Molecular biology and evolutionary biology are in constant danger of diverging totally, both in the problems with which they are concerned, that is, the “how” as against the “why,” and as scientific communities ignorant and disdainful of each other's methods and concepts. The introduction of electrophoresis in evolutionary studies went some way toward impeding that separation and led naturally to an important second stage, the introduction of DNA sequence studies into population genetics.

[t]he ground rule – or perhaps doctrine would be a better term – is that adaptation is a … concept that should be used only where it is really necessary. When it must be recognized, it should be attributed to no higher a level of organization than is demanded by the evidence. In explaining adaptation, one should assume the adequacy of the simplest form of natural selection, that of alternative alleles in Mendelian populations, unless the evidence clearly shows that this theory does not suffice.