John Maynard Smith, 84; Applied Game Theory to Evolution, Asked Why Animals Developed Sex

John Maynard Smith, one of the most influential evolutionary biologists of the latter part of the 20th century, has died. He was 84.

Diagnosed with lung cancer more than a year ago, Maynard Smith died Monday at his home in southeast England, sitting in his high-backed chair and surrounded by his books.

Famed principally for applying a mathematical approach known as game theory to the study of evolution and his work on the evolution of sex, Maynard Smith is credited by colleagues with influencing evolutionary thought on broad areas in the life sciences.

"There is scarcely a branch of evolutionary or population genetic theory that has not been illuminated by his vivid and versatile inventiveness," evolutionary biologist and author Richard Dawkins wrote in 1993. He was one of many scientists who credited Maynard Smith's writings with sparking their interest in the field.

In his principal scientific contribution, Maynard Smith showed that game theory, a branch of mathematics that had previously been applied to economics, could be used to explain many aspects of animal behavior.

It could predict when a creature should fight and when it should back down, or when a male bird should stick around and help care for his young and when he would be better off abandoning the nest for a new mate, and myriad other behavioral choices.

Species, he argued, evolved what he termed "evolutionarily stable strategies" -- rules for responding to circumstances that remained stable in a population, because creatures that deviated from the rules were at a disadvantage.

In another substantial contribution, Maynard Smith tackled the mystery of why creatures evolved to have sex. This is a conundrum in evolutionary biology, because organisms that reproduce "clonally" -- that is, by making exact replicas of themselves without a genetic contribution from a male -- contribute more of their genes to the next generation and should therefore be at a selective advantage.

"Maynard Smith deeply wanted to understand why there are males around -- why on Earth do you need males? Why didn't you just have a population of females?" said Paul Harvey, head of the department of zoology at the University of Oxford. "He gave us all the logical tools for exploring what the answers might be."