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More Evolution by Devolution: Mammalian Hairlessness

Photo credit: Coralie Mercier, via Flickr (cropped).

The argument of biologist Michael Behe’s book Darwin Devolves is that the mechanism of Darwinian evolution absolutely works — by breaking genes, when that provides a selective advantage, not by inventing ingenious novelties in life. Here’s what seems to be an illustration: the loss of fur in certain mammals, for instance elephants, mole rats — and humans.

Instead of being broken, the relevant genes have been turned “off.” From, “Humans Still Have the Genes for a Full Coat of Fur, Scientists Discover,” at Science Alert:

Fur is a defining feature of being a mammal. But bald is beautiful for several mammalian weirdos, including dolphins, mole rats, elephants, and of course, humans. Not to mention a handy adaptation.

Yet all our ancestors had plenty of fur. According to a new study on relatively hairless mammals, we still have the means to be hirsute. Those genes, it seems, have simply been switched off.

In their hunt through nearly 20,000 coding genes, and 350,000 regulatory ones, compared across 62 different mammal species, University of Pittsburgh geneticist Amanda Kowalczyk and her team found a mechanism behind these fascinatingly parallel changes.

This re-emergence of a trait across unrelated lineages is known as convergent evolution. In the case of hairlessness, it evolved independently at least nine different times along different branches of the mammalian family tree.

The selection pressures for this lack of hair are just as varied as the species that have lost their fuzz. 

In elephants, for example, they say hairlessness could be of benefit for keeping cool in the heat.

Adaptation by breaking things or turning them off is evolution in action — just not the kind of creative evolution that requires foresight and planning, and that points, instead, to intelligent design. Here, Dr. Behe discussed Darwin Devolves with Eric Metaxas for Socrates in the City: