History of lactose tolerance

Question

What do such genetic changes tell us regarding the evolutionary history of milk tolerance in human populations?

Answer 1

As per studies, the genes regulating lactose intolerance was quite rapid in evolutionary terms. The ultimate source of variation is mutations in the genes responsible for lactose persistence and carried forward over the generations. About 3000- 7000 years ago, dairy products such as cow's milk, cheese and yoghurt were not in  existence. Only human milk was most likely only consumed by young children.

With domestication of cattle, consumption of non human milk became widely popular. As a result, natural selection gradually switched to favor lactose tolerant people which resulted in the progressive evolution of the gene pools. 

In 2007 by researchers  from University of Mainz, Germany. They analyzed of DNA in bones from 10 Central and Eastern European human skeletons dated between 3,800 and 6,000 years ago. In spite of the fact that these populations seemingly raising milk producing farm animals for hundreds or even thousands of years, the gene that allows lactose tolerance in adults was not common in them. 

In 2007, Sarah Tishkoff, University of Maryland, reported that the mutations among East Africans that keep the lactase gene permanently turned on, are different from those of Europeans who also share this trait. According to her studies, among 43 East African ethnic groups, 3 different mutations leading in lactose tolerance in Africa developed between 2,700 and 6,800 years ago.

Her  research findings  narrates genetic diversity among Africans. She analyzed DNA samples of one ethnic group, the Yoruba of West Africa. Traditionally the the Yoruba group was not involved in cattle herding. There was no mutation for lactase persistence reported in them. Although, a sector of population of West Africans, who were traditionally involved in cattle herding have reported mutation for lactase persistence  Above research findings revealed that nature is getting hold on the environmental challenge with with different successful genetic solutions.