Note 35 — Chapter II · —Classes Of Geographic Influences

According to Virchow, the distinction of races rests upon hereditary variations, but heredity itself cannot become active till the characteristic or Zustand is produced which is to be handed down.35 But environment determines what variation shall become stable enough to be passed on by heredity. For instance, we can hardly err in attributing the great lung capacity, massive chests, and abnormally large torsos of the Quichua and Aymara Indians inhabiting the high Andean plateaus to the rarified air found at an altitude of 10,000 or 15,000 feet above sea level. Whether these have been acquired by centuries of extreme lung expansion, or represent the survival of a chance variation of undoubted advantage, they are a product of the environment. They are a serious handicap when the Aymara Indian descends to the plains, where he either dies off or leaves descendants with diminishing chests.36 [See map page 101.]