Biology and Culture
Mankind Evolving. The Evolution of the Human Species
The appearance slightly more than a century ago, in 1859, of Darwin's On the Origin of Species marked a turning point in the intellectual history of mankind. Darwin ushered in a new understanding of man and his place in the universe. After him the fateful idea that all things change, that they evolve, has become one of the cornerstones on which the thinking of civilized man is based. The universe, inanimate as well as animate matter, human bodily frame as well as man's psyche, the structure of human societies and man's ideas–all have had a history and all are in the process of change at present. Moreover, the changes so far have been on the whole, though not always, progressive, tending toward what we men regard as betterment. Progress in the future is not inevitable; it is not vouchsafed by any law of nature; but it may be striven for.
It is hard for our generation to realize how novel the idea of evolution, in the broadest sense of universal and all-pervading change and development, really is. Marcus Aurelius, the "philosophical emperor" (A.D. 121-180), held that "a wise man considers the periodic destructions and rebirths of the universe, and reflects that our posterity will see nothing new, and that our ancestors saw nothing greater than we have seen."
Infinity is a notion which most people find hard to conceive of. Creation myths were accordingly constructed to show that man and the universe did have a beginning. Once created, they thought, things were established forever. Before the idea of universal change was thrust upon people by evolutionary science, whether they liked it or not, change was regarded with misgiving, as something more apt to result in deterioration than improvement. Deterioration was, indeed, the only kind of "evolution" people could imagine readily: the Age of Gold is far in the past, the Iron Age is our lot. Hindu sages combined this with the idea of eternal recurrence–the ages of benevolent gods are succeeded by ages of less benevolent ones; ours is the age of the terrible goddess Kali; this will end in a cataclysm; whereupon everything will be repeated from the beginning. Even the ancient Greeks, whose wisdom we find so congenial, did not think of evolution. Yes, the world had a start, they thought, but it was not growing progressively better. Although man can aspire to see the beauty of eternal ideas, these ideas are distorted, and only dimly reflected in the things met in the world.
Christianity is a religion that is implicitly evolutionistic, in that it believes history to be meaningful: its current flows from the Creation, through progressive revelation of God to Man, to Christ, and from Christ to the Kingdom of God. Saint Augustine (354-430) expressed this evolutionistic philosophy most clearly. But the Judeo-Christian tradition took over from oriental religions the idea of the Garden of Eden and of the Fall as the beginning of the world's history. Interpreted literally rather than symbolically, this view is anti-evolutionistic. Moreover, almost two millennia of Christian exegesis do not make it clear that the history of man ought to be an evolutionary development, a collaboration of God and Man, rather than a series of fitful interventions by God. Even such forward-looking theologians and philosophers as Niebuhr  and Greene  accept scientific evolutionism as something irresistible but not exactly welcome. For a Catholic viewpoint, presented by a biologically informed author, see Aguirre’s work ; a not so orthodox but a lofty vision of evolution will be found in the inspiring work of Teilhard de Chardin . […]
Man's Animal Ancestry
Darwin supplied the keystone of the arch connecting our understanding of the destiny of the atom with that of the destiny of man. In On the Origin of Species he dealt with man only by implication; in The Descent of Man he reluctantly took the inevitable step and showed that man is a part of nature and kin to all life.
The Darwinian revolution, like most revolutions, had to contend with an opposition. The resistance, desperate but pathetic, put up by religious and other conservatives is too well known to need detailing here. In this Age of Science it seems well-nigh incomprehensible that so many people found the idea of the animal ancestry of man insulting to human dignity. The attitude is well portrayed in the quaint story of the English lady who on being told of Darwin's theories exclaimed: "Descended from the apes! My dear, we hope it is not true. But if it is, let us pray that it may not become generally known." Apes and monkeys were held in low esteem in the folklore of Western peoples; creatures so dirty, ill-smelling, and lascivious did not deserve a place next to man even in the zoological system! Furthermore, to make Darwin's theory as shocking as possible the proposition "man and apes have descended from common ancestors" was garbled into "man has descended from the apes." This, of course, is obvious nonsense, since man's remote ancestors could not have descended from animals which are our contemporaries.
