Evolution, Culture and Human Uniqueness The term "culture" has various meanings but in general it refers to the habits, customs and moral attitudes which govern human behavior. Culture is nongenetic and is transmitted as information from generation to generation in Lamarckian fashion, i.e., acquired through learning and imitation. The rate of cultural transmission is very fast compared with genetic transmission, and, as is obvious from recent technological developments, it can change within the lifetime of a single individual. Cultural Evolution Cultural change can be considered evolutionary if it is directional and builds gradually as "descent with modification" from previous cultural modes; but social scientists are reluctant to accept the concept of cultural evolution. Of those who do, none has so far proposed a satisfactory mechanism to explain the process of cultural evolution. Most scientists who do write of cultural evolution view the process of cultural change as driven by factors analogous to those which drive biological evolution, e.g., cultural selection produces cultural adaptation by acting upon variation introduced by cultural innovation (mutation) and cultural dispersion (migration). For our purposes, we will view cultural change as evolutionary even though this concept does not enjoy universal acceptance. Genes vs. Culture Behavior is just as much an aspect of the phenotype as is morphology and there is no question that much of our behavior is shaped by cultural influence; the real problem from an evolutionary (biological) perspective is the extent, if any, to which genes might influence human behavioral traits. The idea that human behavior is under such as Ardrey and Morris, who contended that we have innate drives that act as instincts, e.g., aggression. This view was opposed by behavioral psychologists, e.g., B. F. Skinner who took the view that our behavior is completely flexible and shaped by learning (prior experience). Today, few, if any, scientists hold that human behavior is largely innate, stereotyped and instinctive - hence, genetically determined. Nor do they hold that human behavior is completely determined by culture. Cultural determinism implies that through behavior modification and socialization techniques individuals could be produced who lacked tendencies toward aggression, selfishness, altruism, parental care and compassion for other human beings. Extreme views of genetic and cultural determinism reflect a nature vs. nurture mentality that is too simple to explain the complex interaction between genes and the environment which forms the foundation for the development of human behavioral characteristics. Although the precise nature of this interaction is unknown and awaits further advances in the field of developmental genetics, a good model for examining causal influences over human behavior was outlined by E. O. Wilson who suggested that genes set limits to a wide range of behavioral responses and that learning (cultural influence) specifies particular forms of behavior as well as its variation both within and between human societies. Unfortunately, the nature-nurture dichotomy (genes vs. the environment) still persists in the thinking of many nonscientists and it leads to a deterministic view of human behavior: we are determined either by our genes or our environment. A more modern view, that adopted by sociobiologists, holds that our behavior is not determined; rather, we are influenced by both genetic tendencies and environmental (cultural) experiences. Hypotheses of Gene-culture Interaction Given the fact that our behavior is influenced by both culture and inherited dispositions resulting from neural circuitry development in the brain (hard wiring of the brain due to genetic influence), how might genes and culture interact to produce the final adult human behavioral phenotype? Several suggestions have been made but these hypotheses are largely speculative. Epigenetic interactions hypothesis One suggestion, which stems from the resolution of the nature-nurture debate, is the epigenetic interactions hypothesis. This hypothesis holds that culture acts as an environmental influence similar to any environmental influence over gene action which occurs during development. Since the brain continues to develop after birth, unlike other organs which are fully formed at birth, learning can influence behavior by modifying nervous circuitry (soft wiring). Consequently, inherited dispositions to certain thought patterns can be modified by learning, e.g., fear of strangers, or specified by learning, e.g., an innate tendency to submit to indoctrination and authority could predispose individuals to be religious and so choose a particular religious affiliation. [Note that I am proposing this only as an example of how general tendencies might be specified by culture and not positing that we have genes for religion; certainly not for particular religious beliefs.] Coupled interactions hypothesis Two other hypotheses have been proposed which separate biological and cultural evolution. One of these, called the coupled interactions hypothesis, proposes that biological and cultural evolution operate through separate processes [see earlier discussion of differences between biological (organic) and cultural (psychosocial) evolution], but that they have the same goal, i.e., individual fitness maximization. Hence, only cultural traits which biologically adapt individuals to their environment will be selected; cultural and biological adaptation, according to this view, are the same. Uncoupled Interactions hypothesis The other hypothesis, the uncoupled interactions hypothesis, proposes that not only are biological and cultural evolution different processes, they have different goals and compete with one another for the behavioral phenotype. Traits which do not contribute to Darwinian fitness might be adapted to attain purely cultural goals. The problem with this hypothesis is that the goal of cultural evolution is not specified, but could be the acquisition of power and/or wealth, the harnessing of energy, or the quest for personal happiness. Thus, celibacy could have adaptive advantage from a cultural perspective even though it has no selective value from a Darwinian perspective. Adaptive Significance of Human Behavior The root question is the extent to which current human behavioral tendencies might have been shaped by natural selection. Genetic change is very slow and is