When science mirrors life: on the origins of the Price equation.

The Price equation was a piece of abstract mathematics. What kind of a connection could it possibly have had to George Price's personal life and biography? Here, I will argue that the initial impetus for Price's foray into mathematical population genetics stemmed from a preoccupation with the origins of family, one that was born following a divorce from his wife and the abandonment of their two young girls. What is special about the Price equation is the way in which it associates statistically between two groups, a 'mother' and 'daughter' population. The association need not mean genetic relatedness in the narrow sense of direct descent, and it allows us to see selection working at different levels simultaneously, a fact that was not lost on William Hamilton. Hamilton was one of the few friends who desperately tried to save Price from falling into the abyss of depression and homelessness in the period following the publication of 'Selection and covariance' (Price 1928 , 520-521 (doi:10.1038/227520a0)). Viewed in this light, the Price equation assumes new meaning. This article is part of the theme issue 'Fifty years of the Price equation'.