From https://en.wikipedia.org/wiki/Lactose_intolerance https://en.wikipedia.org/wiki/Lactose_intolerance, "The frequency of lactose intolerance ranges from 5% i

From https://en.wikipedia.org/wiki/Lactose_intolerance https://en.wikipedia.org/wiki/Lactose_intolerance, "The frequency of lactose intolerance ranges from 5% in Northern European to more than 90% in some African and Asian countries." It seems to depend on the region of the world your ancestors are from. Those cultures which used milk as a food source for adults tend to have lower incidences of lactose intolerance.