Darwin's successors had to labor to adduce proofs that the evolution of the biological world and of man had actually occurred. That was the paramount task which biologists faced in the closing decades of the nineteenth century. The task has been splendidly fulfilled, and the proofs of evolution are now a matter of elementary biology.
However, it is frequently asked, Is evolution a fact or a hypothesis? So stated, the question is meaningless and misleading. The enterprise of science is founded on the hope that all rational beings who investigate and ponder the same evidence, derived ultimately from sense impressions ("facts"), will be led to draw from this evidence the same conclusions. The evidence of biology means to most people familiar with it that the world of life, including man, is a product of an evolutionary development. But there are still a few persons not ignorant of the evidence who insist that evolution is a "mere" hypothesis, which they reject in favor of special creation (is special creation not another hypothesis?).
Nobody beheld the sight of man's ancestors giving rise to men, or of the ancestral horses transforming themselves into modern horses. We cannot re-enact these transformations in our laboratories. Evolutionary changes of this magnitude (sometimes called macro-evolution) take time intervals of much greater orders than the span of human life; they are accordingly not facts observed but events inferred from observed facts. In Lamarck's and Darwin's times evolution was a hypothesis; in our day it is proven. Another proven hypothesis is that the earth executes a complete revolution on its axis once every twenty-four hours.
When a hypothesis has been thoroughly verified, we may take it as a safe guide in our thinking and working activities. Those who are not satisfied that the existing evidence makes acceptance of the evolutionary origin of the living world inevitable are entitled to hold their opinions. The business of proving evolution has reached a stage when it is futile for biologists to work merely to discover more and more evidence of evolution. Those who choose to believe that God created every biological species separately in the state we observe them but made them in a way calculated to lead us to the conclusion that they are products of an evolutionary development are obviously not open to argument. All that can be said is that their belief is an implicit blasphemy, for it imputes to God appalling deviousness.
While the validity of the proposition that man's ancestors were not men cannot at present be reasonably doubted, this does not mean that we know enough about the appearance and habits of our ancestors who lived at different time levels in the past. Such knowledge can be gained with any degree of certainty only through human paleontology, the study of fossil ancestors and collateral relatives of now-living mankind. […]. It should be stressed in this connection that in Darwin's time this evidence was practically nonexistent. The first skull of the Neanderthal race of fossil man was discovered in Germany in 1856, i.e., three years before On the Origin of Species and fifteen years before The Descent of Man. It was regarded by some outstanding anatomists (Virchow), however, as a pathological specimen, and its true significance was appreciated only much later. Similar doubts greeted the discovery in 1889 of an even more important human fossil – Java Man (Homo erectus). It is really only in our century that the variety and number of human and prehuman fossils became great enough to warrant the first, though still hesitant, attempts to reconstruct human ancestry.
In our day the opposition to evolutionism has been thwarted. The notorious trial in 1925 at Dayton, Tennessee, was perhaps the final skirmish. A teacher named Scopes was found guilty of having broken a state law which prohibits the teaching of evolution; but the resulting ridicule heaped on this law produced a diametrically opposite verdict by the world. Strange to say, that law still remains on the statute books of Tennessee, although it is not being enforced. I broke it recently twice in succession within a little more than a month, by lecturing on evolutionistic subjects in institutions of higher learning in the state.
The Evolution of Culture
[…] In his books Darwin confined himself to biological matters, even in The Descent of Man and The Expression of the Emotions in Man and Animals (1872). But others were quite ready to apply his findings, or at least his phrases, to human society and human history. We have seen that Marx thought he was a Darwinist of sorts when he prophesied that human society will end in communism. Spencer (1820-1903), who speculated on evolutionary sociology even before On the Origin of Species was off the press, was among the first to jump on Darwin's band wagon, and he became a biologizing sociologist and sociologizing biologist with an enormous influence on the intellectual climate of his time.
