Biology: Sociobiology

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Biology: Sociobiology


Sociobiology is the study of the biological basis of social behavior in all species of animals, including humans. In 1975 Edward O. Wilson (1929–) wrote Sociobiology: The New Synthesis in which he challenged the philosophical and scientific foundations of the social sciences by applying evolutionary biological theory to the behavioral analysis of social animals and humans.

The fundamental principle of evolutionary theory is that reproductive success is based on the success with which an individual adapts to its environment. Individuals and species that adapt well to their environment have increased reproductive rates and pass their genes on to the next generation more frequently than less-well adapted individuals in that environment. This process is called the natural selection of biological features or traits. Sociobiology expands evolutionary theory to cover social behavior in both animals and humans, positing that behavioral strategies are subject to the same laws of natural selection as other biological traits.

Sociobiology holds that evolution leads to the development of psychological, social, and cultural features just as it results in changes to genes and bodies. In the case of humans, when parents and offspring share physical and social environments, the behavioral effects of inherited genes are reproduced in the new generation. Furthermore, reproductive success is related in most human cultures to greater wealth, social status, and power.

Although applying sociobiology to animal behavior and sociality enjoys wide acceptance, its application to human sociality as outlined in the final chapter of Wilson's book has engendered persistent opposition and controversy. The opposition rejects the idea that the innate physical, intellectual, and creative differences in humans have genetic roots. Opponents believe that such differences are solely produced by social and cultural forces, which are, in turn, strongly influenced by socioeconomic status and society's technological evolution.

Historical Background and Scientific Foundations

In the final chapter of Sociobiology, Dr. Wilson describes a program for future research into the animal roots of human behavior. He proposed a sociobiologic framework for possible evolutionary roots of each aspect of human behavior. These categories, he said, included social organization, cooperation and competition, sex roles, communication, religion, and ethics.

In general, Wilson classifies human behavior into fundamental traits, separating those that are “conservative,” or linked to humanity's primate heritage, from those a “quantum jump” beyond it, which are presumed to have developed during the evolution of early humans, about 2.5 million years ago. Wilson also discusses evolutionary characteristics that he believes developed after humankind's divergence from the primates. Rather than take these observations at face value, however, Wilson suggests readers view them as broad hypotheses that should be tested empirically.

The Plasticity of Social Organization

Wilson notes that the parameters of social organization, including group size, hierarchical properties, and rates of gene exchange between communities, have much greater variability or “plasticity” among human societies than those of primates. This is accompanied by enormous variability in individual behavior—an extreme extrapolation of a trend also apparent in baboons, chimpanzees, other apes, and monkeys.

Wilson hypothesizes that this is due to the evolutionary selection of genes that promote flexibility in social behavior. Conventional wisdom, according to Wilson, says that virtually all differences between cultures are “phenotypic” (learned) rather than genetic, a hypothesis based on observations that certain important aspects of culture can easily be altered in a single generation. Cultural change occurs too quickly to be attributed to evolution. Furthermore, genetic variation between human groups is very limited and cannotexplain the large differences in behavior that exist from one culture to another.

On the other hand, certain aspects of personality that affect cultural variation (e.g., introversion-extroversion measures, neuroticism, dominance, depression, and some forms of mental illness such as schizophrenia) are widely acknowledged to have genetic components. Wilson believes that anthropological genetics could explain the underlying genetic basis for cultural variability, but he also outlines two indirect methods of studying the way in which the human genome influences cultural differences.

First, models based on the most basic aspects of human behavior can be constructed and tested to see how well they predict actual behavior. Wilson cites American psychologist Abraham Maslow's (1908–1970) “hierarchy of human needs” as an attempt to systematize these basic aspects of behavior. He also cites the Skinnerian (see below) approach of George C. Homans (1910–1989) to reduce human behavior to the basic processes of associative learning—stimulus and response.

