Euthenic
measures of this type should be accompanied by counterbalancing measures
of a more eugenic character.
measures of this type should be accompanied by counterbalancing measures
of a more eugenic character.
Applied Eugenics by Roswell H. Johnson and Paul Popenoe
0672, practically zero.
In other words, if the age is known at
which a member of one of these families died, whether it be one month or
100 years, nothing whatever can be predicted about the age at which his
brothers and sisters died.
Remembering that longevity is in general inherited, and that it is found
in the families of all the people of this study (since one in each
fraternity lived to be 90 or over) how is one to interpret this zero
coefficient? Evidently it means that although these people had inherited
a high degree of longevity, their deaths were brought about by causes
which prevented the heredity from getting full expression. As far as
hereditary potentialities are concerned, it can be said that all their
deaths were due to accident, using that word in a broad sense to include
all non-selective deaths by disease. If they had all been able to get
the full benefit of their heredity, it would appear that each of these
persons might have lived to 90 or more, as did the one in each family
who was recorded by the Genealogical Record Office. Genetically, these
other deaths may be spoken of as premature.
In an ordinary population, the age of death is determined to the extent
of probably 50% by heredity. In this selected long-lived population,
heredity appears not to be responsible in any measurable degree
whatsoever for the differences in age at death.
The result may be expressed in another, and perhaps more striking, way.
Of the 669 individuals studied, a hundred--namely, one child in each
family--lived beyond 90; and there were a few others who did. But some
550 of the group, though they had inherited the potentiality of reaching
the average age of 90, actually died somewhere around 60; they failed by
at least one-third to live up to the promise of their inheritance. If we
were to generalize from this single case, we would have to say that
five-sixths of the population does not make the most of its physical
inheritance.
This is certainly a fact that discourages fatalistic optimism. The man
who tells himself that, because of his magnificent inherited
constitution, he can safely take any risk, is pretty sure to take too
many risks and meet with a non-selective--i. e. , genetically, a
premature--death, when he might in the nature of things have lived
almost a generation longer.
It should be remarked that most of the members of this group seem to
have lived in a hard environment. They appear to belong predominantly to
the lower strata of society; many of them are immigrants and only a very
few of them, to judge by a cursory inspection of the records, possessed
more than moderate means. This necessitated a frugal and industrious
life which in many ways was doubtless favorable to longevity but which
may often have led to overexposure, overwork, lack of proper medical
treatment, or other causes of a non-selective death. We would not push
the conclusion too far, but we can not doubt that this investigation
shows the folly of ignoring the environment,--shows that the best
inherited constitution must have a fair chance. And what has here been
found for a physical character, would probably hold good in even greater
degree for a mental character. All that man inherits is the capacity to
develop along a certain line under the influence of proper
stimuli,--food and exercise. The object of eugenics is to see that the
inherent capacity is there. Given that, the educational system is next
needed to furnish the stimuli. The consistent eugenist is therefore an
ardent euthenist. He not only works for a better human stock but,
because he does not want to see his efforts wasted, he always works to
provide the best possible environment for this better stock.
In so far, then, as euthenics is actually providing man with more
favorable surroundings,--not with ostensibly more favorable surroundings
which, in reality, are unfavorable--there can be no antagonism between
it and eugenics. Eugenics is, in fact, a prerequisite of euthenics, for
it is only the capable and altruistic man who can contribute to social
progress; and such a man can only be produced through eugenics.
Eugenic fatalism, a blind faith in the omnipotence of heredity
regardless of the surroundings in which it is placed, has been shown by
the study of long-lived families to be unjustified. It was found that
even those who inherited exceptional longevity usually did not live as
long as their inheritance gave them the right to expect. If they had had
more euthenics, they should have lived longer.
But this illustration certainly gives no ground for a belief that
euthenics is sufficient to prolong one's life _beyond_ the inherited
limit. A study of these long-lived families from another point of view
will reveal that heredity is the primary factor and that good
environment, euthenics, is the secondary one.
