The selective breeding that created the hundreds of modern dog breeds has put purebred dogs at risk for a large number of health problems, affecting both body and behavior.

Molecular biologist Peter Savolainen of the Royal Institute of Technology in Stockholm, Sweden, and his colleagues have studied the origins of domestic dogs using hair samples and mitochondrial DNA.

Discover ancient dog breeds from around the world on our Interactive Map.

Genetics and brain physiology can affect a dog's personality and behavior.

In this Web exclusive video, producer and director Corinna Faith discusses the making of "Dogs That Changed the World."

Americans own 73 million dogs and 90 million cats. Why are we so attached? Watch the full episode now.

Your pet is a member of your family, and there are things you know about your cat or dog that no one else would ever guess. Now it's time to spill!

The results are in! Check out the winners and runners-up in NATURE's Why I Love Cats and Dogs Photo Contest.

When their dog Jerry became ill, Jim and Rene decided to sell their business and their house -- and they hit the road with Jerry.

Underdogs associate producer Aidan Woodward gives a behind-the-scenes look at the making of the film.