The "founding fathers" of evolutionary cultural anthropology are listed by Murdock  and Kroeber  as follows: Bachofen, Maine, Fustel de Coulanges, McLennan, Tylor, Lubbock, Morgan, and Spencer. Excepting Lubbock, who was a biologist, they were sociologists and jurists. But they viewed human societies and institutions in the way zoologists and botanists viewed animals and plants–the existing forms have descended by gradual modifications from very different antecedents.
Tylor staked out the field of cultural anthropology, as the study of culture, in 1871, the same year in which The Descent of Man was published. Culture is "that complex whole which includes knowledge, belief, art, morals, law, custom, and any other capabilities and habits acquired by man as a member of society". The key word in this definition is "acquired"–not inherited biologically as is so much else in body structure, function, and behavior, both in man and in animals. Now, it cannot be too strongly emphasized that what is biologically inherited is not handed down ready-made from ancestors. On the contrary, the characteristics of an individual animal or of a person develop through long and complex interaction between heredity and environment. Culture, however, is something else. It is wholly acquired by human beings from other human beings, and not only by children from their parents as in biological heredity. Culture is acquired by imitation, training, and learning. To be sure, biological heredity may make the acquisition and transmission of culture, or of some of its aspects, more easy or more difficult, but it does not determine just what is acquired or transmitted. Heredity does determine that a person can learn to speak a language or languages, but it does not determine which language he will learn or what he will say. Biological heredity does not transmit characters which a human individual has acquired during his or her lifetime, but culture transmits only such characters.
To have founded the concept of culture is the enduring achievement of the pioneers of cultural evolutionism. But this current of thought has had an extraordinarily uneven career […]. The founding fathers of cultural anthropology had at their disposal even scantier factual data than did their biologist contemporaries. Their speculative reconstructions of the origins and evolutionary changes of human societies were useful as working hypotheses which stimulated the collection of facts that eventually formed the basis of modern cultural anthropology. But the hypotheses themselves generally failed to stand the test of time. Their basic assumption was that the evolution of culture is unilineal, i.e., that all cultures necessarily progress through similar stages of development, which Morgan termed savagery, barbarism, and civilization. Among peoples living in the world at present some are still lingering in savagery, others have attained civilization; presumably the former may eventually also reach civilization, and the nowcivilized ones were once upon a time like the present barbarians and savages. Just why the evolution of culture should always follow the same path was hard to explain; the unilineal character of this evolution was therefore declared a property of human nature–an easy but hardly satisfactory way out.
The theory soon met with difficulties. Cultures do not exist in complete isolation from each other; people may, and often do, borrow a culture ready-made from neighbors, conquerors, or the conquered, and thus skip over some "necessary' ' evolutionary stages. Cultures spread, or diffuse, from one people to another. For a time there was a diffusionist school which believed that culture arose only once, in ancient Egypt, and diffused from there in many directions, carried chiefly by Phoenician mariners.
Also, since savagery, barbarism, and civilization existed contemporaneously, the evolutionary changes obviously did not progress at similar rates in peoples in different parts of the world. Biological racism, which had many influential exponents during the late nineteenth and early twentieth centuries (see below), had an easy explanation–some peoples are by nature incapable of progressing beyond tribal savagery, while others are superior and develop civilizations.
Although cultural evolutionism has no necessary connection with biological racism, some social scientists felt suspicious of both. Nobody was more influential in bringing about a general repudiation of theories of cultural evolution than Franz Boas (1858-1942). Theories of cultural relativism came in vogue instead. No culture is really superior to any other; one should not talk about savagery or barbarism, or even about primitive and advanced cultures; euphemistic adjectives like "preliterate" and "literate" must be used instead. No one culture's way of life is better than another; people live differently, and that is all (see Benedict's Patterns of Culture [Houghton Mifflin: Boston, 1934], probably the most popular treatise on anthropology ever printed).