For this purpose we augment the 100 families of the preceding section by
the addition of 240 more families like them, and we examine each family
history to find how many of the children died before completing the
fourth year of life. The data are summarized in the following table:
CHILD MORTALITY IN FAMILIES OF LONG-LIVED STOCK, GENEALOGICAL RECORD
OFFICE DATA
Size of No. of families No. of families Total no.
family investigated showing deaths of deaths
under 5 years
1 child 6 0 0
2 children 6 0 0
3 " 38 4 5
4 " 40 6 7
5 " 38 4 4
6 " 44 12 13
7 " 34 8 11
8 " 46 13 18
9 " 31 14 20
10 " 27 14 14
11 " 13 6 9
12 " 13 9 16
13 " 1 0 0
14 " 2 0 0
17 " 1 1 2
--- --- ---
340 91 119
The addition of the new families (which were not subjected to any
different selection than the first 100) has brought down the child
mortality rate. For the first 100, it was found to be 7. 5%. If in the
above table the number of child deaths, 119, be divided by the total
number of children represented, 2,259, the child mortality rate for this
population is found to be 5. 27%, or 53 per thousand.
The smallness of this figure may be seen by comparison with the
statistics of the registration area, U. S. Census of 1880, when the child
mortality (0-4 years) was 400 per thousand, as calculated by Alexander
Graham Bell. A mortality of 53 for the first four years of life is
smaller than any district known in the United States, even to-day, can
show for the _first_ year of life _alone_. If any city could bring the
deaths of babies during their first twelve months down to 53 per 1,000,
it would think it had achieved the impossible; but here is a population
in which 53 per 1,000 covers the deaths, not only of the fatal first 12
months, but of the following three years in addition.
Now this population with an unprecedentedly low rate of child mortality
is not one which had had the benefit of any Baby Saving Campaign, nor
even the knowledge of modern science. Its mothers were mostly poor, many
of them ignorant; they lived frequently under conditions of hardship;
they were peasants and pioneers. Their babies grew up without doctors,
without pasteurized milk, without ice, without many sanitary
precautions, usually on rough food. But they had one advantage which no
amount of applied science can give after birth--namely, good heredity.
They had inherited exceptionally good constitutions.
It is not by accident that inherited longevity in a family is associated
with low mortality of its children. The connection between the two facts
was first discovered by Mary Beeton and Karl Pearson in their pioneer
work on the inheritance of duration of life. They found that high infant
mortality was associated with early death of parents, while the
offspring of long-lived parents showed few deaths in childhood. The
correlation of the two facts was quite regular, as will be evident from
a glance at the following tables prepared by A. Ploetz:
LENGTH OF LIFE OF MOTHERS AND CHILD-MORTALITY OF THEIR DAUGHTERS.
ENGLISH QUAKER FAMILIES, DATA OF BEETON AND PEARSON, ARRANGED BY
PLOETZ
Year of life in which mothers died At
all
0-38 39-53 54-68 69-83 84 up ages
No. of daughters 234 304 305 666 247 1846
No. of them who died in
first 5 years 122 114 118 131 26 511
Per cent. of daughters
who died 52. 1 37. 5 29. 9 19. 7 10. 5 27. 7
LENGTH OF LIFE OF FATHERS AND CHILD-MORTALITY OF THEIR
DAUGHTERS
Year of life in which fathers died At
0-38 39-53 54-68 69-83 84 up all
ages
No. of daughters 105 284 585 797 236 2009
No. of them who died in
first 5 years 51 98 156 177 40 522
Per cent. of daughters
who died 48. 6 34. 5 26. 7 22. 2 17. 0 26. 0
To save space, we do not show the relation between parent and son; it is
similar to that of parent and daughter which is shown in the preceding
tables. In making comparison with the 340 families from the Genealogical
Record Office, above studied, it must be noted that Dr. Ploetz' tables
include one year longer in the period of child mortality, being computed
for the first five years of life instead of the first four. His
percentages would therefore be somewhat lower if computed on the basis
used in the American work.
These various data demonstrate the existence of a considerable
correlation between short life (_brachybioty_, Karl Pearson calls it) in
parent and short life in offspring. Not only is the tendency to live
long inherited, but the tendency _not_ to live long is likewise
inherited.
But perhaps the reader may think they show nothing of the sort. He may
fancy that the early death of a parent left the child without sufficient
care, and that neglect, poverty, or some other factor of euthenics
brought about the child's death. Perhaps it lacked a mother's loving
attention, or perhaps the father's death removed the wage-earner of the
family and the child thenceforth lacked the necessities of life.
Dr. Ploetz has pointed out[192] that this objection is not valid,
because the influence of the parent's death is seen to hold good even to
the point where the child was too old to require any assistance. If the
facts applied only to cases of early death, the supposed objection might
be weighty, but the correlation exists from one end of the age-scale to
the other. It is not credible that a child is going to be deprived of
any necessary maternal care when its mother dies at the age of 69; the
child herself was probably married long before the death of the mother.
