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Human evolution still at work, Darwin Day speaker says

Lactose tolerance is a sign that human evolution is still at work, says Briana Pobiner, a paleoanthropologist with the Smithsonian Institution’s National Museum of Natural History.

She was the keynote speaker at Darwin Day, hosted February 11, by Washington University’s Institute for School Partnership. Nearly 50 St. Louis area educators attended the event.

Pobiner, an educator in the museum’s Human Origins Program, says lactose tolerance is one of the best examples of recent human evolution.

“One of the biggest misconceptions is that humans have stopped evolving. That’s not true,” she says. “Dietary evolution is one arena in which we can really see ongoing evidence of human evolution and adaptation.”

Because of an enzyme called lactase, babies can digest lactose or milk sugar without getting an upset stomach.  In most humans, that enzyme recedes around the traditional age of weaning, not allowing them to digest milk as adults, and making them lactose intolerant.

Though the majority of caucasian Americans can digest lactose, they are in the minority. Only 2.4 billion people in the world, about a third of modern humans, can digest lactose.

Pobiner points out that five thousand years ago almost nobody could digest lactose.

So, what happened?

The spread of dairying and the domestication of dairy animals was the main thrust for the evolution of lactose tolerance.

It was literally the difference between life or death for some individuals. Those not able to digest dairy in times of food stress, famine and crop failure likely died.

Nicole Pelch (left) and Bob Flake (right), science teachers at Belleville West High Schoo, have fun taking a selfie with cardboard cutout of Charles Darwin during the ISP's Darwin Day celebration on February 11, 2017.

Nicole Pelch (left) and Bob Flake (right), science teachers at Belleville West High School, have fun taking selfie with cardboard cutout of Charles Darwin during the ISP’s Darwin Day celebration on February 11, 2017.

“There was a really strong selection pressure for the ability to digest milk sugar,” she explained.

The highest concentration of adults who can drink milk descended from northern Europe, western Africa and the Arabian Peninsula.

The DNA of Europeans who lived between 7,000 and 8,000 years ago does not have the genetic mutations for lactose tolerance. However, by five thousand years the mutations began appearing.

“That is really recent and rapid human evolution,” Pobiner says.

Participants also heard from Gautam Dantas, associate professor of molecular microbiology and of pathology and immunology at Washington University School of Medicine. He is a leader in the fields of antibiotic resistance and drug discovery. His discussion centered around combating antibiotic resistant superbugs.

The Darwin Day celebration is made possible by the generous support of David and Marilyn Kirk.

February 2017 | By, Myra Lopez

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