In this video segment from Nature, learn about the evolution of dogs. More than 750 million people share their lives with dogs today. This video explores theories of how dogs became a domestic pet. One theory is ancient people tamed wild wolves. This theory is challenged by the idea that wolves evolved themselves into a different species. Biologist Raymond Coppinger believes human garbage heaps may have caused wolves to be drawn to feed on them. Competition among the wolves may have caused them to transform into "dogs,” that were not frightened of humans who came to the dumps.