the inheritance of mental traits is
proceeding slowly. This is not the fault of the geneticist, but rather
of the psychologist, who has not yet been able to furnish the geneticist
with the description of definite traits of such a character as to make
possible the exhaustive analysis of their individual inheritance. That
department of psychology is only now being formed.

We might even admit that no inherited "unit character" in the mind has
yet been isolated; but it would be a great mistake to assume from this
admission that proof of the inheritance of mental qualities, in general,
is lacking.

The psychologists and educators who think so appear either to be swayed
by metaphysical views of the mind, or else to believe that resemblance
between parent and offspring is the only evidence of inheritance that
can be offered. The father dislikes cheese, the son dislikes cheese.
"Aha, you think that that is the inheritance of a dislike for cheese,"
cries the critic, "but we will teach you better. " An interesting example
of this sort of teaching is furnished by Boris Sidis, whose feelings are
outraged because geneticists have represented that some forms of
insanity are hereditary. He declaims for several pages[31] in this
fashion:

"The so-called scientific method of the eugenists is radically faulty,
in spite of the rich display of colored plates, stained tables,
glittering biological speculations, brilliant mathematical formulae and
complicated statistical calculations. The eugenists pile Ossa on Pelion
of facts by the simple method of enumeration which Bacon and the
thinkers coming after him have long ago condemned as puerile and futile.
From the savage's belief in sympathetic, imitative magic with its
consequent superstitions, omens, and taboos down to the articles of
faith and dogmas of the eugenists we find the same faulty, primitive
thought, guided by the puerile, imbecile method of simple enumeration,
and controlled by the wisdom of the logical _post hoc, ergo propter
hoc_. "

Now if resemblance between parent and offspring were, as Dr. Sidis
supposes, the only evidence of inheritance of mental traits which the
eugenist can produce, his case would indeed be weak. And it is perfectly
true that "evidence" of this kind has sometimes been advanced as
sufficient by geneticists who should have known better. But this is not
the real evidence which genetics offers. The evidence is of numerous
kinds, and several lines might be destroyed without impairing the
validity of the remainder. It is impossible to review the whole body of
evidence here, but some of the various kinds may be indicated, and
samples given, even though this involves the necessity of repeating some
things we have said in earlier chapters. The reader will then be able to
form his own opinion as to whether the geneticists' proofs or the mere
assurances of those who have not studied the subject are the more
weighty.

1. _The analogy from breeding experiments. _ Tame rats, for instance, are
very docile; their offspring can be handled without a bit of trouble.
The wild rat, on the other hand, is not at all docile.

W. E. Castle, of Harvard University, writes:[32] "We have repeatedly
mated tame female rats with wild males, the mothers being removed to
isolated cages before the birth of the young. These young which had
never seen or been near their father were very wild in disposition in
every case. The observations of Yerkes on such rats raised by us
indicates that their wildness was not quite as extreme as that of the
pure wild rat but closely approached it. "

Who can suggest any plausible explanation of their conduct, save that
they inherited a certain temperament from their sire? Yet the
inheritance of temperament is one of the things which certain
psychologists most "view with alarm. " If it is proved in other animals,
can it be considered wholly impossible in man?

2. _The segregation of mental traits. _ When an insane, or epileptic, or
feeble-minded person mates with a normal individual, in whose family no
taint is found, the offspring (generally speaking) will be mentally
sound, even though one parent is not. On the other hand, if two people
from tainted stocks marry, although neither one may be personally
defective, part of their offspring will be affected.

This production of sound children from an unsound parent, in the first
case, and unsound children from two apparently sound parents in the
second case, is exactly the opposite of what one would expect if the
child gets his unsoundness merely by imitation or "contagion. " The
difference can not reasonably be explained by any difference in
environment or external stimuli. Heredity offers a satisfactory
explanation, for some forms of feeble-mindedness and epilepsy, and some
of the diseases known as insanity, behave as recessives and segregate in
just the way mentioned. There are abundant analogies in the inheritance
of other traits in man, lower animals and plants, that behave in exactly
the same manner.