Nor is it credible that the death of the father takes bread from the
child's mouth, leaving it to starve to death in the absence of a pension
for widowed mothers, if the father died at 83, when the "child" herself
was getting to be an old woman. The early death of a parent may
occasionally bring about the child's death for a reason wholly
unconnected with heredity, but the facts just pointed out show that such
cases are exceptional. The steady association of the child death-rate
and parent death-rate _at all ages_ demonstrates that heredity is a
common cause.
But the reader may suspect another fallacy. The cause of this
association is really environmental, he may think, and the same poverty
or squalor which causes the child to die early may cause the parent to
die early. They may both be of healthy, long-lived stock, but forced to
live in a pestiferous slum which cuts both of them off prematurely and
thereby creates a spurious correlation in the statistics.
We can dispose of this objection most effectively by bringing in new
evidence. It will probably be admitted that in the royal families of
Europe, the environment is as good as knowledge and wealth can make it.
No child dies for lack of plenty of food and the best medical care, even
if his father or mother died young. And the members of this caste are
not exposed to any such unsanitary conditions, or such economic pressure
as could possibly cause both parent and child to die prematurely. If the
association between longevity of parent and child mortality holds for
the royal families of Europe and their princely relatives, it can hardly
be regarded as anything but the effect of heredity,--of the inheritance
of a certain type of constitution.
Dr. Ploetz studied the deaths of 3,210 children in European royalty,
from this viewpoint. The following table shows the relation between
father and child:
LENGTH OF LIFE OF FATHERS AND CHILD-MORTALITY OF THEIR CHILDREN IN
ROYAL AND PRINCELY FAMILIES, PLOETZ' DATA
At
Year of life in which fathers died Years all
ages
16-25 26-35 36-45 46-55 56-65 66-75 76-85 86 up
No. of children. 23 90 367 545 725 983 444 33 3210
No. who died in
first 5 years 12 29 115 171 200 254 105 1 887
Per cent. who
died 52. 2 32. 2 31. 3 31. 4 27. 6 25. 8 23. 6 3. 0 27. 6
Allowing for the smallness of some of the groups, it is evident that
the amount of correlation is about the same here as among the English
Quakers of the Beeton-Pearson investigation, whose mortality was shown
in the two preceding tables. In the healthiest group from the royal
families--the cases in which the father lived to old age--the amount of
child mortality is about the same as that of the Hyde family in America,
which Alexander Graham Bell has studied--namely, somewhere around 250
per 1,000. One may infer that the royal families are rather below par in
soundness of constitution. [193]
All these studies agree perfectly in showing that the amount of child
mortality is determined primarily by the physical constitution of the
parents, as measured by their longevity. In the light of these facts,
the nature of the extraordinarily low child mortality shown in the 340
families from the Genealogical Record Office, with which we began the
study of this point, can hardly be misunderstood. These families have
the best inherited constitution possible and the other studies cited
would make us certain of finding a low child mortality among them, even
if we had not directly investigated the facts.
If the interpretation which we have given is correct, the conclusion is
inevitable that child mortality is primarily a problem of eugenics, and
that all other factors are secondary. There is found to be no warrant
for the statement so often repeated in one form or another, that "the
fundamental cause of the excessive rate of infant mortality in
industrial communities is poverty, inadequate incomes, and low standards
of living. "[194] Royalty and its princely relatives are not
characterized by a low standard of living, and yet the child mortality
among them is very high--somewhere around 400 per 1,000, in cases where
a parent died young. If poverty is responsible in the one case, it must
be in the other--which is absurd. Or else the logical absurdity is
involved of inventing one cause to explain an effect to-day and a wholly
different cause to explain the same effect to-morrow. This is
unjustifiable in any case, and it is particularly so when the single
cause that explains both cases is so evident. If weak heredity causes
high mortality in the royal families, why, similarly, can not weak
heredity cause high infant mortality in the industrial communities? We
believe it does account for much of it, and that the inadequate income
and low standard of living are largely the consequences of inferior
heredity, mental as well as physical. The parents in the Genealogical
Record Office files had, many of them, inadequate incomes and low
standards of living under frontier conditions, but their children grew
up while those of the royal families were dying in spite of every
attention that wealth could command and science could furnish.
