By comparing SNPs appearing in mitochondrial DNA and non-recombining Y chromosome, researchers from the Max Planck Institute for Evolutionary Anthropology found that the effective population size of women has been larger than that of men throughout human history.
"Imagine a population of 100 females and 100 males," Max Planck's Mark Stoneking tells the Guardian. "If all the females, but only one of the males reproduced, then while the males and females contribute 50:50 to the next generation, the male contribution is all from just one male." That is, the children will all receive the same Y chromosome, but different mtDNA.
As they report in Investigative Genetics, Stoneking and his colleagues used a capture-based array to target and examine the genetic diversity of NRY sequences from nearly 625 men representing 51 world populations. They also examined mtDNA sequences from the same individuals.
Their simulation indicates that there was an ancestral breeding population of some 60 women and 30 men in Africa that dropped to 25 women and 15 men approximately 75,000 years ago at the time of the out-of-Africa event migrations. As modern humans then moved into Europe about 45,000 years ago, the effective population size was about 100 for women and 30 for men, and the humans settling in Oceania, meanwhile, had ancestral population sizes of about 50 women and 30 men.
"What we've found is that there are significant differences in the history of human males and females in different parts of the world. Understanding why that's the case and what are the social historical processes that led to those differences are what we want to investigate now," Stoneking adds to the Guardian.