The two systems converge on the basis that evolution determines which circumstances appear as “rewards” or “punishments” to the brain's emotive centers. American psychologist B.F. Skinner (1904–1990), the founder of the behaviorist school of psychology, acknowledged the role of genetic factors in mediating the connection between particular stimuli and responses to them by various individuals and species.

The second indirect approach that Wilson proposes uses “phylogenetic analysis,” in which man is compared with other primate species to understand the basic elements of humankind's more complex social behavior. Wilson acknowledges the contribution of various ethologists (zoologists that study inborn animal behavioral patterns) such as Austrian biologist Konrad Lorenz (1903–1989), American playwright and anthropologist Robert Ardrey (1908–1980) and British zoologist and ethologist Desmond Morris (1928–), while pointing out that these writers overreached in trying to explain all social behavior in terms of hypotheses based on the behavior of a few species.

Instead, Wilson favored a rigorous study of biological traits in closely related species (called a “phylogeny” of these traits). “Conservative” traits are fairly constant throughout the primates and are most likely to have persisted into human evolution. These include a social structure based upon aggression and dominance, modulation of responses during aggressive encounters, intensive and prolonged maternal care and socialization of the young, and matrilineal social organization (i.e., tracing of descent and inheritances by siblings with the same mother, often found in primitive but not industrial societies, which are “patrilineal” and trace lineage through the father). Other traits are more labile (variable) across primates and are characteristic of particular species, but could also have high heritability within species.

The plasticity of social organization and the ease of cultural change (and its rapidity compared to biological evolution) could thus be explained in terms of variability among humans in these labile traits—those most likely to differ from one society to another. This comparative ethological approach, Wilson notes, would shed little light on unique human traits that have no analog in primate societies, including “true” language (as opposed to inborn or very concrete symbols used in communication among primates), elaborate culture, continuous sexual arousal and activity throughout the year (instead of being confined to periods of female estrus or “heat”), incest taboos and marriage exchange rules, and the cooperative division of labor between adults.

Barter and Reciprocal Altruism

Wilson observes that sharing is uncommon among primates, but is so strongly characteristic of human societies that it rivals the level of sharing among termites and ants. This sharing gives rise to economic life, beginning with what Wilson calls “true bartering,” made possible by man's high intelligence and infinite ability to symbolize practically anything. In his view, money almost paradoxically becomes the embodiment of reciprocal altruism since it has no intrinsic value in itself, being comprised of pieces of paper and scraps of metal. Backed as it is by humanity's phenomenal urge to cooperate (in the form of governments), it becomes both valuable and versatile, usable in exchange for almost anything.

Citing the anthropologist Claude Lévi-Strauss (1908–) in Les Structures élémentaires de la parenté (The Elementary Structures of Kinship), Wilson outlines how barter, the foundation of economic life, begins in primitive societies with the trading of foodstuffs and (especially) women, leading to the formalization of marital exchanges designed to further transmit the genes of older males. These rules, especially in polygynous societies, insure political and genetic advantage to a tribe's older men. Exogamy, the requirement to marry outside of a tribe, leads to considerable gene flow between tribes. A consequence of these kinship rules is a high degree of genetic similarity observed among tribal groups within societies.

Bonding, Sex, and Division of Labor

Wilson observes that all human societies, from a band of hunter-gatherers to the populace of an American industrial city, are organized around the households of nuclear families. The integrity of family units is maintained by visits (or letters or phone calls) and the exchange of gifts. Sexual activity is fairly continuous throughout the menstrual cycle, which helps cement the emotional and sexual bonds of the nuclear family, and has little to

do with ovulation and procreation. Kinship bonds also increase the cohesiveness of human groups, since they increase the conflict-free emigration of young members between families and clans, bind alliances between clans and tribes, and facilitate mutual support between tribal subgroups during hard times. This type of altruistic support is unknown among social primates. Wilson opines that the moralistic rules governing the behavior of individuals in even the most complex industrial societies, in which kinship is either extremely attenuated or nonexistent, are essentially the same rules that govern the members of hunter-gatherer societies.

