~5000 BCE The Male Line CollapsesAround seven thousand years ago the male line narrows to almost nothing. Genetics records it as a collapse in the number of men passing on a Y chromosome — at its most extreme, as though one man reproduced for every seventeen women. The female line shows no such thing.Where this sits. I had this as mass genocide. The genetics measures how many men reproduced, not how many died — a man who leaves no sons vanishes from the record while living a full life. And the leading explanation is not warfare: patrilineal clans splitting along family lines produce the same signature with nobody killed (Nature Communications, 2024).