If the infant mortality problem is to be solved on the basis of
knowledge and reason, it must be recognized that sanitation and hygiene
can not take the place of eugenics any more than eugenics can dispense
with sanitation and hygiene. It must be recognized that the death-rate
in childhood is largely selective, and that the most effective way to
cut it down is to endow the children with better constitutions. This can
not be done solely by any euthenic campaign; it can not be done by
swatting the fly, abolishing the midwife, sterilizing the milk, nor by
any of the other panaceas sometimes proposed.
But, it may be objected, this discussion ignores the actual facts.
Statistics show that infant mortality campaigns _have_ consistently
produced reductions in the death-rate. The figures for New York, which
could be matched in dozens of other cities, show that the number of
deaths per 1,000 births, in the first year of life, has steadily
declined since a determined campaign to "Save the Babies" was started:
1902 181
1903 152
1904 162
1905 159
1906 153
1907 144
1908 128
1909 129
1910 125
1911 112
1912 105
1913 102
1914 95
To one who can not see beyond the immediate consequences of an action,
such figures as the above indeed give quite a different idea of the
effects of an infant mortality campaign, than that which we have just
tried to create. And it is a great misfortune that euthenics so often
fails to look beyond the immediate effect, fails to see what may happen
next year, or 10 years from now, or in the next generation.
We admit that it is possible to keep a lot of children alive who would
otherwise have died in the first few months of life. It is being done,
as the New York figures, and pages of others that could be cited, prove.
The ultimate result is twofold:
1. Some of those who are doomed by heredity to a selective death, but
are kept alive through the first year, die in the second or third or
fourth year. They must die sooner or later; they have not inherited
sufficient resistance to survive more than a limited time. If they are
by a great effort carried through the first year, it is only to die in
the next. This is a statement which we have nowhere observed in the
propaganda of the infant mortality movement; and it is perhaps a
disconcerting one. It can only be proved by refined statistical methods,
but several independent determinations by the English biometricians
leave no doubt as to the fact. This work of Karl Pearson, E. C. Snow, and
Ethel M. Elderton, was cited in our chapter on natural selection; the
reader will recall how they showed that nature is weeding out the
weaklings, and in proportion to the stringency with which she weeds them
out at the start, there are fewer weaklings left to die in succeeding
years.
To put the facts in the form of a truism, part of the children born in
any district in a given year are doomed by heredity to an early death;
and if they die in one year they will not be alive to die in the
succeeding year, and vice versa. Of course there are in addition infant
deaths which are not selective and which if prevented would leave the
infant with as good a chance as any to live.
In the light of these researches, we are forced to conclude that
baby-saving campaigns accomplish less than is thought; that the supposed
gain is to some extent temporary and illusory.
2. There is still another consequence. If the gain is by great exertions
made more than temporary; if the baby who would otherwise have died in
the first months is brought to adult life and reproduction, it means in
many cases the dissemination of another strain of weak heredity, which
natural selection would have cut off ruthlessly in the interests of race
betterment. In so far, then, as the infant mortality movement is not
futile it is, from a strict biological viewpoint, often detrimental to
the future of the race.
Do we then discourage all attempts to save the babies? Do we leave them
all to natural selection? Do we adopt the "better dead" gospel?
Unqualifiedly, no! The sacrifice of the finer human feelings, which
would accompany any such course, would be a greater loss to the race
than is the eugenic loss from the perpetuation of weak strains of
heredity. The abolition of altruistic and humanitarian sentiment for the
purpose of race betterment would ultimately defeat its own end by making
race betterment impossible.
But race betterment will also be impossible unless a clear distinction
is made between measures that really mean race betterment of a
fundamental and permanent nature, and measures which do not.
We have chosen the Infant Mortality Movement for analysis in this
chapter because it is an excellent example of the kind of social
betterment which is taken for granted, by most of its proponents, to be
a fundamental piece of race betterment; but which, as a fact, often
means race impairment. No matter how abundant and urgent are the reasons
for continuing to reduce infant mortality wherever possible, it is
dangerous to close the eyes to the fact that the gain from it is of a
kind that must be paid for in other ways; that to carry on the movement
without adding eugenics to it will be a short-sighted policy, which
increases the present happiness of the world at the cost of diminishing
the happiness of posterity through the perpetuation of inferior strains.
While some euthenic measures are eugenically evils, even if necessary
ones, it must not be inferred that all euthenic measures are dysgenic.
Many of them, such as the economic and social changes we have suggested
in earlier chapters, are an important part of eugenics. Every euthenic
measure should be scrutinized from the evolutionary standpoint; if it is
eugenic as well as euthenic, it should be whole-heartedly favored; if it
is dysgenic but euthenic it should be condemned or adopted, according to
whether or not the gain in all ways from its operation will exceed the
damage.