Cultural evolutionism probably reached an all-time low in popularity in the thirties, but a strong revival appears to have set in, especially in the postwar years. (It may be noted that the theory of savagery, barbarism, civilization, and socialism as successive stages of human development has enjoyed steady favor in the Soviet Union because it happened to have been mentioned favorably in the writings of Engels and in other communist scriptures.)
Cultural evolutionism has recently been espoused by White , Childe , Steward , and Sahlins and Service . This is not the place to attempt an analysis of their views; they are by no means in agreement on all points. Thus Steward proposes a theory of multilinear evolution: cultural developments occur differently in different "culture areas," of which the world has several. However, these different developments still pass through some broadly similar stages, which are stressed as significant. A modern form of unilineal evolutionism has been propounded by White, Sahlins, Service, and their collaborators, who argue that evolutionary changes of culture are of two kinds–general and specific. Their general unilineal evolution involves the passage of cultures from lower levels of development to higher levels; the levels are characterized best of all by the efficiency with which the energy resources of the environment are exploited. Specific evolution is adaptation of cultures to the diversity of local conditions; this is what historians are mainly concerned with.
A biologist cannot fail to note that "general evolution" sounds very much like what on the biological level is represented by the hypothesis of autogenesis or orthogenesis. This notion proved to be unprofitable as a working hypothesis and is now a minority view. It might be better to distinguish evolutionary changes in cultures as analogous to anagenesis and cladogenesis in biological evolution. Perhaps Birdsell , Braidwood and Reed , Braidwood , Murdock , and Willey  are closest to a synthesis of the unilineal and multilineal views of the evolution of culture. The revival of evolutionism in cultural anthropology has not to date restored the mutual understanding between biologists and anthropologists which prevailed in the early post-Darwinian era, but the hope that it may yet do so should not be abandoned.
Social Darwinism and Racism
Man's efforts to know himself are often frustrated by his propensity to deceive himself. The industrial revolution failed to benefit everybody equally. In cities of nineteenth-century Europe and America poverty and squalor persisted cheek by jowl with mounting comfort and luxury. This was nothing really new; disparities of wealth and social status have been increasingly a part of the social scene ever since simple food-gathering economies and low population densities gave way to more complex economic arrangements and growing populations. What was novel was the rapid carving up of the world into colonial empires. Most of mankind became "subject races," to be uplifted and perhaps even civilized; the pedagogic method was to put the subjects to work for the profit of their white masters. If some of the latter felt a need to put their consciences at rest, a church hymn solved the problem:
To complement this with a scientific justification seemed, as time went on, highly desirable to more and more people. Social Darwinists found that Darwin, or his theory, accomplished the purpose very nicely; all you needed to assume was that Darwin had discovered not merely the laws of biological evolution but also those governing the life of human societies. […], it was the phraseology more than the essence of Darwinism which lent itself easily to abuse by social Darwinists.
Actually, the "struggle" in the "struggle for life" was to Darwin a metaphor. This struggle is not necessarily contention, warfare, or bloodshed. Animals and plants "struggle" to avoid the perils of cold, heat, desiccation, drowning, gale winds, etc., but they do not freeze, burn, or drown other individuals of their own or of other species. "Natural" in "natural selection" does not mean savagery or conditions preceding or excluding man-made changes in the environment. Natural selection is going on in all human societies, from the technologically most primitive to the most advanced. Natural selection is simply the antonym of artificial selection. The former means differential reproduction of carriers of different genetic endowments owing to their adaptedness or shortcomings in a given environment, while the latter implies choice or culling of parents or of their progenies for some purpose or with an end in view. Who is the "fittest" in the evolutionary "survival of the fittest" is a most complex matter which has not been fully clarified even yet. One thing which is clear is that the fittest is not necessarily a romantic figure, or a victorious conqueror, or a superman. He is most likely to be merely a prolific parent.
