General Discussion

Centuries of carrying messages over the hilly trails must have led to some form of selection for good runners, even if only social and economic. If successful runners had more children, and/or married relatives of other good runners, or more of their children survived, you'd end up with a statistically significant accumulation of genes which favor the physiology of good runners.

Similar things have happened in ancient societies where one's choice of profession is often dictated by birth -- pursuing your father's profession even may be forced in some cases. Political and social classes, not to mention ethnic associations, may also limit your options. Apparently, if you meet someone unusually tall and strong in Japan, he may be descended from a long line of sawyers -- men who cut trees into boards before sawmills were mechanized -- who were allowed much larger rations of rice than other workers (carbo-loading ! ), by law.