New research reveals that human evolution continues in real-time on the Tibetan Plateau, where populations have developed remarkable adaptations to survive at extreme altitudes. Anthropologist Cynthia Beall and her team found that women with specific oxygen-transport traits have higher reproductive success rates, passing these survival characteristics to future generations.

Over 10,000 years of settlement, Tibetan bodies have evolved to maximize oxygen delivery without thickening blood, a condition that would strain the heart. The study examined 417 women aged 46 to 86 living above 3,500 meters, measuring hemoglobin levels and oxygen saturation. Women with average hemoglobin but high oxygen saturation showed the highest reproductive success, demonstrating natural selection in action.

These adaptations include wider left heart ventricles and increased blood flow to the lungs, enabling efficient oxygen transport in low-oxygen environments. While cultural factors like early marriage and reproduction also influence birth rates, the physical traits remain significant. This ongoing natural selection provides scientists with a rare opportunity to observe human evolution as it happens, offering insights into how our species continues to adapt to environmental challenges.