Social Darwinists did not know, or did not want to know, any of these subtleties and qualifications. They equated affluence and occupation of the seats of the mighty with biological fitness, and economic laissez faire, cut-throat competition, and rivalry with natural selection. Solid and conservative citizens thought all along that success in business is a fair measure of a person's worth; social Darwinists explained that it is also a measure of biological fitness. Sumner (1840-1910), an American ideologist of social Darwinism, taught that "the millionaires are a product of natural selection, acting on the whole body of men to pick out those who can meet the requirements of certain work to be done." On the other hand, "the strong and the weak are terms which admit of no definition unless they are made equivalent to the industrious and the idle, the frugal and the extravagant. ... If we do not like the survival of the fittest, we have only one possible alternative, and that is the survival of the unfittest." John D. Rockefeller, Sr., wholeheartedly agreed. "The growth of a large business is merely a survival of the fittest. ... It is merely the working-out of a law of nature and a law of God". A good many lesser lights either welcomed these views or acquiesced in them. Such views became and continue to be the stock in trade of conservatives, but nowadays most people feel something awkward about them, and they are voiced in political discussions more often than committed to print.
Social Darwinism went beyond glorifying rugged individualism although man is too obviously a social animal and group loyalties may at times transcend individual self-interests. (Statesmen and politicians, too, are adept at utilizing these emotions.) Social Darwinists supposed that human progress demands a struggle and competition not only between individuals but also between social classes, nations, states, and races. This kind of struggle was regarded as the superior, specifically human, form of natural selection. Gobineau in fact anticipated social Darwinism by proclaiming the existence of a biological master race, the Nordics, while Darwin was still working on his theories in private. Talking about biologically superior and inferior races soon became popular with influential people. The proponents of such beliefs were most vociferous in Germany; among them were Houston Chamberlain, who was born an Englishman, and Wagner, who is better remembered as a composer of music. The climactic denouement of racist ideas occurred in Hitler's attempt to conquer the world for the Master Race.
Racism was far from endemic in Germany, however. An ideologist of the British Empire announced that "the English were by nature a people destined to rule the inferior races of the world to the benefit of both parties." The United States Senate was told in 1899 that "God has not been preparing the English-speaking and Teutonic peoples for a thousand years for nothing but vain and idle self-admiration … He has made us adept in government that we may administer government among savages and senile people". I always remember a "gentleman" from Alabama who argued with some eloquence the inadvisability of spreading education among Mexicans, a race biologically fitted solely to be servants. Nor have theories of this sort appealed exclusively to large and powerful nations; group pride goes easily with imagining oneself a member of a small, downtrodden, but superior elite. […]
Ectogenetic, Autogenetic, and Biological Theories of Evolution
Change, whether in biological evolution or in human affairs, may come from without or from within, from external or from internal causes. The genetic endowment of a species or a population, or the structure of a society, may be shaped by the environment. Evolutionary changes imposed from without the organism are called ectogenetic. Autogenetic theories hold, on the contrary, that evolutionary changes stem from within the organism; the environment might play a minor role–it might perhaps speed the evolution up or slow it down, but would not determine just what kind of change takes place.
