Sociobiology is the systematic study of animal and human social behavior from the perspective of biological evolution, especially from the gene’s point of view. An evolutionary approach to social behavior means to focus not on the proximate mechanisms (e.g., biochemical or humoral) that cause a particular behavior, but mostly (even exclusively, if possible) on so-called ultimate explanations, which aim to discover why proximate behavioral machineries work that way and how they evolved as a result of natural selection.
The term sociobiology was coined by Harvard entomologist Edward O. Wilson in his book Sociobiology: The New Synthesis (1975). His bulky book is a valuable summary and synthesis of several new ideas about the evolution of animal societies developed in the U.S. and Britain between the mid-1960s and the mid-1970s. However, in the last chapter of his book, Wilson extended this newly emerging evolutionary approach to the social behavior of human species, which became the main reason for strong criticism of all sociobiology.
Most cultural and social anthropologists, sociologists, and philosophers felt and still feel insulted by the reduction of human behavior to what they called a biological and genetic determinism, which is, however, not a goal of sociobiology. They perceive socio-biology to be a modern renewal of Social Darwinism with all its objectionable consequences—justification of racial, economic, and gender inequalities—and a new pseudo-scientific apology for political conservatism. As a consequence of massive—and mostly unfair—criticism, sociobiology soon became an intellectual dirty word in academic circles. Today, the term sociobiology is seldom used by evolutionary biologists; however, sociobiological research is not dead. Sociobiological principles have become crucial parts of contemporary ethology, behavioral ecology, and evolutionary psychology.
Sociobiology has had a major impact on the conceptual revolution toward a gene-centered view of evolution. This paradigm shift in evolutionary theory was ingeniously and widely popularized by Oxford zoologist Richard Dawkins in his book The Selfish Gene (1976).
Altruism is often thought to be a distinguished mark of civilized human behavior, a quintessence of humanism that differentiates us from the brute and selfish world of animals as well as from barbaric Hobbesian human societies. In this popular scenario, the natural human default is selfishness; humans are born as self-oriented, egoistic beings who have to learn as they grow through enculturation and socialization how to behave altruistically and prosocially. However, this view of Nature as “red in tooth and claw,” which seems to be so well described in terms of “struggle for survival,” is seriously undermined by the existence of altruistic behavior among animals.
A generally accepted explanation of animal altruism until the 1970s was group selection theory, which states that evolution works for the benefit of species rather than individual organisms. For example, through natural selection, organisms can develop special mechanisms (e.g., physiological, behavioral) that sense population density and can put limits on individual reproduction in order to prevent population overgrowth. By those evolved mechanisms, short-term individual and selfish reproduction interests are counterselected in favor of long-term population survival. Group selection theory has been refuted on theoretical as well as on empirical grounds, and contemporary biologists consider it to be a fallacy. Any population of reproductive altruists would be extremely vulnerable to spontaneous selfish mutants that are not genetically disposed to control their reproduction. A population of genetically determined altruists would then quickly turn to a population of genetically determined self-seekers. Group selection is not impossible, but is very rare.
However, from a classical Darwinian point of view there is nothing more altruistic than sacrificing one’s own reproduction in favor of others. One can easily see why the Darwinian evolutionary parameter “fitness” is, in fact, misleading if we understand it as “survival success.” It is not survival itself that counts in evolution but producing offspring. Evolutionary biologists now prefer to talk about “reproductive success” instead of “fitness.” But then, how can sterile castes of social insects evolve by natural selection? Darwin was aware of the paradox of sterility in social insects like ants, bees, and termites, and he mentioned it in The Origin of Species (1859) as “by far the most serious special difficulty which my theory has encountered.”