measured in terms of hundreds of generations (human generation time is about 25 years). It is highly unlikely therefore that genetic change has produced behavioral tendencies adaptive to today's modern society. Any genetic influences over our behavior would have to have been adapted to the environment which existed when we were in the hunter-gatherer stage of our evolution, which stage accounted for about 90% of our species' history. By using the principle of sequences we can reconstruct early human behavior by studying existing cultures which most closely reflect the hunter-gatherer life style. The Kung people (Kalahari Bushmen) of southern Africa provide us with a model of this stage, although they certainly do not have to contend with environmental forces, e.g., animal predators and competitors, which were important to our ancestors. Hence, what we learn about the Kung and other existing pre-industrial or pre-state cultures only approximates the social organization and culture of our primitive ancestors. We can surmise from the study of living hunter-gatherer societies that our primitive forebears led a harsh life. They lived in small nomadic bands consisting largely of related individuals. There was little or no social stratification and the roles of men and women, although different (men hunted and protected the band from outside danger; women gathered roots, nuts, fruits and berries, prepared the meals and took care of children until they were weaned), were considered to be equal in importance. There was a high premium on sharing and cooperation, for each individual's survival depended on support from the others in the band. Childcare, after weaning, was a cooperative venture with all members of the band supporting the parents. Children learned their roles in society by watching and imitating adults and older children. This level of cooperation is in sharp contrast to the competition which organizes social structure in other mammalian species - except for certain carnivores, e.g., wild dogs, which hunt in packs. Most likely human cooperation is due, at least in part, to the fact that we lack the specialized structures of other mammals for individual defense and hunting, and so must rely on cooperation for survival. Natural selection in the form of reciprocal altruism, kin selection, or both shaped our social behavior so that we had a basic concern for the well-being of others, and this trait led to the degree of cooperation that enabled culture to become a dominant force over our behavior. Evidence for a Genetic Basis for Human Behavior Any evolutionary influence over human behavior from a biological point of view requires that human behavioral traits have at least some heritability; otherwise natural selection would have no effect on behavioral variation. Since genes cannot be seen, however, the only way to establish a genetic background for behavioral phenotypes is through breeding experiments; yet, moral constraints prevent us from experimenting with humans in this way. In the absence of direct evidence for genetic influence, evolutionists must resort to indirect forms of evidence to bolster their position. Two types of indirect evidence exist: natural experiments and arguments from analogy, neither of which possesses the degree of precision, control and certitude associated with breeding experiments. Natural experiments Natural experiments consist of unusual situations which have an effect similar to that of controlled experiments designed to separate genetic and environmental effects. Two such natural experiments will be presented here. 1. Monozygotic twins (identical twins formed from the splitting of a single zygote) separated from birth and raised in different households provide an opportunity for assessing the role of genes in influencing behavior. Since these twins are genetically identical and were raised under different environments, any simil- arity between the two suggests (but does not demonstrate) genetic influence. A recent study of such twins at the Univerity of Minnesota Medical School has produced some astounding results in revealing similarities previously thought to be the product of cultural influence, e.g., choice of professions, preference for the same brand of consumer product, and even names of wives and children. As expected, these twins were almost identical in basic physiological responses such as brain wave pattern, pulse rate, etc., but the same result in personality profile was totally unexpected. The cultural similarity might be explained by hypothesizing that genes predispose individuals to screen the environment in a certain manner and so come to be influenced by the same cultural pressures - even when reared apart. In no way does this study suggest that genes control consumer preference or choice of profession. 2. Adopted children can be compared both to their natural and foster parents to shed some light on the possible role of genes behind behavior. Any similarity to natural parents would suggest genetic influence, while similarity to foster parents would indicate an environmental influ- ence. Obviously, due to the lack of genetic identity between offspring and natural parents, this form of comparison is not as useful as that described above for identical twins. Argument from analogy The argument from analogy is weaker than evidence from natural experiments because it is based on correlations which assume some underlying causative mechanism. The problem with analogical reasoning is that correlation only suggests and by no means demonstrates causation. Darwin used analogical reasoning to convince his colleagues that natural selection was a causative agent behind evolutionary change. He cited the success of animal breeders in modifying the characteristics of domesticated animals (artificial selection) and suggested that environmental pressures in nature could act in similar fashion. We often use the argument from analogy in our own lives, but are unaware of so doing. Whenever we purchase a new product based on previous experience with the company which produces it, we are basing our choice on analogical reasoning since we have no way of knowing how satisfied we will be with the product until we try it. Applied to behavior the argument from analogy has two uses. 1. Some aspects of human behavior are known to have a genetic basis, e.g., schizophrenia and manic depression. By way of analogy it could be argued that other behavioral traits also