A DNA analysis of the genetics of men who lived in Iberian Peninsula, modern-day Spain and Portugal, 4500 years ago revealed that their Y chromosomes have altered or changed due to foreign fusion with local residents, thus making the region's male genetic legacy totally disappear.

According to researchers who examined 8000 years of genetics, Iberia experienced massive changes in ancestry, as waves of hunter-gatherers, farmers, Romans, and others from Anatolia, North Africa and central Europe mixed with the local population over the course of thousands of years.

In a few hundred years, almost all the Y chromosomes from Iberian farmers disappeared and were substituted by the central Europeans farmers’ DNA, which means that around 40% of the genetic heritage of the Spanish and Portuguese was replaced by genes from the newcomers.

Perhaps the steppe migrants had far more children than the small population of local farmers, eventually swamping out their DNA, said population geneticist David Reich at Harvard Medical School in Boston.

“Being able to analyze nearly 400 individuals is crazy. Thanks to them, we now have a much richer picture of all the different peoples who inhabited the Iberian Peninsula and how they shaped present-day populations," said Iñigo Olalde, a population geneticist who led the study.