Before bottled water, the only supply of safe drinking water was in boiled or fermented form. As late as the 18th century in Europe, the rich drank nothing but wine, beer, coffee, and tea. They risked death otherwise. The habit dies hard.
More than 70% of western Europeans by descent can drink milk as adults, compared with less than 30% of people from parts of Africa, eastern and south-eastern Asia and Oceania.
Biologists have found evidence that the people with the highest frequency of milk-digestion ability were the ones with a history of pastoralism. The Tutsi of central Africa, the Bedouin of the desert, the Irish, Czech and Spanish people - this list of people has almost nothing in common except that they all have a history of herding sheep, goats or cattle. They are the champion milk digesters of the human race.
~Matt Ridley
The Origins of Virtue and Genome
