Flipping through Ronald Fisher’s The Genetical Theory of Natural Selection this morning, I was reminded of this quite stunning factoid from the 1912 Australian Census:
The extraordinary variation in fertility in Man has been noticed in a somewhat different manner by Dr. D. Heron, using material provided by the deaths (30,285 males and 21,892 females) recorded in the Commonwealth of Australia for 1912. Heron finds that half of the total number of children come from families of 8 or more, which are supplied by only one-ninth of the men or one-seventh of the women of the previous generation. It would be an overstatement to suggest that the whole of this differential reproduction is selective; a substantial portion of it is certainly due to chance, but on no theory does it seem possible to deny that an equally substantial portion is due to a genuine differential fertility, natural or artificial, among the various types which compose the human population.
As Fisher suggests, some of this variation must be due to luck, but how different might a population with this level of variation in reproductive success look several generations later?