TITLE PAGE

 

Committee on Research in the Life Sciences

Report Panel #20: Biology and the Future of Man

Panel Members: Th. Dobzhansky
Rene Dubos
D. R. Goddard

. Lederberg

..V. Neel

. Notestein

R. R. Revelle

C. Stern (Chairman)

Cee] Smee

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TABLE OF CONTENTS

The Nature of Man . . . 2. © © «© © «© © «© © © @ © © ¢

3
War and the Future of Man, . . gw e we ween ee we 4
Biology and Medicine. . 1. 1 1 ew we we ee ee we
Genetic Diseases . 2 6 6 we ww ew eee ee eee 7
Early Environmental Influences... ......4.
The Demographic Need for Biological Knowledge . . . .. . 11
Man and His Environment... . 6. . 6. ew we we ee 18
Selection and the Variability of Man, 2... 1... 2... 21
Controlled Sex Determination . . 1. 1. 1 6 6 ee ee ee 25

Guarding the Genetic Quality of Man . te ee we ee 26
Differential Fertility. 2. 6. 6 6 6 6 ue ww ew ew ew we BF
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BIOLOGY AND THE FUTURE OF MAN
The Nature of Man

 

The future of man will depend on many events, some consciously decided upon and
others happening without intention. Social organizations through their political leaders
will determine on peace or war, on the use of conventional or nuclear weapons, on the en--
couragement or discouragement of measures to limit the growth of populations, on the
degree of increase in food production and on the conservation of a healthy environment or
its degradation. These decisions will unconsciously affect the composition of the human
species, Some groups which genetically differ from others will grow in numbers, others
will decline either relatively or absolutely. Thus in the seventeenth century the Europeans
and their descendants on other continents made up approximately 20 per cent of the world's
population; in 1940 they represented nearly 40 per cent of all. people. It appears that an
opposite trend -- a relative increase of Asian and African people ~- has set in more re-
cently. Neither of these trends had been planned. Rather, they were the results of com-
plex circumstances such as the opening up to immigration of sparsely inhabited continents,
of the industrial revolution, of the introduction of contraceptive devices and of improvements
in medical knowledge and of public health measures,

Man is a social being in two senses of the term social. He is social in his being
part of the systems of social organizations which are the unique attributes of man, from
the relatively primitive to the most elaborate social structures. He is social also in his
being one of many animal species who have developed social systems such as small family.
associations, larger herds, packs, up to highly specialized communities such as are found
among bees, ants and termites with their biological castes of queens, workers, males and
soldiers.

Man is an animal in other ways as well. In form and function, development and
growth, reproduction, aging and death he is a biological entity who shares the attributes
of physical life with the millions of plant and animal species to whom he is related. This
has been known since prescientific times. It became part of well established science long
before the theory of evolution was proposed. It is the reason why studies of fungi and mice,
flies and rabbits, weeds and cats and many other types of organisms all have contributed

to understanding man and to improving his health and biological well-being, and why future
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studies with experimental organisms will have their bearing on man's own future.

Man's mental attributes form a superstructure which does not exist independently of
his organismal construction. Human thought is based on the human brain, and the brain
of each person is one of the derived, developed expressions of the genes which he inherited
from his parents. Man's capacities are thus linked to his genes whose chemical molecular
nature is now understood to a very high degree. Although the social creations of man have
an existence of their own and are transmitted by social inheritance from generation to
generation, they depend for their persistence and change on the genetic endowments of the
biological human beings who are subjected to them and who at the same time make them
possible.

The biological discoveries of the nineteenth and twentieth centuries presage further
developments which will enable man to mold his own future evolution. The world of the
highly planned and controlled test-tube babies of "Brave New World" which Aldous Huxley
foresaw forty years ago is certain to become biologically feasible. There is, however, a
time interval between feasibility and social adoption which may be very long. Social systems
in spite of changes in some aspects have great inertia which is the more resistant to change
the more a change would require abandonment of age-long practices. Nevertheless, it seems
unlikely that the inertia of social systems will inhibit forever even the most fundamental
changes, but such changes in attitude may relegate the human use of biological procedures
to a very distant future, long after they have been tested in cattle, monkeys and apes. It is
possible that this view of social inertia is based overly much on past experience. It may be
argued that the radically increased opportunities for obtaining information on all kinds of
subjects which are available to almost all members of modern populations will possibly
greatly reduce social inertia, even to an undesirable or dangerous degree. This may be
particularly true of the peer-oriented or "teen-age" cultures which seem to be a phenomenon
of "advanced" societies. The strength of social inheritance from generation to generation may
be much less in the future with the result that adoption of new biological technologies may be
much more rapid than in the past.

In the following pages, biology and the future of man will be mostly considered for the
short range period ahead as defined by the length of about two human generations or about
half a century. Selecting a few examples, we may consider what is likely and what is unlikely
to happen, what can be hoped for and what feared and what should be done.

In such. considerations, man should be ultimately taken as inclusive of all human beings

on our planet. The brotherhood of all men is not only an ethical imperative but biologically
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it is based on their common descent and on the magnitude of the shared genetic heritage.
Actually mankind is divided into so-called nations which insist on their sovereign status

and the short range future of man will be different from one so-called sovereign group to
another. Our discussion, therefore, will mainly reflect the prospects in developed countries
and regions.

War and the Future of Man

 

The considerations of the future of man which follow presuppose that mankind will
not be subjected to a nuclear holocaust. If such an event would occur, the problems of

retaining or reestablishing
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social organization, the breakdown of health services including the production of drugs,
antibiotics and immunizing agents and the ensuing threat of world-wide epidemics would
take precedence over all other aspects concerning biology and the future of man. It may
well be that modern technology is powerful enough to make complete extermination of man
a possibility. To accomplish such a deed would require not only overwhelming use of
nuclear bombs over large areas of the globe but in addition a deliberate effort to distribute
lethal fall-out radiation evenly over all inhabited regions. Barring such limitless designs,
mankind would probably survive a nuclear war. Radiation biology has demonstrated that
the acute dose of irradiation which kills human beings after momentary exposure is rela-
tively low. Direct radiation from nuclear bombs would therefore take an immense toll,
but the survivors weuld be able again to repopulate the earth. Those who survived the
immediate impact of nuclear explosions would be subjected to chronic irradiation from
fall-out which would likely lead to a variety of deleterious effects. In addition to the dam-
age to their own bodies, the survivors would produce egg or sperm cells which as the
result of radiation would contain many new mutations leading to abnormal offspring.
Nevertheless, the radiation dose which the survivors would have received from the initial
exposure and the accumulation of fall-out radiation might often be low enough to enable
them to produce also normal appearing and functioning children, provided the survivors
would still want to create a new generation.

Similar consideration may apply to the possibility of wide-spread use of biological
warfare. The constructive understanding of life which Biology provides can now be used
for wholesale destruction of life, All war in our time and in the future is liable to grow
beyond control, whether it be conducted with physical, chemical or biological means or
with combinations of all of them. A future for man can be assured only when the ultimate

danger of modern war is fully recognized and mankind abandons warfare.

