sociobiology

sociobiology Some animals lead very solitary lives, but others, including humans, live in complex social groups. Sociobiology is the branch of biology that deals with the behaviour of these social animals. The term was coined by the Harvard entomologist, Edward O. Wilson, whose book of the same name brought to a wider public several important developments in theoretical biology that had been made during the 1960s and 1970s.

These developments addressed the phenomenon of altruism, which had long been seen as a problem in evolutionary biology (see evolution). Altruism is defined by biologists as any act that makes the recipient more likely to survive and reproduce while reducing the donor's own reproductive success. Since natural selection cares only about reproductive success, it seemed that altruism could not have evolved by such a process. And yet it was everywhere visible, from the parental care exhibited by mammals and birds to the selfless devotion of worker ants to their nest.

In the 1960s and 1970s, two solutions were proposed to this problem. The first of these was the theory of kin selection, which was first proposed by W. D. Hamilton in 1964. Hamilton argued that the spread of a gene did not depend only on its effects on the reproductive success of the body in which it sat, but also on its effects on the reproductive success of close kin, because they are likely to carry the same gene. A gene that caused its owner to risk his or her life to save several siblings, each of whom has a 50% chance of having the same gene, would spread quickly through the population, even if it often caused its owner to die childless. As Richard Dawkins put it graphically in The Selfish Gene (1976), the theory of kin selection showed that genes could proliferate by helping copies of themselves in other bodies.

Hamilton's theory of kin selection explains altruism between closely related individuals, but what about altruism between unrelated organisms? This is where the second solution to the problem of altruism comes in. In 1971, Robert Trivers argued that altruism may often be merely apparent, since it will turn out on a closer analysis to be a reciprocal exchange of favours. Trivers dubbed the phenomenon ‘reciprocal altruism’, and argued that the appearance of altruism is generated by the fact that the reciprocation may not be immediate. For example, a vampire bat may give up some of its food to a hungry companion one day without any immediate reward, but only because it expects that the favour will be returned in the future. In the years following Trivers' initial paper many biologists thought that reciprocal altruism was widespread in the animal kingdom. More recently, however, considerable doubt has been cast on this assumption.

The theories of kin selection and reciprocal altruism have led to much productive research in animal behaviour. When applied to human behaviour, however, they have generated much more controversy. Wilson's Sociobiology, for example, unleashed a torrent of criticism when it was published in 1975. Although he dedicated only a short final chapter of the book to human behaviour, the ensuing debate focused almost entirely on the possibility of applying sociobiological tools to humans. Social scientists, in particular, objected to such biological explanations on the grounds that they did not do justice to the rich cultural variability of human behaviour (see instinct).

After the initial backlash against sociobiology in the late 1970s, attempts to apply theories such as those of Hamilton and Trivers to human behaviour regained popularity during the 1990s. The second generation of sociobiologists, who are much more circumspect in avoiding some of the brash pronouncements of the 1970s, go under the name of ‘evolutionary psychologists’. Evolutionary psychology, while in many ways the heir of sociobiology, differs in stressing the importance of the mental mechanisms that mediate selective pressures and behaviour. It is thus more mentalist than sociobiology, and draws on the explanatory tools of cognitive science, such as the use of the language of information processing to describe the mind.

However, unlike cognitive scientists of a more classical bent, evolutionary psychologists reject the idea of a central ‘executive’ within the mind, arguing instead that co-ordinated behaviour emerges from a collection of psychological mechanisms, none of which is ‘in control’. These ‘mental modules’ are thought to be designed by natural selection to solve adaptive problems that were recurrently faced by our ancestors. For example, it is has been hypothesized that there is a module for detecting cheats, another for recognizing faces, and so on.

Like sociobiology, evolutionary psychology has attracted more than its fair share of critics. Some of these attack evolutionary psychology for allegedly excessive speculation, while others have ethical and political objections. Evolutionary psychologists reject both kinds of criticism. The debate goes on.

Dylan Evans

Bibliography

Pinker, S. (1997). How the mind works. Penguin, Harmondsworth.
Wilson, E. O. (1975). Sociobiology: the new synthesis. Harvard University Press, Cambridge, MA.

See also evolution, human; genetics, human.