Humans Are Evolving in Front of Our Eyes on the Tibetan Plateau
sciencealert.com
sciencealert.com
More likely is "birds of a feather flock together", the people who went up the mountain found it less uncomfortable than others.
Next they'll be calling the height of basketball players evolution.
They found that women in these extremely high communities had more children if they were genetically predisposed to tolerate low-oxygen conditions better.
It's about as direct evidence of natural selection as you can get.