In general, euthenics, when not accompanied by some form of selection
(i. e. , 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.
which a member of one of these families died, whether it be one month or
100 years, nothing whatever can be predicted about the age at which his
brothers and sisters died.
Remembering that longevity is in general inherited, and that it is found
in the families of all the people of this study (since one in each
fraternity lived to be 90 or over) how is one to interpret this zero
coefficient? Evidently it means that although these people had inherited
a high degree of longevity, their deaths were brought about by causes
which prevented the heredity from getting full expression. As far as
hereditary potentialities are concerned, it can be said that all their
deaths were due to accident, using that word in a broad sense to include
all non-selective deaths by disease. If they had all been able to get
the full benefit of their heredity, it would appear that each of these
persons might have lived to 90 or more, as did the one in each family
who was recorded by the Genealogical Record Office. Genetically, these
other deaths may be spoken of as premature.
In an ordinary population, the age of death is determined to the extent
of probably 50% by heredity. In this selected long-lived population,
heredity appears not to be responsible in any measurable degree
whatsoever for the differences in age at death.
The result may be expressed in another, and perhaps more striking, way.
Of the 669 individuals studied, a hundred--namely, one child in each
family--lived beyond 90; and there were a few others who did. But some
550 of the group, though they had inherited the potentiality of reaching
the average age of 90, actually died somewhere around 60; they failed by
at least one-third to live up to the promise of their inheritance. If we
were to generalize from this single case, we would have to say that
five-sixths of the population does not make the most of its physical
inheritance.
This is certainly a fact that discourages fatalistic optimism. The man
who tells himself that, because of his magnificent inherited
constitution, he can safely take any risk, is pretty sure to take too
many risks and meet with a non-selective--i. e. , genetically, a
premature--death, when he might in the nature of things have lived
almost a generation longer.
It should be remarked that most of the members of this group seem to
have lived in a hard environment. They appear to belong predominantly to
the lower strata of society; many of them are immigrants and only a very
few of them, to judge by a cursory inspection of the records, possessed
more than moderate means. This necessitated a frugal and industrious
life which in many ways was doubtless favorable to longevity but which
may often have led to overexposure, overwork, lack of proper medical
treatment, or other causes of a non-selective death. We would not push
the conclusion too far, but we can not doubt that this investigation
shows the folly of ignoring the environment,--shows that the best
inherited constitution must have a fair chance. And what has here been
found for a physical character, would probably hold good in even greater
degree for a mental character. All that man inherits is the capacity to
develop along a certain line under the influence of proper
stimuli,--food and exercise. The object of eugenics is to see that the
inherent capacity is there. Given that, the educational system is next
needed to furnish the stimuli. The consistent eugenist is therefore an
ardent euthenist. He not only works for a better human stock but,
because he does not want to see his efforts wasted, he always works to
provide the best possible environment for this better stock.
In so far, then, as euthenics is actually providing man with more
favorable surroundings,--not with ostensibly more favorable surroundings
which, in reality, are unfavorable--there can be no antagonism between
it and eugenics. Eugenics is, in fact, a prerequisite of euthenics, for
it is only the capable and altruistic man who can contribute to social
progress; and such a man can only be produced through eugenics.
Eugenic fatalism, a blind faith in the omnipotence of heredity
regardless of the surroundings in which it is placed, has been shown by
the study of long-lived families to be unjustified. It was found that
even those who inherited exceptional longevity usually did not live as
long as their inheritance gave them the right to expect. If they had had
more euthenics, they should have lived longer.
But this illustration certainly gives no ground for a belief that
euthenics is sufficient to prolong one's life _beyond_ the inherited
limit. A study of these long-lived families from another point of view
will reveal that heredity is the primary factor and that good
environment, euthenics, is the secondary one.
For this purpose we augment the 100 families of the preceding section by
the addition of 240 more families like them, and we examine each family
history to find how many of the children died before completing the
fourth year of life. The data are summarized in the following table:
CHILD MORTALITY IN FAMILIES OF LONG-LIVED STOCK, GENEALOGICAL RECORD
OFFICE DATA
Size of No. of families No. of families Total no.
family investigated showing deaths of deaths
under 5 years
1 child 6 0 0
2 children 6 0 0
3 " 38 4 5
4 " 40 6 7
5 " 38 4 4
6 " 44 12 13
7 " 34 8 11
8 " 46 13 18
9 " 31 14 20
10 " 27 14 14
11 " 13 6 9
12 " 13 9 16
13 " 1 0 0
14 " 2 0 0
17 " 1 1 2
--- --- ---
340 91 119
The addition of the new families (which were not subjected to any
different selection than the first 100) has brought down the child
mortality rate. For the first 100, it was found to be 7. 5%. If in the
above table the number of child deaths, 119, be divided by the total
number of children represented, 2,259, the child mortality rate for this
population is found to be 5. 27%, or 53 per thousand.
