The Evolutionary Unit of Measurement

The starting point of Darwin's theory of evolution is precisely the existence of those differences between individual members of a race or species which morphologists for the most part rightly neglect. The first condition necessary, in order that any process of Natural Selection may begin among a race, or species, is the existence of differences among its members; and the first step in an enquiry into the possible effect of a selective process upon any character of a race must be an estimate ...

 Campbell's Rule of Design Through Evolution

We should think of it like this - evolutionary theory describes how design is created by the competition between replicators. Genes are one example of a replicator and memes another. The general theory of evolution must apply to both of them, but the specific details of how each replicator works may be quite different. This relationship was clearly seen by the the American psychologist Donald Campbell (1960, 1965) long before the idea of memes was invented. He argued that organic evolution, ...