Aha! This vindicates my assertion that we should change language so that people are either normal or lactose-resistant, instead of lactose-intolerant and normal.
Thanks to gregoryp™ for the reference.
A surprisingly recent instance of human evolution has been detected among the peoples of East Africa. It is the ability to digest milk in adulthood, conferred by genetic changes that occurred as recently as 3,000 years ago, a team of geneticists has found.