Regular readers of this weblog know that there are some quick "back of the envelope" prediction equations that one can appeal to to get a rough sense of how quickly evolution can proceed. For example, the time until fixation of a neutral (no selection + or -) mutant is
4Ne
generations, where Ne is the effective breeding population. On a quantitative polygenic trait the response to selection, R is proportional to
h^2
, the heritability, multiplied by the selection coefficient, S (
R = h^2*S
being the classic empirical breeder's equation). Nevertheless, sometimes it is important to get an empirical feel for how quickly selection, mutation and drift can operate together (along with migration) to shape, exhaust and replenish variation. With that in mind, I was talking to a physical anthropologist the other day and he mentioned a curious fact, Amerindians are generally built as if they were a Arctic ...
