Mechanism of Evolution

Microevolution refers to evolutionary change on a small scale — specifically, change in allele frequencies within a single population — and is driven by four fundamental forces: natural selection, genetic drift, mutation and gene flow, each covered in its own subsection below. Alongside natural selection, humans can also act as a selective agent through artificial selection — the deliberate exploitation of forests, oceans and fisheries, or the use of pesticides, herbicides and drugs, as well as the long history of selectively breeding many distinct dog varieties from a single ancestral species. The logic used in this chapter is that if humans can generate substantial new variety within a species in a relatively short span of time through artificial selection, then nature — with far g …