How Cats Hung on to Their Wild Hearts

— -- The family cat may sit on your lap for hours, purring in domestic bliss as it savors human companionship, but underneath that friendly fur beats the heart of a lion.

An international team of scientists led by geneticist Wes Warren of the Washington University School of Medicine in St. Louis has completed the first comparative analysis of the complete genomes of wild and domesticated animals, including some of our favorite friends: dogs and cats.

They found some differences, caused by genetic changes driven by humans through selective breeding programs, but the differences between cats and their wild kinfolk is not all that great, Warren said in a telephone interview. It is not nearly as great, for example, as the difference between dogs and wolves.

Dogs have been domesticated for about twice as long as cats, and despite human efforts to push the domesticated cat further away from wild varieties, "the cat has still maintained more of its wild cat genome, as in behavior characteristics, than the dog," he said, so cats should be considered "semi-domesticated."

"Many cat owners will vouch for this," he added. "If you release your cat at night it will go out and hunt and be as efficient as a wild cat at catching mice and birds and many other critters."

Other scientists agree. Researchers at the University of Illinois at Urbana-Champaign attached radio collars equipped with tilt and vibration sensors to snoop on the lives of 42 cats over a two-year period. The subjects included both feral and domesticated cats, and the study concluded that there's a lot going on out there under the cover of darkness.

The domesticated cats tended to stay closer to home than the wild variety, but they strayed farther than their owners would have expected, the researchers noted.

Other studies have shown that domestic cats routinely mate with feral cats, but the Illinois study revealed that it's not exactly a blissful relationship.

The leading causes of death among the feral cats were fights with other cats and disease, so when the family kitten goes out to play it may come back with scars and diseases that can be passed on to other cats.

The researchers found one feral cat that would wait behind a house each night for a pet cat to emerge, and then chase it out of its own backyard. Another pet got chased out of a dairy barn.

That kind of shaky co-existence undoubtedly dates back to when the first cat joined ranks with humans, whenever that was. The best evidence so far of the first attempts at domestication comes from the archaeological discovery in Cyprus a decade ago of the bones of a cat and a human buried together, suggesting a real friendship between felines and humans.

Some scientists, including researchers at the University of California, Davis, who studied 11,000 cats, or their remains, believe the domestication process really began in a Middle East region called the "Fertile Crescent." That area is also known as the "cradle of civilization" because rich natural resources there gave birth to the agricultural era.

Cats were welcomed by the nascent farmers around 5,000 years ago because, as we all know, they are great mousers. And mice, like other rodents, can destroy a crop by devouring the grains and seeds.

So the cat, like the dog much earlier, was welcomed into the human family because it could be useful.