Domestication makes ya dumb and sick, says study. (paraphrased)

domesticationSome quotes from the article:

The general combination of traits in domesticated mammals is an ensemble that we will refer to as the “domestication syndrome” (DS) […] In this article, we will present a new hypothesis about the nature and origin of the DS, proposing that the unifying feature underlying its diverse traits is their shared developmental connection via neural crest cells, the multipotent stem cells that arise in vertebrate embryos from the dorsal part of the neural tube.

As the brief review above makes clear, the main morphological components of the DS can all be explained by the derivation of the affected tissues from neural crest. […]

A wide range of genes are known to play crucial roles in neural crest specification, migration, and postmigratory interactions. Given the biological importance of NCC-derived tissues, it is unsurprising that knockouts of these genes are frequently lethal in the homozygous organism, and often severely debilitating even in heterozygotes. Such conditions have long been known, and are given the generic designation “neurocristopathies” in medicine […]

A third, poorly understood, neurobiological aspect of domestication involves changes in the central nervous system. Brain size is significantly reduced in most domesticated animals, relative to their wild-type ancestors, but to a variable degree. This reduction, which is particularly prominent in the forebrain, is very significant in some species; for example, domestic pig brains are 35% smaller than expected for the same size wild boar, their presumed wild ancestor. […] Rather than overall brain size reduction, it seems more likely that reductions of particular components of the forebrain, such as the amygdala or other components of the limbic system, play the important roles in tameness.

[…] feral domesticates retain their small brains after as many as 40 generations back in the wild. […]

Another recently identified human neurocristopathy of interest is Mowat-Wilson syndrome, a rare syndrome featuring microcephaly, specific narrowing of the jaw, and a host of other neural-crest-related symptoms (e.g., changes in ear morphology, heart disease) along with mental retardation and epilepsy. Interestingly, patients with this syndrome are reported to “have a happy demeanour with frequent smiling” (Mowat et al. 2003), consistent with the behavioral changes seen during animal domestication. The genetic basis of Mowat-Wilson is clear, mainly involving mutations of the ZEB2 gene, also known as SIP1.

Citation: Wilkins, Fitch and Wrangham. 2014. “The ‘Domestication Syndrome’ in Mammals: A Unified Explanation Based on Neural Crest Cell Behavior and Genetics.” Genetics, Vol. 197, 795–808 July 2014 795

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