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Ancient Wars And Clan Structure Decimated Y Chromosome Genetic Diversity 7,000 Years Ago

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Men receive their Y chromosomes from their fathers, but a new study suggests that the Y chromosome was nearly erased from history.

What Happened To Ancient Men?

New research revealed that there was once a bottleneck or a collapse of the Y chromosome, which is the sex chromosome that is only in men. This started 7,000 years ago and ended roughly 5,000 years ago.

The findings were published in a study on May 25 in Nature Communications.

The collapse of the Y chromosome can be attributed to two main factors. First, there was a likely an ancient period of ruthless war. Most of the male population on Earth was affected, but women were largely left alone. This was probably because men participated in those wars and not women.

The other big culprit was the conflict between patrilineal clans. For generations, men in those clans were associated with their male ancestors and carried on the Y chromosome. With men being slaughtered, there were fewer Y chromosomes to go around in the clan. It was so bad that there was only one man for every 17 women during this time.

This collapse of the Y chromosome occurred rather recently from a biological standpoint. New changes in society likely played a role in it.

How Did Researchers Discover This About The Y Chromosome?

For years, scientists knew about this possible bottleneck in human history, but there was disagreement if this actually occurred. Tian Chen Zeng, a Stanford undergraduate in sociology, hypothesized about the theory. He shared his concept with another student, Alan Aw.

"He was really waxing lyrical about it," Aw said to Heritage Daily.

The students worked with Marcus Feldman, a professor of biology in Stanford's School of Humanities and Sciences, to conduct their research.

To reach their conclusion, they used mathematical models and computer simulations of men in different clans fighting over resources to survive. As the simulation continued, the researchers noticed that the Y chromosome lost its diversity over time. To get the best results, they also accounted for male lineages that survived this historic collapse.

"Our hypothesis explains the bottleneck as a consequence of intergroup competition between patrilineal kin groups, which caused cultural hitchhiking between Y-chromosomes and cultural groups and reduction in Y-chromosomal diversity," the researchers wrote in their study.

The researchers understand that their model has some scientific limitations because it is only a simulation. However, it does serve as a reasonable way to describe the downfall of the Y chromosome during this era.

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