Role-Playing and Polyethism

Wilson ascribes the complexity of human societies to the intelligence and role-playing flexibility of individuals and notes that extremely complex contemporary society, with its constant demands for fulfillment of multiple roles, presses the limits of individual adaptiveness and leads to problems of self-identity. He explores the development of social classes and castes and observes that while one would expect a great deal of genetic differences or “stratification” between classes to develop over time, assuming that individual characteristics such as intelligence and energy have a genetic basis, there appear to be few genetic differences between classes and little evidence for hereditary solidification of social status. He also notes that cultural evolution is too fluid and pathways for upward mobility are too numerous to allow for genetic segregation by social class. Since the factors for human success are myriad, (intelligence, energy, drive, creativity, entrepreneurship, etc.) and likely to be polygenic (and residing on multiple chromosomes), forces that favor genetic diversity prevail, and the correlations between particular genetic traits and social success are loose. Wilson thus deems the formation of stable groups of genes within social classes to be extremely unlikely.

Nevertheless, he allows for the formation of particular basic types of human beings based on complexes of genetic factors (polyethism) and offers several examples, including homosexuals and the prevalence of people who are predominantly verbal versus people who are predominantly action-oriented or “doers.” He admits that there is currently no way to know whether these human types are truly genetic or are instead triggered entirely by experiences in early childhood.


Language is pivotal to all human social behavior and consists of words, which have arbitrary symbolic definitions and complex grammar that imparts meaning above and beyond these definitions, creating a nearly infinite number of messages that can be transmitted between individuals. Wilson believes that the development of human speech represents a quantum jump in evolution beyond that of primates. Furthermore, even nonverbal human communication is itself immensely richer than that of primate species. He notes the divergence of the human vocal apparatus from that of the chimpanzee and how its versatility was essential to the evolution of human speech.

The final chapter of Sociobiology devotes considerable space to the exploration of the deep structure of language; Wilson declares that this discipline is ripe for the application of rigorous theory and experimental investigation. Music has a similar capacity for unlimited arbitrary symbolization as well as rules of phrasing and order that make it analogous (and complementary) to language itself.


Culture has permeated nearly every aspect of human life, and, according to Wilson, is not genetically determined. The human capacity for and the overwhelming tendency to develop cultures, according to Wilson, have evolvedfar beyond those possessed by monkeys and chimpanzees. Wilson defines culture as a hierarchical system of environmental tracking devices that are largely adaptive in a Darwinian sense (that is, they help people survive and reproduce). Cultural behaviors change in response to the environment to which they are targeted; for example, nomadic lifestyles based on grazing animals can give way to settled agricultural lifestyles based on raising crops as rainfall increases in a region.

Evolving technology changes both the physical environment and the significance of its various features (e.g., air-conditioning reduces the impact of high temperatures on economic activity in modern cities) and is an example of a rapidly changing feature of human culture. Slowly changing aspects are rituals and sacred religious beliefs. Wilson notes that humans are easy to indoctrinate and, indeed, he says, seek indoctrination.


In advancing the idea that ethics is grounded in biology, Wilson begins by explaining the “intuitionist” ethical system formulated by American philosopher John Rawls (1921–2002), in which the principles of “justice as fairness” are those that he believes free, rational people would choose if they were beginning a relationship in which they have equal advantages. The intuitionist framework treats the brain and its emotive states as a “black box” and, according to Wilson, does not explain or predict human behavior nor does it consider the ecological and genetic consequences of adhering to its principles.

On the other hand, “ethical behaviorism,” the first attempt to conceptualize ethics in biological terms, as explained by J.F. Scott, holds that morality is learned entirely by operant conditioning—behavior shaped by rewards and punishments. In this view, as humans grow up they internalize the behavioral norms of society.

