The evolutionary origin of the domestic dog has long been a point of controversy, some authorities saying wolves were the progenitors while others point to the coyote or the jackal. All are closely related members of the same genus, Canis, and wolves, dogs and coyotes can interbreed.
Now comes Stanley J. Olsen, an anthropologist and vertebrate paleontologist at the University of Arizona. In a book summarizing 30 years of examining skeletons of fossil wolves and early dogs, Olsen says all domestic dogs can trace their ancestry back to a small variety of wild Asian wolf.
Olsen suggests that while wolves evolved in North America, some migrated across the Bering land bridge to Asia hundreds of thousands of years ago. The North American wolves grew larger, but their Asian cousins shrank to the proportions that would become familiar in the dog.
In Asia, human beings and small wolves were living side by side at least 300,000 years ago. Though their bones are found with those of people, there is no skeletal evidence of domestication until about 10,000 years ago. Then the animals' faces become shorter and the teeth smaller -- altogether more doglike.
Olsen also favors the wolf as ancestor because its social behavior is closest to that of the dog. He speculates that early peoples admired wolves because of their family-oriented pack system and humanlike practice of hunting in coordinated groups.
He imagines that early peoples tamed wolves by bringing pups into camp, perhaps after killing the mother. As the pups grew, they would regard the humans as part of their social group and soon prove their value as watchdogs by growling at intruders