Another predatory mammal species, wolves, presents a curious chapter in this story, not because of their own behavior, but because of a separate species that evolved from wolves sometime between 15,000 and 50,000 years ago. Wolves organize themselves around a strict hierarchy led by alpha males and alpha females, but they are also quite intelligent and display occasional glimmers of curiosity. Considerable evidence indicates that way back when human beings were first realizing that other species could be trained to help with various chores, little wolf pups were volunteering for the job, playing with little human children, and getting protection and food as a reward for good behavior. Over the millennia, some wolves evolved into dogs, and dogs have eventually outcompeted wolves dramatically by forming partnerships with their eventual masters, who were even smarter and more skilled with tools.


As civilized human communities emerged from the struggles of prehistoric life, largely through the domestication of edible plants, edible animals, and other animals recruited for work and play, a wide range of dog breeds cropped up. Some specialized in tracking, pointing at, and retrieving prey; some in pulling sleds over snow and ice; some in herding sheep; and some in simply being cute and cuddly playmates. Dogs now show up in a dazzling array of breeds, though they are all one species, from tiny miniatures to massive mastiffs. Dogs have been remarkably successful, not through fierce domination or brute strength (though that may come in handy now and then) but mostly through friendly collaboration with a more powerful and more intelligent species–namely, us.


Anyone who doubts the overwhelming evidence of the evolution of dogs from wolves, or even the impact of biological evolution in general, should consider the purposeful attempt to duplicate this evolutionary process starting with foxes. Starting in 1959, a Russian zoologist named Dmitry Belyayev began breeding foxes by selecting for traits like courage and intelligence. He chose foxes because they seemed as close to wolves as any other species, and then he studied the behavior of young foxes to select the ones who seemed the most likely to become tame. As it turned out, the young foxes who made the grade showed more than average courage, more than average curiosity, and more than average intelligence–to overcome the fear of larger human beings with powerful tools, to recognize friendly tones of voice and gestures, and to come close enough to receive some food and stroking.


Belyayev mated the most courageous, curious, and intelligent foxes and repeated the process over a string of generations. After just a few generations, the young fox pups showed shorter snouts, floppy ears, and a measure of willingness to interact playfully with human beings–just like the dogs who evolved from wolves. The ultimate meaning of this process seems to suggest that courage, curiosity, intelligence, and willingness to cooperate for the greater good of the larger community are all preferable in the long run to brute competition, savage selfishness, and fierce rivalry. In several respects, dogs and Belyayev’s semi-dogs are like immature wolf or fox pups who never fully grow up but remain content to follow orders and play with their human masters.

In this context, the function of play behavior is significant in itself. Extensive esearch has shown that play functions to strengthen social bonds, provide opportunities to learn right from wrong (such as how hard to bite and what gestures are off limits), increase physical fitness, and practice important skills in a safe arena. In general, animals play under the same conditions as humans — when “work” is done, meaning after other needs such as safety, food, and shelter are met and when everyone is relaxed and feeling good. And research suggests that they play for the same reason as humans: because it’s fun.

Next Up: Chimps