It was William D. Hamilton (1936-2000), a PhD student at London University, who recognized the pivotal role of altruism and its extreme form, sterility, in evolutionary theory. In 1964 he published a mathematical theory of a new concept, “inclusive fitness” (later known as the theory of kin selection), which became a Holy Grail of sociobiology. It was generally known that fitness parameters actually represent the number of copies of a gene passed to the next generation, rather than the number of offsping produced by parents. But only Hamilton understood that copies of genes are multiplied not only directly, passing from parents to their own offspring, but also indirectly (with a probability that depends on degree of relatedness) through offspring of their relatives, and this indirect reproductive gain has to be included in a fitness parameter. Hamilton discovered a mathematical formula (known as Hamilton’s rule), which shows that from a gene’s point of view, there are conditions under which a gene responsible for altruistic behavior will evolve: the reproductive benefit to the recipient of the altruistic act multiplied by degree of relatedness has to be higher than the reproductive cost to the altruistic individual. Hamilton is now considered by some to be the greatest evolutionist of the second half of the 20th century since Darwin.
It is estimated that eusocial species with sterile castes, like ants and bees, appeared several times independently during Hymenoptera evolution. Hamilton’s rule offers an explanation for this evolutionary tendency. Due to a special haplodiploid reproduction of Hymenoptera (males are haploid because they come from unfertilized eggs, females are diploid), the coefficient of relatedness between female worker bees is 0.75, but between bee mother (queen) and her offspring only 0.50. It follows, according to Hamilton’s rule, that from a gene’s perspective there will be more copies of a gene produced if female workers support the reproduction of their mother and take care of their sisters instead of having their own offspring (all other things being equal).
Based on Hamilton’s rule, Richard Alexander, a zoologist from Michigan University, predicted the existence of a eusocial mammal living in a similar way as social insects, and this animal species was in fact later discovered on the Horn of Africa. Naked mole rats (Heterocephalus glaber) built subterranean tunnel systems inhabited by a colony of 70-80 members. There is only a single reproductive female, a queen, which mates only with one to three males who are brothers. Due to systematic inbreeding, the coefficient of relatedness among members of a colony is as high as 0.85.
A gene-centered perspective is able to explain unexpected altruistic behavior, and it is also able to elucidate unexpected antagonistic behavior, such as between parents and their offspring. It was Robert Trivers, then at Harvard University, who pointed in 1974 to a parent-offspring conflict over parental investment. An individual offspring is more closely related to itself than to its siblings and parents; therefore, a child is selected to demand more parental investment for itself than for its siblings, which is more than a parent is selected to offer, since parents are equally related to all their offspring. Trivers ingeniously recognized that such fitness conflict can be behind offspring manipulative behavior to compel more care than it is in the interest of parents to give. For example, sending false signals to the parents that the offspring is younger than it really is, or per-forming a temper tantrum behavior (familiar not only to our own species, but also to young pelicans, baboons, or chimpanzees) in order to solicit extra parental care.
One of the most common objections to sociobiology is that there are many examples of altruistic behavior between genetically nonrelated individuals, even between members of phylogenetically distant species, as in many cases of symbiosis, which obviously cannot be explained by kin selection. Robert Trivers proposed a theory of reciprocal altruism. The idea is very simple: an individual can be selected for altruistic behavior to a genetically unrelated individual if it is reciprocated later. The major problem is that this system is vulnerable to cheaters and freeloaders. However, using a game theory approach (iterated Prisoner’s Dilemma game) and computer simulations, he was able to demonstrate that under specific conditions, which can be met in nature, various cooperative strategies can be selected.
Sociobiology has been “dissolved” into modern ethology, behavioral ecology, and recently into evolutionary psychology. During the past three decades, scientists engaging in sociobiological research continually have been sharpening their conceptual thinking, improving their methodology in a way that cannot be easily accused of creating only evolutionary “just-so-stories,” and they have successfully accumulated empirical data in support of sociobiological principles.
- Alcock, J. (2001). The triumph of sociobiology. Oxford: Oxford University Press.
- Cronk, L., Chagnon, N., & Irons, W. (Ed.). (2000). Adaptation and human behavior: Evolutionary foundations of human behavior. New York: Aldine de Gruyter.
- Segerstrale, U. (2000). Defenders of the truth: The battle for science in the sociobiology debate and beyond. Oxford: Oxford University Press.