Opposed to this conception is the “developmental-genetic conception” of ethical behavior expounded by American psychologist Lawrence Kohlberg (1927–1987). Kohlberg classifies moral judgment into levels and stages of development: 1) the most primitive level is that moral value is defined by punishment and reward; 2) at a slightly more advanced level, moral value resides in filling the correct roles to maintain order and meet others' expectations; and 3) at the level of highest development, moral value resides in conforming to shared standards, rights, and duties. These stages reflect the level of development typically achieved by young children, adolescents, and mature adults respectively, because selfish children, peer-bonding adolescents, and judiciously altruistic adults may have selective advantages at each stage of life and state of society. These categories may also describe the stages of moral development achievable by the human species as it diverged from other primates. Wilson avoids any attempt to impose a universal code of ethics because this would inevitably conflict with selective advantages inherent in different types of behavior among various groups, leading to the intractable moral dilemmas of modern society.

Wilson critiques both ethical concepts by noting that behaviorism postulates a mechanism (operant conditioning or stimulus-response according to rewards and punishments) without any empirical evidence, while the cognitive-developmental theory provides substantial experimental evidence (such as Piaget's elaborate experiments) but doesn't postulate a mechanism. Characteristically, Wilson expresses confidence that the two will eventually merge as data accumulates; he believes that ethical behavior appeals to the brain's innate emotional predisposition and that people learn through conditioning that rewards ethical behavior.

A Research Agenda for Sociobiology

The principles of sociobiology as applied to human societies have given rise to determined opposition among scholars, especially sociologists and anthropologists. They charge that sociobiology espouses biological determinism—the belief that biological factors explain human behavior. Social sciences over the past century, on the other hand, have sought to explain human behaviors in terms of social structure and cultural learning. Social scientists's fundamental disagreement with sociobiology is that it appears to disregard the role of mind, learning, and reason.

Cultural anthropology, for example, focuses on the way in which an individual participates in and adapts to a culture, which itself is an adaptation by a society over time to the natural environment, expressed in terms of technology, social relationships, and beliefs. When E.O. Wilson first expounded the principles of sociobiology, it appeared that he wanted to replace the paradigm that people are free of instinctual predispositions and develop personalities that reflect social organization and cultural learning. He proposed that human behavior is determined by evolutionary adaptation over millennia, and variation in behavior reflects a genetic equilibrium fostered by the evolutionary environment. Thus cultural learning can maximize or detract from individual fitness, but culture's function is to improve the reproductive fitness of its participants.

Sociobiologic Explanations of Social Behavior

As stated above, the final chapter of Sociobiology: The New Synthesis broadly outlines an ambitious research agenda for the new scientific discipline of sociobiology. Wilson theorizes that precious little is known about humankind's relatively recent and crucial evolutionary divergence from the cercopithecoids (the great apes),during which the major distinguishing aspects of human sociality (true language, intense cooperation, and continuous sexuality) emerged. Therefore, while biologists can surmise that human sociality has a genetic basis, Wilson acknowledges that this is a long way from tying any particular social trait to the human genome. Sociobiology's path is similar to that for any scientific discipline: the careful definition of particular behaviors or social traits, the painstaking linking of these behaviors to physiological and biochemical variables, and the tracing of these variables to genetic variation.

The fundamental and crudest form of sociobiologic explanation appears simplistic: A behavioral trait exists because it maximizes the transmission of particular genes that maximize biological fitness. Such basic explanations are also difficult to prove false, since almost every trait that exists could be imagined to have some kind of fitness advantage under some circumstances. Traits that are maladaptive to particular environmental conditions will not persist, because individuals with them will have lower survival and reproduction rates.

Since there is only a very sparse record of the prehistoric conditions that led to the evolutionary “quantum jumps” that now separate humans and primates, observational evidence for any particular sociobiologic hypothesis is nearly impossible to produce. Biologists at Stanford University have devised a framework for empirical investigation of sociobiologic hypotheses that supplements the ideas for further research that Wilson originally advanced. Their goal is to distinguish between the proximate and the ultimate causes of human behavior.

