An international team of scientists has explored ancient DNA of about 300 individuals from the Iberian Peninsula, suggesting that unique male genes were almost wiped out by migrant farmer 4,500 years ago, according to two studies published by Current Biology and Science.
The first study dealt with hunter-gatherers and early farmers living in Iberia — now Portugal and Spain — between 6,000 and 13,000 years ago. The second survey looked into individuals based in Iberia over the past 8,000 years.
The researchers, in particular, discovered that Y chromosomes of locals living on the Iberian Peninsula during the Bronze Age were supplanted by those of men who migrated to the area at the time.
“This is one of the strongest pieces of evidence in ancient-DNA research of sex bias in the prehistoric period”, Inigo Olalde, study author and postdoctoral fellow at Harvard Medical School, pointed out.
The scientists also found that as of 2,500 B.C., much of the Iberian population’s DNA has been replaced with that of people from central Europe who showed genetic ancestry from the Russian steppe. This led to the locals and the central Europeans interbreeding in the next few years.
Carles Lalueza-Fox, co-senior study author and principal investigator of the Paleogenomics Lab at the Institute of Evolutionary Biology, touted “astonishing” data which he said “suggest there was a major genetic change that is not obvious from the archaeological record”.
Commenting on the findings, Olalde, in turn, noted that “it would be a mistake to jump to the conclusion that Iberian men were killed or forcibly displaced as the archaeological record gives no clear evidence of a burst of violence in this period”.
In another surprise discovery, the researchers detected North African ancestry in the DNA of one person who was buried in Iberia between 2,400 and 2,000 B.C. This added to their understanding that people moved between Africa and Europe as well, apparently being involved in trade.
David Reich, co-senior study author and professor of genetics at the HMS Blavatnik Institute, stressed that beyond the insights, the survey “provides about the history of Iberia itself, it highlights the potential of future studies that focus on ancestry changes over time using large sample sizes in relatively small regions of the world”.