The Price equation

Abstract

Following the development of the Price equation, Price went on to make two other major contributions to evolutionary theory. The first of these was to formally prove and provide an interpretation for R.A. Fisher's fundamental theorem of natural selection, a mathematical result that had perplexed population geneticists for decades. The theorem states that the change in the mean fitness of the population under the action of natural selection is proportional to the variance in fitness, and Fisher claimed that it captured the directional, improving action of natural selection as the builder of organismal adaptations. Price explained that Fisher's theorem was a partial result, a description of the action of the natural selection effect with all other evolutionary effects stripped away, and the theorem is easily proven using the Price equation:(3)Price's final contribution was the first explicit application of game theory to evolutionary biology, in a seminal article co-authored with John Maynard Smith entitled The Logic of Animal Conflict. This is widely regarded as one of the most important developments of evolutionary theory, and has launched a highly successful programme of research. It is Maynard Smith who is usually attributed with this breakthrough, and indeed he played the major role in its development. But the idea originated with Price, in an unpublished manuscript that Maynard Smith had reviewed for Nature. Maynard Smith later explained that “Dr Price is better at having ideas than at publishing them. The best I can do therefore is to acknowledge that if there is anything in the idea the credit should go to Dr Price and not to me”.Price's inability to focus on publishing his theoretical insights was due to a sudden religious experience in the summer of 1970 and a shift of priorities in his life. It is not known what in particular led Price, formerly a hardline atheist, down this avenue, although he did mention to Hamilton that a series of coincidences had forced him to conclude that God existed. He came to regard his equation as a gift from God and, taking a very literal interpretation of the New Testament, gave up science in order to dedicate his life to altruism. He sheltered the homeless in his flat, and gave away all his money and possessions to the poor and needy, and his life spiralled out of control. He became deeply depressed shortly after Christmas of 1974, and was found dead in his squatter's tenement on the 6th of January 1975. He had cut his throat with nail scissors.