Take, for example, the strong preference many people have for sweet foods. The existence of taste receptors for sweetness reinforces this preference, and the existence of these receptors is the proximate explanation of the prevalence of preferring sweet foods. Evolutionary biologists would say, however, that because such foods are a source of quick energy, that people have receptors for sweetness because eating sweet foods maximized their fitness. The Stanford group stipulates that to avoid being overly simplistic and unfalsifiable, sociobiologic hypotheses must describe the explanandum (the thing that needs to be explained) precisely, and explain its function in terms of evolutionary history.

A second example is the prevalence of sex-role stereotypes across cultures. Social scientists have often assumed that humans are born with no innate predispositions or mental contents (a tabula rasa, or blank slate). They explain sex differences in children's behavior by hypothesizing that they were created by the differential treatment of parents who held sex-role stereotypes. However, the Stanford group claims that research shows no clear causal link between these stereotypes, parental behavior, and ensuing child behavior.

Sociobiologists argue that the innate differences in babies and children trigger parents' differential treatment of boys and girls. They also cite the Trivers-Willard hypothesis, which states that females with low status and less access to resources tend to have more female offspring, and those with high status and more access to resources tend to have more male offspring.

To bring this hypothesis to bear on humans, Valerie Grant in 1990 added an additional hypothesis that high social status affects a woman's physiology in a way that influences both the sex of her child and her parenting style. Thus socially dominant women have higher testosterone levels, which, as a proximate cause, would make them more active, assertive, and independent than other women. Their child rearing style would be affected in terms of an ultimate mechanism of enhanced fitness in Grant's hypothesis, because boys should gain higher fitness from the parenting style that a dominant woman would tend to use, and girls might gain higher fitness from the parenting style that a subordinate woman would tend to use. Although Grant's model will need to survive an empirical test, it demonstrates the attempt by sociobiologists to integrate physiological, psychological, and evolutionary dimensions of behavioral phenomena by focusing on the ultimate function of behavioral strategies that are sensitive to particular social contexts.

Sociobiological explanations must not only provide ideas but place the explanandum in a theoretical context. To do so, behaviors must be described, and descriptions are controversial. Traditional social science's attempts to explain specific behaviors usually leave large unexplained areas and are generally of uncertain predictive value. In particular, these approaches do not attempt to explain behavior in functional terms except in the sense of the “natural history” of social life. In other words, sociologists explain behaviors in the context of a sociocultural system, but do not attempt to explain the existence of the sociocultural system itself in an ultimate sense.

Altruism and Selfishness: An Example of Sociobiologic Explanation

Darwin's arguments for natural selection do not characterize the evolutionary process as “selfish” or “altruistic,” but rather as functional, so that adaptive traits are those that help organisms solve problems. Selection increases the frequency of adaptive traits that give their bearers advantages in the competition for reproductive success, and these advantages can occur through either altruistic or selfish traits. There are mathematical formulae arising from game theory that demonstrate the cost-benefit analysis of the conditions under which altruism or cooperation is favored or disfavored by selection, but contemporary evolutionists know that evolution is a high-wire act that balances individual and group interests.

Research into the phenomena of selfishness and altruism affords examples of how sociobiological explanations can be tested empirically. The first step is to outline the core principles of the sociobiology research program in philosophical terms. The second step is to define specific examples or variants of the selfishness/altruistic behavioral continuum, e.g., ranging from “selfish cheater” to “unselfish cooperator,” with the latter presumed to be much more common than the former. “Normal” behavior is cooperation for mutual benefit, although there are many opportunities for cheating and sometimes people who usually behave normally take advantage of these opportunities. Cheating occurs when one person accepts help from another, but either does not reciprocate or reciprocates less than the other.

