If the process could
continue
for a few hundred years more, Dr.
Applied Eugenics by Roswell H. Johnson and Paul Popenoe
, eugenics) ultimately defeats its own end.
If it is accompanied
by rational selection, it can usually be indorsed. Eugenics, on the
other hand, is likewise inadequate unless accompanied by constant
improvement in the surroundings; and its advocates must demand euthenics
as an accompaniment of selection, in order that the opportunity for
getting a fair selection may be as free as possible. If the euthenist
likewise takes pains not to ignore the existence of the racial factor,
then the two schools are standing on the same ground, and it is merely a
matter of taste or opportunity, whether one emphasizes one side or the
other. Each of the two factions, sometimes thought to be opposing, will
be seen to be getting the same end result, namely, human progress.
Not only are the two schools working for the same end, but each must
depend in still another way upon the other, in order to make headway.
The eugenist can not see his measures put into effect except through
changes in law and custom--i. e. , euthenic changes. He must and does
appeal to euthenics to secure action. The social reformer, on the other
hand, can not see any improvements made in civilization except through
the discoveries and inventions of some citizens who are inherently
superior in ability. He in turn must depend on eugenics for every
advance that is made.
It may make the situation clearer to state it in the customary terms of
biological philosophy. Selection does not necessarily result in
progressive evolution. It merely brings about the adaptation of a
species or a group to a given environment. The tapeworm is the stock
example. In human evolution, the nature of this environment will
determine whether adaptation to it means progress or retrogression,
whether it leaves a race happier and more productive, or the reverse.
All racial progress, or eugenics, therefore, depends on the creation of
a good environment, and the fitting of the race to that environment.
Every improvement in the environment should bring about a corresponding
biological adaptation. The two factors in evolution must go side by
side, if the race is to progress in what the human mind considers the
direction of advancement. In this sense, euthenics and eugenics bear the
same relation to human progress as a man's two legs do to his
locomotion.
Social workers in purely euthenic fields have frequently failed to
remember this process of adaptation, in their efforts to change the
environment. Eugenists, in centering their attention on adaptation, have
sometimes paid too little attention to the kind of environment to which
the race was being adapted. The present book holds that the second
factor is just as important as the first, for racial progress; that one
leg is just as important as the other, to a pedestrian. Its only
conflict with euthenics appertains to such euthenic measures as impair
the adaptability of the race to the better environment they are trying
to make.
Some supposedly euthenic measures opposed by eugenics are not truly
euthenic, as for instance the limitation of a superior family in order
that all may get a college education. For these spurious euthenic
measures, something truly euthenic should be substituted.
Measures which show a real conflict may be typified by the infant
mortality movement. There can be no doubt but that sanitation and
hygiene, prenatal care and intelligent treatment of mothers and babies,
are truly euthenic and desirable. At the same time, as has been shown,
these euthenic measures result in the survival of inferior children, who
directly or through their posterity will be a drag on the race. Euthenic
measures of this type should be accompanied by counterbalancing measures
of a more eugenic character.
Barring these two types, euthenics forms a necessary concomitant of the
eugenic program; and, as we have tried to emphasize, eugenics is
likewise necessary to the complete success of every euthenic program.
How foolish, then, is antagonism between the two forces! Both are
working toward the same end of human betterment, and neither can succeed
without the other. When either attempts to eliminate the other from its
work, it ceases to advance toward its goal. In which camp one works is
largely a matter of taste. If on a road there is a gradient to be
leveled, it will be brought down most quickly by two parties of workmen,
one cutting away at the top, the other filling in the bottom. For the
two parties to indulge in mutual scorn and recrimination would be no
more absurd than for eugenics and euthenics to be put in opposition to
each other. The only reason they have been in opposition is because some
of the workers did not clearly understand the nature of their work. With
the dissemination of a knowledge of biology, this ground of antagonism
will disappear.
APPENDIX A
OVARIAN TRANSPLANTATION
In 1890, W. Heape published an account of some experiments with rabbits.
Taking the fertilized egg of an angora rabbit (i. e. , a long-haired,
white one) from the oviduct of its mother previous to its attachment to
the wall of the uterus, he transferred it to the uterus of a Belgian
hare, a rabbit which is short-haired and gray. The egg developed
normally in the new body and produced an animal with all the
characteristics, as far as could be seen, of the real mother, rather
than the foster-mother. Its coat was long and white, and there was not
the slightest trace of influence of the short, gray-haired doe in whose
body it had grown.
Here was a case in which environment certainly failed to show any
modifying influence. But it was objected that the transplanted egg was
already full-grown and fertilized when the transfer was made, and that
therefore no modification need be expected. If the egg were transferred
at an earlier stage, it was thought, the result might be different.
W. E. Castle and J. C. Phillips therefore undertook an experiment to
which this objection should not be possible. [195]
"A female albino guinea-pig just attaining sexual maturity was by an
operation deprived of its ovaries, and instead of the removed ovaries
there were introduced into her body the ovaries of a young black female
guinea-pig, not yet sexually mature, aged about three weeks. The grafted
animal was now mated with a male albino guinea-pig. From numerous
experiments with albino guinea-pigs it may be stated emphatically that
normal albinos mated together, without exception, produce only albino
young, and the presumption is strong, therefore, that had this female
not been operated on she would have done the same. She produced,
however, by the albino male three litters of young, which together
consisted of six individuals, all black. The first litter of young was
produced about six months after the operation, the last about one year.
The transplanted ovarian tissue must have remained in its new
environment therefore from four to ten months before the eggs attained
full growth and were discharged; ample time, it would seem, for the
influence of a foreign body upon the inheritance to show itself were
such influence possible. "
While such experiments must not be stretched too far, in application to
the human species, they certainly offer striking evidence of the fact
that the characters of any individual are mainly due to something in the
germ-plasm, and that this germ-plasm is to a surprising degree
independent of any outside influence, even such an intimate influence as
that of the body of the mother in which it reaches maturity.
APPENDIX B
"DYNAMIC EVOLUTION"
As C. L. Redfield has secured considerable publicity for his attempt to
bolster up the Lamarckian theory, it deserves a few words of comment.
His contention is that "the energy in animals, known as intelligence and
physical strength, is identical with the energy known in mechanics, and
is governed by the same laws. " He therefore concludes that (1) an animal
stores up energy in its body, in some undescribed and mystical way, and
(2) that in some equally undescribed and mystical way it transmits this
stored-up energy to its offspring. It follows that he thinks superior
offspring are produced by parents of advanced age, because the latter
have had more time to do work and store up energy for transmission. In
his own words:
"Educating the grandfather helps to make the grandson a superior
person. . . . We are, in our inheritance, exactly what our ancestors
made us by the work they performed before reproducing. Whether our
descendants are to be better or worse than we are will depend upon
the amount and kind of work we do before we produce them. "
The question of the influence of parental age on the characters of the
offspring is one of great importance, for the solution of which the
necessary facts have not yet been gathered together. The data compiled
by Mr. Redfield are of value, but his interpretation of them can not be
accepted for the following reasons.
1. In the light of modern psychology, it is absurd to lump all sorts of
mental ability under one head, and to suppose that the father's exercise
of reasoning power, for example, will store up "energy" to be manifested
in the offspring in the shape of executive or artistic ability. Mental
abilities are much subdivided and are inherited separately. Mr.
Redfield's idea of the process is much too crude.
Moreover, Mr. Redfield's whole conception of the increase of
intelligence with increase of age in a parent shows a disregard of the
facts of psychology. As E. A. Doll has pointed out,[196] in criticising
Mr. Redfield's recent and extreme claim that feeble-mindedness is the
product of early marriage, it is incorrect to speak of 20-, 30-, or
40-year standards of intelligence; for recent researches in measurement
of mental development indicate that the heritable standard of
intelligence of adults increases very little beyond the age of
approximately 16 years. A person 40 years old has an additional
_experience_ of a quarter of a century, and so has a larger mental
content, but his intelligence is still nearly at the 16-year level.
Mental activity is the effect, not the cause, of mental growth or
development. Education merely turns inherent mental powers to good
account; it makes very little change in those powers themselves. To
suppose that a father can, by study, raise his innate level of
intelligence and transmit it at the new level to his son, is a naive
idea which finds no warrant in the known facts of mental development.