Genetic or social change may also result from interplay between an organism or a culture on the one hand and the environment on the other. This is the view espoused in biology by theories subsumed under the labels of Darwinism, Neo-Darwinism, and more recently the biological, or synthetic, theory of evolution. Marxists, too, have claimed that their ideas about the development of human societies somehow parallel the Darwinian theories of evolution, but these are remote analogies at best and they need not concern us here. Early in the current century there was much discussion among biologists who preferred ectogenesis and those who favored autogenesis as an explanation of evolution. These early theories have been shown to be untenable and as this is largely a dead issue at present, we may deal with it only briefly. Lamarckism (or, more correctly, Neo-Lamarckism), though thoroughly discredited, has been revived under the names of Michurinism and Lysenkoism. The environment is believed to alter the heredity directly, and the sequence of such alterations is assumed to represent evolution. Thus the alterations induced in, say, the inhabitants of warm climates will differ from those in cold climates, and different races, species, genera, etc., will eventually emerge. This may seem plausible at first glance; indeed, since the environment can modify the phenotype, why not the genotype also? Experimental evidence shows unambiguously, however, that environmentally induced changes in the phenotype, so-called acquired traits, are not inherited. Another stumbling block of Lamarckian theories has been their inability to explain why so many environmentally induced changes happen to be adaptive, i.e., improve the harmony between the organism and its environment. Why, for example, should muscular exercise strengthen the muscles rather than weaken them? Believers in ectogenesis have to resort to explicit or implicit assumptions, ascribing to the organism an inscrutable capacity to react adaptively to environmental requirements. But this is verbiage, not explanation. No theory of evolution which leaves the phenomenon of adaptedness an unexplained mystery can be acceptable.
Autogenetic theories envisage the world of life as something like a music box, the spring of which was wound up on the day of creation and which can play the tunes stored in it from the beginning but no new ones. The authors of theories called orthogenesis, nomogenesis, aristogenesis, etc. claimed that it was precisely to explain the apparent purposefulness of life that they assumed that this purposefulness was an intrinsic property of life itself. But does this really explain anything? The primordial virus or the primeval amoeba are alleged to have contained, in a latent state, all the organic forms which developed from them, including man. Evolution was a kind of strip tease, peeling off one disguise after another, until its final, and perhaps most nearly perfect, product stood revealed. And this process of gradual unwrapping of organic forms happened miraculously to fit the environments which prevailed when these successive forms made their appearance! Some of the evolutionary theories of culture likewise assume "rectilinear evolution," unfolding of potentialities contained in the culture itself, i.e., a kind of autogenesis.
Many evolutionary lines ended in extinction. How do the autogenetic theories reconcile this with the belief in an intrinsic purposefulness of life? They have to make an additional assumption–that the primordial organism contained the seeds not only of evolutionary progress but also of evolutionary senescence and demise. The career of an evolutionary line is compared with the life of an individual–there are, supposedly, evolutionary birth, youth, maturity, senescence, and death. This is good enough as a metaphor but unsatisfactory as an explanation.
For a time the autogenetic theories of evolution were in vogue, especially among paleontologists and comparative morphologists. They had rather more adherents in continental Europe than in England or America, a fact which Northrop relates to basic philosophic trends in the respective countries. It has been a great achievement of Simpson and of Rensch to show that there is nothing in the evidence gathered by paleontology and morphology that would warrant the assumption of autogenesis, and that the data at hand are quite compatible with the biological theory of evolution.
This theory, let us make it clear from the outset, recognizes that adaptation to the environment is the main causative agent of organic evolution. In this sense, evolutionary changes come from the environment. Assertions made by Lysenko and his henchmen, that geneticists deny that the genetic endowment of a living species can be changed by the environment, are nonsense. The point is, however, that the changes are mediated by natural selection. And it is because the changes are brought about by natural selection that most of them further the congruity between the organism and its environment.
On the other hand, the environment does not impose changes on the organism. The biological theory of evolution is not so artlessly mechanistic as alleged by some followers of autogenesis. The relations in evolution between the environment and the organism are best epitomized by Toynbee's winged phrase–"challenge and response." It is a living species which may respond to the challenges of the environment by adaptive alterations. But on the other hand, it may not respond adequately and may die out or become less well adapted. The response depends on the availability at the proper time and place of suitable raw materials–mutations and gene combinations.
Organic and Superorganic
Ortega y Gasset has epitomized the point of view of many social scientists and humanists as "Man has no nature, what he has is history". The polar opposite is the view of Darlington: "The materials of heredity contained in the chromosomes are the solid stuff which ultimately determines the course of history," and "the structure of a society rests on the stuff in the chromosomes and on the changes it undergoes."
