Razib Khan writes in The New York Times that it’s commonplace to call our cats “pets.” But anyone sharing a cat’s household can tell you that, much as we might like to choose when they eat in the morning, or when they come inside for the night, cats are only partly domesticated.

The likely ancestors of the domestic dog date from more than 30,000 years ago. But domestic cats’ forebears join us in the skeletal record only about 9,500 years ago. This difference fits our intuition about their comparative degrees of domestication: Dogs want to be “man’s best friend”; cats, not so much.

Domestic cats are not just wildcats that tolerate humans in exchange for regular meals. They have smaller skulls in relation to their bodies compared with wildcats, and are known to congregate in colonies. But in comparison with dogs, cats have a narrower range of variation in size and form.

Wesley C. Warren, an author of the study, notes that domestic cats have excellent hunting skills, like their wild ancestors. This, too, supports the notion that cats are only semi-domesticated.

Comparing the genomes of the wildcat and the domestic cat added much to what we had known. Michael J. Montague, the lead author, told me he’d anticipated that the two genomes would be very similar, but our study found a specific set of differences in genes involved in neuron development. This brain adaptation may explain why domestic cats are docile.