One of the most remarkable human adaptations has an origin that's not precisely human.

The physiological ability of ethnic Tibetans to thrive at miles-high elevations, unaffected by oxygen levels that leave lowlanders gasping, appears to have originated with Denisovans, a close relative of Neanderthals.

Following on the news earlier this year that many modern humans have quite a bit of Neanderthal DNA, the finding is the latest example of the complex anthropological tapestry that is our genome. It also hints at a perhaps underappreciated reason for Homo sapiens' tremendous success: After leaving Africa, our ancestors picked up traits from the locals.

"Maybe this happened many times throughout human history, and we just happened to detect it