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Thursday, March 11, 2010

Report from the LI Conference, part 9

With the overview talks done, we finally get to the meat of the conference.

The first section was devoted to the question: What Is the Prevalence of Lactose Intolerance, and How Does This Prevalence Differ by Race, Ethnicity, and Age?

Population Genetics: Evolutionary History of Lactose Tolerance in Africa
Sarah A. Tishkoff, Ph.D.
Associate Professor
Departments of Genetics and Biology
David and Lyn Silfen University
University of Pennsylvania

Holy smoke. That Sarah Tishkoff?

For the fans of population genetics out there, yes, I got to hear from Sarah Tishkoff herself. Why is this a big deal? Let's go back in time, to a post I made in 2006, quoting Scientific American.

According to University of Maryland biologist Sarah Tishkoff, the lead author of a study appearing in today's Nature Genetics, the mutation allowing them to "get milk" arose so quickly and was so advantageous that "it is basically the strongest signal of selection ever observed in any genome, in any study, in any population in the world."

What this means is that despite the nonsensical statements that "humans were never meant to drink cow's milk," lactose tolerance or lactase persistence is such an overwhelmingly positive mutation in humans that multiple populations, totally independent from one another, selected for that version of the gene. Being able to tolerate milk products must have significant advantages. The exact nature of those advantages are still not completely certain. The nutrients that dairy provide are "obvious," to use her word. But even the fact that milk is a drinkable fluid, containing water, may have been of critically importance in areas like Africa, where supplies of potable drinking water were often rare.

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