2. In his entire conception of the storing-up and transmission of
energy, Mr. Redfield has fallen victim to a confusion of ideas due to
the use of the same word to mean two different things. He thinks of
energy as an engineer; he declares the body-cell is a storage battery;
he believes that the athlete by performing work stores up energy in his
body (in some mysterious and unascertainable way) just as the clock
stores up energy when it is wound. The incorrectness of supposing that
the so-called energy of a man is of that nature, is remarkable. If,
hearing Bismarck called a man of iron, one should analyze his remains to
find out how much more iron he contained than ordinary men, it would be
a performance exactly comparable to Mr. Redfield's, when he thinks of a
man's "energy" as something stored up by work.
As a fact, a man contains less energy, after the performance of work,
than he did at the start. All of his "energy" comes from the metabolism
of food that he has previously eaten. His potential energy is the food
stored up in his body, particularly the glycogen in the liver and
muscles. [197]
Why, then, can one man run faster than another? Mr. Redfield thinks it
is because the sprinter has, by previous work, stored up energy in his
body, which carries him over the course more rapidly than the sluggard
who has not been subjected to systematic training. But the differences
in men's ability are not due to the amount of energy they have stored
up. It is due rather to differences in their structure (using this word
in a very broad sense), which produce differences in the efficiency
with which they can use the stored-up energy (i. e. , food) in their
bodies. A fat Shorthorn bull contains much more stored-up energy than
does a race horse, but the latter has the better structure--coordination
of muscles with nervous system, in particular--and there is never any
doubt about how a race between the two will end. The difference between
the results achieved by a highly educated thinker and a low-grade moron
are similarly differences in structural efficiency: the moron may eat
much more, and thereby have more potential energy, than the scholar; but
the machine, the brain, can not utilize it.
The effects of training are not to store up energy in the body, for it
has been proved that work decreases rather than increases the amount of
energy in the body. How is it, then, that training increases a man's
efficiency? It is obviously by improving his "structure," and probably
the most important part of this improvement is in bringing about better
relations between the muscles and the nerves. To pursue the analogy
which Mr. Redfield so often misuses, the effect of training on the human
machine is merely to oil the bearings and straighten out bent parts, to
make it a more efficient transformer of the energy that is supplied to
it.
The foundation stone of Mr. Redfield's hypothesis is his idea that the
animal by working stores up energy. This idea is the exact reverse of
the truth. While the facts which Mr. Redfield has gathered deserve much
study, his idea of "Dynamic Evolution" need not be taken
seriously. [198]
APPENDIX C
THE "MELTING POT"
America as the "Melting Pot" of peoples is a picture often drawn by
writers who do not trouble themselves as to the precision of their
figures of speech. It has been supposed by many that all the racial
stocks in the United States were tending toward a uniform type. There
has never been any real evidence on which to base such a view, and the
study completed in 1917 by Dr. Ales Hrdlicka, curator of the
division of physical anthropology of the U. S. National Museum, furnishes
evidence against it. He examined 400 individuals of the Old White
American stock, that is, persons all of whose ancestors had been in the
United States as far as the fourth ascending generation. He found little
or no evidence that hereditary traits had been altered. Even the
descendants of the Pilgrim Fathers, the Virginia cavaliers, the
Pennsylvania Dutch and the Huguenots, while possibly not as much unlike
as their ancestors were, are in no sense a blend.
The "Melting Pot," it must be concluded, is a figure of speech; and as
far as physical anthropology is concerned, it will not be anything more
in this country, at least for many centuries.
Announcing the results of study of the first 100 males and 100 females
of his series,[199] Dr. Hrdlicka said, "The most striking result of
the examinations is the great range of variation among Old Americans in
nearly all the important measurements. The range of variation is such
that in some of the most significant determinations it equals not only
the variation of any one group, but the combined variations of all the
groups that enter into the composition of the Americans. " This fact
would be interpreted by the geneticist as an evidence of hybridity. It
is clear that, at the very beginning, a number of diverse, although not
widely differing, stocks must have made up the colonial population; and
intermarriage and the influence of the environment have not welded these
stocks into one blend, but have merely produced a mosaic-like mixture.
This is good evidence of the permanence of inherited traits, although
it must be qualified by the statement that it does not apply equally to
all features of the body, the face, hands and feet having been found
less variable, for instance, than stature and form of head.
[Illustration: THE "MEAN MAN" OF THE OLD WHITE AMERICAN STOCK
FIG. 45. --Anthropologists have an ideal "mean man," whose every
feature measures the arithmetic mean or average of that feature in all
the individuals of his race. The above diagram drawn to scale from Dr.
Hrdli[vc]ka's measurements represents the mean man of Colonial ancestry.
The outline of the face is almost oblong; the head is high and
well-developed, particularly in the regions which are popularly supposed
to denote superior intelligence. In general, it is a highly specialized
type, denoting an advanced evolution. ]
The stature of both American men and women is high, higher than the
average of any European nation except the Scotch. The individual
variation is, however, enormous, amounting to 16. 4% of the average in
males and nearly 16% in females. For males, 174 cm. is the average
height, for females 162. The arm spread in males is greater than their
stature, in females it is less.
The average weight of the males is 154 lbs. [typo: missing comma? ] of the
females 130. Taking into consideration the tall stature, these weights
are about equal to those among Europeans.
The general proportions of the body must be classed as medium, but great
fluctuations are shown.
The face is, in general, high and oval; in females it occasionally gives
the impression of narrowness. The forehead is well developed in both
sexes. The nose is prevalently long and of medium breadth, its
proportions being practically identical with those of the modern
English. The ears are longer than those of any modern immigrants except
the English. The mouth shows medium breadth in both sexes, and its
averages exactly equal those obtained for modern French.
One of the most interesting results is that there were obtained among
these first 200 individuals studied no pronounced blonds, although the
ancestry is North European, where blondness is more or less
prevalent. [200] The exact distribution is:
Male Female
Light-brown 12% 16%
Medium-brown to dark 77 68
Very dark 11 6
Golden-red and red 0 10
Dr. Hrdlicka's classification of the eye is as follows:
Male Female
Gray 2% 4%
Greenish 7 10
Blues 54 50
Browns 37 36
The head among Old Americans is in many cases notable for its good
development, particularly in males. Among 12 groups of male
immigrants[201] measured at Ellis Island under Dr. Hrdlicka's
direction in recent years, not one group quite equals in this respect
the Americans, the nearest approach being noted in the Irish, Bohemians,
English, Poles, and North Italians. The type of head, however, differs
among the Americans very widely, as is the case with most civilized
races at the present day.
Head form is most conveniently expressed by means of the cephalic index,
that is, the ratio of breadth to length. Anthropologists generally speak
of any one with an index of 75 (or where the breadth is 75% of the
length) and below this as dolichocephalic, or long-headed; from 75 to 80
is the class of the mesocephalic, intermediates; while above 80 is that
of the subbrachycephalic and brachycephalic, or round-headed. For the
most part, the Old Americans fall into the intermediate class, the
average index of males being 78. 3 and that of females 79. 5.
Barring a few French Huguenots, the Old Americans considered here are
mostly of British ancestry, and their head form corresponds rather
closely to that of the English of the present day. In England, as is
well known, the round-headed type of Central and Eastern Europe, the
Alpine or Celto-Slav type, has few representatives. The population is
composed principally of long-headed peoples, deriving from the two great
European stocks, the Nordic and the Mediterranean. To the latter the
frequency of dark hair and brown eyes is probably due, both in England
and America.
While the average of the Old Americans corresponds closely to the
average of the English, there is a great deal of variation in both
countries. Unfortunately, it is impossible to compare the present
Americans with their ancestors, because measurements of the latter are
lacking. But to assume that the early colonists did not differ greatly
from the modern English is probably justifiable. A comparison of modern
Americans (of the old white stock) with modern English should give basis
for an opinion as to whether the English stock underwent any marked
modifications, on coming to a new environment.
It has already been noted that the average cephalic index is practically
the same; the only possibility of a change then lies in the amount of
variability. Is the American stock more or less variable? Can a
"melting pot" influence be seen, tending to produce homogeneity, or has
change of environment rather produced greater variability, as is
sometimes said to be the case?
