Adults learn to drink milk
A mutation letting adults digest lactose spreads faster than almost any other human gene.
- When
- —
- Duration
- 1.7 thousand years
- Known to
- ± 1 thousand years
- Era
- Neolithic, Holocene
All mammals stop producing lactase after weaning; a regulatory variant that keeps it switched on into adulthood arises in Europe and, separately, several times in Africa and Arabia. It spreads under some of the strongest selection known in the human genome. Notably, dairying comes first by thousands of years — people were processing milk into low-lactose cheese and yoghurt long before they could drink it fresh — and recent work suggests famine and disease, not milk drinking itself, drove the selection.