Domesticated animals transitioned from wild beasts into furry friends thousands of years ago, but scientists have not yet fully explained how taming also altered animals’ appearances. In 2014, researchers took steps toward the answer.
In July, three scientists presented the idea that slight alterations in some cells could account for physical attributes that go hand-in-hand with tameness (SN: 8/23/14, p. 7). The cells, called neural crest cells, migrate through embryos and contribute to the development of many parts of the body, including the face, pigment cells and adrenal glands — the source of the fight-or-flight response.
Humans choosing companionable animals unwittingly selected creatures with slight impairments in neural crest cell function, the scientists reasoned. That explains why domesticated animals display other effects of faulty neural crest cells: white-spotted coats, floppy ears and juvenile faces, traits collectively called domestication syndrome.
Previous explanations for individual domesticated traits often didn’t explain why tame animals had other associated features, says Greger Larson, a geneticist at the University of Oxford. The neural crest cell hypothesis may not be correct, but it does give researchers an idea to test, he says.
Researchers studying cat domestication discovered variants in many genes that set house cats apart from wild cats. But it wasn’t obvious why those genetic tweaks would be linked to domestication, says Wesley Warren, a geneticist at Washington University in St. Louis. But the neural crest cell paper “started to help us make sense of some things we were seeing,” he says. Warren and colleagues realized that five genes they identified as domestication signatures are important for neural crest cell function (SN: 12/13/14, p. 7). Those findings support the emerging hypothesis.
Not everyone is convinced that neural crest cells explain tame animals’ features. People probably weren’t picking animals based on tameness alone, says Leif Andersson, a geneticist at Uppsala University in Sweden. Humans may have chosen animals with coat colors that made them easier to spot in a field, for instance.