The smallness of this figure may be seen by comparison with the
statistics of the registration area, U. S. Census of 1880, when the child
mortality (0-4 years) was 400 per thousand, as calculated by Alexander
Graham Bell. A mortality of 53 for the first four years of life is
smaller than any district known in the United States, even to-day, can
show for the _first_ year of life _alone_. If any city could bring the
deaths of babies during their first twelve months down to 53 per 1,000,
it would think it had achieved the impossible; but here is a population
in which 53 per 1,000 covers the deaths, not only of the fatal first 12
months, but of the following three years in addition.
Now this population with an unprecedentedly low rate of child mortality
is not one which had had the benefit of any Baby Saving Campaign, nor
even the knowledge of modern science. Its mothers were mostly poor, many
of them ignorant; they lived frequently under conditions of hardship;
they were peasants and pioneers. Their babies grew up without doctors,
without pasteurized milk, without ice, without many sanitary
precautions, usually on rough food. But they had one advantage which no
amount of applied science can give after birth--namely, good heredity.
They had inherited exceptionally good constitutions.
It is not by accident that inherited longevity in a family is associated
with low mortality of its children. The connection between the two facts
was first discovered by Mary Beeton and Karl Pearson in their pioneer
work on the inheritance of duration of life. They found that high infant
mortality was associated with early death of parents, while the
offspring of long-lived parents showed few deaths in childhood. The
correlation of the two facts was quite regular, as will be evident from
a glance at the following tables prepared by A. Ploetz:
LENGTH OF LIFE OF MOTHERS AND CHILD-MORTALITY OF THEIR DAUGHTERS.
ENGLISH QUAKER FAMILIES, DATA OF BEETON AND PEARSON, ARRANGED BY
PLOETZ
Year of life in which mothers died At
all
0-38 39-53 54-68 69-83 84 up ages
No. of daughters 234 304 305 666 247 1846
No. of them who died in
first 5 years 122 114 118 131 26 511
Per cent. of daughters
who died 52. 1 37. 5 29. 9 19. 7 10. 5 27. 7
LENGTH OF LIFE OF FATHERS AND CHILD-MORTALITY OF THEIR
DAUGHTERS
Year of life in which fathers died At
0-38 39-53 54-68 69-83 84 up all
ages
No. of daughters 105 284 585 797 236 2009
No. of them who died in
first 5 years 51 98 156 177 40 522
Per cent. of daughters
who died 48. 6 34. 5 26. 7 22. 2 17. 0 26. 0
To save space, we do not show the relation between parent and son; it is
similar to that of parent and daughter which is shown in the preceding
tables. In making comparison with the 340 families from the Genealogical
Record Office, above studied, it must be noted that Dr. Ploetz' tables
include one year longer in the period of child mortality, being computed
for the first five years of life instead of the first four. His
percentages would therefore be somewhat lower if computed on the basis
used in the American work.
These various data demonstrate the existence of a considerable
correlation between short life (_brachybioty_, Karl Pearson calls it) in
parent and short life in offspring. Not only is the tendency to live
long inherited, but the tendency _not_ to live long is likewise
inherited.
But perhaps the reader may think they show nothing of the sort. He may
fancy that the early death of a parent left the child without sufficient
care, and that neglect, poverty, or some other factor of euthenics
brought about the child's death. Perhaps it lacked a mother's loving
attention, or perhaps the father's death removed the wage-earner of the
family and the child thenceforth lacked the necessities of life.
Dr. Ploetz has pointed out[192] that this objection is not valid,
because the influence of the parent's death is seen to hold good even to
the point where the child was too old to require any assistance. If the
facts applied only to cases of early death, the supposed objection might
be weighty, but the correlation exists from one end of the age-scale to
the other. It is not credible that a child is going to be deprived of
any necessary maternal care when its mother dies at the age of 69; the
child herself was probably married long before the death of the mother.
