Importance of ancestral DNA ages

Abstract

Recent publications consider the age of a common ancestor of samples of human DNA sequences^{1,2,3,4,5,6,7,8,9}. In particular, variation in Y chromosomes has been interpreted by different authors to give very different estimates of the time to the most recent common ancestor of the sample^{1,2,3,4,5,6,7,8}. The cause of the differences is that the data are being interpreted by various authors in terms of their preferred models of human demography. The data are so lacking in power that these estimates depend hardly at all on the data, and almost entirely on the demographic model assumed. However, if we knew the demography of early humans, we would have no real interest in the time to the most recent common ancestor of an individual gene, as the time is important only because it tells us about the demography.