where in this world is it believed that lactose tolerance develped? why?

Answer 1

do you mean lactose intolerance?
that developed in people who historically were not exposed to lactase and dairy products. like Native Americans, Asians, Southern Italians...most American adults have it too, from O.D.ing on too much dairy their whole life, too much and you get that reaction.
BUT LACTOSE "tolerance" may have developed in Africa, as North Africans were the first to domesticate cattle. Hope this helps.

Answer 2

Lactose intolerance has been around for a very long time but was not identified until fairly recently. It's a common condition that usually shows itself in adulthood and many have it but after the age of 2 the body's production of lactase begins to decline. It can be mild, moderate or a complete intolerance. A mild tolerance can, over time, become a complete intolerance. Milk contains a sugar, lactose, that is normally metabolized by an enzyme, lactase, produced by the body. When the body no longer produces the enzyme in a sufficient amount or at all, it is said that this person is lactose intolerant. It's not an allergy but an intolerance and some researchers have reason to believe that it may be in part hereditary.

Adults don't need cow's milk. It was never meant for human consumption.