The Domesticated Brain

The brains of domestic animals tend to share a number of traits in common. Perhaps the most common trait is relative reduction of overall brain size in domestic as compared to wild ancestors, though this is not always present with domestication, and is often complicated by changes in overall body size. Reduction of size is not uniformly represented in all brain structures and tends to disproportionately affect a fairly consistent set of structures. These tend to be telencephalic structures and disproportionately affect olfactory and limbic structures across a diverse group of domesticated mammals. These changes may reflect selection that affects social and sexual behaviors that are maladaptive in domestic conditions and eliminated by selective breeding or are simply no longer of reproductive value and have degenerated due to relaxed selection. The signature pattern of specific brain structure changes can in this way provide evidence to distinguish between these two processes associated with domestication understood broadly.