Almost every year for the past decade, a Chinese crested has won the World's Ugliest Dog Contest in Petaluma, California. This year was no exception.

The 2012 winner, crowned on June 22, is eight-year-old Mugly, a bald and beady-eyed crested who sports stringy whiskers weirdly reminiscent of dental floss. (See a picture of Miss Ellie, 2009 World's Ugliest Dog.)

What makes the dog so ugly is its signature hairlessness, said Adam Boyko, an authority on canine genetics at Cornell University.

"If you see a lot of hairless people, for instance, all of a sudden you're going to start noticing moles and weird skin," Boyko said. "It just makes everything else that's weird stand out more." In the case of the Chinese crested, the crinkly, mottled skin is prominently displayed.





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"Presumably it's just an ancient mutation that happened one time, and breeders liked it and propagated it," Boyko said. "You don't see packs of wild hairless dogs running around." (Read Boyko's thoughts on the roots of semiwild "village" dogs.)

Geneticist Teresa Gunn agreed. "It's all because of people, not natural evolution," said Gunn, of the McLaughlin Research Institute, who studies the evolution of canine breeds.

"It's people saying, Yeah, let's have small dogs. Let's have hairless dogs, because we don't want them to shed, or because we live somewhere hot, or, you know, just because they're weird."

How does hairlessness affect the dog?

"We don't really know [of any benefits]. Maybe [the dog] cools off faster," Boyko muses. "But then there's also sunburn. In Peru hairless dogs are almost always wearing sweaters. When you take them off you can see tan lines."