The process of reciprocation can take many years and requires a detailed accounting, good memory, and a battery of emotional responses including guilt, fairness, moralistic aggression, gratitude, and sympathy for the cost-benefit accounting to come out even. As an example, people feel guilt when they are expected to reciprocate but cheat instead. Their sense of fairness arises from sensitivity to whether costs are in proportion to benefits to self and others. Gratitude arises from having received a benefit without having first donated a benefit to another party; people who have been fooled by cheaters evoke sympathy.

Modern Cultural Connections

Sociobiology as a discipline will not thrive unless it can help unravel contemporary sociocultural and psychological issues and solve problems. To illustrate sociobiologists's attempts to shed light on sociocultural issues, this section addresses the phenomena of sociopathy and adoption.

Sociopathy as a Fitness Strategy

To sociobiologists, normal people are reciprocal altruists (those who act for the benefit of others without expecting immediate gain) who are sometimes tempted to cheat. Sociopaths adopt cheating as their primary strategy—when they can get away with it. This behavior can be explained in proximate terms by a life history involving biological, psychological, and sociocultural variables.

Can sociopathy as a primary behavioral strategy be adaptive? In 1995 ethologist Linda Mealey (1955–2002) identified certain ancestral conditions that could have made it so. She followed a strict process for the construction of sociobiologic explanations, first hypothesizing the adaptive function of a behavior such as cheating. Secondly, she identified an evolutionary model that pertains to the evolution of sociopathy as an adaptive behavior. Third, she connected the evolutionary models to the distinctive attributes of that behavior. Fourth, she postulated one or more life-history strategies (for example, adapting to a history of domestic violence). Fifth, she gathered multidisciplinary (biological, psychological, sociocultural) evidence to support her causal model. She distinguished causal links from correlations, and found causal pathways for the development of sociopathy. Mealey's process of integration yielded a dual-pathway evolutionary biopsychosocial model of sociopathy that has been evaluated by various commentators.

All life histories, according to this concept, are genetically determined, but genetic and environmental influences vary in each. In Mealey's theory of sociopathy, the genes of primary sociopaths give them the potential to cheat in much the same way under almost every circumstance, while the genes of secondary sociopaths give them the potential to vary their cheating behavior as developmental and social environments change. Sociopaths are products of natural selection for a high frequency of cooperators and a low frequency of cheaters, but these evolved strategies become manifest in individuals as the result of specific proximate mechanisms involving various psychological, familial, social, and cultural conditions. Thus the sociopath comes into being as a result of nurture (or the lack thereof), but sociobiologic research is designed to show how “nurture operates via nature,” as well as the converse. So, for example, better child nurturance in the family might avoid the emergence of sociopathy in individuals who could be inclined that way.

According to Mealey's explanation, an adaptive function of cheating is to raise one's reproductive advantage, adopting such a strategy becomes a competitive disadvantage (especially for males) with respect to the ability to obtain resources and mating opportunities. The oretically, those individuals who are the least likely to out-compete other males in a status hierarchy (e.g., within the nuclear family), or to achieve mates through female choice, are the ones most likely to adopt a cheating strategy. In humans, competitive disadvantage could be related to a variety of factors, including age, health, physical attractiveness, intelligence, socioeconomic status, and social skills. On the psychological side, heritable temperament factors suggest that, especially for males, genetic risk of delinquency is tied to the temperamental attributes of anger, impulsivity, and deceitfulness.

However, this same analysis found that environmental factors related academic non-achievement with juvenile delinquency. And while about half of delinquents studied later outgrew their delinquency, juvenile delinquency remains the single-best predictor of criminality in adults. These findings provide evidence for Mealey's two-pathway model in that a gene-environment interaction (a) would create at least two possibleroutes to sociopathy, one more heritable and one less so; and (b) the less-heritable pathway would predict developmentally and environmentally dependent individual differences in antisocial behavior. Furthermore, statistically significant environmental factors found in other studies cited by Mealey varied within families and were more significant for males than for females. Biological factors, including low monoamine oxidase (MAO) levels and high testosterone levels have also been correlated with sociopathic and criminal behavior in various studies, thus adding potential biological mechanisms to Mealey's model, which are essential if it is to have evolutionary plausibility.

