Does Darwin's theory say that we'll evolve even further than we already have?

Dogs are self-domesticated, like cats, pigs and goats. They are descended from wolves who were a little lazier and more tolerant than their pack-mates, and sidled into our camps to eat the trash in our middens. (Pigs and goats also came for the trash, whereas cats came for the rodents.)

So they originally self-selected for a scavenger's diet and we reinforced that trait. 12,000 years of domestication--in a species with a six-month breeding cycle--has resulted in a few genetic differences between Canis lupus familiaris and C. lupus lupus.

• Since brain tissue requires a lot of protein for maintenance, dogs have somewhat smaller brains than wolves.
• Since living in a mixed-species pack was a new experience for earth's animals, dogs are much more social and gregarious than wolves, generally treating strangers with cautious cordiality instead of starting a fight.
• Since dogs have to accept humans as their pack leaders, they have a much weaker alpha instinct than wolves--feral dogs packs typically number in the dozens.
• Dog teeth are somewhat differently shaped than wolf teeth. They gave up the ability to rapidly rip the flesh off of a fresh kill before the larger predators show up to steal it, in favor of being able to eat carrots.

So it stands to reason that if returned to the wild, a dog would not fare as well as the wolves who decided to turn down the offer of becoming scavengers instead of hunters.

Nonetheless, dogs have a pack-social instinct and are loyal to their pack-mates. Feral packs include dogs of all sizes. After a couple of generations of random mating they tend toward the ancestral size standard anyway--not quite as big as the average wolf but about the size of a coyote: plenty big enough to hunt. If civilization broke down and dogs had to fend for themselves, they could feed on the detritus of our cities long enough to return to that standard.

And don't forget that most small dogs are descended from terriers: dogs that chase burrowing animals into their homes. They'll get the food that the big dogs can't dig up.

 

Every domestic animal breeder is familiar with Belyaev's work by now.

It's certainly valid, but it does not factor in the self-selection of omnivorous scavengers in proximity to human settlements. The early Neolithic humans probably did not have to give any attention or effort to the domestication of wolves, because the ones who chose to live the easy life of midden-browsing were already the ones who were more curious about new and different environments than their old pack-mates who remained hunters. The ones who were not as afraid of proximity to another pack-social species and who in fact learned to understand our habits and even read our facial expressions and body language. The ones who didn't mind conceding the competition for leadership when the reward was having perfectly good food (by their standards) literally tossed at them because they were closer to camp than the dump was; who didn't panic and start growling when baby wolves and baby humans began naively playing together and then fell asleep in a big warm pile.

We don't even know when humans began breeding dogs. The Agricultural Revolution was the discovery of the twin technologies of plant cultivation and animal husbandry; but I suspect that plants were domesticated first since they don't run away or fight back... and because humans continued to hunt long after the dawn of the Neolithic Era, and even after it gave way to Civilization, the Bronze Age, the Iron Age, the Industrial Revolution and the Age of Electronics. The first Stone Age villages might have had only crops and no herds, so that humans would not have had any expertise with breeding animals when the first wolves asked to join them in what proved to be a sweet deal for both species.

Any selective breeding might have been purely natural, as any individuals of domestic litters who were not comfortable living among us simply walked away and resumed the predatory lifestyle--or were executed for trying to eat the baby humans.