Warring patrilineal clans blamed for ancient men shortage

Recent genetic research suggests that the number of reproducing men plummeted around 5,000 to 7,000 years ago. Scientists think this population dropped by 95 percent. Now researchers have an explanation. Warring patrilineal clans—where membership follows the male line—could be to blame. In 2015 scientists identified a historical bottleneck, where the diversity of the Y chromosome—which is passed from father to son—appeared to collapse. No such pattern was found in the mitochondrial DNA—which is passed from mother to child. This suggests no big changes in the number of reproducing women at the time.

After the advent of farming some 12,000 years ago, hunter-gatherer societies began to morph into larger, patrilineal clans, where women could move and marry between different clans but men stayed put. The team’s models and simulations backed up the idea of warring, patrilineal clans. When competing patrilineal groups fought and wiped each other out in their simulations, Y chromosome diversity took a nosedive. 5,000 to 7,000 years ago wasn’t the best time to be a male, unless you were a member of one of those very few clans we are all now descended from.