Biology and Medicine

The most immediate impact of biology on man takes place by way of medical pro-
cedures, Biological research and medical research are intimately intertwined and their
discoveries often cannot be assigned clearly to one discipline or the other. The benefits
of such studies apply to inmmerable individual events, taking place before birth and

extending through infancy, childhood and adulthood to old age. The prolongation of life
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expectancy at birth is one of the impressive over-all measures of the success of medicine.
Nevertheless, it should be emphasized that even in affluent societies this prolongation is
primarily due to a reduction if not a near abolition of infant mortality. Increases in life
expectancy past the age of 45 have remained smaller although by no means negligible.
Different medically advanced countries still have different life expectancies and infant
mortalities. It is noteworthy and regrettable that the United States has not yet succeeded
to equal the best records of other countries. Future advances in the control of disease will
come from better epidemiological knowledge, improved control of the environment and
deeper understanding of the regulation of life processes. Many of these advances will be
' based on applications of the fundamental information provided in recent years by molecular
biology, the science which interprets all life processes in terms of individually simple interactions
of molecules. Still other advances will come from pure technology applied to deficiencies
in the function of whole organs. An artificial lung external to the body replaces the physical
action of the muscles necessary for breathing, an artificial kidney serves as a chemical
device for removing substances from the blood when the biological excretory organs cannot
perform that function. Artificial blood vessels made of industrially manufactured tubing can
serve as substitutes for defective natural vessels, and artificial hearts can, at least for some
time, take over the pumping function of the inborn organ. And if artificial structures are
at present still less adequate than natural ones, transplantation of organs from one person,
alive or after death, to another offers another avenue to saving of life. Transplantation
itself involves the serious problems of immunological incompatibility of the tissues of donor
and host with the threatened subsequent rejection of the transplant as well as its causing
reactions in the host. Modern biology, however, in experiments with chickens and mice
and with cultured human blood cells is well on its way to learn how to minimize such antagon-
istic effects either by the right choice of relatively compatible tissue constitutions, by the
production of immunological tolerance or by combination of both procedures.

These insights and techniques are capable of prolonging life beyond the normal span
but they are creating great new difficulties. One of these is external and linked to social
organization. It relates to the availability of the artificial machines, and the natural parts
used in transplantation. It relates equally to the availability of physicians and specialized
personnel required to apply the techniques of surgery and control of intricate instruments.
Millions of individuals would profit from the transplantation of organs or from the use of

the new spare parts but for years the supply will be inadequate to fill the demand. The
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ethical conflicts are crushing which the physician faces when he is forced to decide who
is to benefit and who is to be denied vital help. At present the occasions for such decisions

are still rare since the numbers of available natural organs or substitute technological
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“organs” are so limited. In the future, numerous new devices will be invented and the
problems of assigning them to specific patients at the cost of withholding them from others
will increase in frequency. Furthermore, even if suchdevices could be made available in
large numbers, the cost of keeping a small fraction of the population alive may be so high
in terms of the gross national product as to compete seriously with other needs for the
well being of the population.

Another difficulty goes even deeper. Relatively little progress has been made in pro-
longing the adequate functioning of the human brain. The perpetuation of the physical
workings of many parts of the body has not been accompanied by a perpetuation of its nor-
mal mental aspects. Here lies a great challenge for basic research and the beneficial
application of the insights to be hoped for. Some of the best minds among biologists,
psychologists and physical scientists have recently turned their efforts to neurophysiology
and brain function. Their studies should help to understand the riddle of the physical basis
of the mind as well as to discover fundamental procedures for alleviating the tragic situation
of keeping the body alive without the full mental attributes which characterize a normal per-
' son. One may confidently expect progress in prolonging the physical and mental health of
the aged but even then the problem of disharmonious functioning will be present at the end
period of a more extended life span. Biology as the science of life has to be complemented
by new insights in the biology of death. The application of such insights will intensify the
concern with questions which already demand answers. How much is society justified in
keeping the aged alive when all mental functions have ceased which distinguish human beings
from vegetating bodies? Where is the limit of anguish and material burden which the rela-
tives of such aged persons and which society at large can bear concerning a problem which is
increasing in frequency and severity? Medical research in aging involves the whole range
of biological phenomena, from a study of the molecular changes of such substances as the
collagen in our connective tissues and bones to the study of the most complex functioning of
the central nervous system with its basis for consciousness, learning, reasoning, memory
and other psychological attributes. Support of research in aging and support of the aged cannot
be considered separately from economic and demographic facts. The need for support of
research which will benefit the physical as well as mental health of the new-born and that of
young people in general may compete in terms of personnel and material resources with the

requirements of research on aging. The need for dedicating large-scale support to children
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and adolescents may limit the support society can devote to keeping the aged alive beyond
a reasonable state.
Genetic Diseases
The main illnesses of man have changed greatly in importance during the last hundred

years. Infectious diseases have been combatted effectively as their biological nature became
clarified. For example, malaria was recognized as being caused by mosquito-born protozoa,
tuberculosis by bacteria, and influenza by viruses. Sulfa drugs and the antibiotics were found
to kill the infectious agents without damaging the host. Other diseases, like rickets and

scurvy, were shown not to be caused by the presence of an abnormal agent but by the absence

of normally required substances, the vitamins. Recognition of needs for vitamins have
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greatly reduced such deficiency diseases. Many diseases which still plague man are "inborn
errors” which, as the effects of abnormal genotypes, lead to gross congenital malformations
or to subtle derangements of metabolism. Some of these inborn errors are now understood
in biochemical terms. Phenylketonuria, to take a famous example, is an inherited condition
in which an enzyme, formed in the liver of normal persons, is not synthesized in the liver
of affected persons. A single kind of gene present in normals and absent in phenylketonurics
is responsible for the difference. The result of the absence of the enzyme is an accumulation
of a substance, phenylalanine, in the blood, which normally is transformed by the enzyme
into some other substance. The accumulation results in brain damage expressing itself in
mental defect. The gene effect can also be discovered soon after birth by the presence of an
abnormal derivative of phenylalanine in the urine. It took twenty years to unravel the bio-
chemistry and genetics of the disease. Only then did it become possible to devise a treatment
for it. Phenylalanine is a constituent of proteins which are an essential part of our diet. If
beginning with infancy a phenylketonuric individual is given a special diet very low in phenyla-
lanine, development may proceed in improved fashion and the mental abilities of the child may
approach normality.

It is hardly more than ten years since phenylketonuria has been treated this way and the
last word has not yet been said about the degree of success. Nevertheless, phenylketonuria
is an example of modern medicine's attack on genetic disease. Although the defective gene
itself which is responsible for the absence of the enzyme cannot be cured, its effect can be
circumvented. Such procedures have been termed euphenic, "eu" meaning well, and 'phene"
meaning appearance, Euphenics can overcome the ill effects of the genetic endowment to
a greater or lesser degree. There are many ways for euphenic treatment of unfavorable
genotypes. Thus, in diabetes, a genetic disease with apparently a more complex biological
basis than in phenylketonuria, abnormalities in the production or utilization of the hormone
insulin exist which result in defects of carbohydrate metabolism, In this case the defect is
overcome to a considerable extent by furnishing the body with insulin from the outside. Or,
in a congenital malformation such as cleft lip and palate, modern plastic surgery is able not
only to save the life of severely affected infants but also to produce an esthetically acceptable
appearance. It is clear that a euphenic solution has to be discovered separately for each genetic

effect. Only a few such solutions have been found and further search will be an important area

of biological efforts. Such work illustrates the fact, first clearly demonstrated in studies
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of plants and animals, that genetic determination of abnormalities does not imply an unchange-
able fate. In man, many genetic errors may be made more or less innocuous by biomedical
treatment. There is valid reason to expect that future work will greatly extend the range of
euphenics to errors which are still beyond repair.

Early Environmental Influences

 

External conditions may not only ameliorate genetic defects, but they can also depress ©
normal development. Expressed in a different way, inadequate environments may lead to
defects in genetically adequate persons and improvement of the environment may tend to
decrease defectiveness. One area to which interests have been directed more recently is
that of the effects of early environmental influences,

As commonly used, the phrase "early influences" denotes the conditioning of behavior
by the experiences of very early life. Early experiences, however, do more than condition
behavioral patterns; they also affect profoundly and lastingly most biological characteristics
of the adult. In animals and men, events occurring during the prenatal or early post-natal
period condition the initial growth rate, maximum adult size, efficiency in utilization of food,
resistance to malnutrition, to infection, and to other forms of stress.

