How has ancient DNA rewritten the story of human migration across Europe?

The answer

Ancient DNA analysis, particularly from the work of geneticist David Reich at Harvard, has revealed that modern Europeans descend from three major migrations, not one. First, hunter-gatherers arrived around 45,000 years ago. Then, Anatolian farmers migrated in around 7000 BCE, largely replacing the hunter-gatherers. Finally, Yamnaya pastoralists from the Pontic Steppe swept across Europe around 3000 BCE, contributing up to 75% of the ancestry in northern Europeans. A landmark 2015 study in Nature analyzing 69 ancient genomes showed these Yamnaya migrants spread Indo-European languages across the continent, fundamentally reshaping European genetics and culture.