Your Adorable Dog's and Cat's Cute Features May be Linked to a Genetic Deficit Due to Domestication

How cute is your dog? It may have evolved to be more adorable than its wild ancestors during the domestication process. Now, researchers have uncovered the underlying link between "cute" traits and a group of embryonic stem cells.

Researchers have long noticed that domesticated mammals are more tame and tend to have floppier ears, more patches of white fur, and more juvenile faces with smaller jaws. Yet until now, they haven't been able to explain this particular pattern. Scientists have discovered that the underlying link between these features could be the group of embryonic stem cells called the neural crest.

Neural crest cells are formed near the developing spinal cord of early vertebrate embryos. As the embryo matures, the cells migrate to different parts of the body and give rise to many tissue types. These tissues include pigment cells and parts of the skull, jaws, teeth and ears, as well as the adrenal glands, which are the center of the "fight-or-flight" response.

"When humans bred these animals for tameness, they may have inadvertently selected those with mild neural crest deficits, resulting in smaller or slow-maturing adrenal glands," said Adam Wilkins, one of the researchers, in a news release. "So, these animals were less fearful."

Neural crest deficits can also cause depigmentation in some areas of skin, resulting in white patches, and can also cause malformed ear cartilage, tooth anomalies, and jaw development changes. This means that selecting for neural crest deficits could actually explain the changes seen in domesticated animals, such as dogs.

"Because Darwin made his observations just as the science of genetics was beginning, the domestication syndrome is one of the oldest problems in the field," said Wilkins. "So it was tremendously exciting when we realized that the neural crest hypothesis neatly ties together this hodge-podge of traits."

Currently, this hypothesis still needs to be tested; but it's certainly one that's worth experimentation. Tests of the neural crest hypothesis may not be far off since other scientists are mapping genes that have been altered by domestication.

The findings are published in the journal Genetics.