Early influences affect some of the most obvious characteristics of human populations.
Throughout the past century, for example, there has been a constant trend toward greater
size, and earlier sexual maturity of children. This phenomenon was first detected in the
United States, then in other Western countries; it is now particularly striking in Japan and
in other areas that have adopted Western ways of life. Evidence for increased growth is
provided by the greater heights and weights of children at each year of age; by the faster
growth rates during adolescence for both boys and girls; and by the earlier age of the first
" menstrual period,

Early influences can also affect growth, mental ability, and health in a deleterious
manner, This is readily documented in the underprivileged areas of the world and in the
economically deprived segments of our own populations. Very high infant mortality, slow
rate of growth during childhood and adolescence, physical and mental lethargy continuing
throughout life, are among the pathological manifestations commonly observed in deprived
social groups. These disorders are not racially determined, For example, they are found
alike among the deprived Indians of Central America and among the populations of European
origin who share the Indians’ ways of life. In contrast, these disorders are rare among
Indians and Latin people born and raised in social and economic environments similar to

those now prevailing in the prosperous communities of the United States and Europe,
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Epidemiological studies of human populations provide evidence that the most important
effects of the environment are those experienced during early childhood. When environmental
agencies act on the human organism before puterty, their anatomical, physiological, and
psychological effects are to a large extent irreversible; the fact that the various tissues and
organs develop at different rates after conception and birth accounts for the existence of
several "critical" periods in giving complete or partial irreversibility to responses that the
developing organism makes to environmental forces. In the human species, the critical
periods for the development of the various mental capacities probably occur before the age of
6 - 8, a phenomenon of great relevance to the determination of "intelligence" in different
socio-economic and ethnic groups. In contrast to the effects of the environment before the
termination of critical periods, they are more likely to be reversible when experienced
after the end of differentiation and development.

Practically all effects of prenatal and early post-natal influences so far recognized by
clinical and epidemiological studies of human populations occur also in other animal species.
A large variety of stimuli, acting on the pregnant animal during gestation, or on the young
shortly after birth, can affect almost every type of phenotypic expression throughout adult
life. This is true whether animals live under natural conditions or in the laboratory.

Exposure to toxic agents; malnutrition, undernutrition or overnutrition; overt or
subclinical infections; mothering” deficiency of the lactating dam; emotional disturbances
of the mother or of the young; crowding, isolation and other forms of social deprivation --
are but a few of the variables that have been used to design experimental models for the study
of the effects of early influences. The effects of these influences on adult life have been
studied with regard to anatomical structures, physiological characteristics, metabolic
activities, behavioral patterns, and learning ability. In all cases "critical periods" have
been recognized, differing as to initiation and duration depending upon the nature of the
early influence, and of the effect studied.

Many experiments have been made in various animal species, and they have led to
the development of several reproducible models, but the body of knowledge concerning the
effects of early influences is nevertheless extremely superficial and indeed episodic. Even
the phenomena that have been most extensively studied -- such as imprinting, the fixation
during a critical period of a young animal's life, of the stimulus which subsequently elicits
a particular response -- are poorly understood even though highly reproducible in their
details. In the absence of broad scientific generalizations, it is not possible at present to
extrapolate from one animal species to another, let alone to man. Yet there is no doubt that

early influences are of great
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importance in human life; knowledge of their potentialities points to the safest and most
effective way of affecting the physical as well as mental development of man.

The study of the effects of early influences can be conducted at several different levels.

a) Epidemiological observations in man, taking advantage of the fact that the different
human societies exhibit an extremely wide range of customs with regard to gestation, parturi-
tion, lactation, physical and behavioral management during the early postnatal period. Dif-
ferences in social patterns can be considered as experiments on man, carried out without
awareness of their consequences, that cry out for careful description and analysis.

b) Development and refinement of experimental models in various animal species,
To yield the greatest scientific rewards, these models will have to use laboratory animals
of known genetic and experiential history. It will be essential furthermore that these animals
be kept under observation throughout their whole life span and preferatly for several succes-
sive generations. Needless to say such longitudinal studies will require much improved animal
quarters, extensive facilities for recording and retrieving information, and probably a new
type of scientific organization,

c) Analysis of the mechanisms through which early influences exert their lasting
effect. It is neither possible, nor necessary to discuss or even list here the many types of
experimental approaches that will have to be followed in such analysis. It is worth pointing
out, however, that understanding of the mechanisms through which early influences condition
the fate of the adult will go far toward giving a new and more dynamic character to anatomical,
physiological, metabolic, and behavioral studies. Environmental stimuli are most effective
in shaping the phenotypic expressions of the genotype when they impinge on the organism
during the early phases of its differentiation and development.

The Demographic Need for Biological Knowledge

 

It is now common knowledge that the upsurge in the growth of human populations con-
stitutes one of the major problems for the immediate future of man. In view of the world's
problems of population growth, it is difficult to exaggerate the urgency of deepening our biologi-
cal knowledge of man and his environment. By the end of the century, a brief thirty-three
years from now, there is every reason to expect that the world will have almost twice its
present population. Unless forestalled by a worldwide holocaust, the world in the year 2000.
will almost surely have not fewer than five billion people, and the number may well exceed
seven billion. World population will rise from the present figure of 3.4 billion to seven billion

even if the present rate of growth declines, and since the means for improving the control of
~]2=
disease are already at hand, the seven billion figure would be reached even if present

birth rates were to be considerably reduced. This growth is occurring most rapidly in
the newly developing nations where abject poverty is widespread, the mass of the popula-
tion is uneducated, and the modern sectors of the economies are poorly developed.

Moreover, coming demands on the biosphere are not to be measured exclusively by
the expected growth of numbers. The present population is badly nourished, and popular
aspirations for improved living conditions are high. Even a doubling of per capita consump-
tion of food, clothing and shelter would leave present aspirations unfulfilled. If political
order is to be maintained, it is not unreasonable to expect that the demands on the biosphere
by the end of the century will be from four to six times those of the present. The problems
of attaining such increases become staggering when we realize that the end of the century
is so close that this year's infants will then be in the heart of their childbearing period.
Moreover, a reasonable regard for the human heritage requires that the needs be met
without despoiling either the quality of man or the material base from which he draws his
life. |

Clearly a catalog of needed knowledge is a catalog of an entire field -- the nature of
man and his modes of change, the extra-human biosphere, and its interaction with man
and with the physical environment. But this is just another way of saying that man's destiny
turns on his knowledge of himself and of his total environment -- inanimate, biological and
social, In the face of a desperate situation, almost nothing becomes irrelevant in the entire
spectrum of basic and applied science.

In the long run it is clear that: (1) population growth cannot continue indefinitely, and
(2) if we can have a world in which the major populations have been brought to a high level
of education and scientific achievement, the ultimate constraints to population growth will
not appear until populations become larger than they are now. Such a world might, and
probably would, find it desirable on humane and esthetic grounds to check its growth far
short of the numbers that could be supported in considerable affluence by economies that
continue to develop their basic and applied sciences. To such a world a knowledge of the
gene pool, and of its potentialities for change, might be more important than anything else,
because in the last analysis man's destiny lies in his nature.

