Memetics must be able to provide a convincing account of how the three essential elements of evolutionary theory – selection, variation and replication – work in culture. The preceding four chapters have taken on this challenge but have in the process raised a variety of questions on which the credibility of meme theory is equally dependent.

Selection

“Selection” means that some replicators are favoured, survive and propagate, while others fail and become extinct. Genes are selected via their phenotypic effects, and the evidence for such selection is therefore to be sought at the level of the phenotype. Nor is it hard to find. An abundance of extant and extinct species – living organisms, creatures that have been wiped out within living memory, and fossil records – all contribute towards the plausibility of natural selection in biology.

If memes, like genes, are selected via their phenotypic effects, then it is at the phenotypic level that we must search for the evidence for their selection, too. Again, there is plenty of evidence for selection in culture: theories, tunes and methods that are popular at present; ideas that have been rejected within living memory; written records of the theories, fashions, skills and music of past generations, all demonstrate the differential survival of certain areas of culture.

The previous chapter's discussion provides, in addition, some theoretical insight into the selectional pressures on memes: the limited capacity and attention span of human brains; assembling compatibility pressures; a variety of constraints specific to the different cultural areas; the physical, genetic, memetic and psychological environment; to a certain extent the content of the memes themselves.