William D. Hamilton | Biography

William D. Hamilton, considered by many the most influential evolutionary biologist of his generation, is best known for his genetic explanation of altruism. Hamilton argued in the 1960's that humans and other animals have a genetic tendency to act in ways that favor the survival of their relatives, and thus, perpetuate their own genetic profile. In considering the genetic basis of human behavior, Hamilton looked at what genes do, and how their choices are not really choices at all, but the effect of genetic programming.

Born in Cairo, Egypt, where his father was working as a civil engineer, Hamilton grew up in England and studied Zoology at Cambridge University. He continued his studies as a postgraduate at the London School of Economics and University College, London. Years later, Hamilton reflected that his work was largely ignored, and he was not even given a desk at University College. A retiring student and scholar, Hamilton's mathematically dense studies of evolution were nearly incomprehensible to most of his professors and colleagues. After finishing his postgraduate work, Hamilton worked as a biologist and as a lecturer at Imperial College, London, where he started writing about evolution and the genetic basis of behavior. Hamilton's breakthrough work "The Evolution of Social Behavior" was published in 1964 by the relatively obscure Journal of Theoretical Biology, after being rejected by Nature magazine.

Hamilton's work on inclusive fitness, also called kin selection, uses mathematical odds to predict when an individual will sacrifice him or herself for others. Hamilton determined that the rate of self-sacrifice rises when the individual's sacrifice will protect family members. A biologist influenced by Hamilton, J.B.S. Haldane, described the theory of kin selection by saying, "one would lay down his life for three brothers, five uncles, or nine first cousins." This hierarchy is determined by genetic proximity of brothers, uncles, and cousins (in descending order) to the sacrificial person.

Kin selection suggests that selfish behavior does not always benefit one's self directly, but may do so indirectly through sacrifice that enables the perpetuation of an individual's family. Thus, Hamilton is able to make sense of behaviors that appear to incur more costs than benefits by measuring their advantageous effect on family members. For instance, the theory of kin selection helps to provide a genetic basis for parental caregiving. While a mother may expend energy for the good of her child, she is also perpetuating her own genes by securing the health of the child. Hamilton's determination of the selfish purpose of altruism continues Mendel's study of breeding that, over generations, follows mathematically predictable patterns.

In suggesting that altruism is genetically determined, Hamilton explained a facet of behavior that Darwin's theory of survival of the fittest did not allow for. In fact, natural selection actually favors the altruistic or selfish gene because although it incurs risk to its actor, by promoting a greater number of relatives than the individual altruist (who chooses between himself and three brothers, for instance), it actually promotes the perpetuation of more familial genes than the individual altruist possesses.

Hamilton's theory of a genetic basis for altruism finds statistical evidence for behavior patterns, which makes human choices look genetically or instinctively determined. This is a translation of intuitive or emotional behaviors into mathematical probability. Feelings or personality have little to do with our behavior according to this genetic understanding of human actions.

Hamilton's theory inspired E.O. Wilson's Sociobiology and Richard Dawkins's The Selfish Gene. Many scientists regard these Hamilton-inspired works as perhaps the most important evolutionary theory since Darwin.

Hamilton died in 2000, at age 63, after contacting malaria during field work in the Congo. At the time of his last endeavor, Hamilton was attempting to gather evidence for an unpopular theory, that the AIDS epidemic was caused by contaminated a polio vaccine.