But today's most urgent problems are not those of a world of highly educated and
prosperous populations, They are the problems of moving from our present position of
widespread poverty and mass illiteracy to a high stage of worldwide education and prosperity.
To do so we must survive the crisis of population growth with sufficient political and social

coherence to permit the sensible application of our developing science. The difficulty about
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crises is precisely that they place such a heavy discount on matters of future as compared
to those of immediate relevance, Many of these immediate problems lie in the social,
economic and political fields, but it is to the biological aspects of the emergency problems
that our attention is here directed.

The first and most basic problem is that of food. The facts need not be spelled out.

It is only necessary to note that: (1) most of the world is undernourished; (2) populations

in the Americas south of the U.S., in Asia, and in Africa are growing at between 2,3 and 4
per cent per year; and (3) agricultural production is barely keeping pace with population
growth and in some instances is falling behind. Production per acre has been increasing
rapidly in the highly developed areas of the world, but it has been rising very little in the
underdeveloped nations. In the latter, gains in production have come primarily from the
extension of acreage rather than from increased product per acre. Moreover, the constraints
to the extension of acreage are becoming all too visible in many of the most densely settled
parts of the world. -

These facts suggest that: (1) there indeed will be starvation with tragic checks to
population growth unless there is a prompt and major rise in production, and therefore
(2) the most urgent need is for the application of existing knowledge rather than for the devel-
opment of basic science. Indeed, the practical application of our present basic science would
go far toward coping with the problems of food supply during the present century. The prob-
lems are applied ones of a practical nature but they are nevertheless squarely in the scientific
field. Basic theory does not bring increased production without a great deal of scientific work
on local soil and water, crop management, animal husbandry, pest control and fertilizer. Our
basic science gives us the principles and tells us how to go about learning to apply them, but
it still does not tell us in precise and local terms how to do the multitude of things that must
be done. There is a vast amount of particular and detailed scientific work that must be done,
much of it at the local level, before our basic science can yield essential gains in the production
of food and fiber, The emergency need in agriculture is for great increases in applied work and
-in training for such work.

The fact that much of the basic sciences is a product of a.small number of nations and
civilizations does not mean that the basic sciences-cannot be learned, devel oped and applied —
by other populations. Even though we have no means at present of comparing the genetic
endowments of different ethnic groups, it is clear that great reservoirs of trainable genotypes

exist in all of them. The shortage of brain power in the world at large, which can be applied
-]4-
to the immediate problems of agricultural production is not due to biological limitations
of genetic endowments in different human groups, but to the limitations of education. Each
area is potentially able to produce the numerous persons who are needed to explore and
solve the specific problems which the region poses. These problems, obviously, are not
restricted to agriculture. A corps of local specialists is equally needed so that each popu-
lation may share in the beneficial results of industrial and scientific technology.

The emergency problem of population growth involves much more than merely increas-
ing agricultural production. The constraints to population size are all too visible in the tra-
ditional self-sufficient agrarian society. Such societies have never been able to combine
high population density with good health and relative freedom from poverty. On the other
hand, it is hard to specify the limits to the density of population that can be supported in
health and prosperity by a highly educated population making sophisticated uses of inanimate
energy and raw materials, and continuing to develop both its basic science and technology.
One would hope that such a world population would want to limit its size before it was compelled
to do so to protect either its health or its prosperity. The emergency problem is not that
of keeping the population below some particular figure. The emergency problem is that of
attaining as rapidly as possible high levels of education, science and technology for a major-
ity of the members of the human race.

If this estimate of the situation is correct, the problem is not that of population size
itself but of the speed of modernization and the extent to which it is checked by the speed of
population growth. The speed of modernization turns on many factors, among other things
on the national and international allocation of resources as, for example, space, war,
schools and factories. But basically it also depends, even down to quite local levels, on
the extent to which the growth of production outstrips that of population. Investment in devel-
opment can be made only after the current costs of growth have been met.

One way to find income for development is to increase production. Another way is to
decrease reproduction, and both ways are clearly needed. The two are not quite on an equal
footing. It is not difficult to imagine too much production of the wrong kind, but it is difficult
to imagine too much production as such. On the other hand, some methods to decrease the
rate of population growth that would be undesirable in nature, in amount, or both are all too
evident. As a practical maiter we need not be concerned, because no one will advocate re-
ducing growth by increasing death rates for his own group, and in the newly developing

countries there is no practical possibility of bringing rates of natural increase below one
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per cent per year in the near future Moreover, populations that have learned to reduce
their fertility to the point where even with good health growth amounts to only one per cent
should encounter no substantial difficulty in reaching a stationary position if that is clearly
desirable. It may be justifiably asked, however, how many countries can be expected to do
this soon enough.
If the foregoing is correct then the second most important emergency problems of
a biological nature are those concerned with a reduction of human fertility. In the long
run birth rates must come down if death rates are to stay low, and in the short run lower
fertility would speed the process of modernization by widening the difference between the
growth rates of population and of production. Reductions of the birth rate in the under-
developed countries have an additional advantage. High birth rates produce high proportions
of young people. In fact, virtually every country with 40 or more births per 1000 population
has more than 40 per cent of its total population at ages under 15. In the advanced countries
low birth rates give between 25 and 30 per cent of the total at ages under 15. A reduction in
birth rates brings down rates of growth and reduces the proportion in the ages of childhood
dependency. Correspondingly, it increases the proportion of the population in the productive
years of life.
Indeed, very high birth rates speed population growth in two ways: (1) they swell the
entering stream of life, and (2) by creating young populations they cut the rate of depletion
‘through death. -Today, the lowest crude death rates (i.e. annual deaths per 1000 population
uncorrected for age) are not found in the most highly developed countries. The world's
lowest crude death rates are found in such places as Taiway, Singapore, Puerto Rico and
Chile, where the health protection is good and where a history of high birth rates has left
a young population. In the long run, reductions in birth rates reduce growth both directly
and indirectly by increasing the average age and, other things being equal, the death rate.
Clearly the possibilities of modernization would be greatly enhanced if rates of growth
could be cut in 15 years from, say, three per cent to one per cent by reductions in birth rates.
This would mean that populations now growing at rates that double their size in 23 years would
come to a rate that would give them 69 years in which to absorb the increase. It would mean
that the burden of natural increase in the newly developing countries would then be about that
experienced by the United States last year.
One of the most important aspects of the population problem is the attitude of people

toward a preferred family size. Although it is true that most societies and individuals desire
-l5a-

to limit the size of families, they are usually not in favor of a family size corresponding to

zero growth of the population. Efforts of family planning have fallen short of accomplishing

the fundamental goal of changing the attitudes of people from a desire for overall increase in
population to a recognition that in the end the mean family size has to be limited to a replace-
ment value.

Apart from influencing the motives of people in regard to family size, nothing can do more

to help obtain reductions of fertility than the development of more efficient, cheap, safe and
acceptable methods of contraception. It is often pointed out that people will use even the best

of methods only when they want to have fewer children and
-16-

much is often made of the fact that in the developing countries people place a high value on
large numbers of children. It is also true that strongly motivated couples wiil utilize inade-
quate methods of birth control and crude abortions, and that weakly motivated populations need
the best possible methods. Today, the situation is much more nearly ready for the widespread
practice of contraception than is commonly supposed. More than half of the population of the
newly developing nations live under governments that have decided as a matter of national
policy to foster the spread of family planning. The list includes most of the countries of
Asia, and a goodly number in Africa and Latin America. Most of these countries are develop-
ing educational programs to interest and inform their people, and service programs to give
them supplies. Careful surveys of attitudes toward reproduction have been made in some
20 countries. They have shown that virtually everywhere the majority of women want to limit
their childbearing. This does not mean that they want only two or three children. But it does
mean that they want to stop before their families get truly large. Moreover, where services
and supplies are made available women are coming seeking them in large numbers. Taiwan,
South Korea, Hong Kong and Singapore have clearly reduced their birth rates through their
family planning programs. In short, there is the appropriate governmental policy, the
demonstrated interest, and the beginnings of actual success in reducing birth rates. Nothing
in the biological field would help speed the process more than the development of better methods
of contraception. Nevertheless, it must be stressed that further changes in attitudes to family
limitation are still greatly needed. It is not sufficient to help couples plan for limited family
size as long as the size desired remains much above that needed for checking population growth.

