At it Mark Thomas, of University College, London, "presented evidence about one of the strongest forces that has driven human evolution in Europe over the past 20,000 years: milk." according to an article by Alvin Powell of the Harvard News Office. Here's his summary of what Thomas had to say.
Thomas' research showed that a gene variant for "lactase persistence" (LP) that allows humans to digest milk into adulthood — uncommon in most adult animals and in many human societies — swept across Europe sometime in the last 20,000 years.
To spread so rapidly, Thomas said, the gene must have conveyed an extraordinary survival advantage to those possessing it. Though science has not yet identified the specific advantages at play in early Europe, there are several potential candidates. Among them is that milk provides a ready source of calories, protein, calcium, and fat, particularly during the winter or during crop boom-and-bust cycles. It also provides an uncontaminated source of fluids, perhaps lessening illness and parasitic infections; and obtaining it may be a more economical use of lands than farming.
"In Europeans, this is probably the most strongly selected part of the genome in the last 20,000 years," Thomas said.
Thomas found that the gene variant coincided well with the rise of animal domestication, indicating that humans became dairy farmers almost as soon as they began to keep animals.
To track the gene's spread across Europe, Thomas designed a computer model that took into account both archaeological and genetic data. He then ran multiple simulations, randomly changing other variables and looking for patterns that matched what is known today.
The closest matches pegged the rise of milk-drinking Europeans to about 7,400 years ago in central Europe. The spread matched the known rapid spread of Europe’s first farmers, the Linearbandkeramik culture.
"The spread of the LP variation was shaped by selection and by an underlying demographic process, the spread of farming," Thomas said.
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