Common Descent

In 2007, I went with a group of science teachers to some workshops led by the bigwigs at the American Museum of Natural History. The curator of vertebrate paleontology went first, talked about cladistics and the biological species concept, and we talked some about how bacteria made this concept so problematic- they can exchange DNA with each other even when they’re not closely related.

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Next came Ian Tattersall, a great physical anthropologist who presented a brilliant hour-long lecture on human evolution culminating in the Lascaux caves and other Cro-Magnon artifacts.

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I loved teaching evolution, so I’d already seen a lot of them, but he really tied everything together in a coherent way. Then, he said, in a not hidden note of relief- “and now thanks to the Blombos caves in South Africa, we have evidence that symbolic reasoning dated from 75,000 years ago in Africa, not from the later Cro-Magnon dates in Europe.” And he showed the marks on ocher that were found at Blombos.

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By way of wrapping up, he said, “we can be sure that no human evolution is happening now, the population is too big.”

This was the coda to the remembrance Tattersall published of Stephen Jay Gould several years back:

There is no doubt whatsoever that Gould’s humane and passionate writing in defense of racial equality will be looked upon by future anthropologists and historians as a beacon of rational positivism in an age in which genetic reductionism was showing alarming signs of resurgence—as indeed it still is, as race-stratified genome-wide association studies continue to dominate research on human variation. As Gould’s longtime friend, the anthropologist Richard Milner, told a correspondent from Discover magazine: “Whatever conclusions he reached, rightly or wrongly, he did with complete conviction and integrity. He was a tireless combatant against racism in any form, and if he was guilty of the kind of unconscious bias in science that he warned against, at least his bias was on the side of the angels.”

When I used to teach human evolution to middle schoolers, I used to mention that the Neanderthals had larger brains than modern humans, but that modern humans’ greater ability to coordinate through language and specialization led them to displace the Neanderthals. Not sure how I’d change that lesson now.

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