have a genetic base. 2. Humans share a phylogenetic affinity with other mammal species known to have little cultural influence over their behavior. A genetic basis behind human traits which are similar to those in related species for which a genetic basis has been demonstrated through breeding experiments can reasonably be suspected through analogical reasoning. The Problem of Culture The problem with analogy underscores the whole problem culture poses for evolutionary biologists: culture can mimic traits known to have a biological (= genetic) basis in other animals; hence, it is not valid to argue for a genetic basis to human traits simply because human behavior conforms to the predictions of evolutionary theory. Our species possesses by far the most flexible behav- ioral patterns observed in the animal kingdom and caps an evolutionary trend of increasing flexibility in behavior due to learning associated with phylogenetic complexity. With culture we have taken a quantum leap into the new realm of psychosocial evolution. Nonetheless, we are also biological beings whose traits have been shaped by natural selection operating in the organic sector of evolution. Debate over the role of genes and culture in shaping our behavior will continue until more definitive evidence has been produced to decide the issue. Nevertheless, our capacity for culture separates us from all other species and makes us unique - but just how unique are we? Human Uniqueness In a sense every species is unique in that it represents an evolutionary experiment in coping with demands imposed by a varied environment. Our enormous capacity for cultural transmission of learned experience, however, truly distinguishes us from all other animal species in a manner that transcends other species-specific differences. Just how great is this difference and how do we explain it within an evolutionary paradigm? Difference in kind vs. difference in degree In comparing two objects we customarily view differences as either qualitative (difference in kind) or quantitative (difference in degree). Mortimer Adler, a contemporary American philosopher and educator, suggests three different levels of distinctiveness which should be analyzed in dealing with the question of human uniqueness: difference in degree, superficial difference in kind and radical difference in kind. If one object possesses characteristics not found at all in another, the difference is purely qualitative and is referred to as a radical difference in kind, for example, the difference between a circle and a triangle. If the difference can be bridged by some intermediary and so represents a threshold break in an otherwise smooth continuum, then the difference represents a superficial difference in kind - one that appears to be qualitative but can be reduced to a quantitative difference. The difference between the three phases of water (solid, liquid and gas - ice, water and steam) represents a superficial difference in kind because these different appearances of the same molecule can be explained quantitatively by threshold changes in a continuous temperature gradient. Finally, if the difference between two objects is completely quantitative, the difference is called a difference in degree, e.g., different colors in a continuous electromagnetic spectrum. Difference between Humans and Nonhumans How should we view human uniqueness in terms of these three categories? Until quite recently, all available evidence pointed to the inescapable conclusion that the difference between humans and nonhuman species was one of a radical difference in kind. This conclusion fit in comfortably with a static worldview and human origin via creation. The gap between humans and nonhumans was simply too large to be bridged by evolutionary theory. For most of our civilization's history we have viewed the world as static and changeless. Western intellectual thought is rooted in the philosophy of Plato and Aristotle which posited an immutable, eternal universe. This world view was theologized by St. Thomas Aquinas who accounted for human nature as the act of divine creation. When all we had to rely on for comparison between ourselves and nonhumans was morphological and behavioral data obtained from existing species, the gap between humans and other species could only be interpreted as constituting a radical difference in kind. Our poetry, art, philosophy, science and technology clearly made us unique - so much so that we obviously were the object not only of divine creation, but also of divine favor. We were created superior to all other species and, as revealed by Holy Scripture, with the power of dominion over them. Aside from our own historical development, the world as we saw it was interpreted as the world that had existed unchanged from the moment of creation. Early in the 19th century, however, this view began to unravel. Georges Cuvier, a staunch creationist and the father of paleontology and comparative anatomy, correctly interpreted fossil evidence as indicating the existence of extinct species. His interpretation revealed for the first time a world of the past different from the modern one - a difference not of human making - and opened the door to the concept of evolution and the theories of Lamarck and Darwin which challenged the prevailing static worldview. Later, scientific discoveries in a number of different fields began to close the gap between humans and nonhumans. Paleontological evidence provided a graded series of hominids from the australopithecines to the three different species of the genus Homo and implicated either phyletic evolution or speciation in our origin. Molecular data demonstrated how close were are genetically to our nearest living ancestors, the great apes, despite the obvious difference in appearance between us. Behavioral studies further narrowed the gap. Until recently, culture was considered to be a uniquely human attribute. Tool use and later tool making were believed to be a distinguishing characteristic of humans until naturalists reported observations of sea otters using rocks as anvils to break open shellfish, of Galapagos finches molding twigs to probe holes in trees to obtain insect larvae, and of chimpanzees fashioning sticks to extract termites from their mounds. Today, we are aware of precultural tendencies (if not primitive cultures) in Japanese macaques (arboreal monkeys) which have learned under modified environmental conditions to wash sweet