W. D. Hamilton turned kindness toward relatives into a simple equation
Why would an animal sacrifice itself for another? W. D. Hamilton's answer, published in 1964, was that helping a relative can spread your own genes, provided the benefit multiplied by your genetic relatedness outweighs the cost. Reviewers struggled with the mathematics, yet Richard Dawkins later called him the greatest Darwinian of his lifetime.
Hamilton was born in Cairo in 1936, the second of seven children of New Zealand parents, an engineer and a physician. Growing up in Kent, he collected butterflies, and E. B. Ford's book on them introduced him to natural selection and genetics at about ten. At 12 he was badly hurt playing with explosives his father had kept from making grenades for the Home Guard, losing parts of several fingers. At Cambridge he found many biology teachers oddly lukewarm about evolution.
Ronald Fisher and J. B. S. Haldane had glimpsed the puzzle of helping kin without properly formulating it. Working through examples, Hamilton noticed the same figure kept appearing, Sewall Wright's coefficient of relationship, a value between 0 and 1. His rule applied neatly to ants, bees and wasps, whose odd sex-determination system leaves females more closely related to sisters than to their own potential offspring, which could explain sterile workers raising siblings. Two referees passed over his papers; the third, John Maynard Smith, saw their importance, though the pair later clashed over credit. Largely ignored at first, the work reached a wide audience through Dawkins's 1976 book The Selfish Gene, helpfully, since Hamilton was a poor lecturer.
While lecturing at Imperial College, his study of unusual sex ratios in wasps introduced the unbeatable strategy, which Maynard Smith and George Price developed into the evolutionarily stable strategy of game theory. He also analysed spite, harming others at a cost to oneself, and argued it rarely becomes elaborate. At Michigan, where students staged sit-ins over his ties to sociobiology, he worked with Robert Axelrod on the prisoner's dilemma.
Hamilton championed a Red Queen view of sex: shuffling genes keeps offspring one step ahead of parasites, which in turn keep adapting. He even suggested algae release sulphur compounds that seed clouds to help disperse themselves. Late in life he backed the now-discredited idea that HIV came from 1950s polio vaccine trials, travelling to the Congo in 2000 to test it. He died that March.
Source: W. D. Hamilton
