The taming of the neural crest: a developmental perspective on the origins of morphological covariation in domesticated mammals

Abstract

Studies on domestication are blooming, but the developmental bases for the generation of domestication traits and breed diversity remain largely unexplored. Some phenotypic patterns of human neurocristopathies are suggestive of those reported for domesticated mammals and disrupting neural crest developmental programmes have been argued to be the source of traits deemed the ‘domestication syndrome’. These character changes span multiple organ systems and morphological structures. But an in-depth examination within the phylogenetic framework of mammals including domesticated forms reveals that the distribution of such traits is not universal, with canids being the only group showing a large set of predicted features. Modularity of traits tied to phylogeny characterizes domesticated mammals: through selective breeding, individual behavioural and morphological traits can be reordered, truncated, augmented or deleted. Similarly, mammalian evolution on islands has resulted in suites of phenotypic changes like those of some domesticated forms. Many domesticated mammals can serve as valuable models for conducting comparative studies on the evolutionary developmental biology of the neural crest, given that series of their embryos are readily available and that their phylogenetic histories and genomes are well characterized.

Is evolution of domestication driven by tameness? A selective review with focus on chickens

“…It has recently been suggested that the domesticated phenotype could be caused by a general embryological effect acting on the neural crest cells (Sánchez-Villagra et al, 2016).…”

Revisiting two hypotheses on the “domestication syndrome” in light of genomic data

“…Although the domestication of each species must have involved direct or indirect selection for docility (lack of fear) and tameness (ability to be handled by humans), the domesticated breeds of the different mammalian species all share a distinctive suite of physical and physiological traits, not seen in their wild progenitors. The suite of traits is neither universal amongst species nor amongst all breeds of a given species (Sanchez-Villagra et al, 2016). Nevertheless, it is sufficiently generic to be seen as a signature feature of mammalian domestication.…”

“…The particular secondary morphological and physiological traits that mark the domesticated state include: floppy ears, smaller jaws, smaller teeth, pigmentation changes in the coats (toward white and brown spots), reductions in adrenocortical hormone titers, increased frequency of estrus cycles, reduction in brain size, and alterations in concentration of several brain neurotransmitters. (For a comprehensive tally of which domestication-specific traits appear in the different mammalian species that have been domesticated, see Figure 1 of Sanchez-Villagra et al, 2016. ) This condition has been dubbed the "domestication syndrome", abbreviated here as the DS.…”

Chicken domestication : Effects of tameness on brain gene expression and DNA methylation

“…Behavioural changes include reduced fear, aggressiveness and antipredator responses, increased sociability, and altered vocalization patterns [1,[13][14][15][16]. As summarized by Sánchez-Villagra et al [17], the dog is the clearest example of a domestic species with the highest account of phenotypic changes.…”