The thesis to be set forth in the present book is that man has both a nature and a "history." Human evolution has two components, the biological or organic, and the cultural or superorganic. These components are neither mutually exclusive nor independent, but interrelated and interdependent. Human evolution cannot be understood as a purely biological process, nor can it be adequately described as a history of culture. It is the interaction of biology and culture. There exists a feedback between biological and cultural processes.
Darwin's successors strove mightily and succeeded in satisfying themselves and in convincing others that man is a zoological species and kin to everything that lives. But scientists are humans, and they are tempted to think that their discoveries explain everything instead of something. Some biologists fancied that, since man's ancestors were animals, man also is "nothing but an animal," and that their findings confer upon them a competence to plan man's future "from here to eternity." This is a specimen of "genetic" fallacy, to which geneticists are, we may be assured, no more prone than other people. The fallacy has, however, made biology an easy prey to social Darwinists, racists, and unscrupulous politicians.
Social scientists reacted to the exaggerated biologism by a converse exaggeration. Human evolution is evolution of culture, and – although a human genetic endowment was needed to initiate the process – "cultural evolution is an extension of biological evolution only in a chronological sense". Closely related is the so-called hypothesis of the psychic unity of mankind, one of the formulations of which is that "there are no known differences among races of men which either interfere with or facilitate the learning of cultural forms." A similar view is a part of the official creed in the Soviet Union. Biological evolution gave rise to a being capable of doing "work" (i.e., of making and using tools). This was a "sharp break," "saltation," and "discontinuity" in man's evolution; he no longer evolves biologically; biological evolution is entirely replaced by social evolution, the course of which is charted in Marxist scriptures. The view that man's biological evolution has come to a halt and that he now evolves only culturally has been adopted also by some eminent Western biologists (rather inconsistently with their other teachings).
Dichotomies are tempting; to dichotomize is one way to clarify an argument. But the dichotomy of biological and cultural evolution is misleading if pushed too far. Viewed in the perspective of time, the development of the human symbolic faculty and cultural transmission was certainly a radical innovation. Cassirer rightly said: "This new acquisition transforms the whole of human life. As compared with the other animals man lives not merely in a broader reality; he lives, so to speak, in a new dimension of reality." Having produced man, the evolution of the cosmos has perhaps entered a new eon. And yet, man's capacity for culture did not appear all at once, complete and finished. The germs of this capacity, or raw materials from which it could be formed, exist in the animal world. Nor is it in the least probable that this capacity, once formed, is fixed forever and can neither develop further nor retrogress.
Biological heredity is transmitted through the sex cells; and barring mutation, nobody can transmit to his descendants any genes other than those which he himself received from his parents. Acquired traits are not transmitted biologically. Culture is wholly acquired by learning and imitation, and transmitted entirely by teaching and precept. How can processes so profoundly different interact and influence one another? An imaginary example may illustrate this. Suppose that, through a genetic change, mankind comes to consist entirely of women capable of unisexual reproduction (by parthenogenesis); in Muller's utopia, it might be possible to perpetuate a mankind consisting only of males. An enormous number of cultural traits and processes connected with sex and the division of labor between women and men would then lapse or be modified, while new ones would probably be worked out. Or consider a perhaps less far-fetched possibility. Mutual attachment between parents and children may persist for the duration of their lives, or parents may be spurned by their children, or vice versa. If persistence of family cohesion were biologically more advantageous than its early dissolution, or vice versa, genetic factors might conceivably be selected to bolster one or the other of these tendencies.
The interrelations between the biological and the cultural components of human evolution may be brought out perhaps most clearly if we consider that they serve the same basic function adaptation to and control of man's environments. Most contemporary evolutionists are of the opinion that adaptation of a living species to its environment is the chief agency impelling and directing biological evolution. As stated above, the adaptation takes place through natural selection, which promotes the survival and reproduction of the carriers of some genetic endowments and inhibits others. The construction of man's body and the conformation of his intellect developed as they did because they made our species biologically highly successful (which is not saying that man's biological frame is the acme of perfection in all respects). The genetic basis of man's capacity to acquire, develop or modify, and transmit culture emerged because of the adaptive advantages which this capacity conferred on its possessors.