Today, in the developed nations, contraception has changed rapidly from the conventional,
methods to the combination steroid pill. In the under-developed countries, the new contraceptors
are mainly using the modern plastic intrauterine device (IUD). Neither method is perfect, but
both methods, are spectacularly effective and successful when compared with the
conventional contraceptives.

It has been the intrauterine device that has given the encouragement to governments of
underdeveloped nations to build the organizations they require to spread family planning

practices. Because those organizations are being built, the next technological innovation can
-17-

be introduced much more rapidly. It is because they have effective methods, hope for
better ones, and have the organizations to make use of them, that such countries as South
Korea, Taiwan, India and Pakistan begin to talk about cutting their birth rates in half in

15 years. If they could do so, their long-run problems of modernization and economic de-
velopment would be greatly simplified.

The world needs better methods than are now available. Clearly the pill and the
intrauterine device represent major innovations because they separate contraception from
coitus, and both are safe and effective. The intrauterine device is probably at a very early
stage of development. We know that there are too many patients who spontaneously eject it,
who bleed and have discomfort. On the other hand, apparently the majority of those who
accept it wear it without awareness and with very high effectiveness. It now seems that two
to three years after acceptance 50 per cent or more of women are continuing to wear their
devices. It is likely that better procedures, better materials, and better shapes will lead
to a greatly improved experience. Investigation must also seek to solve the riddle of the
intrauterine's mode of action and to ameliorate its occasional side effects.

Similar work is needed on the steroid pills to reduce their side effects, to minimize
their effects on lactation, to reduce their costs and, perhaps most important of all, to
find out systematically and in sustained fashion the actual experience of those who take them.

Work is going forward in a number of places with doses of progestins so small that
they seem to limit their effect to the uterine level. Similarly, much work is needed to find
means of replacing the oral route of administration with a depot injection, i.e. an injection
allowing a steadier rate of absorption and hence, possibly lighter and longer-lasting doses.
It would be highly desirable, of course, to have a method that is permanent until positive
measures are taken to counteract the contraceptive. Children are often conceived as a
consequence of careless contraceptive practice. Doubtless birth rates could drop faster
if there were a method in which carelessness meant failure to counteract a contraceptive.
Clearly, however, such developments could pose serious problems of personal freedom unless
the counteracting agent were freely available.

Only a beginning has been made in basic research. Among other things, we need to
know a great deal more about tubal events, including gamete transport, fertilization and
zygote physiology. The fields of neuro-endocrinology, immunological suppression of repro-
duction, blastocyst nidation, gonadotropin chemistry and mechanisms of hormone action

urgently need development. A crash program of basic research might produce very
-18-

important results. The fundamental knowledge, the techniques, and the requisite base of
professional skill for such an effort are now beginning to appear.

Perhaps a word about the merits of basic as compared to applied research is relevant.
In the long run, of course, all practical results depend on basic research. But in the long
run populations will take on multiples of what they are now unless death rates rise. Indeed,
unless birth rates drop immediately and substantially the world's population may well increase
by more than 50 per cent in the next 15 years. In the past decade it has been the applied work
based on many years of preceding basic research that made possible the contraceptive pills,
the intrauterine devices and consequently the beginnings of a birth rate decline in some of the
newly developing areas. It seems likely that the intensification of applied work holds the
greatest possibility of yielding practical results in the next few years. Basic research continues
to be greatly needed in order to prepare for new advances in areas already worked upon and
perhaps for completely new approaches in population control. In addition, however, the intensi-
fication and enlargement of practical work is an urgent necessity. This expansion of practical
work should not occur at the cost of efforts in basic research. However, on the problem of
population control which confronts mankind now, time is an important dimension which must
be met by greatly intensified applied studies.

Basic research is greatly needed in another aspect of population control, the problems
of the possible long term effects of various contraceptive techniques. To some extent this can
be explored by epidemiological methods analogous to the studies of the relation between smoking
and cancer. Such epidemological work should be complemented by research which hopefully
would result in predicting effects through thorough knowledge of the full physiology of operation
of contraceptives.

Man and His Environment

 

For thousands of years past man has changed his general environment. Deforestation
and primitive methods of agriculture have denuded whole areas and exposed their soil to
erosion. Excessive hunting of animals for food and of the large predatory animals in self-
defense has wiped out many species either wholly or in many regions. Recently the rise
in population density and the developments of modern industry have led to pollution of air,
water and soil. In addition, deliberate large-scale use of pesticides has started a chain in
which such substances are accumulatedin plant and animal tissues and, if taken in with human
food, become deposited in the human body. Similarly, the routine addition of antibiotics to
the feed of domestic animals may lead to ingestion of such chemicals by man. The effects of
these changes in man's environment are not known.

It may well be that some of the agents to which man is now exposed will cause serious
-18a-

diseases, shortening of the life span, decreased fertility, and deleterious mutational changes

in genes. Such possible effects may be numerous and yet difficult to discover. This, however,
does not imply that dangers do not exist. It has taken decades to establish the relation between
smoking of cigarettes and lung cancer and the same may hold true for the relation between new

factors in our environment and new diseases (see Reports on Environmental Health, and on

Ecology).
-19-

Unlike the effects of acute heavy doses of deleterious substances, which lead to severe
immediate illness, pollutants are taken up in small amounts and over long periods. Their
effect, therefore, may be delayed for years or even decades. Moreover, different individ-
uals may react differently to the same exposure of a foreign substance. Some may excrete
more of it than others and thus unload the body. Some may decompose the agent in their
tissues where others may leave it unchanged. Some may be more resistant to its effect.

If, as an arbitrary figure, 1 in 1, 000 individuals will suffer ill effects from a specific agent,
only very large-scale studies of whole population groups will reveal them. Such studies
would have to make use of large cohorts of individuals which are followed in their pattern

of diseases, fertility and life span over very long periods -- longer than the life span of a
single generation of investigators. There is some precedent for such studies in the research
on the relation of smoking to lung cancer, but the scale of such studies must be greatly expanded.
And it may be remarked that while 1 incident in 1,000 seems a small effect, in a population of
200 million it would signify as many as 200, 000 individuals who experience damage.

What has been said for contaminants of the environment applies in different form to
substances which are intentionally ingested. Only large-scale epidemiological research will
reveal whether the contraceptive pills have or have not long-range effects on their consumers,
and whether this is true for the variety of pain killers, sleeping pills and tranquilizers. The
Federal record systems, and particularly those of the Veterans Administration and the
Department of Defense are already available for epidemiological and veterans follow-up studies.
They could be made still more valuable by the availability of record linkages, the system of
linking together the many independent records of births, illnesses, deaths, of defense and
social security agencies and many others. While this system entails the possibility of intru-
sion into the privacy of individuals, it should be possible to erect safeguards against misuse.
Such safeguards will be effective if a climate of opinion prevails that welcomes the attainment
of useful information and at the same time frowns on attempts of authoritarian types toward
improper exploitation of linked data. Man's biological future depends on knowledge of his
experiences, good and bad, and record linkage is one important means of acquiring such
knowledge.

