An anonymous reader quotes a report from Science Magazine: A new study — citing genetic evidence from a disorder that in some ways mirrors elements of domestication — suggests modern humans domesticated themselves after they split from their extinct relatives, Neanderthals and Denisovans, approximately 600,000 years ago. Domestication encompasses a whole suite of genetic changes that arise as a species is bred to be friendlier and less aggressive. In dogs and domesticated foxes, for example, many changes are physical: smaller teeth and skulls, floppy ears, and shorter, curlier tails. Those physical changes have all been linked to the fact that domesticated animals have fewer of a certain type of stem cell, called neural crest stem cells.
Giuseppe Testa, a molecular biologist at University of Milan in Italy, and colleagues knew that one gene, BAZ1B, plays an important role in orchestrating the movements of neural crest cells. Most people have two copies of this gene. Curiously, one copy of BAZ1B, along with a handful of others, is missing in people with Williams-Beuren syndrome, a disorder linked to cognitive impairments, smaller skulls, elfinlike facial features, and extreme friendliness. To learn whether BAZ1B plays a role in those facial features, Testa and colleagues cultured 11 neural crest stem cell lines: four from people with Williams-Beuren syndrome, three from people with a different but related disorder in which they have duplicates instead of deletions of the disorder’s key genes, and four from people without either disorder. Next, they used a variety of techniques to tweak BAZ1B’s activity up or down in each of the stem cell lines. That tweaking, they learned, affected hundreds of other genes known to be involved in facial and cranial development. Overall, they found that a tamped-down BAZ1B gene led to the distinct facial features of people with Williams-Beuren syndrome, establishing the gene as an important driver of facial appearance. “When the researchers looked at those hundreds of BAZ1B-sensitive genes in modern humans, two Neanderthals, and one Denisovan, they found that in the modern humans, those genes had accumulated loads of regulatory mutations of their own,” the report says. “This suggests natural selection was shaping them. And because many of these same genes have also been under selection in other domesticated animals, modern humans, too, underwent a recent process of domestication.”
The findings have been reported in the journal Science Advances.