The amount of variability is most conveniently measured by a coefficient
known as the standard deviation ([Greek: s]), which is small when the
range of variation is small, but large when diversity of material is
great. The following comparisons of the point at issue may be made. [202]
Avg. [Greek: s]
100 American men 78. 3 3. 1
1011 Cambridge graduates (English males) 79. 85 2. 95
For the men, little difference is discernible. The Old Americans are
slightly more long-headed than the English, but the amount of variation
in this trait is nearly the same on the two sides of the ocean.
The average of the American women is 79. 5 with [Greek: s] = 2. 6. No
suitable series of English women has been found for comparison. (203) It
will be noted that the American women are slightly more round-headed
than the men; this is found regularly to be the case, when comparisons
of the head form of the two sexes are made in any race.
In addition to establishing norms or standards for anthropological
comparison, the main object of Dr. Hrdlicka's study was to determine
whether the descendants of the early American settlers, living in a new
environment and more or less constantly intermarrying, were being
amalgamated into a distinct sub-type of the white race. It has been
found that such amalgamation has not taken place to any important
degree. The persistence in heredity of certain features, which run down
even through six or eight generations, is one of the remarkable results
brought out by the study.
If the process could continue for a few hundred years more, Dr.
Hrdlicka thinks, it might reach a point where one could speak of the
members of old American families as of a distinct stock. But so far this
point has not been reached; the Americans are almost as diverse and
variable, it appears, as were their first ancestors in this country.
APPENDIX D
THE ESSENCE OF MENDELISM
It is half a century since the Austrian monk, Gregor Mendel, published
in a provincial journal the results of his now famous breeding
experiments with garden peas. They lay unnoticed until 1900, when three
other breeders whose work had led them to similar conclusions, almost
simultaneously discovered the work of Mendel and gave it to the world.
Breeding along the lines marked out by Mendel at once became the most
popular method of attack, among those who were studying heredity. It
became an extremely complicated subject, which can not be grasped
without extended study, but its fundamentals can be briefly summarized.
Inherited differences in individuals, it will be admitted, are due to
differences in their germ-plasms. It is convenient to think of these
differences in germ-plasms (that is, differences in heredity) as being
due to the presence in the germ-plasm of certain hypothetical units,
which are usually referred to as factors. The factor, nowadays, is the
ultimate unit of Mendelian research. Each of these factors is considered
to be nearly or quite constant,--that is, it undergoes little, or no
change from generation to generation. It is ordinarily resistant to
"contamination" by other factors with which it may come in contact in
the cell. The first fundamental principle of Mendelism, then, is the
existence of relatively constant units, the Mendelian factors, as the
basis for transmission of all the traits that go to make up an animal or
plant.
Experimental breeding gives reason to believe that each factor has one
or more alternatives, which may take its place in the mechanism of
heredity, thereby changing the visible character of the individual plant
or animal in which it occurs. To put the matter a little differently,
one germ-cell differs from another in having alternatives present in
place of some of the factors of the latter. A given germ-cell can never
have more than one of the possible alternatives of each factor. These
alternatives of a factor are called its allelomorphs.
Now a mature germ-cell has a single system of these factors: but when
two germ-cells unite, there result from that union two kinds of
cells--namely, immature germ-cells and body-cells; and both these kinds
of cells contain a double system of factors, because of course they have
received a single entire system from each parent. This is the second of
the fundamental principles of Mendelism: that the factors are single in
the mature germ-cell, but in duplicate in the body-cell (and also in the
immature germ-cell).
In every cell with a double system of factors, there are necessarily
present two representatives from each set of allelomorphs, but these may
or may not be alike--or in technical language the individual may be
homozygous, or heterozygous, as regards the given set of alternative
factors. Looking at it from another angle, there is a single visible
character in the plant or animal, but it is produced by a double factor,
in the germ-plasm.
When the immature germ-cell, with its double system of factors, matures,
it throws out half the factors, retaining only a single system: and the
allelomorphic factors which then segregate into different cells are, as
has been said above, ordinarily uninfluenced by their stay together.
But the allelomorphic factors are not the only ones which are segregated
into different germ-cells, at the maturation of the cell; for the
factors which are not alternative are likewise distributed, more or less
independently of each other, so that it is largely a matter of chance
whether factors which enter a cross in the same germ-cell, segregate
into the same germ-cell or different ones, in the next generation. This
is the next fundamental principle of Mendelism, usually comprehended
under the term "segregation," although, as has been pointed out, it is
really a double process, the segregation of alternative factors being a
different thing from the segregation of non-alternative factors.
From this fact of segregation, it follows that as many kinds of
germ-cells can be formed by an individual, as there are possible
combinations of factors, on taking one alternative from each pair of
allelomorphs present. In practice, this means that the possible number
of different germ-cells is almost infinitely great, as would perhaps be
suspected by anyone who has tried to find two living things that are
just alike.
[Illustration: THE CARRIERS OF HEREDITY
FIG. 46. --Many different lines of study have made it seem
probable that much, although not all, of the heredity of an animal or
plant is carried in the nucleus of the germ-cell and that in this
nucleus it is further located in little rods or threads which can be
easily stained so as to become visible, and which have the name of
chromosomes. In the above illustration four different views of the
nucleus of the germ-cell of an earthworm are shown, with the chromosomes
in different stages; in section 19 each chromosome is doubled up like a
hairpin. Study of the fruit-fly Drosophila has made it seem probable not
only that the hypothetical factors of heredity are located in the
chromosomes, but that each factor has a perfectly definite location in
its chromosome; and T. H. Morgan and his associates have worked out an
ingenious method of measuring the distance from either end, at which the
factor lies. Photomicrograph after Foot and Strobell. ]
Such is the essence of Mendelism; and the reader is probably ready to
admit that it is not a simple matter, even when reduced to the
simplest terms. To sum up, the principal features at the base of the
hypothetical structure are these:
1. There exist relatively constant units in the germ-plasm.
2. There are two very distinct relationships which these units may show
to each other. Two (or more) unit factors may be alternatives in the
mechanism of inheritance, indicating that one is a variation (or loss)
of the other; or they may be independent of each other in the mechanism
of inheritance.
3. The mature germ-cell contains a single system of independent factors
(one representative from each set of alternates).
The immature germ-cells, and body-cells, have double systems of
independent factors (two from each set of alternatives).
4. The double system arises simply from the union of two single systems
(i. e. , two germ-cells), without union or even contamination of the
factors involved.
In the formation of a single system (mature germ-cells) from a double
(immature germ-cells), pairs of alternates separate, passing into
different germ-cells. Factors not alternates may or may not
separate--the distribution is largely a matter of chance.
Such are the fundamental principles of Mendelism; but on them was early
grafted a theoretical structure due mainly to the German zoologist,
August Weismann. To understand his part in the story, we must advert to
that much mooted and too often misunderstood problem furnished by the
chromosomes. (See Fig. 46. ) These little rods of easily stained
material, which are found in every cell of the body, were picked out by
Professor Weismann as the probable carriers of heredity. With remarkable
acuteness, he predicted their behavior at cell-division, the intricate
nature of which is usually the despair of every beginner in biology.
When Mendelian breeding, in the early years of this century, showed
temporary pairing and subsequent separation of units in the
germ-cell, it was soon realized that the observed facts of breeding
fitted to a nicety the observed facts (predicted by Weismann) of
chromosome-behavior; for at each cell-division the chromosomes, too,
pair and separate again. The observed behavior of transmitted characters
in animals and plants followed, in so many cases, the observed behavior
of the chromosomes, that many students found it almost impossible to
believe that there was no connection between the two, and Dr. Weismann's
prediction, that the chromosomes are the carriers of heredity, came to
be looked on as a fact, by many biologists.
But when so much of Professor Weismann's system was accepted, other
parts of it went along, including a hypothetical system of "determiners"
in the chromosome, which were believed to determine the development of
characters in the organism. Every trait of an animal or plant, it was
supposed, must be represented in the germ-plasm by its own determiner;
one trait, one determiner. Did a notch in the ear run through a
pedigree? Then it must be due to a determiner for a notch in the ear in
the germ-plasm. Was mathematical ability hereditary? Then there must be
a determiner, the expression of which was mathematical ability.
For a while, this hypothesis was of service in the development of
genetics; some students even began to forget that it was a hypothesis,
and to talk as if it were a fact. But the exhaustive tests of
experimental breeding of plants and animals have long caused most of the
advanced students of genetics to drop this simple hypothesis.
In its place stands the factorial hypothesis, evolved by workers in
America, England, and France at about the same time. As explained in
Chapter V, this hypothesis carries the assumption that every visible
character is due to the effects of not one but many factors in the
germ-cell.
In addition to these fundamentals, there are numerous extensions and
corollaries, some of them of a highly speculative nature. The reader who
is interested in pursuing the subject farther must turn to one of the
text-books on Mendelism.
In plant-breeding a good deal of progress has been made in the exact
study of Mendelian heredity; in animal breeding, somewhat less; in human
heredity, very little. The reason is obvious: that experiments can not
be made in man, and students must depend on the results of such matings
as they can find; that only a very few offspring result from each
mating; and that generations are so long that no one observer can have
more than a few under his eyes. These difficulties make Mendelian
research in man a very slow and uncertain matter.
Altogether, it is probable that something like a hundred characters in
man have been pointed out as inherited in Mendelian fashion. A large
part of these are pathological conditions or rare abnormalities.
But the present writers can not accept most of these cases. It has been
pointed out in Chapter V that there are good reasons for doubting that
feeble-mindedness is inherited in a simple Mendelian fashion, although
it is widely accepted as such. We can not help feeling that in most
cases heredity in man is being made to appear much simpler than it
really is; and that particularly in mental characters, analysis of
traits has by no means reached the bottom.
If we were asked to make out a list of characters, as to the Mendelian
inheritance of which there could be little doubt, we would hardly be
able to go farther than the following:
The sex-linked characters (one kind of color-blindness, hemophilia, one
kind of night-blindness, atrophy of the optic nerve, and a few other
rare abnormalities).
Albinism. This appears to be a recessive, but probably involves multiple
allelomorphs in man, as in other animals.
Brachydactyly, apparently a dominant. This is so much cited in
text-books on Mendelism that the student might think it is a common
character. As a fact, it is extremely rare, being found in only a few
families. The similar trait of orthodactyly or symphalangism, which
likewise appears to be a good Mendelian dominant, seems to exist in only
one family. Traits like these, which are easily defined and occur very
rarely, make up a large part of the cases of probably Mendelian
heredity. They are little more than curiosities, their rarity and
abnormal nature depriving them of evolutionary significance other than
to demonstrate that Mendelian heredity does operate in man.
White blaze in the hair or, as it might better be called to show its
resemblance to the trait found in other mammals, piebaldism. A rather
rare dominant. [204]
Huntington's Chorea, which usually appears to be a good dominant,
although the last investigators (Muncey and Davenport) found some
unconformable cases.
A few abnormalities, such as a premature graying of the hair (one family
cited by K. Pearson) are well enough attested to be admitted. Many
others, such as baldness, are probably Mendelian but not yet
sufficiently supported by evidence.
None of these characters, it will be observed, is of much significance
eugenically. If the exact manner of inheritance of some of the more
important mental and physical traits were known, it would be of value.
But it is not a prerequisite for eugenic action. Enough is known for a
working program.
To sum up: the features in the modern view of heredity, which the reader
must keep in mind, are the following:
1. That the various characters which make up the physical constitution
of any individual plant or animal are due to the action (concurrently
with the environment, of course) of what are called, for convenience,
factors, separable hypothetical units in the germ-plasm, capable of
independent transmission.
2. That each visible character is due to the cooperative action of an
indefinitely large number of factors; conversely, that each of these
factors affects an indefinitely large number of characters.
APPENDIX E
USEFUL WORKS OF REFERENCE
The most complete bibliography is that published by the State Board of
Charities of the State of New York (_Eugenics and Social Welfare
Bulletin_ No. III, pp. 130, Albany, 1913).
An interesting historical review of eugenics, with critical comments on
the literature and a bibliography of 100 titles, was published by A. E.
Hamilton in the _Pedagogical Seminary_, Vol. XXI, pp. 28-61, March,
1914.
Much of the important literature of eugenics has been mentioned in
footnotes. For convenience, a few of the books which are likely to be
most useful to the student are here listed:
GENETICS AND EUGENICS, by W. E. Castle. Harvard University
Press, Cambridge, 1916.
HEREDITY AND ENVIRONMENT IN THE DEVELOPMENT OF MEN, by Edwin G.
Conklin. Princeton University Press, 1915.
HEREDITY IN RELATION TO EUGENICS, by C. B. Davenport, Henry
Holt and Co. , New York, 1911.
ESSAYS IN EUGENICS, by Francis Galton. Eugenics Education
Society, London, 1909.
BEING WELL-BORN, by Michael F. Guyer. Indianapolis,
Bobbs-Merrill Co. , 1916.
THE SOCIAL DIRECTION OF HUMAN EVOLUTION, by W. E. Kellicott.
New York, 1911.
THE PHYSICAL BASIS OF SOCIETY, by Carl Kelsey. New York, D.
Appleton & Co. , 1916.
EUGENICS, by Edward Schuster. Collins' Clear Type Press, London
and Glasgow, 1913.
HEREDITY, by J. Arthur Thompson. Edinburgh, 1908.
GENETICS, by Herbert E. Walter. The Macmillan Co. , New York,
1913.
AN INTRODUCTION TO EUGENICS, by W. C. D. Whetham and C. D.
Whetham. Macmillan and Co. , London, 1912.
HEREDITY AND SOCIETY, by W. C. D. Whetham and C. D. Whetham.
Longmans, Green & Co. , London, 1912.
THE FAMILY AND THE NATION, by W. C. D. Whetham and C. D.
Whetham. Longmans, Green & Co. , London, 1909.
The publications of the Galton Laboratory of National Eugenics,
University of London, directed by Karl Pearson, and of the Eugenics
Record Office, Cold Spring Harbor, Long Island, N. Y. , directed by C. B.
Davenport, furnish a constantly increasing amount of original material
on heredity.
The principal periodicals are the _Journal of Heredity_ (organ of the
American Genetic Association), 511 Eleventh St. , N. W. , Washington, D.
C. (monthly); and the _Eugenics Review_ (organ of the Eugenics Education
Society), Kingsway House, Kingsway, W. C. , London (quarterly). These
periodicals are sent free to members of the respective societies.
Membership in the American organization is $2 a year, in the English 1
guinea a year, associate membership 5 shillings a year.
APPENDIX F
GLOSSARY
ACQUIRED CHARACTER, a modification of a germinal trait after
cell fusion. It is difficult to draw a line between characters that are
acquired and those that are inborn. The idea involved is as follows: in
a standard environment, a given factor in the germ-plasm will develop
into a trait which varies not very widely about a certain mean. The mean
of this trait is taken as representing the germinal trait in its typical
condition. But if the environment be not standard, if it be considerably
changed, the trait will develop a variation far from the mean of that
trait in the species. Thus an American, whose skin in the standard
environment of the United States would be blonde, may under the
environment of Cuba develop into a brunette. Such a wide variation from
the mean thus caused is called an acquired character; it is usually
impressed on the organism after the germinal trait has reached a full,
typical development.
ALLELOMORPH (one another form), one of a pair of factors which
are alternative to each other in Mendelian inheritance. Instead of a
single pair, there may be a group of "multiple allelomorphs," each
member being alternative to every other member of the group.
ALLELOMORPHISM, a relation between two or more factors, such
that two which are present in one zygote do not both enter into the same
gamete, but are separated into sister gametes.
BIOMETRY (life measure), the study of biology by statistical
methods.
BRACHYDACTYLY (short-finger), a condition in which the bones,
particularly of the fingers and toes, fail to grow to their normal
length. In well-marked cases one of these is a reduction from three
phalanges or joints to two.
CHARACTER (a contraction of "characteristic"), a term which is
used, often rather vaguely, to designate any function, feature, or organ
of the body or mind.
CHROMOSOME (color body, so called from its affinity for certain
stains), a body of peculiar protoplasm, in the nucleus of the cell. Each
species has its own characteristic number; the cells of the human body
contain 24 chromosomes each.
CONGENITAL (with birth), present at birth. The term fails to
distinguish between traits which are actually inherited, and
modifications acquired during prenatal life.
by rational selection, it can usually be indorsed. Eugenics, on the
other hand, is likewise inadequate unless accompanied by constant
improvement in the surroundings; and its advocates must demand euthenics
as an accompaniment of selection, in order that the opportunity for
getting a fair selection may be as free as possible. If the euthenist
likewise takes pains not to ignore the existence of the racial factor,
then the two schools are standing on the same ground, and it is merely a
matter of taste or opportunity, whether one emphasizes one side or the
other. Each of the two factions, sometimes thought to be opposing, will
be seen to be getting the same end result, namely, human progress.
Not only are the two schools working for the same end, but each must
depend in still another way upon the other, in order to make headway.
The eugenist can not see his measures put into effect except through
changes in law and custom--i. e. , euthenic changes. He must and does
appeal to euthenics to secure action. The social reformer, on the other
hand, can not see any improvements made in civilization except through
the discoveries and inventions of some citizens who are inherently
superior in ability. He in turn must depend on eugenics for every
advance that is made.
It may make the situation clearer to state it in the customary terms of
biological philosophy. Selection does not necessarily result in
progressive evolution. It merely brings about the adaptation of a
species or a group to a given environment. The tapeworm is the stock
example. In human evolution, the nature of this environment will
determine whether adaptation to it means progress or retrogression,
whether it leaves a race happier and more productive, or the reverse.
All racial progress, or eugenics, therefore, depends on the creation of
a good environment, and the fitting of the race to that environment.
Every improvement in the environment should bring about a corresponding
biological adaptation. The two factors in evolution must go side by
side, if the race is to progress in what the human mind considers the
direction of advancement. In this sense, euthenics and eugenics bear the
same relation to human progress as a man's two legs do to his
locomotion.
Social workers in purely euthenic fields have frequently failed to
remember this process of adaptation, in their efforts to change the
environment. Eugenists, in centering their attention on adaptation, have
sometimes paid too little attention to the kind of environment to which
the race was being adapted. The present book holds that the second
factor is just as important as the first, for racial progress; that one
leg is just as important as the other, to a pedestrian. Its only
conflict with euthenics appertains to such euthenic measures as impair
the adaptability of the race to the better environment they are trying
to make.
Some supposedly euthenic measures opposed by eugenics are not truly
euthenic, as for instance the limitation of a superior family in order
that all may get a college education. For these spurious euthenic
measures, something truly euthenic should be substituted.
Measures which show a real conflict may be typified by the infant
mortality movement. There can be no doubt but that sanitation and
hygiene, prenatal care and intelligent treatment of mothers and babies,
are truly euthenic and desirable. At the same time, as has been shown,
these euthenic measures result in the survival of inferior children, who
directly or through their posterity will be a drag on the race. Euthenic
measures of this type should be accompanied by counterbalancing measures
of a more eugenic character.
Barring these two types, euthenics forms a necessary concomitant of the
eugenic program; and, as we have tried to emphasize, eugenics is
likewise necessary to the complete success of every euthenic program.
How foolish, then, is antagonism between the two forces! Both are
working toward the same end of human betterment, and neither can succeed
without the other. When either attempts to eliminate the other from its
work, it ceases to advance toward its goal. In which camp one works is
largely a matter of taste. If on a road there is a gradient to be
leveled, it will be brought down most quickly by two parties of workmen,
one cutting away at the top, the other filling in the bottom. For the
two parties to indulge in mutual scorn and recrimination would be no
more absurd than for eugenics and euthenics to be put in opposition to
each other. The only reason they have been in opposition is because some
of the workers did not clearly understand the nature of their work. With
the dissemination of a knowledge of biology, this ground of antagonism
will disappear.
APPENDIX A
OVARIAN TRANSPLANTATION
In 1890, W. Heape published an account of some experiments with rabbits.
Taking the fertilized egg of an angora rabbit (i. e. , a long-haired,
white one) from the oviduct of its mother previous to its attachment to
the wall of the uterus, he transferred it to the uterus of a Belgian
hare, a rabbit which is short-haired and gray. The egg developed
normally in the new body and produced an animal with all the
characteristics, as far as could be seen, of the real mother, rather
than the foster-mother. Its coat was long and white, and there was not
the slightest trace of influence of the short, gray-haired doe in whose
body it had grown.
Here was a case in which environment certainly failed to show any
modifying influence. But it was objected that the transplanted egg was
already full-grown and fertilized when the transfer was made, and that
therefore no modification need be expected. If the egg were transferred
at an earlier stage, it was thought, the result might be different.
W. E. Castle and J. C. Phillips therefore undertook an experiment to
which this objection should not be possible. [195]
"A female albino guinea-pig just attaining sexual maturity was by an
operation deprived of its ovaries, and instead of the removed ovaries
there were introduced into her body the ovaries of a young black female
guinea-pig, not yet sexually mature, aged about three weeks. The grafted
animal was now mated with a male albino guinea-pig. From numerous
experiments with albino guinea-pigs it may be stated emphatically that
normal albinos mated together, without exception, produce only albino
young, and the presumption is strong, therefore, that had this female
not been operated on she would have done the same. She produced,
however, by the albino male three litters of young, which together
consisted of six individuals, all black. The first litter of young was
produced about six months after the operation, the last about one year.
The transplanted ovarian tissue must have remained in its new
environment therefore from four to ten months before the eggs attained
full growth and were discharged; ample time, it would seem, for the
influence of a foreign body upon the inheritance to show itself were
such influence possible. "
While such experiments must not be stretched too far, in application to
the human species, they certainly offer striking evidence of the fact
that the characters of any individual are mainly due to something in the
germ-plasm, and that this germ-plasm is to a surprising degree
independent of any outside influence, even such an intimate influence as
that of the body of the mother in which it reaches maturity.
APPENDIX B
"DYNAMIC EVOLUTION"
As C. L. Redfield has secured considerable publicity for his attempt to
bolster up the Lamarckian theory, it deserves a few words of comment.
His contention is that "the energy in animals, known as intelligence and
physical strength, is identical with the energy known in mechanics, and
is governed by the same laws. " He therefore concludes that (1) an animal
stores up energy in its body, in some undescribed and mystical way, and
(2) that in some equally undescribed and mystical way it transmits this
stored-up energy to its offspring. It follows that he thinks superior
offspring are produced by parents of advanced age, because the latter
have had more time to do work and store up energy for transmission. In
his own words:
"Educating the grandfather helps to make the grandson a superior
person. . . . We are, in our inheritance, exactly what our ancestors
made us by the work they performed before reproducing. Whether our
descendants are to be better or worse than we are will depend upon
the amount and kind of work we do before we produce them. "
The question of the influence of parental age on the characters of the
offspring is one of great importance, for the solution of which the
necessary facts have not yet been gathered together. The data compiled
by Mr. Redfield are of value, but his interpretation of them can not be
accepted for the following reasons.
1. In the light of modern psychology, it is absurd to lump all sorts of
mental ability under one head, and to suppose that the father's exercise
of reasoning power, for example, will store up "energy" to be manifested
in the offspring in the shape of executive or artistic ability. Mental
abilities are much subdivided and are inherited separately. Mr.
Redfield's idea of the process is much too crude.
Moreover, Mr. Redfield's whole conception of the increase of
intelligence with increase of age in a parent shows a disregard of the
facts of psychology. As E. A. Doll has pointed out,[196] in criticising
Mr. Redfield's recent and extreme claim that feeble-mindedness is the
product of early marriage, it is incorrect to speak of 20-, 30-, or
40-year standards of intelligence; for recent researches in measurement
of mental development indicate that the heritable standard of
intelligence of adults increases very little beyond the age of
approximately 16 years. A person 40 years old has an additional
_experience_ of a quarter of a century, and so has a larger mental
content, but his intelligence is still nearly at the 16-year level.
Mental activity is the effect, not the cause, of mental growth or
development. Education merely turns inherent mental powers to good
account; it makes very little change in those powers themselves. To
suppose that a father can, by study, raise his innate level of
intelligence and transmit it at the new level to his son, is a naive
idea which finds no warrant in the known facts of mental development.
2. In his entire conception of the storing-up and transmission of
energy, Mr. Redfield has fallen victim to a confusion of ideas due to
the use of the same word to mean two different things. He thinks of
energy as an engineer; he declares the body-cell is a storage battery;
he believes that the athlete by performing work stores up energy in his
body (in some mysterious and unascertainable way) just as the clock
stores up energy when it is wound. The incorrectness of supposing that
the so-called energy of a man is of that nature, is remarkable. If,
hearing Bismarck called a man of iron, one should analyze his remains to
find out how much more iron he contained than ordinary men, it would be
a performance exactly comparable to Mr. Redfield's, when he thinks of a
man's "energy" as something stored up by work.
As a fact, a man contains less energy, after the performance of work,
than he did at the start. All of his "energy" comes from the metabolism
of food that he has previously eaten. His potential energy is the food
stored up in his body, particularly the glycogen in the liver and
muscles. [197]
Why, then, can one man run faster than another? Mr. Redfield thinks it
is because the sprinter has, by previous work, stored up energy in his
body, which carries him over the course more rapidly than the sluggard
who has not been subjected to systematic training. But the differences
in men's ability are not due to the amount of energy they have stored
up. It is due rather to differences in their structure (using this word
in a very broad sense), which produce differences in the efficiency
with which they can use the stored-up energy (i. e. , food) in their
bodies. A fat Shorthorn bull contains much more stored-up energy than
does a race horse, but the latter has the better structure--coordination
of muscles with nervous system, in particular--and there is never any
doubt about how a race between the two will end. The difference between
the results achieved by a highly educated thinker and a low-grade moron
are similarly differences in structural efficiency: the moron may eat
much more, and thereby have more potential energy, than the scholar; but
the machine, the brain, can not utilize it.
The effects of training are not to store up energy in the body, for it
has been proved that work decreases rather than increases the amount of
energy in the body. How is it, then, that training increases a man's
efficiency? It is obviously by improving his "structure," and probably
the most important part of this improvement is in bringing about better
relations between the muscles and the nerves. To pursue the analogy
which Mr. Redfield so often misuses, the effect of training on the human
machine is merely to oil the bearings and straighten out bent parts, to
make it a more efficient transformer of the energy that is supplied to
it.
The foundation stone of Mr. Redfield's hypothesis is his idea that the
animal by working stores up energy. This idea is the exact reverse of
the truth. While the facts which Mr. Redfield has gathered deserve much
study, his idea of "Dynamic Evolution" need not be taken
seriously. [198]
APPENDIX C
THE "MELTING POT"
America as the "Melting Pot" of peoples is a picture often drawn by
writers who do not trouble themselves as to the precision of their
figures of speech. It has been supposed by many that all the racial
stocks in the United States were tending toward a uniform type. There
has never been any real evidence on which to base such a view, and the
study completed in 1917 by Dr. Ales Hrdlicka, curator of the
division of physical anthropology of the U. S. National Museum, furnishes
evidence against it. He examined 400 individuals of the Old White
American stock, that is, persons all of whose ancestors had been in the
United States as far as the fourth ascending generation. He found little
or no evidence that hereditary traits had been altered. Even the
descendants of the Pilgrim Fathers, the Virginia cavaliers, the
Pennsylvania Dutch and the Huguenots, while possibly not as much unlike
as their ancestors were, are in no sense a blend.
The "Melting Pot," it must be concluded, is a figure of speech; and as
far as physical anthropology is concerned, it will not be anything more
in this country, at least for many centuries.
Announcing the results of study of the first 100 males and 100 females
of his series,[199] Dr. Hrdlicka said, "The most striking result of
the examinations is the great range of variation among Old Americans in
nearly all the important measurements. The range of variation is such
that in some of the most significant determinations it equals not only
the variation of any one group, but the combined variations of all the
groups that enter into the composition of the Americans. " This fact
would be interpreted by the geneticist as an evidence of hybridity. It
is clear that, at the very beginning, a number of diverse, although not
widely differing, stocks must have made up the colonial population; and
intermarriage and the influence of the environment have not welded these
stocks into one blend, but have merely produced a mosaic-like mixture.
This is good evidence of the permanence of inherited traits, although
it must be qualified by the statement that it does not apply equally to
all features of the body, the face, hands and feet having been found
less variable, for instance, than stature and form of head.
[Illustration: THE "MEAN MAN" OF THE OLD WHITE AMERICAN STOCK
FIG. 45. --Anthropologists have an ideal "mean man," whose every
feature measures the arithmetic mean or average of that feature in all
the individuals of his race. The above diagram drawn to scale from Dr.
Hrdli[vc]ka's measurements represents the mean man of Colonial ancestry.
The outline of the face is almost oblong; the head is high and
well-developed, particularly in the regions which are popularly supposed
to denote superior intelligence. In general, it is a highly specialized
type, denoting an advanced evolution. ]
The stature of both American men and women is high, higher than the
average of any European nation except the Scotch. The individual
variation is, however, enormous, amounting to 16. 4% of the average in
males and nearly 16% in females. For males, 174 cm. is the average
height, for females 162. The arm spread in males is greater than their
stature, in females it is less.
The average weight of the males is 154 lbs. [typo: missing comma? ] of the
females 130. Taking into consideration the tall stature, these weights
are about equal to those among Europeans.
The general proportions of the body must be classed as medium, but great
fluctuations are shown.
The face is, in general, high and oval; in females it occasionally gives
the impression of narrowness. The forehead is well developed in both
sexes. The nose is prevalently long and of medium breadth, its
proportions being practically identical with those of the modern
English. The ears are longer than those of any modern immigrants except
the English. The mouth shows medium breadth in both sexes, and its
averages exactly equal those obtained for modern French.
One of the most interesting results is that there were obtained among
these first 200 individuals studied no pronounced blonds, although the
ancestry is North European, where blondness is more or less
prevalent. [200] The exact distribution is:
Male Female
Light-brown 12% 16%
Medium-brown to dark 77 68
Very dark 11 6
Golden-red and red 0 10
Dr. Hrdlicka's classification of the eye is as follows:
Male Female
Gray 2% 4%
Greenish 7 10
Blues 54 50
Browns 37 36
The head among Old Americans is in many cases notable for its good
development, particularly in males. Among 12 groups of male
immigrants[201] measured at Ellis Island under Dr. Hrdlicka's
direction in recent years, not one group quite equals in this respect
the Americans, the nearest approach being noted in the Irish, Bohemians,
English, Poles, and North Italians. The type of head, however, differs
among the Americans very widely, as is the case with most civilized
races at the present day.
Head form is most conveniently expressed by means of the cephalic index,
that is, the ratio of breadth to length. Anthropologists generally speak
of any one with an index of 75 (or where the breadth is 75% of the
length) and below this as dolichocephalic, or long-headed; from 75 to 80
is the class of the mesocephalic, intermediates; while above 80 is that
of the subbrachycephalic and brachycephalic, or round-headed. For the
most part, the Old Americans fall into the intermediate class, the
average index of males being 78. 3 and that of females 79. 5.
Barring a few French Huguenots, the Old Americans considered here are
mostly of British ancestry, and their head form corresponds rather
closely to that of the English of the present day. In England, as is
well known, the round-headed type of Central and Eastern Europe, the
Alpine or Celto-Slav type, has few representatives. The population is
composed principally of long-headed peoples, deriving from the two great
European stocks, the Nordic and the Mediterranean. To the latter the
frequency of dark hair and brown eyes is probably due, both in England
and America.
While the average of the Old Americans corresponds closely to the
average of the English, there is a great deal of variation in both
countries. Unfortunately, it is impossible to compare the present
Americans with their ancestors, because measurements of the latter are
lacking. But to assume that the early colonists did not differ greatly
from the modern English is probably justifiable. A comparison of modern
Americans (of the old white stock) with modern English should give basis
for an opinion as to whether the English stock underwent any marked
modifications, on coming to a new environment.
It has already been noted that the average cephalic index is practically
the same; the only possibility of a change then lies in the amount of
variability. Is the American stock more or less variable? Can a
"melting pot" influence be seen, tending to produce homogeneity, or has
change of environment rather produced greater variability, as is
sometimes said to be the case?