Even more subtle than the effect of specific agents on man may be the effects of the
changes in his general living. Urban aggregation has removed many men from natural sur-
roundings. The level of environmental noise caused by industrial procedures and automobile

and airplane engines has added a new dimension to sensory exposure. The crowding together
of individuals in overpopulated regions has changed greatly the interrelations between people

who only a few thousand years ago formed small bands with minor contact
-20-
with one another, The modern development of the science of animal behavior is beginning to
give some insight into the interrelations between genetically founded behavioral attitudes and
the effects of training and of the individual's environment on overt behavior. We are prone
to think of hostility, crime and other antisocial behavior as conditioned by social circumstances.
There is indeed ample evidence for it. We do not know, however, how much of personel
unhappiness and social distress is a consequence of man's basic biological nature in conflict
with an unnatural social and an unnatural non-human environment. The stereotyped movements
of caged polar bears and of other animals in captivity have their analogies in mentally ill patients.
These modes of abnormal behavior may only be extreme expressions of maladjustments of the
human animal. It may well be that research in behavioral biology will furnish deep insights into
man's nature and that application of these insights may lead in the distant future to fundamentally
new measures of environmental engineering. These will endeavor to fit the environment to man
instead of leaving man unfit for the environments which he created. A minor, yet perhaps
important tool for such studies are the variety of non-human primates, apes and monkeys.
Every effort should be made to assure their survival as species,

Scientific advancement enabled man to triumph over his environment. With technological
skills and machinery we are able to move, change, and control our natural resources for our ag-
riculture, forestry, fisheries, recreation, and urban and industrial development. Civilization
depends and will continue to depend upon the renewable resources of the environment -- land (soil),
water, air and populations of plants and animals both wild and cultivated. Fortunately, the public
is becoming increasingly concerned about the status of these resources and the vital role they
play in our survival and general well-being.

. Environmental pollution has become of increasing concern as the human population con-
_gregates in cities and occupies more of the landscape. ‘The public will be pressing for a
greater understanding of the function and interaction (ecology) of biological and physical
elements of the environment and to apply this understanding to the management of renewable
resources to supply man's food, clothing, and shelter. Future needs will call for more than
just the maintenance of these biological essentials of life, because the public is becoming:
aware of the importance of beauty in its surroundings.

In the future, biologists should work jointly with engineers to design cities of quality
and beauty. Structures for dwellings and industry should be surrounded by green lawns and

plantings of ornamental trees, shrubs, and flowers. Whether in the city or country, clean
-21-

air and water will be the desired standard. Through care and planning in the sciences of
agriculture and forestry, the landscape of the country will be conserved at the same time
taking on a simple charm without billboards and auto grave yards. Certain areas will be
preserved forever wild for recreation. Environmental biologists along with other interested
scientists shall be leaders in developing a strategy for the wise use of our renewable resources
while at the same time attaining an attractive environment. (These topics are treated in detail
in the earlier section on renewable resources.) Clearly, however, the attainment of such
goals does not depend alone on the technical skills of biologists and other scientists and
engineers. Fundamentally, people must have the desire to live in harmonious environments.
Without broad social motivation supporting their use, the knowledge and the skills of the
specialists will lie fallow.

Selection and the Variability of Man

 

Even without scientific knowledge of genetics in the past man has been able to create
a great variety of genetically different strains of domesticated animals and plants. The
main agent of such breeding has been selection of desired types. The wild ancestors of
cattle, dogs, chickens, wheat, corn and all other organisms appear rather uniform. Neverthe-
less special procedures such as close inbreeding have shown that a very great amount of
concealed genetic variation is present behind the apparent uniformity. This variation enables
man to select for traits which appear desirable to him. It has been such selection which
led to the establishment of cattle specialized for milk or for meat production, the astonishing
manifoldness of races in dogs, and of the types of chickens high bred for egg laying or for meat
yield. Similarly, selection has led to disease resistance, heat tolerance and other physiological
states. In plants, strains have been selected which are adapted to many climatic and soil con-
ditions, as well as for yields which surpass by far those attained in the wild state.
In man selection has gone on without conscious direction. The different racial groups

of mankind differ from one another in many ways. The significance of most of these differ-
ences is unknown or at least only incompletely understood. Why do the average body sizes
of different populations vary from the pygmies of Africa to the tall Watusis of the same

. continent, from the shorter Southern Mediterraneans to the taller Scots? Why are the facial
features of the Orientals different from those of the Caucasians? It is possible that some of
these differences just happened to arise by the chance sampling of genetic types in the distant
past when man lived in very small widely separated groups. It is suspected that many others

of these differences were the result of natural selection. Dark pigmentation of the skin is an
-2la-

asset in the tropics where protectionof the tissues against too much ultraviolet radiation is
necessary. Light pigmentation is an asset in northern regions where enough ultraviolet ight
must penetrate below the surface to transform ergosterol into vitamin D. Long limbs are
advantageous as radiators of heat in desert people while short extremities are useful for
conserving body heat in arctic climates. What is useful, natural selection preserves, and

what is of negative value it rejects.
-22-
While it is obvious that the racial groups of mankind differ from one another in
specific ways, there is an inclination to consider each such group as rather uniform in
itself. This, however, is far from true. The multitude of differences in facial features,
body build, height, and other physical as well as mental traits should long have served to
correct the false impression of uniformity within given populations. Moreover the poly-
morphic nature of any human group -- and that of every other species studied intensely,
e.g. cattle, chickens, flies -- has become dramatically clear in recent years. Every
human group contains a great variety of genes for alternative blood group properties, proteins,
and enzymes and new polymorphisms are constantly added to our knowledge. Thus, in every
population there are people belonging to blood group M, others to N and still others to MN,
Why should there be a variety of genes determining these properties instead of a single type
best fitted to survival and therefore having become fixed by natural selection? What is not
-only the biological but also the sociological significance of polymorphism? Our inability to
answer these questions for most, if not all human polymorphisms is evidence for fundamental
gaps in our understanding of the genetics of human populations. There must exist selective
forces of such nature as to retain variety of genes rather than eliminate. all but one of each
kind. How these forces act specifically, so as to enhance survival of one gene under certain
genetic or environmental circumstances and to decrease its survival under other circumstances
is not known and needs to be established in each individual case. If we do not know how we
became polymorphic in the past and how we retain the polymorphism at present we cannot
expect to predict the future. We are only beginning to be able to define some of the key
problems in the biological future of our species and are still groping our way towards finding
the means of their solution.
The complexity of selective forces is likely to make necessary the follow-up from
birth to death of exceedingly large cohorts and their analysis will require the use of very
powerful computers. The biological insights to be gained will teach us the causes of the
great load of biological losses in the form of abortions, stillbirths, prereproductive deaths,
‘deaths before the end of the reproduction period and of reduce fertilities and infertility.
Notwithstanding the complexity of genetic population dynamics man has reached the
stage where certain gross interference with natural conditions has become possible. It
would not take many generations to breed Caucasians whose average adult body size is four
feet or Japanese of 6 feet average height. We could breed for obesity or leanness, blue eyes
or black, wavy or wiry hair and any one of the physical attributes in which human beings vary.

We could also breed for mental performance: high and low scores in overall] intelligence tests,
~23 -
for special properties like spatial or verbal capacities, perhaps even for cooperativeness
or disruptive behavior. Most of these traits vary not only genetically but also under the
influence of environmental factors, as for example size and weight with food, mental scores
with social attitudes and educational opportunities. This, however, does not negate genetic
components in the determination of the variety of traits, The "heritability" of a trait which
is a measure of the part which genes play in the observed variability of the trait may be
large or small. More research in respect to heritability of human traits is needed but it is
clear already that selection can be effective even with traits of very low heritability.

