The impact of innovation and technological advancement can be seen in the spread of humans around the world after the development of complex stone tools, or the explosion of industry during the industrial revolution. But events like these in prehistory have not just left their mark in the physical record in the form of tools and bones, but it seems that traces of it can also be found in our DNA. A new study has revealed differing expansions of the male genetic line, which are seemingly linked to human development.
The largest ever study of global genetic variation in the human Y chromosome analyzed over 1,200 different men from 26 separate populations. The male Y chromosome is interesting because as only men inherit it and pass it on, it “bears a unique record of human history,” write the authors of the paper, published in Nature genetics. In a similar way that surnames can be traced back down the male line, the Y chromosome can be used to look back tens of thousands of years.
Using the data from these men, they were able to build up a tree of their relatedness. It allowed the researchers to see not only how all men are descended from a single man who lived around 190,000 years ago, about the time when most anthropologists think that modern humans emerged, but also how different sub groups are related. Some parts of the tree, the researchers note, were more like bushes, with multiple linages coming off a single point.
“This pattern tells us that there was an explosive increase in the number of men carrying a certain type of Y chromosome, within just a few generations,” explained Dr. Yali Xue from the Wellcome Trust Sanger Institute, and lead author of the study. “We only observed this phenomenon in males, and only in a few groups of men.” One such group were those who are native to the Americas. The team was able to date this explosion to around 15,000 years ago, the point in time when humans were first thought to have colonized the continent, arriving in a land where resources were in huge abundance, and obviously allowing the human population to massively expand.
But looking to the other side of the Atlantic, they also found an explosion in the male chromosome, but this time dating to around 5,000 years ago, during the Neolithic. “Half of the Western European population is descended from just one man,” Dr. Chris Tyler-Smith, who co-authored the paper, told The Telegraph. “We can only speculate as to what happened.”
He suggests that it was advances in technology – possibly metallurgy, wheeled transport, or organized warfare – which was controlled by a small group of men who were therefore controlling reproduction and dominating the population that could have caused these results. This, interestingly, could match in with the period in which it is thought that one Bronze Age group, the Yamnaya culture, swept across the continent. Perhaps their superior technological skills therefore allowed them to dominate over the tribes already present at the time.