Wim E. Crusio criticized Mealey's evolutionary reasoning as logically flawed. He found that the evidence she presented in favor of a genetic contribution to the causation of sociopathy is speculative and confounded with environmental factors. He argued that, given the potentially large societal impact of sociobiologic speculation on the roots of criminality, extraordinary caution in interpreting data is called for. In general, he states, sociobiologists demonstrate a cavalier attitude regarding the potential harm in attributing a genetic cause to any type of human behavior, since such attribution will reduce the sense in society that such behavior can be altered for the common good. This could lead to relegating individuals such as criminals to an incorrigible status, reducing the incentive to provide rehabilitation or corrective services.

Sociobiology and Adoption: An Empirical Test of a Sociobiologic Hypothesis

Daniel K. Brannan, a biology professor at the Abilene Christian University, tested a sociobiologic hypothesis pertaining to adoption behavior. He explored whether or not evolutionary explanations of altruism show that self-sacrificial behavior is a biological adaptation, a religious ideal, or some combination of the two. To do so, he tested whether adoptive behavior, since it appears to be genetically altruistic, is “pure” self-sacrifice in the religious sense, or whether it has pro-social and egoistic explanations that are amenable to evolutionary explanations.

Brannan considered three hypotheses regarding the sociocultural and biological antecedents of adoption behavior. The first is that adoption is not influenced by evolutionary adaptation but reflects learned cultural beliefs about the value of children and the nature of kinship. The prediction based on such a hypothesis is that there would be great cross-cultural variability in patterns of adoption, but studies suggest that this is not the case, and that considerable cross-cultural homogeneity in adoption patterns exists. The second hypothesis is that if adoption is evolutionarily adaptive, one would expect it to be more common among genetic relatives or reciprocating non-relatives. One might also expect that adopting parents would be limited to the infertile, who are forced to adopt non-relatives. The third possibility that he considers is that there is an attraction to neonatal features shaped in an earlier evolutionary environment that is currently misdirected in industrial societies. For example, in small hunter-gatherer groups, fitness might be maximized by providing for abandoned or orphaned children in order to increase the group's future population and because, in such a small group, the probability of genetic relationship is high, given the prevalence of cuckolding.

Nevertheless, the adoption of non-relatives occurs with fairly stable but low frequency in industrial societies where the probability of kinship with the adoptee is practically zero, so the impulse to adopt can be seen as “misdirected” from the perspective of maximizing reproductive fitness. Brannan maintains that data collected in industrial societies show that Darwinian explanations are sufficient in both traditional and industrial societies to explain adoption. In traditional societies, adoption can be almost completely explained by maximizing group (inclusive) fitness and reciprocity, while in industrial societies both these mechanisms as well as proximate ones operate through “misdirected” adaptive behaviors.

Fertile women with only one biological child (not considered a full genetic complement of offspring) are extremely unlikely to adopt. Fertile women with two or more children were much more likely to adopt than those with one child, perhaps because they already have a full complement of genes in the next generation and an adoptive child represents a minor burden. These results are as expected from an evolutionary viewpoint. Women who know or believe that they are fertile wait until they have a full complement of genes in the next generation prior to adopting.

Studies also show that few women with fecundity problems choose adoption. These few adoptions can be explained simply by the misdirected adaptation hypothesis: a proximate explanation that people desire children even when having them no longer has the evolutionary effect of maximizing reproductive success. Brannan concludes that adoption does not necessarily appear to be altruism in the ideal, religious sense.

