Issue Date: July 16, 2007
Warning: This page does not contain anything about chemistry or the chemical enterprise. It's about cats.
One of the things I love about science is that it is often done just because people have a burning desire to know things about the world, even if the knowledge gained doesn't have any particular use.
While I was on vacation recently with my wife visiting Vancouver and Vancouver Island, Canada, I read reports in the New York Times and Toronto's Globe and Mail (which seems to function as Canada's USA Today) about research on the domestication of cats. The report in the Times included a striking photograph of what was identified as an African wildcat with its jaws locked firmly around the neck of a dead bird. The cat looked identical to any tabby you might see lounging around someone's house.
I am a sucker for cats. I grew up on a small farm in New Jersey where we grew soybeans. We regularly stored several hundred bushels of beans in the barn over the winter, and we always had a number of farm cats living in the barn. Each spring brought a litter or two of kittens, which my sister and I delighted in playing with.
I've owned, or been owned by, cats most of my adult life. We currently have two, McMurphy, an aloof black tabby also referred to as "The Prince"—which gives you a hint as to his status in our household—and Sylvester, a mostly black, fairly obese cat who is clearly insane.
The research referred to in the newspaper stories was reported in a recent issue of Science (DOI: 10.1126/science.1139518). It was carried out by David Macdonald, a zoologist at the University of Oxford, and 12 coworkers at nine institutions around the world. The researchers' goal was to determine which of five recognized subspecies of wildcat, Felis silvestris, gave rise to the domestic cat. The five subspecies (not to be confused with North American wildcat or bobcat, Felis rufus) range across Europe, Asia, and Africa.
The researchers report that the "earliest evidence of cat-human association involves their co-occurrence in Cyprus [burial site] deposits aged at 9,500 years ago." However, they point out, the exact relationship of domestic cats, sometimes considered to be a distinct subspecies of F. silvestris, and the five subspecies of wildcats remained unclear. Researchers did not know, for instance, whether cats had been domesticated in a single location or several across Eurasia and Africa.
Macdonald and coworkers obtained tissue from 979 cats on three continents, including all subspecies of wildcats and fancy breed domestic cats. They extracted DNA and genotyped 851 cats for 36 variable short tandem repeat (STR) sequences and sequenced 2,604 base pairs of mitochondrial DNA genes from 742 cats.
Their analysis shows that the five subspecies of wildcats are distinct and diverged from a common ancestor on the order of 230,000 years ago. The domestic cat is descended exclusively from the Near Eastern wildcat, F. s. lybica. Mitochondrial DNA analysis suggests at least five female wildcats were the progenitors of modern domestic cats.
The researchers write: "The domestication of wild species to complement human civilization stands as one of the more successful 'biological experiments' ever undertaken. For cats, the process began over 9,000 years ago as the earliest farmers of the Fertile Crescent domesticated grains and cereals as well as livestock animals. In parallel, the endemic wildcats of the region may have adapted by both regulating the rodents in the grain stores and abandoning their aggressive wild-born behaviors."
The descendents of those self-domesticated felines were subsequently transported by humans around the world, where some of them wound up in our barn in New Jersey doing just what their ancestors did in the Fertile Crescent.
Thanks for reading.
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