Culture is, however, an instrument of adaptation which is vastly more efficient than the biological processes which led to its inception and advancement. It is more efficient among other things because it is more rapid-changed genes are transmitted only to the direct descendants of the individuals in whom they first appear; to replace the old genes, the carriers of the new ones must gradually outbreed and supplant the former. Changed culture may be transmitted to anybody regardless of biological parentage, or borrowed ready-made from other peoples. In producing the genetic basis of culture, biological evolution has transcended itself – it has produced the superorganic.
Yet the superorganic has not annulled the organic. The hypothesis of the psychic unity of mankind is justified to the extent that all members of the species Homo sapiens free of overt pathology are capable of learning a symbolic language and a variety of cultural forms. This only means that the capacity has become established as a species characteristic, like the erect posture, ability to subsist on diverse diets, absence of a breeding season, a brain size exceeding that of other living primates, and much else besides. But it does not follow that the genetic variability affecting the capacity to learn has suddenly evaporated in human populations. This is unlikely on theoretical grounds, and is contradicted by much evidence. Why do so many people insist that biological and cultural evolutions are absolutely independent? I suggest that this is due in large part to a widespread misunderstanding of the nature of heredity. As will be shown in more detail in the following chapters, biological heredity, which is the basis of biological evolution, does not transmit cultural, or for that matter physical, traits ready-made; what it does is determine the response of the developing organism to the environment in which the development takes place. To say that cancer runs in families does not mean that every member of these families dies of cancer, and the inheritance of longevity does not guarantee a long life to some and a short one to others–apart from accidents, one's life may be prolonged or shortened by the environmental hazards which one meets, and by how one chooses to live (but this choice may, in turn, be partly conditioned by one's genes).
The statement that the "intelligence" (or whatever it is that is measured by intelligence tests and expressed as IQ) is in part conditioned by heredity does not mean that some people are born clever and others stupid. It only means that, when brought up in certain environments, some persons come to possess higher IQ's than others. If the former were placed in conditions unfavorable for mental development, their IQ's might decline, while the latter might acquire higher IQ's in more favorable and stimulating environments. A group of persons who show in a certain environment a lower average IQ than another group may exhibit a higher intelligence in another environment. This is not merely a theoretical possibility. American Negro draftees during the First World War had a lower mean IQ than did the white draftees. Some people who were greatly pleased by this had their enthusiasm dampened by the finding that the mean IQ of the Negro draftees from Northern states was higher, not lower, than that of the white draftees from Southern states. All of which does not signify that intelligence is either hereditary or environmental; it rather suggests that the observed variation in intelligence has both genetic and environmental components.
Human Evolution as a Unified Process
Tax  has stated succinctly the relationships between human biology and culture:
"Culture is part of the biology of man, of course, even though it is passed on socially and not through genes. It is a characteristic of our species, as characteristic as the long neck of the giraffe. The general biological questions asked about the giraffe's neck are also questions to be asked about the civilization of man. Culture is part of the evolution of man. Man is evolving continually as a species, perhaps more rapidly now than any other species."
Human evolution is not completed or discontinued. This is true of its biological and its cultural aspects. These aspects are different enough to make it legitimate, and indeed necessary, to study them with the aid of different methods. As pointed out above, our genes determine our ability to learn a language or languages, but they do not determine just what is said. The structure of neither the vocal cords nor the brain cells would explain the difference between the speeches of Billy Graham and of Julian Huxley. The fact which must be stressed, because it has frequently been missed or misrepresented, is that the biological and cultural evolutions are parts of the same natural process. This process, human evolution, must eventually be brought under human control. Here mankind will meet the greatest challenge of its biological and cultural histories. To deal with this challenge successfully, knowledge and understanding of evolution in general, and of the unique aspects of human evolution in particular, are essential.
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