I have evolution and selective breeding on the brain as I'm finally reading Guns, Germs and Steel, which answers all those questions you never thought to ask, like "Why didn't we domesticate zebras?" (Answer: they bite and don't let go.)
And so when I last took my dog to the field across the street from our new digs in Northampton, MA, I couldn't help but think the following: after thousands of years of survival of the fittest, learned behavior and so forth, dogs have scored an extremely secure niche in the human world. For proof, consider the (shameful) existence of cupcakes for dogs.
Formerly dogs had to be good hunters and guardians to earn a spot at the campfire, as well as the bones and scraps of the kill. But today's dog earns its keep by doing goofy stuff like this.
My dog Oli, the pinnacle of canine evolution, has perfected his meal ticket by perfecting his desirability in terms of companionship. Because who could answer "no" to the question so clearly posed by the above photo: won't you be my pal?