This could also be explained by convergent evolution [1] where a similar trait was created by an independent evolutionary path.

The wiki page for 'High-altitude adaptation' in humans even mentions that adaptation to high altitude arose independently among different highlanders as a result of convergent evolution. [2]

[1] https://en.wikipedia.org/wiki/Convergent_evolution

[2] https://en.wikipedia.org/wiki/High-altitude_adaptation_in_hu...