In particular, more than a half (four of seven: Cacna2d3, Mapk1, Pomc, and Syn1) of underexpression cases found here associate domestication with anxiety, which is the key trait for mutual trust within a human–pet pair, as demonstrated for dogs (Zapata et al., 2016), sheep (Coulon et al., 2014), and guinea pigs (Kaiser et al., 2015). This evidence concerns the gene MAPK1 and Anxiety.