So there you have it. Dogs are for love, affection, and making us better humans.

Just as there are fashions in dog breeds—remember the Shih Tzu?—there are fashions in dog evolutionary theories. The “newest version of the domestication hypothesis,” according to Homans, “posits that humans did not necessarily select dogs to breed based on their attention and skill at responding to human cues. Rather, the tamest and least situationally aggressive dog had those qualities built in.” An even newer theory, though, published in the January 23 issue of Nature, takes domestication in a wholly different direction. The wolves that became dogs, its authors argue upon examination of the entire wolf and dog genomes, were the ones whose bodies were best able to digest the starches that newly agricultural humans left behind in the trash.