William Donald Hamilton FRS (1 August 1936 – 7 March 2000) was an English evolutionary biologist whom Richard Dawkins praised as one of the greatest evolutionary theorists of the 20th century.^[1]

Hamilton became famous through his theoretical work on kin selection and altruism. He explained its genetic basis, and this was a key part of the gene-centered view of evolution. In doing this, he became one of the forerunners of sociobiology, as popularized by E.O. Wilson. Hamilton was certainly a big influence on Dawkins. He also published important work on sex ratios and the evolution of sex. From 1984 to his death in 2000, he was the Royal Society Research Professor at Oxford University. He died of malaria contracted in the Democratic Republic of the Congo.

Hamilton's equation describes whether or not a gene for altruistic behaviour will spread in a population.^[2] The gene will spread if rxb is greater than c:

${\displaystyle rb>c\ }$

where:

• ${\displaystyle c\ }$ is the reproductive cost to the altruist,
• ${\displaystyle b\ }$ is the reproductive benefit to the recipient of the altruistic behavior, and
• ${\displaystyle r\ }$ is the probability, above the population average, of the individuals sharing an altruistic gene – the "degree of relatedness".

Hamilton started to publish his collected papers starting in 1996, with short essays giving each paper context. He died after the preparation of the second volume, so the commentaries for the third volume came from his coauthors.

• Hamilton, W.D. (2005). Narrow Roads of Gene Land: Volume 1: Evolution of Social Behaviour. Oxford University Press on Demand. ISBN 978-0-7167-4530-3.
• Hamilton, W.D. (2001). Narrow Roads of Gene Land: Volume 2: Evolution of Sex. Oxford University Press. ISBN 978-0-19-850336-1.
• Hamilton, W.D. (2005). Narrow Roads of Gene Land - The Collected Papers of W.D. Hamilton: Volume 3 - Last Words. Oxford University Press on Demand. ISBN 0-19-856690-5.