Challenging Previous Violence Theories: Unraveling the Social Factors Behind Global Male Population Decline Thousands of Years Ago

A recent study by a French research team from CNRS, MNHN, and Paris Cité University suggests that the decline in the male population worldwide thousands of years ago may have been more due to social change rather than an unprecedented wave of violence. The team’s theory is that this decline occurred as societies transitioned from diverse reproductive systems to ones based on patrilineal lines, where men were aligned based on their fathers’ clans.

This shift took place at the end of the Neolithic period, between 3,000 and 5,000 years ago, resulting in a significant decrease in Y chromosome diversity. This decline was only recently identified through analysis of current men’s Y chromosomes. A study in 2015 revealed a collapse of male genetic diversity about 5,000 years ago, with one man for every 17 women involved in reproduction in Europe.

The decline was particularly severe in Europe but also affected regions like the Near East, Siberia, and Africa over a broader timeframe. Contradicting previous theories of violent clan warfare leading to the loss of Y chromosome diversity, the new study suggests that social organization played a key role in this historical shift. The rise of agro-pastoral economies favored patrilineal systems where clans with more power or resources were more successful in reproduction.

The team collected over a thousand genomes from patrilineal populations and found significant loss of Y chromosome diversity in segmental patrilineal systems. They attribute this social transition to the rise of agro-pastoral economies which favored patrilocality and patrilineality. Future research aims to explore these patterns across different continents to provide region-specific insights into this historical shift.

Overall, this study challenges traditional views about population decline and provides new evidence that social changes can have profound effects on human reproduction patterns over long periods.