Nepal high-altitude study reveals ongoing human evolution

A study published in the journal Proceedings of the National Academy of Sciences provides evidence of ongoing human evolution in the high-altitude regions of Nepal. Anthropologist Cynthia Beall from Case Western Reserve University studied 417 women, aged 46 to 86, who have lived their entire lives at altitudes exceeding 3,500 meters.

The research found that reproductive success in these populations is not driven by the highest hemoglobin levels, but rather by an intermediate balance. While higher oxygen saturation is essential for more children, excessively high hemoglobin can make blood too viscous and difficult to pump.

Additionally, women with the highest reproductive success exhibited higher pulmonary blood flow and larger left ventricles, suggesting evolutionary remodeling of the heart and lungs to manage low oxygen environments. Beall describes these findings as a real-world case of natural selection in progress.