Note 104 — Chapter XI
Reading edition
It is objected that if the long-lived marry each other, the short-lived will also marry each other and thus the race will gain no more than it loses. The reply to this is that the short-lived will marry in fewer numbers, as some of them die prematurely; that they will have fewer children; and that these children in turn will tend to die young. Thus the short-lived strains will gradually run out, while the long-lived strains are disseminated.