If man has reached the stage of being potentially able to select his own genetic consti-
tution he has not yet made use of his power. Selection is a harsh process. To make speedy
progress reproduction should be limited primarily to those who possess genotypes for the
desired traits. Who will decide what is desirable? How much genotypic and phaenotypic
‘variability would be optimal in the human society? Who would dare to prohibit procreation
to a majority of men and women? May we expect changes in attitudes of whole societies so that
they would accept the self-control of human evolution at the cost of foregoing the private
decisions of most people to propagate themselves in their own children? It would not seem
likely that such changes in attitudes will come soon. The future of man, however, will
extend over incomprehensibly long times, long enough not only to ponder possibilities but
also to explore them in actuality.

In order to overcome some of the objections to all-out self-selection by man, the late
geneticist H. J. Muller was an advocate of partial selection for the betterment of mankind.
Starting from the practice of using artificial insemination in sheep and cattle, Muller proposed
the deep-freeze storage of the sperm of the most distinguished men. Such storage was intended
to extend over a long period -- perhaps until decades after the death of the sperm donors -~"
in order to give perspective to the judgment of their being unusually distinguished. The sperm
of those who withstood the test of time would then be made available to married couples. A
child produced by insemination with donor sperm would have the wife and the donor as its
biological parents while the husband would, like an adoptive parent, exert his influence on the
child by his personal attributes. This scheme of procedures has a low genetic efficiency as
compared to procedures in animal breeding. Its emotional appeal too is limited. Yet its
control over man's genetic future granting its limitations, is accomplished by methods which
leave room for free choice. Moreover they are already employed in numerous cases of

infertility of a husband without, however using the opportunity to choose unusually distinguished
sperm donors.

A much more efficient and a most revolutionary way of selecting for specific human
genotypes has been suggested on the basis of experiments with frogs and other amphibians, --
experiments whose original purpose had nothing to do with plans for genetic selection. It is
possible to take a frog egg before fertilization, remove its nucleus and instead of fertilizing
it with sperm implant the nucleus of a body cell from a frog embryo. Such an egg can develop
into a normal frog individual. It has the same genetic constitution as the frog embryo whose
body cell provided the transplanted nucleus. If the method of nuclear transplantation with
resulting full development should become successful with the nuclei of body cells of adult
individuals and if it could be applied to man, a most powerful means of controlling the genetic
constitution of future generations would become available. Such a method avoids a great drawback
which is inherent in the use of normal eggs and normal sperm in selection experiments. The
process of formation of germ cells in the ovaries and testes brings it about that any germ cell
of even the most distinguished individual carries no more than one half of his genes but also
each given germ cell differs from all others by carrying a different assortment of one half
of the thousands or hundred thousands of genes. The use of selected sperm from selected men
does not, therefore, provide a means of transmitting their genetic constitution. It increases
the probability that certain genes which lead to desired effects will increase in the population
but, as already mentioned, the efficiency of the method is low. Moreover, the different genes
of an individual do not produce their effects in isolation from one another. A person may be
distinguished less by having specific genes and more by having specific combinations of them.
These combinations have an overwhelming chance of being broken up in the formation of germ
cells. The nuclei of body cells, in contrast to those of germ cells, retain the totality of the
person's genes so that a child produced by an enucleated egg which was supplied the nucleus of
a body cell would genetically be equivalent to an identical twin of the donor of the body cell.
Husbands might wish to have daughters who were identical genetically to their wives. This
could be accomplished by using a nucleus from the wife's body tissues. Wives might want
to have sons identical to their husbands. Other couples might wish to propagate the genotypes
of unrelated persons. Moreover any desired multiple number of such a genetic twin could be
produced. It would require the collection of unfertilized eggs from the oviducts of many women,
removal of the egg nuclei and replacement by the nuclei of body cells of the chosen man or
woman. This would be followed by return of the eggs to the uteri of women who then would

undergo a normal pregnancy. In this way one could produce identical copies by the tens,
~24a-

hundreds or thousands of any person judged admirable: Mozarts, Shakespeares, Lincolns
and Einsteins.

Technically, it is still a long way from the use of frogs eggs to those of humans, but
what can be done in frogs today will hardly not be possible in man tomorrow. The biological

problem
-25-
now is primarily one of skill and development of detailed procedures. The first steps would
probably be the extension of the experiments from amphibians to laboratory mammals. Once
successful in mice or rabbits there would be practical applications to animal breeding. Prize
bulls or cows would be perpetuated by identical "offspring" derived from their body cells.
From there the steps toward potential human use would not be difficult technically. If there
is a strong wish to make such potentialities a reality, it could probably be accomplished within
a few decades. Whether there would be general social acceptance for the practice of such
radically new procedures in a foreseeable future is a question for which the sociologist and
behavioral scientist will have to provide the answer. In any case it seems not too early to
ponder the personal and social implications of success at the biological level.

Controlled Sex Determination

 

The method of transplantation of nuclei of body cells into enucleated eggs as applied to
man would provide a means of determining the sex of "one's" children. The nucleus of the
body cell of a male will cause the development of a boy, that of the body cell of a female
the development of a girl. Independently of this kind of controlled sex determination methods
are bound to be discovered which will enable true parents to have children of specified sex.
More than a half a century has passed by now since it is known that a man produces two kinds
of sperm cells in about equal numbers. In addition to 22 chromosomes visibly alike in all
sperm, the nucleus of one kind possesses a relatively large chromosome, the X chromosome
and the nucleus of the other kind, a small chromosome, the Y chromosome. In conception,
X sperm is female-determining, Y sperm male-determining. It is obvious that it should
become possible to separate the two kinds of sperm either by biological or by purely physical
methods such as differential centrifuging or sedimentation. No success, however, has been
attained yet in spite of some promising leads. If success comes, insemination with the
X or Y fraction of semen will assure control of the sex of the offspring. Application to animal
breeding would be of economic importance as in the production of mainly females in dairy cattle.
If applied to man, subtle psychological changes in the population might be expected. It is likely
that no great deviations from a 1:1 sex ratio would result since most parents of more than one
child seem to desire children of both sexes. The sequence of sexes ina family may, however,
change considerably. Instead of the uncontrolled random sequence of boys and girls, it may
well be that the majority of firstborn would be boys and that of second-born girls. Since position
in the birth order has an effect on both physical and personality traits of the developing offspring
the consequences of the first- borns being all boys and the second-borns all girls, may be

reflected in behavorial shifts of the population.
-26-

Guarding the Genetic Quality of Man

 

Concern for the quality of the genetic endowment of man has focussed on two
aspects, One of these places emphasis on the genetic load which is represented by clearly
abnormal inherited traits. The other stresses the desirability of not simply guarding
against frank abnormality but particularly against lowering of averages of endowments within
the range of normality for such traits as intelligence and other mental attributes. Even
beyond this latter goal measures have been proposed for raising existing averages by increasing
the genetic endowment of the population. Measures against the transmission of clearly un-
desirable traits lie within the sphere of negative or preventive eugenics while measures for
increasing the frequency of desirable traits fall within positive or progressive eugenics.
Preventive and progressive eugenics are fully compatible with one another although their
application offers different problems. It is easier to obtain agreement as to what is regarded
as undesirable than what is desirable, Eugenic thinking should, be encouraged notwithstanding
tragic errors of the past.