Nor is it credible that the death of the father takes bread from the
child's mouth, leaving it to starve to death in the absence of a pension
for widowed mothers, if the father died at 83, when the "child" herself
was getting to be an old woman. The early death of a parent may
occasionally bring about the child's death for a reason wholly
unconnected with heredity, but the facts just pointed out show that such
cases are exceptional. The steady association of the child death-rate
and parent death-rate _at all ages_ demonstrates that heredity is a
common cause.
But the reader may suspect another fallacy. The cause of this
association is really environmental, he may think, and the same poverty
or squalor which causes the child to die early may cause the parent to
die early. They may both be of healthy, long-lived stock, but forced to
live in a pestiferous slum which cuts both of them off prematurely and
thereby creates a spurious correlation in the statistics.
We can dispose of this objection most effectively by bringing in new
evidence. It will probably be admitted that in the royal families of
Europe, the environment is as good as knowledge and wealth can make it.
No child dies for lack of plenty of food and the best medical care, even
if his father or mother died young. And the members of this caste are
not exposed to any such unsanitary conditions, or such economic pressure
as could possibly cause both parent and child to die prematurely. If the
association between longevity of parent and child mortality holds for
the royal families of Europe and their princely relatives, it can hardly
be regarded as anything but the effect of heredity,--of the inheritance
of a certain type of constitution.
Dr. Ploetz studied the deaths of 3,210 children in European royalty,
from this viewpoint. The following table shows the relation between
father and child:
LENGTH OF LIFE OF FATHERS AND CHILD-MORTALITY OF THEIR CHILDREN IN
ROYAL AND PRINCELY FAMILIES, PLOETZ' DATA
At
Year of life in which fathers died Years all
ages
16-25 26-35 36-45 46-55 56-65 66-75 76-85 86 up
No. of children. 23 90 367 545 725 983 444 33 3210
No. who died in
first 5 years 12 29 115 171 200 254 105 1 887
Per cent. who
died 52. 2 32. 2 31. 3 31. 4 27. 6 25. 8 23. 6 3. 0 27. 6
Allowing for the smallness of some of the groups, it is evident that
the amount of correlation is about the same here as among the English
Quakers of the Beeton-Pearson investigation, whose mortality was shown
in the two preceding tables. In the healthiest group from the royal
families--the cases in which the father lived to old age--the amount of
child mortality is about the same as that of the Hyde family in America,
which Alexander Graham Bell has studied--namely, somewhere around 250
per 1,000. One may infer that the royal families are rather below par in
soundness of constitution. [193]
All these studies agree perfectly in showing that the amount of child
mortality is determined primarily by the physical constitution of the
parents, as measured by their longevity. In the light of these facts,
the nature of the extraordinarily low child mortality shown in the 340
families from the Genealogical Record Office, with which we began the
study of this point, can hardly be misunderstood. These families have
the best inherited constitution possible and the other studies cited
would make us certain of finding a low child mortality among them, even
if we had not directly investigated the facts.
If the interpretation which we have given is correct, the conclusion is
inevitable that child mortality is primarily a problem of eugenics, and
that all other factors are secondary. There is found to be no warrant
for the statement so often repeated in one form or another, that "the
fundamental cause of the excessive rate of infant mortality in
industrial communities is poverty, inadequate incomes, and low standards
of living. "[194] Royalty and its princely relatives are not
characterized by a low standard of living, and yet the child mortality
among them is very high--somewhere around 400 per 1,000, in cases where
a parent died young. If poverty is responsible in the one case, it must
be in the other--which is absurd. Or else the logical absurdity is
involved of inventing one cause to explain an effect to-day and a wholly
different cause to explain the same effect to-morrow. This is
unjustifiable in any case, and it is particularly so when the single
cause that explains both cases is so evident. If weak heredity causes
high mortality in the royal families, why, similarly, can not weak
heredity cause high infant mortality in the industrial communities? We
believe it does account for much of it, and that the inadequate income
and low standard of living are largely the consequences of inferior
heredity, mental as well as physical. The parents in the Genealogical
Record Office files had, many of them, inadequate incomes and low
standards of living under frontier conditions, but their children grew
up while those of the royal families were dying in spite of every
attention that wealth could command and science could furnish.
If the infant mortality problem is to be solved on the basis of
knowledge and reason, it must be recognized that sanitation and hygiene
can not take the place of eugenics any more than eugenics can dispense
with sanitation and hygiene. It must be recognized that the death-rate
in childhood is largely selective, and that the most effective way to
cut it down is to endow the children with better constitutions. This can
not be done solely by any euthenic campaign; it can not be done by
swatting the fly, abolishing the midwife, sterilizing the milk, nor by
any of the other panaceas sometimes proposed.
