Genes in Populations: Backward in Time

11.11 Summary

In this chapter we have turned the Wright-Fisher model of gene dynamics on its head. Given a sample of n genes, their lineages coalesce into common ancestors as we move backward in time. If we trace back the gene genealogies until the most recent common ancestor of the entire sample, this sample genealogy is called the coalescent. Coalescent theory allows the derivation of important evolutionary quantities such as the number of segregating sites expected under neutrality. In addition, the coalescent is routinely used as a very efficient tool for simulating gene samples under a diverse range of evolutionary scenarios, including recombination and selection.