Euphenics, the engineering of human development so as to overcome the detrimental
expression of abnormal genotypes has led to a relaxation of selection against them, Formerly
most phenylketonuric children were unable to reproduce; when treated from birth with suitable
diet they will now presumably, marry and have offspring. Thus, instead of the "extinction"
of the genes responsible for the disease whenever an affected individual does not transmit
them to the next generation, the genes will now have a chance to be preserved. This should
lead to an increase in the frequency of these genes in future generations and consequently an
increase in phenylketonurics, And what is valid for phenylketonuria is similarly valid for
all the other genetic afflictions which can now be neutralized by various treatments. This may
_ be illustrated by pyloric stenosis, an abnormal constriction at the junction of the stomach and
intestine. It is a relatively common disease of the new born occuring in about 5 out of 1000
live male births and in 1 out of 1000 live female births. Formerly, many infants died as a
result of this condition but 50 years ago an operative procedure was designed which permits
survival and normal health. Pyloric. stenosis has a genetic basis. It is evident that the
death of an affected baby results in the elimination of the responsible genotype from the
_ population, Correspondingly, the survival and later reproduction of a surgically treated
child wtimately results in the perpetuation of its genotype. It has been shown indeed that
among the offspring of successfully treated persons the frequency of infants with pyloric stenosis
is from 10 to 70 times higher than in the general population. These children, after having been

operated upon, will again later produce a surplus of their own affected kind.
-27-
Thus, in successive generations a continuous increase of the disease must be expected.

In detail the speed of accumulation of unfavorable genes in the population depends on
many factors. Generally, it will be a very slow process which for centuries will have no
easily recognizable effects. Moreover many a "bad" gene whose effects are overcome
euphenically may be said to have lost its "badness", wholly or to a large degree so that its
accumulation no longer represents a serious biological load even though it may represent a
considerable economic load. In addition such accumulation may be slowed down if genetic
counseling leads certain carriers of such genes to reduce the number of children born to them
or even to refrain from having children. Such counselling is already effective in many cases.
Often it can assure worried persons that their fears of defective offspring are unjustified or
at least greatly exaggerated, but at times the predicted likelihood of severely abnormal
offspring is high. More knowledge of the inheritance and the variability in expression of the
numerous kinds of human defects accumulates yearly and the outlook for improved foundations
for counselling is favorable. It should be added that the possibility has been discussed that the
great insights of modern molecular biology may make it possible in the future to replace
specific undesirable genes in a person's cells by desirable ones brought in from the outside.
Many biologists think, however, that the prospects for such genetic surgery are doubtful in
the foreseeable future.

Differential Fertility

From time to time serious questions are raised about the long-range biological
(and for that matter social) effects of differential fertility on the characteristics of populations.
These questions arise because there is generally an inverse relation between fertility! and socio-
economic status whether measured in terms of occupational status, education, or income, and
because there are differences in the fertility of the major races. There are also substantial
differences in the fertility of the major religious groups. The maximum fertility is found
among Moslems, with Hindus and Buddhists next. Christians as a group have lower fertility,
and among Christians in the United States the Catholics have higher fertility than the Protestants
asa whole. In worldwide terms, however, Catholics run the gamut of all experience, from
very low fertility (for example, in North Italy) to the highest fertility in the world in some parts
of Latin America. In general, the Jews have the lowest fertility »f any of the world's major

religions.

In this context the word fertility will be employed in its demographic usage indicating the

nuinber of offspring produced and not in the sense of the opposite to sterility.
-28-
In this summary account, only a few sweeping propositions can be ventured.

1, A great deal is known about the actual differences in the fertility of broad socio-

- economic, racial and regional groups, but very little is known about the significance of

these differences for either the social or the biological heritage. Many discussions of

these matters cannot be backed up by sound evidence but recently new beginnings are being
made to obtain valid information.

2. In biological terms it is probable that differences in reproductive performances
among individuals of varying characteristics within all groups are much more important
than differences in the average performance between the highly heterogeneous social
groupings for which data are readily available.

3. In the developed world, as birth rates have moved downward from those character-
izing the mid-nineteenth century to their present position, there has been a tendency for
‘the inverse relation between socio-economic status and fertility to become first stronger
and then to weaken, The small-family pattern has tended to come first in the upper classes
and in the urban sectors of the population, and only later to spread throughout the society.
As progressively larger numbers of governments in the newly developing countries mount
national programs to spread the practice of family planning by means of the new and highly
effective methods of contraception, it is likely that the trend in the lower social strata of
the populations will follow those of the upper strata more closely.

4, Inthe white population of the United States the differences narrowed substantially
during the postwar rise of the birth rate, which was more pronounced in the urban and
upper-class groups than in the rural and lower economic strata, The inverse relation
remains, however, partly because of an earlier age at marriage in the lower-class groups.

‘However, it is also clear, and particularly in the poverty groups, that much of the higher -
fertility of the lower status groups would disappear if contraceptive information and services
were made readily available.

5. In the United States, the fertility of Negroes differs from that of the white popula -
tion mainly as a consequence of their lower educational, economic and social status. When
one compares similar educational, income and occupations groups, the differences are
greatly reduced and in certain cases even reversed.

From a genetic view point differences in fertility among groups of people are important
only when these groups differ in their genetic endowments, From a general point of view
only those genetic differences count which bear on the mental, behavioral, and social aspects

which are characteristic of man.
-29-

There is no doubt that a large part of the variability of mental, behavioral and social
traits is accountable by the graded differences in non-genetic factors such as wealth and
poverty, intellectual stimulation and its absence, attitudes of encouragement and discourage-
ment. There is an immediate task before mankind in seeing that these non-genetic factors
are adjusted so that each individual realizes his genetic potential to the fullest. At the
same time, however, when the performance of unchanged genotypes may be improved in
this way, intense studies on the exisiting genetic variability may make possible the design
of realistic blueprints for the control of man's biological make-up. These plans will take
account of a future deeper understanding of that concept the "gene pool", which abstracts
the genic content of populations from its actual existence in living individuals. In abstract
terms control of the genetic future of man consists of manipulation of the gene pool. In
concrete terms such manipulation is accomplished by specified reproductive patterns of
individuals. The choice between various future plans must be based on value judgments. In
order to use the powers of self-control of his evolution man must be clear about the values
toward whose realization he is to strive.

When, in the future, populations do not expand any more, it will be desirable to
provide social incentives for the perpetuation of certain genotypes and social discouragement
for that of others. At the present time of quantitatively dangerous population growth, social
pressures might best be directed to lower reproduction in general without qualitative con-
siderations.

Man's view of himself has undergone many changes. From a unique position in the
universe the Kopernican revolution has reduced him to an inhabitant of one of perhaps many
planets. From a unique position among organisms the Darwinian revolution has assigned him
a place among the millions of other species which evolved from one another. Yet, man has
overcome the limitations of his origin. Nature in him has reached beyond the hard regular-
ities of physical phenomena and beyond the realization of crganic configurations. Man, the
creation of Nature, has transcended her. From a product of circumstances, he has risen

to responsibility.
References

Brown, Lester R.: Man, Land and Food. 1963. Foreign Agriculture Economic Report No. ll,

U. S. Department of Agriculture, Washington, D.C.

Committee on Science and Public Policy, National Academy of Science 1963, The Growth

of World Population, Publ. 1091, National Academy of Science - National Research Council.

Glass, B., The Biology of Nuclear War, 1962. The American Biology Teacher, Vol. 24,
pages 407 - 425.

Lederberg, J., 1966. Experimental Genetics and Human Evolution. American Natural-

.ist, 100: 519 - 531.
Muller, H. J., 1967. Proceedings of the Third International Congress of Human Genetics 1966,

Roslansky, J. D. (Edit.) 1967, Genetics and the Future of Man. Appleton-Century-Crofts:
New York, N. Y.

Sonneborn, T. M. (ed.). 1965. Control of Human Heredity and Evolution. The MacMillan Co.,
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