potatoes in sea water to remove sand and enhance flavor, sort out wheat kernels by putting them in water, and even to swim and exploit sea weed as a food source. Nongenetic modification of behavior has also been observed in the English titmouse, a small bird, which learned how to uncap milk bottles left on doorsteps and steal the surface cream. This habit presumably originated through the creative endeavors of a single individual and then spread like wildfire to neighboring districts as other birds imitated the discoverer of the trick. Thus, the rudiments of culture at least are to be found in other animal species. What accounts for the enormous capacity for cultural modification of behavior which characterizes Homo sapiens? In May, 1989 Jared Diamond speculated on this problem in an article entitled "The Great Leap Forward" published in Discover. Diamond noted that Stone Age cultures in Europe, Asia and Africa produced remarkably similar artifacts until the rise of Cro- Magnon people about 35,000 years ago. At about this date in history the Neandertals became extinct and a great diversity in cultural artifacts appeared in the archaeological record both within and between geographically separated populations. Diamond suggested that this "Great Leap Forward" in culture was the result of oral communication developed by the Cro-Magnon people. Before speech evolved, cultural transmission was achieved largely through imitation which explains why material culture was so uniform worldwide. When physical changes in the body evolved to permit speech and the intricacies of language developed to permit effective communication, individual creativity and the exchange of ideas through dialogue resulted in the observed diversity of cultural artifacts. Although this diversity became evident in the archaeological record about 35,000 years ago, Diamond suggests that the development of oral communication was gradual and so predated its manifestation in material culture. Just when the capacity for speech evolved may never be known. Thus, of all the features which distinguish us from other animals, the most important may have been the evolution of speech. This capacity enhanced societal cohesion and catapulted us into our current technological age which continues to turn out "artifacts" at an exponential rate. Little wonder that we have so vastly surpassed the achievements of our nearest relatives that it appears we were specially created! Evolution and Human Uniqueness When viewed in any cross section of time, the products of an historical process appear to be static. Evolution forces us to view the universe with a dynamic perspective: move back in time and the differences which exist today diminish, move forward and they become exaggerated. From an evolutionary perspective the gap between ourselves and other species is not so great as to preclude a mechanistic interpretation of its development. Theodosius Dobzhansky, a population geneticist who did much to advance the cause of evolutionary theory, once cautioned against oversimplification in considering the problem of human uniqueness. If emphasized too much, our uniqueness poses an obstacle to evolutionary interpre- tation; if taken too lightly, our novelty is overlooked. Dobzhansky considered the difference between ourselves and the great apes to be an example of "evolutionary transcendence" wherein a discontinuity emerged which greatly impacted on the future course of evolution. Other examples of evolutionary transcendence include the origin of eukaryotic cells, flowering plants and tetrapod verte- brates in the organic sector, and the use of fire, domestication of animals, discovery of agriculture and development of industry in the psychosocial or cultural sector of evolution. How might human uniqueness be classified from an evolutionary perspective? If human uniqueness is viewed as the product of speciation from our hominid ancestors, then it could be classified as a superficial difference in kind. This view fits into the punctuationalist model of macroevolution. On the other hand, if we view the evolution of speech, bipedalism and large cranial capacity as the product of a gradual transition over time rather than as a sudden quantum leap, then human uniqueness could be classified as a difference in degree consistent with phyletic evolution and the gradualist perception of macro- evolution. In either case the origin of human uniqueness is placed firmly within an evolutionary paradigm. At this point it might be argued that we have failed to consider a human quality which does not appear in any other species and thus constitutes a radical difference in kind between humans and nonhumans. Modern scientific discovery may have narrowed the gap between ourselves and other animals, but has not obliterated it, nor even substantially diminished it's magnitude. We alone possess a moral sense and the capacity to behave ethically through our faculties of intellect and free will (traditionally called the soul) - which faculties enable us to distinguish right from wrong and then make moral choices for which we are held personally responsible. These two faculties unite us as a species so that there are no degrees of being human. This view of human uniqueness is more difficult to reconcile with macroevolutionary process because there is no precursor upon which evolution could build. Moreover, such a unique attribute, found in no ancestor, fits well with the idea of creation. The problem for evolutionists, then, is to explain the adaptive significance of morality and the mechanism whereby it evolved. The Darwinian revolution is new and its full ramifications have yet to be explored. We are the product of both biological and cultural evolution. In the light of this insight we will have to grapple with some profound philosophical questions. Do we humans possess a common biological nature which, if understood, could form the basis for absolute, ethical values; or is human nature so culturally malleable that the determination of right and wrong depends upon social conventions which vary from culture to culture? Is human behavior determined by culture, genes or a combination of both to the extent that free will is an illusion, or are we free to choose between alternative courses of action and so be held responsible for our actions? Can evolutionary theory explain the origin of our unique moral sense. These questions will be the focus of our next topic: Evolution and Ethics.