According to a genetic study carried out by German researchers at the Max Planck Institute for Evolutionary Anthropology in Leipzig, female populations have been more numerous than male populations throughout human history.
The research used a new technique that makes it possible to more accurately compare the Y chromosome inherited from the father with the maternally inherited mitochondrial DNA. Specifically, the Y chromosome (NRY) was compared with the mitochondrial DNA (mtDNA) of 623 males from 51 populations and the analysis showed that there were more females than males before humans migrated from Africa and that demographic trend held for almost all subsequent migrations.
Among the probable main causes of this tendency is polygyny , a common practice in many cultures whereby a male mates with several females. The fact that, in most societies, women tend to move to live with their husbands has also played a role.
This has resulted in women having made a greater genetic contribution than men to the world population.
The results confirmed previous findings, such as that when human populations are compared on a global scale, there are greater genetic differences in paternal NRY than in mtDNA. However, these differences are not as large as previously thought, and the authors were surprised to note a substantial variation in the relative amounts of differentiation of NRY versus mtDNA at the regional level.
The authors of the research found that there was less paternal genetic diversity in the African populations they studied , which could be a direct result of the Bantu expansion into eastern and southern Africa, which began around 3,000 years ago. In samples taken in America, initial results also suggest greater genetic diversity from the mother, indicating that there were fewer males than females among the original colonizers.
For Mark Stoneking, from the Department of Evolutionary Genetics at the Max Planck Institute and one of the authors of the study, ” the new sequencing technique eliminates previous biases and provides a rich source of information about our genetic history. It allows us to take a closer look at the differences. regions in populations and provides information on the impact of sexual bias processes on human genetic variation “.
