What might a posthuman dog look like? It’s hard to say, because morphological features will evolve in response to ecological pressures, feeding ecologies, and distinct features of the ecological niche that a given population of dogs might fill. Dogs are already the most morphologically diverse mammalian species on the planet. Think of the huge size difference between, for example, the teacup Maltipoo and the Irish wolfhound. One possibility is that dogs will eventually all become of medium size – say 35 lbs (15 kg), give or take. An equally viable possibility is that dogs of the future will speciate over time into smaller and larger types. The shape and size of physical characteristics such as ears, tails and noses will similarly evolve in response to unique demands of ecological niche, feeding ecology, mating strategies and social structure. To take just one example, the shape and size of ears will represent a set of tradeoffs reflective of the competing demands of climate, geography and feeding ecology, among other things. Bigger ears may pick up sounds better than smaller ears, and would aid dogs in locating prey, but they might also be problematic in very cold temperatures because there is more surface area for heat loss. In cold climates, smaller ears and slightly less acute hearing might be worth the tradeoff for protection against the cold.

Natural selection will quickly weed out physical traits that are maladaptive, such as extremely foreshortened snouts, excessive skin folds, and extremely long or short limbs. Floppy ears and curly tails would also likely disappear because they inhibit dog-to-dog communication and serve no functional purpose; so, too, would spotted and bi- and tricoloured coats.

Dogs have been selectively bred by humans for certain behavioural traits, including a general propensity for friendliness and malleability, and breed-specific functional skills such as pointing, fetching, herding and guarding. Selection for these traits has been driven by an interest in the physical characteristics of dogs, by the usefulness of these traits in relation to human pursuits, and, over the past century or two, by human aesthetic whims and fancies. Taken outside the context of human-canine relations, some of these physical and behavioural traits may serve dogs well. Others not so much.