Key ideas from David Reich

• "The standard model is basically this: modern humans separated from a group ancestral to Denisovans and Neanderthals somewhere 500,000-750,000 years ago" - David, but mitochondrial and Y chromosome data suggest much more recent gene flow around 300,000-400,000 years ago
• "5-10% of random deaths" from Yersinia pestis (plague) 4000-5000 years ago in western Eurasia suggests this single pathogen may have killed a quarter to half of the population over millennia
• "About 4500 years ago in Britain, within 100 years, 90% of farmers were gone, replaced by migrants from the steppe" - David, documenting the Yamnaya expansion across Europe
• "The proportion of non-Africans ancestors who are Neanderthals is not 2%... it's more like 10-20%" - David, explaining that Neanderthal DNA was selected against after mixing
• Methylation patterns in ancient genomes reveal "a huge statistical signal" in the vocal tract on the modern human lineage, suggesting language-related changes absent in Neanderthals and Denisovans
• "Almost every group in the world is the result of many mixture events as profound as" Europeans and Africans mixing in the Americas - David on the ubiquity of ancient population mixing
• Natural selection in the last 10,000 years in Europe shows "extreme overrepresentation" of changes affecting immune and cardiometabolic traits, with "downward selection against body fat" and type 2 diabetes predisposition