Men who lived on the Iberian Peninsula 4500 years ago …were replaced as new farming cultures swept into the region and drove them out of the gene pool. …The findings suggest that far from being an isolated cul-de-sac of Europe, Iberia experienced massive changes in ancestry, as waves of hunter-gatherers, farmers, Romans, and others mixed with the local population over the course of thousands of years.
…Central Europeans who were descendants of herders from the grasslands of Eastern Europe and Russia, appeared in Iberia, starting in the early Bronze Age 4500 years ago. They probably introduced an early Indo-European language. …At first, the European farmers lived alongside the farmers already in Spain. ….But within a few hundred years, nearly all the Y chromosomes from Iberian farmers were gone—and replaced by the central Europeans farmers’ DNA.
This meant that somehow, the new migrants replaced 40% of genetic heritage of the Spanish and Portuguese. …”The archaeological record gives no clear evidence of a burst of violence in this period.”
…Still more immigrants came in historical times: first Romans and then Muslim North Africans. At one point 500 years ago, far more people of North African ancestry lived in Spain than today, before Christian kingdoms pushed the Muslim states south and eventually expelled them.