However Brannan does present an interesting evolutionary model even for the religiously motivated and idealistic type of adoption, albeit rare. Biology can explain reciprocity and inclusive fitness mechanisms while cultural transmission helps explain pro-social and cooperative behaviors and symbolic thinking explains group inclusiveness. But to explain the rare behavior of saints and celibates, a further explanation in terms of the human capacity to idealize is necessary. Brannan concludes with a thought that in many ways is the antithesis of E.O. Wilson's dark musings at the conclusion ofSociobiology in which he voices the fear that once humans finally understand themselves down to the very neuron and gene, they might not like what they learn—they might find themselves locked into an evolutionary course that might not be welcome. Brannan holds out the hope that altruism, the cooperative elevation of the entire species, provides humanity with a hopeful purpose even in the face of what may actually be an absurd universe, provided that people act on it rather than sit passively, waiting for a future of conflict and futility to happen to them.


Probably the most important consequence of sociobiology to social science and psychology is the notion that while individual human behavior, social structure, and cultural adaptation are amazingly malleable, human biology constrains them at both the individual and socio-cultural levels. Sociobiologists hold that the ideological and technological limits to which individuals and societies can adapt have been set by the phylogenetic characteristics of human nature developed over the past two million years. Barring further uncharacteristically rapid biological evolution, human societies that have been advocated by various political and social movements will probably not come to pass. For example, Wilson opined in an interview that Karl Marx was right, except that he was thinking about the wrong species, and Marxism as a philosophy might be on target for ants, but will never thrive among human beings without the kinds of tyranny and repression characteristic of Stalin and Mao in order to enforce an unnatural “equality.” The innate behavioral and emotional differences between the sexes—from childhood play preferences to the likelihood of developing sociopathy—may never be erased by upbringing and social conditioning without unacceptable psychosocial consequences.

Sociobiology has been condemned as “bad science” and worse by behavioral and social scientists. Its constraints on human nature might block sociopolitical paths in which individual or social differences are eliminated on one hand, or excessively emphasized and channeled on the other for political ends. In spite of academic and political opposition, sociobiology continues to build an empirical research foundation. Sociobiologists theorize that evolutionary models do not prove anything and suggest alternative hypotheses to be explored and substantiated. Furthermore, the discipline seeks increased emphasis on understanding and solutions for the difficult problems of modern society: war, crime, poverty, and psychosocial stress.

See Also Biology: Evolutionary Theory; Biomedicine and Health: Psychology and Psychiatry.



Casti, John L., and Anders Karlqvist. Cooperation and Conflict in General Evolutionary Processes. New York: Wiley Interscience, John A. Wiley and Sons, 1995.

Darwin, Charles. The Descent of Man and Selection in Relation to Sex. London: John Murray, 1871.

Darwin, Charles. The Expression of Emotions in Man and Animals. London: John Murray, 1872.

Darwin, Charles. On the Origin of Species by Means of Natural Selection. London: John Murray, 1859.

Mealey, Linda. Sex Differences: Development and Evolutionary Strategies. New York: Academic Press, 2000.

Wilson, Edward O. Sociobiology: The New Synthesis. 25th anniversary ed. Cambridge, MA: Harvard University Press, 2000.


Crusio, Wim E. “The Sociopathy of Sociobiology.” Behavioral and Brain Sciences 18, no. 3 (1995) 552.

Mealey, Linda. “The Sociobiology of Psychopathy: An Integrated Model.” Behavioral and Brain Sciences 18, no. 3 (1995): 523.

Trivers, R.L. “The Evolution of Reciprocal Altruism.” Quarterly Review of Biology 46 (1971): 35–57.

Web Sites

Human Nature Review. (accessed November 18, 2007).

New Criterion Online. “Exorcising Sociobiology.” (accessed November 18, 2007).

Roes, Frans. “Speak Darwinists! Edward O. Wilson.” (accessed November 18, 2007).

Kenneth T. LaPensee

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