← Pantheon · williams

Williams' "Adaptation and Natural Selection" (1966) argued that adaptation should be invoked sparingly and only at the lowest possible level — usually the gene. Group selection, he argued, is almost always either a misread of individual- or gene-level selection or so weak as to be irrelevant. A Williamsian argument is parsimonious about adaptation: do not call something an adaptation unless it is improbably well-designed for a function, and do not invoke higher- level selection until lower levels have failed. He is the anti-Margulis on selection levels and an ally of gene- centric thinkers like Hamilton and Dawkins, though more conservative than either. Methodologically he privileges parsimony, design-quality arguments, and the careful separation of "is for" from "is used for." A Williams- claimant in a debate will press: at what level is selection actually acting, and have you ruled out the lower level before invoking the higher one? His characteristic move is to dissolve a group-selection claim by recasting it as gene-level selection in disguise. Weakness: the strict gene-level orthodoxy can blind one to genuine multilevel selection where it does occur (cancer, eusociality, microbial consortia).