Shared reproductive disruption, not neural crest or tameness, explains the domestication syndrome.

Altered neural crest cell (NCC) behaviour is an increasingly cited explanation for the domestication syndrome in animals. However, recent authors have questioned this explanation, while others cast doubt on whether domestication syndrome even exists. Here, we review published literature concerning this syndrome and the NCC hypothesis, together with recent critiques of both. We synthesize these contributions and propose a novel interpretation, arguing shared trait changes under ancient domestication resulted primarily from shared disruption of wild reproductive regimes. We detail four primary selective pathways for 'reproductive disruption' under domestication and contrast these succinct and demonstrable mechanisms with cryptic genetic associations posited by the NCC hypothesis. In support of our perspective, we illustrate numerous important ways in which NCCs contribute to vertebrate reproductive phenotypes, and argue it is not surprising that features derived from these cells would be coincidentally altered under major selective regime changes, as occur in domestication. We then illustrate several pertinent examples of Darwin's 'unconscious selection' in action, and compare applied selection and phenotypic responses in each case. Lastly, we explore the ramifications of reproductive disruption for wider evolutionary discourse, including links to wild 'self-domestication' and 'island effect', and discuss outstanding questions.

Female status, food security, and stature sexual dimorphism: Testing mate choice as a mechanism in human self-domestication.

OBJECTIVES: Humans exhibit multiple anatomical and behavioral signatures of domestication syndrome, leading evolutionary-minded scholars to suggest Homo sapiens is a "self-domesticated" species. We examined one of three mechanisms proposed to explain human self-domestication-that is, intersexual selection against reactive aggression. We hypothesized that this process has been, at least in part, caused by context-dependent female preferences for less-aggressive males. We predicted that societies where women have higher social status will show relatively elevated signs of self-domestication-as indicated by lower stature sexual dimorphism (SSD)-and that this relationship should be mediated by food security. MATERIALS AND METHODS: To test our prediction, we used male and female stature data for 28 societies from the Standard Cross-Cultural Sample. We applied multivariate regression to examine our hypothesis while controlling for theoretically important confounders. RESULTS: We found convincing support for the prediction that the relationship between SSD and female status is mediated by food security. As predicted, higher female status was associated with less sexual dimorphism and the effect is stronger when food resources are secure. DISCUSSION: Context-dependent female mate choices significantly contribute to lower SSD, suggesting female mate choice is likely to have played an influential role in human self-domestication. Future research on this theme will benefit by including more of the expected symptoms of human self-domestication and examining other potential drivers of this process.