Epigenetics?

https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3905637/

http://www.pnas.org/content/107/39/16757.full

https://www.scientificamerican.com/article/how-much-of-human...

Better muscle to support a growing skeleton? Better bone (marrow) growth? Or more iron, calcium, and vitamin b, d support immune and metabolism systems?

Checkout: https://thepaleodiet.com/north-american-plains-indians-tall-...

Europeans are also taller than South Asians and their diet also contain more protein.