Solution for Domestication Traits Riddle (What We’ve Come to…)
Certain common traits in different domesticated mammal species first noted by Charles Darwin nearly a century and a half ago, had remained unexplained since then. Among these are tamer outlook of domesticated species compared to their ancestors, floppy ears, white fur patches, smaller jaws.
Now, however, a perspective article published in the journal GENETICS appears to have identified the root cause for all these common traits: A group of pluripotent embrionic stem cells dubbed “neural crest”, which, during the early stages of the development of the embryo, straddles theforming neural tube. As the embryo develops, these cells migrate to different parts to form different tissues. Among these are pigment cells responsible for skin colors as well as such structures as facial bones , cartilage and teeth. Neural crest is also responsible for glands which secrete the hormone adrenaline which affects the “fight-or-flight” choice of an animal in the face of a threat. Neural crests are also credited with an indirect role in brain development.
The hypothesis proposed in the paper authored by Adam Wilkins of Berlin’s Humboldt University, Richard Wrangham from Harvard and Tecumseh Fitch of the University of Vienna ties the common traits of the “domestication syndrome”, to the impaired development or migration of these cells.
"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," Wilkins says. "So, these animals were less fearful."
Among other effects caused by defects in neural crest cells is the depigmentation of skin regions causing white patches, malformed cartilage resulting in floppy ears and changes ,in teeth and jaw structures.
As a chemical signal sent by these cells plays an important role in the smooth development of the forebrain, researchers speculate that changes in neural crests could also be responsible in the reduced forebrain size of domesticatedspecies.
Pointing to the accelerated mapping of the changes brought about by domestication among rats, foxes and dogs, researchers believe the test of the hypothesis is not very far off.
- 1. “Domestication syndrome: White patches, baby faces and tameness”, Genetics Society of America, 14 July, 2014
- 2. “Neural crest”, http://en.wikipedia.org/wiki/Neural_crest