Figure 2.

Diagrammatic representation of the neural crest hypothesis of the domestication syndrome, illustrating how selection for tameness, leading to decreased neural crest input into the sympathetic and adrenal systems, would cause the other observed components of the domestication syndrome as unselected by-products, resulting in a “mild neurocristopathy.” Arrows indicate predicted directions of influence on traits discussed in the text, as separated into direct and indirect developmental (mechanistic) effects.