 Indeed, he thought that the fluctuating selection pressure caused by variations in abundance “invalidates” Wright’s Shifting Balance Theory of Evolution, which he referred to as “far-fetched”. Interestingly, Ford and his colleagues believed that genetic subdivision of the sort postulated by Wright would promote rapid evolution but for reasons very different from Wright’s and by different genetic mechanisms (natural selection instead of random genetic drift, local selection, and interdemic selection). Ford (1975: 40–44) argued that subdivision of a large, geographically extensive population into relatively small groups promotes rapid evolution because, 