But, it may be objected, this discussion ignores the actual facts.
Statistics show that infant mortality campaigns _have_ consistently
produced reductions in the death-rate. The figures for New York, which
could be matched in dozens of other cities, show that the number of
deaths per 1,000 births, in the first year of life, has steadily
declined since a determined campaign to "Save the Babies" was started:
1902 181
1903 152
1904 162
1905 159
1906 153
1907 144
1908 128
1909 129
1910 125
1911 112
1912 105
1913 102
1914 95
To one who can not see beyond the immediate consequences of an action,
such figures as the above indeed give quite a different idea of the
effects of an infant mortality campaign, than that which we have just
tried to create. And it is a great misfortune that euthenics so often
fails to look beyond the immediate effect, fails to see what may happen
next year, or 10 years from now, or in the next generation.
We admit that it is possible to keep a lot of children alive who would
otherwise have died in the first few months of life. It is being done,
as the New York figures, and pages of others that could be cited, prove.
The ultimate result is twofold:
1. Some of those who are doomed by heredity to a selective death, but
are kept alive through the first year, die in the second or third or
fourth year. They must die sooner or later; they have not inherited
sufficient resistance to survive more than a limited time. If they are
by a great effort carried through the first year, it is only to die in
the next. This is a statement which we have nowhere observed in the
propaganda of the infant mortality movement; and it is perhaps a
disconcerting one. It can only be proved by refined statistical methods,
but several independent determinations by the English biometricians
leave no doubt as to the fact. This work of Karl Pearson, E. C. Snow, and
Ethel M. Elderton, was cited in our chapter on natural selection; the
reader will recall how they showed that nature is weeding out the
weaklings, and in proportion to the stringency with which she weeds them
out at the start, there are fewer weaklings left to die in succeeding
years.
To put the facts in the form of a truism, part of the children born in
any district in a given year are doomed by heredity to an early death;
and if they die in one year they will not be alive to die in the
succeeding year, and vice versa. Of course there are in addition infant
deaths which are not selective and which if prevented would leave the
infant with as good a chance as any to live.
In the light of these researches, we are forced to conclude that
baby-saving campaigns accomplish less than is thought; that the supposed
gain is to some extent temporary and illusory.
2. There is still another consequence. If the gain is by great exertions
made more than temporary; if the baby who would otherwise have died in
the first months is brought to adult life and reproduction, it means in
many cases the dissemination of another strain of weak heredity, which
natural selection would have cut off ruthlessly in the interests of race
betterment. In so far, then, as the infant mortality movement is not
futile it is, from a strict biological viewpoint, often detrimental to
the future of the race.
Do we then discourage all attempts to save the babies? Do we leave them
all to natural selection? Do we adopt the "better dead" gospel?
Unqualifiedly, no! The sacrifice of the finer human feelings, which
would accompany any such course, would be a greater loss to the race
than is the eugenic loss from the perpetuation of weak strains of
heredity. The abolition of altruistic and humanitarian sentiment for the
purpose of race betterment would ultimately defeat its own end by making
race betterment impossible.
But race betterment will also be impossible unless a clear distinction
is made between measures that really mean race betterment of a
fundamental and permanent nature, and measures which do not.
We have chosen the Infant Mortality Movement for analysis in this
chapter because it is an excellent example of the kind of social
betterment which is taken for granted, by most of its proponents, to be
a fundamental piece of race betterment; but which, as a fact, often
means race impairment. No matter how abundant and urgent are the reasons
for continuing to reduce infant mortality wherever possible, it is
dangerous to close the eyes to the fact that the gain from it is of a
kind that must be paid for in other ways; that to carry on the movement
without adding eugenics to it will be a short-sighted policy, which
increases the present happiness of the world at the cost of diminishing
the happiness of posterity through the perpetuation of inferior strains.
While some euthenic measures are eugenically evils, even if necessary
ones, it must not be inferred that all euthenic measures are dysgenic.
Many of them, such as the economic and social changes we have suggested
in earlier chapters, are an important part of eugenics. Every euthenic
measure should be scrutinized from the evolutionary standpoint; if it is
eugenic as well as euthenic, it should be whole-heartedly favored; if it
is dysgenic but euthenic it should be condemned or adopted, according to
whether or not the gain in all ways from its operation will exceed the
damage.
In general, euthenics, when not accompanied by some form of selection
(i. e. , 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.
