David Reich says that around 4500 years ago, the existing Y-chromosomes in Iberia were almost entirely replaced. “The collision of these two populations was not friendly; instead, the men who arrived almost completely pushed out the local men.” Spanish scientist Íñigo Olalde said that after the transition. populations had “40% of their genetic information and 100% of their Y chromosomes from the migrants.”
Which is considerably more drastic than what happened when the Spanish and Portuguese conquered and settled Latin America – even though that was aided by catastrophic new diseases. Apparently some of the Iberians ended up speaking Indo-European languages while others did not. We’ve seen other examples of male mediated-conquests, and language acquisition can go either way: Melanesians conquered Fiji, largely replacing the Y chromosomes, without replacing the language. In Vanuatua, multiple waves of invasion almost completely replaced the whoe genome while preserving Polynesian. But the Spanish and Portuguese imposed their languages, as did Aryans in India, and fairly small numbers of Turks and Magyars.