The amount of variability is most conveniently measured by a coefficient
known as the standard deviation ([Greek: s]), which is small when the
range of variation is small, but large when diversity of material is
great. The following comparisons of the point at issue may be made. [202]
Avg. [Greek: s]
100 American men 78. 3 3. 1
1011 Cambridge graduates (English males) 79. 85 2. 95
For the men, little difference is discernible. The Old Americans are
slightly more long-headed than the English, but the amount of variation
in this trait is nearly the same on the two sides of the ocean.
The average of the American women is 79. 5 with [Greek: s] = 2. 6. No
suitable series of English women has been found for comparison. (203) It
will be noted that the American women are slightly more round-headed
than the men; this is found regularly to be the case, when comparisons
of the head form of the two sexes are made in any race.
In addition to establishing norms or standards for anthropological
comparison, the main object of Dr. Hrdlicka's study was to determine
whether the descendants of the early American settlers, living in a new
environment and more or less constantly intermarrying, were being
amalgamated into a distinct sub-type of the white race. It has been
found that such amalgamation has not taken place to any important
degree. The persistence in heredity of certain features, which run down
even through six or eight generations, is one of the remarkable results
brought out by the study.
If the process could continue for a few hundred years more, Dr.
Hrdlicka thinks, it might reach a point where one could speak of the
members of old American families as of a distinct stock. But so far this
point has not been reached; the Americans are almost as diverse and
variable, it appears, as were their first ancestors in this country.
APPENDIX D
THE ESSENCE OF MENDELISM
It is half a century since the Austrian monk, Gregor Mendel, published
in a provincial journal the results of his now famous breeding
experiments with garden peas. They lay unnoticed until 1900, when three
other breeders whose work had led them to similar conclusions, almost
simultaneously discovered the work of Mendel and gave it to the world.
Breeding along the lines marked out by Mendel at once became the most
popular method of attack, among those who were studying heredity. It
became an extremely complicated subject, which can not be grasped
without extended study, but its fundamentals can be briefly summarized.
Inherited differences in individuals, it will be admitted, are due to
differences in their germ-plasms. It is convenient to think of these
differences in germ-plasms (that is, differences in heredity) as being
due to the presence in the germ-plasm of certain hypothetical units,
which are usually referred to as factors. The factor, nowadays, is the
ultimate unit of Mendelian research. Each of these factors is considered
to be nearly or quite constant,--that is, it undergoes little, or no
change from generation to generation. It is ordinarily resistant to
"contamination" by other factors with which it may come in contact in
the cell. The first fundamental principle of Mendelism, then, is the
existence of relatively constant units, the Mendelian factors, as the
basis for transmission of all the traits that go to make up an animal or
plant.
Experimental breeding gives reason to believe that each factor has one
or more alternatives, which may take its place in the mechanism of
heredity, thereby changing the visible character of the individual plant
or animal in which it occurs. To put the matter a little differently,
one germ-cell differs from another in having alternatives present in
place of some of the factors of the latter. A given germ-cell can never
have more than one of the possible alternatives of each factor. These
alternatives of a factor are called its allelomorphs.
Now a mature germ-cell has a single system of these factors: but when
two germ-cells unite, there result from that union two kinds of
cells--namely, immature germ-cells and body-cells; and both these kinds
of cells contain a double system of factors, because of course they have
received a single entire system from each parent. This is the second of
the fundamental principles of Mendelism: that the factors are single in
the mature germ-cell, but in duplicate in the body-cell (and also in the
immature germ-cell).
In every cell with a double system of factors, there are necessarily
present two representatives from each set of allelomorphs, but these may
or may not be alike--or in technical language the individual may be
homozygous, or heterozygous, as regards the given set of alternative
factors. Looking at it from another angle, there is a single visible
character in the plant or animal, but it is produced by a double factor,
in the germ-plasm.
When the immature germ-cell, with its double system of factors, matures,
it throws out half the factors, retaining only a single system: and the
allelomorphic factors which then segregate into different cells are, as
has been said above, ordinarily uninfluenced by their stay together.
But the allelomorphic factors are not the only ones which are segregated
into different germ-cells, at the maturation of the cell; for the
factors which are not alternative are likewise distributed, more or less
independently of each other, so that it is largely a matter of chance
whether factors which enter a cross in the same germ-cell, segregate
into the same germ-cell or different ones, in the next generation. This
is the next fundamental principle of Mendelism, usually comprehended
under the term "segregation," although, as has been pointed out, it is
really a double process, the segregation of alternative factors being a
different thing from the segregation of non-alternative factors.
From this fact of segregation, it follows that as many kinds of
germ-cells can be formed by an individual, as there are possible
combinations of factors, on taking one alternative from each pair of
allelomorphs present. In practice, this means that the possible number
of different germ-cells is almost infinitely great, as would perhaps be
suspected by anyone who has tried to find two living things that are
just alike.
[Illustration: THE CARRIERS OF HEREDITY
FIG. 46. --Many different lines of study have made it seem
probable that much, although not all, of the heredity of an animal or
plant is carried in the nucleus of the germ-cell and that in this
nucleus it is further located in little rods or threads which can be
easily stained so as to become visible, and which have the name of
chromosomes. In the above illustration four different views of the
nucleus of the germ-cell of an earthworm are shown, with the chromosomes
in different stages; in section 19 each chromosome is doubled up like a
hairpin. Study of the fruit-fly Drosophila has made it seem probable not
only that the hypothetical factors of heredity are located in the
chromosomes, but that each factor has a perfectly definite location in
its chromosome; and T. H. Morgan and his associates have worked out an
ingenious method of measuring the distance from either end, at which the
factor lies. Photomicrograph after Foot and Strobell. ]
Such is the essence of Mendelism; and the reader is probably ready to
admit that it is not a simple matter, even when reduced to the
simplest terms. To sum up, the principal features at the base of the
hypothetical structure are these:
1. There exist relatively constant units in the germ-plasm.
2. There are two very distinct relationships which these units may show
to each other. Two (or more) unit factors may be alternatives in the
mechanism of inheritance, indicating that one is a variation (or loss)
of the other; or they may be independent of each other in the mechanism
of inheritance.
3. The mature germ-cell contains a single system of independent factors
(one representative from each set of alternates).
The immature germ-cells, and body-cells, have double systems of
independent factors (two from each set of alternatives).
4. The double system arises simply from the union of two single systems
(i. e. , two germ-cells), without union or even contamination of the
factors involved.
In the formation of a single system (mature germ-cells) from a double
(immature germ-cells), pairs of alternates separate, passing into
different germ-cells. Factors not alternates may or may not
separate--the distribution is largely a matter of chance.
Such are the fundamental principles of Mendelism; but on them was early
grafted a theoretical structure due mainly to the German zoologist,
August Weismann. To understand his part in the story, we must advert to
that much mooted and too often misunderstood problem furnished by the
chromosomes. (See Fig. 46. ) These little rods of easily stained
material, which are found in every cell of the body, were picked out by
Professor Weismann as the probable carriers of heredity. With remarkable
acuteness, he predicted their behavior at cell-division, the intricate
nature of which is usually the despair of every beginner in biology.
When Mendelian breeding, in the early years of this century, showed
temporary pairing and subsequent separation of units in the
germ-cell, it was soon realized that the observed facts of breeding
fitted to a nicety the observed facts (predicted by Weismann) of
chromosome-behavior; for at each cell-division the chromosomes, too,
pair and separate again. The observed behavior of transmitted characters
in animals and plants followed, in so many cases, the observed behavior
of the chromosomes, that many students found it almost impossible to
believe that there was no connection between the two, and Dr. Weismann's
prediction, that the chromosomes are the carriers of heredity, came to
be looked on as a fact, by many biologists.
But when so much of Professor Weismann's system was accepted, other
parts of it went along, including a hypothetical system of "determiners"
in the chromosome, which were believed to determine the development of
characters in the organism. Every trait of an animal or plant, it was
supposed, must be represented in the germ-plasm by its own determiner;
one trait, one determiner. Did a notch in the ear run through a
pedigree? Then it must be due to a determiner for a notch in the ear in
the germ-plasm. Was mathematical ability hereditary? Then there must be
a determiner, the expression of which was mathematical ability.
