Close to half of American dog owners - 46 percent - own mutts. While American Kennel Club registrations have declined in recent years, purebreds are still the dog of choice, with 61 percent of those who have dogs opting for them, according to a 2005-2006 report by the American Pet Products Manufacturing Association. (The overlap is from those who own both.)

Dogs, scientists believe, originated from a population of wolves that lived in China 15,000 to 40,000 years ago and became domesticated by humans. For centuries, they were bred and chosen for their working skills, such as herding, hunting or guarding.

Gradually, they made the transition from worker to companion. Today, they are chosen more for their looks than anything else, with TV shows and movies playing a big role in determining the next "hot" breed of dog.

Hottest now are "designer dogs," such as the labradoodle and the goldendoodle, originally developed by crossing poodle and retriever.

"These mixed-breed dogs are the latest craze," Shain said. "Everybody wanted a pug, now everybody wants a puggle. Certain dogs rise and fall, and everybody wants to have the latest 'it' dog."

Sometimes, the surge in popularity is followed by a surge of that breed showing up in shelters. But the vast majority of homeless dogs are still mutts like Ace.

Ace and I stopped in three neighborhoods in 21229. We visited a firehouse, talked with some families and traipsed around a park. Ace did a lot of sniffing, but he always does. He made a couple of friends, but no one recognized him.

As we called it a day, I began to realize the only one who might know where Ace came from was not a person at all.

It was Ace.

Too bad dogs can't talk.

Or can they?