Last week we discussed how domestication has not much changed cats. Dogs, however, long ago signed a contract which allows us to remake them in whatever image people have in mind. In terms of genetics it’s hard to imagine another species quite so “Silly Putty” (think Chihuahua vs. Mastiff), which probably contributes a great deal to the “man’s/woman’s best friend” title: we humans love best what we can shape to meet our own wants and expectations.

Long before our earliest ancestors began messing around with farming and crafting bronze, early humans and the grey wolf became partners. Wolf skulls, teeth, paws and eventually body shape shrank, they accepted us in the role of alpha previously held by one of their own, and they learned to read our expressions as we learned to read theirs: they became dogs as we became Homo sapiens, and we became codependents.

So whereas cats have remained pretty much unchanged, what is it about the dog that has allowed them to be so “plastic”…? The answer: time plus human desire. Unexpected physical quirks (the result of natural mutation) are common enough, and it has long been a human trait to build on animals’ natural mutation by selectively breeding those who exhibit it. In simplest terms, if you want a really tall dog then take two comparatively tall dogs and ask them to make a litter; there’s a good chance several of those pups will be tall too, as will their own offspring. Obviously the risks of inbreeding are significant in terms of overall health, but this is the basic formula. While most of the selective breeding of cats has occurred within the last century, breeding dogs for certain traits (whether intentionally by humans, or simply because those with the more “desirable” trait were able to survive around humans and to produce young) goes back much, much further. Herding goats in mountainous regions called for certain traits, as did guarding our property, as did ferreting out ferrets and other tunnel dwelling animals which stole our grain and chickens. Dogs are a product of what we demanded.