For a while, this hypothesis was of service in the development of
genetics; some students even began to forget that it was a hypothesis,
and to talk as if it were a fact. But the exhaustive tests of
experimental breeding of plants and animals have long caused most of the
advanced students of genetics to drop this simple hypothesis.
In its place stands the factorial hypothesis, evolved by workers in
America, England, and France at about the same time. As explained in
Chapter V, this hypothesis carries the assumption that every visible
character is due to the effects of not one but many factors in the
germ-cell.
In addition to these fundamentals, there are numerous extensions and
corollaries, some of them of a highly speculative nature. The reader who
is interested in pursuing the subject farther must turn to one of the
text-books on Mendelism.
In plant-breeding a good deal of progress has been made in the exact
study of Mendelian heredity; in animal breeding, somewhat less; in human
heredity, very little. The reason is obvious: that experiments can not
be made in man, and students must depend on the results of such matings
as they can find; that only a very few offspring result from each
mating; and that generations are so long that no one observer can have
more than a few under his eyes. These difficulties make Mendelian
research in man a very slow and uncertain matter.
Altogether, it is probable that something like a hundred characters in
man have been pointed out as inherited in Mendelian fashion. A large
part of these are pathological conditions or rare abnormalities.
But the present writers can not accept most of these cases. It has been
pointed out in Chapter V that there are good reasons for doubting that
feeble-mindedness is inherited in a simple Mendelian fashion, although
it is widely accepted as such. We can not help feeling that in most
cases heredity in man is being made to appear much simpler than it
really is; and that particularly in mental characters, analysis of
traits has by no means reached the bottom.
If we were asked to make out a list of characters, as to the Mendelian
inheritance of which there could be little doubt, we would hardly be
able to go farther than the following:
The sex-linked characters (one kind of color-blindness, hemophilia, one
kind of night-blindness, atrophy of the optic nerve, and a few other
rare abnormalities).
Albinism. This appears to be a recessive, but probably involves multiple
allelomorphs in man, as in other animals.
Brachydactyly, apparently a dominant. This is so much cited in
text-books on Mendelism that the student might think it is a common
character. As a fact, it is extremely rare, being found in only a few
families. The similar trait of orthodactyly or symphalangism, which
likewise appears to be a good Mendelian dominant, seems to exist in only
one family. Traits like these, which are easily defined and occur very
rarely, make up a large part of the cases of probably Mendelian
heredity. They are little more than curiosities, their rarity and
abnormal nature depriving them of evolutionary significance other than
to demonstrate that Mendelian heredity does operate in man.
White blaze in the hair or, as it might better be called to show its
resemblance to the trait found in other mammals, piebaldism. A rather
rare dominant. [204]
Huntington's Chorea, which usually appears to be a good dominant,
although the last investigators (Muncey and Davenport) found some
unconformable cases.
A few abnormalities, such as a premature graying of the hair (one family
cited by K. Pearson) are well enough attested to be admitted. Many
others, such as baldness, are probably Mendelian but not yet
sufficiently supported by evidence.
None of these characters, it will be observed, is of much significance
eugenically. If the exact manner of inheritance of some of the more
important mental and physical traits were known, it would be of value.
But it is not a prerequisite for eugenic action. Enough is known for a
working program.
To sum up: the features in the modern view of heredity, which the reader
must keep in mind, are the following:
1. That the various characters which make up the physical constitution
of any individual plant or animal are due to the action (concurrently
with the environment, of course) of what are called, for convenience,
factors, separable hypothetical units in the germ-plasm, capable of
independent transmission.
2. That each visible character is due to the cooperative action of an
indefinitely large number of factors; conversely, that each of these
factors affects an indefinitely large number of characters.
APPENDIX E
USEFUL WORKS OF REFERENCE
The most complete bibliography is that published by the State Board of
Charities of the State of New York (_Eugenics and Social Welfare
Bulletin_ No. III, pp. 130, Albany, 1913).
An interesting historical review of eugenics, with critical comments on
the literature and a bibliography of 100 titles, was published by A. E.
Hamilton in the _Pedagogical Seminary_, Vol. XXI, pp. 28-61, March,
1914.
Much of the important literature of eugenics has been mentioned in
footnotes. For convenience, a few of the books which are likely to be
most useful to the student are here listed:
GENETICS AND EUGENICS, by W. E. Castle. Harvard University
Press, Cambridge, 1916.
HEREDITY AND ENVIRONMENT IN THE DEVELOPMENT OF MEN, by Edwin G.
Conklin. Princeton University Press, 1915.
HEREDITY IN RELATION TO EUGENICS, by C. B. Davenport, Henry
Holt and Co. , New York, 1911.
ESSAYS IN EUGENICS, by Francis Galton. Eugenics Education
Society, London, 1909.
BEING WELL-BORN, by Michael F. Guyer. Indianapolis,
Bobbs-Merrill Co. , 1916.
THE SOCIAL DIRECTION OF HUMAN EVOLUTION, by W. E. Kellicott.
New York, 1911.
THE PHYSICAL BASIS OF SOCIETY, by Carl Kelsey. New York, D.
Appleton & Co. , 1916.
EUGENICS, by Edward Schuster. Collins' Clear Type Press, London
and Glasgow, 1913.
HEREDITY, by J. Arthur Thompson. Edinburgh, 1908.
GENETICS, by Herbert E. Walter. The Macmillan Co. , New York,
1913.
AN INTRODUCTION TO EUGENICS, by W. C. D. Whetham and C. D.
Whetham. Macmillan and Co. , London, 1912.
HEREDITY AND SOCIETY, by W. C. D. Whetham and C. D. Whetham.
Longmans, Green & Co. , London, 1912.
THE FAMILY AND THE NATION, by W. C. D. Whetham and C. D.
Whetham. Longmans, Green & Co. , London, 1909.
The publications of the Galton Laboratory of National Eugenics,
University of London, directed by Karl Pearson, and of the Eugenics
Record Office, Cold Spring Harbor, Long Island, N. Y. , directed by C. B.
Davenport, furnish a constantly increasing amount of original material
on heredity.
The principal periodicals are the _Journal of Heredity_ (organ of the
American Genetic Association), 511 Eleventh St. , N. W. , Washington, D.
C. (monthly); and the _Eugenics Review_ (organ of the Eugenics Education
Society), Kingsway House, Kingsway, W. C. , London (quarterly). These
periodicals are sent free to members of the respective societies.
Membership in the American organization is $2 a year, in the English 1
guinea a year, associate membership 5 shillings a year.
APPENDIX F
GLOSSARY
ACQUIRED CHARACTER, a modification of a germinal trait after
cell fusion. It is difficult to draw a line between characters that are
acquired and those that are inborn. The idea involved is as follows: in
a standard environment, a given factor in the germ-plasm will develop
into a trait which varies not very widely about a certain mean. The mean
of this trait is taken as representing the germinal trait in its typical
condition. But if the environment be not standard, if it be considerably
changed, the trait will develop a variation far from the mean of that
trait in the species. Thus an American, whose skin in the standard
environment of the United States would be blonde, may under the
environment of Cuba develop into a brunette. Such a wide variation from
the mean thus caused is called an acquired character; it is usually
impressed on the organism after the germinal trait has reached a full,
typical development.
ALLELOMORPH (one another form), one of a pair of factors which
are alternative to each other in Mendelian inheritance. Instead of a
single pair, there may be a group of "multiple allelomorphs," each
member being alternative to every other member of the group.
ALLELOMORPHISM, a relation between two or more factors, such
that two which are present in one zygote do not both enter into the same
gamete, but are separated into sister gametes.
BIOMETRY (life measure), the study of biology by statistical
methods.
BRACHYDACTYLY (short-finger), a condition in which the bones,
particularly of the fingers and toes, fail to grow to their normal
length. In well-marked cases one of these is a reduction from three
phalanges or joints to two.
CHARACTER (a contraction of "characteristic"), a term which is
used, often rather vaguely, to designate any function, feature, or organ
of the body or mind.
CHROMOSOME (color body, so called from its affinity for certain
stains), a body of peculiar protoplasm, in the nucleus of the cell. Each
species has its own characteristic number; the cells of the human body
contain 24 chromosomes each.
CONGENITAL (with birth), present at birth. The term fails to
distinguish between traits which are actually inherited, and
modifications acquired during prenatal life.
