> Suppose you buy a bag of seed corn from a hardware store. This is not some sort of fancy cloned corn, but ordinary genetically varied corn of the sort that fa

> Suppose you buy a bag of seed corn from a hardware store. This is not some sort of fancy cloned corn, but ordinary genetically varied corn of the sort that farmers planted long before there was a science of genetics. Grow one handful of it in a carefully controlled environment in which the seeds get uniform illumination and uniform nutrient solution. The corn plants will vary in height, and because the environment is uniform, the heritability of height will be 100 percent. Now take another handful of corn from the same bag, and grow it in a similarly uniform environment but with a uniformly poor nutrient solution. Again, the plants will vary in height, but all will be stunted. Once more the heritability of height is 100 percent. Despite the 100 percent heritabilities of height within each group, the difference in height between the groups is entirely environmentally caused. So we can have total heritability within groups, substantial variation between groups, but no genetic difference between the groups. https://web-archive.southampton.ac.uk/cogprints.org/230/1/199712003.html https://web-archive.southampton.ac.uk/cogprints.org/230/1/19...