Tuesday, May 26, 2009

Evolution of the Modern House Cat

-Alyssa Martin

Why have cats become such a fixture in the human home when they have little to offer people in the way of survival? Most animals that have become domesticated served some purpose or another – sustenance, labor, clothing, etc. – and were pack-oriented and conducive to confinement. Recent studies on the evolution of the modern house cat have shed light on this curiosity, and have dispelled some of our misconceptions about the cat’s origins.

According to an article in the Scientific American, scholars originally believed that “the ancient Egyptians were the first to keep cats as pets, starting around 3,600 years ago.” Just as Darwin believed that the pigeons of England were descended from a common rock pigeon, scholars maintained that all domesticated cats descend from a common Felix silvestris or wildcat. Because the wildcat has emerged all across the Old World (from Scotland to Mongolia), oftentimes breeding freely with the domestic cat, scientists have had a difficult time uncovering the origins of the wildcat.

In 2000, a genetic team set out to solve this mystery by analyzing the DNA samples (mitochondrial and microsatellite) of “some 979 wildcats and domestic cats in southern Africa, Azerbaijan, Kazakhstan, Mongolia and the Middle East.” The origins of the house cat would depend upon where the closest regional resemblance between wildcat DNA and domestic cat DNA could be established.

The results showed five genetic groupings or lineages, including the four wildcat subspecies “F. silvestris silvestris in Europe, F.s. bieti in China, F.s. ornata in Central Asia and F.s. cafra in southern Africa.” The fifth wildcat subspecies, F.s. lybica in the Middle East, also included all domestic cat DNA’s sampled. Clearly, domestic cats originated in the Middle East. Scientists were able to roughly establish when domestication occurred by examining the archaeological record, which showed that the first evidence of a pet cat emerged in Cyprus around 9,5000 years ago. Scientists inferred that cats must have been taken to Cyprus by boat from the Levantine coast; this suggests that “people had a special, intentional relationship with cats nearly 10,000 years ago in the Middle East,” or when the first civilizations emerged in the Fertile Crescent.

Because of the limited utility of cats for humans, it is likely that cats gravitated toward humans rather than vice versa. Scientists now believe that the emergence of the house mouse, Mus musculus domesticus, coincided with the emergence of the house cat, which was eager to exploit this development – “in the lingo of evolutionary biology, natural selection favored those cats that were able to cohabitate with humans and thereby gain access to the trash and mice.” As cats began dispensing with rodents, people probably saw the merit in keeping them (apart from their obvious aesthetic appeal).

Ultimately, domestication likely took thousands of years, as “the lack of human influence on breeding and the probable intermixing of house cats and wildcats militated against rapid taming.” It was not until Egyptian paintings from around 3,600 years ago that scholars were able to confirm full and robust cat domestication. In fact, the Egyptians were known for cat worship, as the cat goddess Bastet became the official deity of Egypt. Although Egypt tried to block the export of cats, cats were eventually propagated on grain ships and throughout the Roman Empire. Interestingly, “because no native wildcats with which the [domestic] newcomers could interbreed lived in the Far East, the Oriental domestic cats soon began evolving along their own trajectory.” This occurrence fostered genetic drift, which in turn led to the appearance of the very distinct Korat, Siamese, and Burman.

Breeding for particular traits did not occur among cats until relatively recently in the British Isles. In 1871, the “first proper fancy cat breeds—breeds created by humans to achieve a particular appearance—were displayed at a cat show” in London. A closer look at the cat genome has begun to reveal the origin of certain traits like tabby patterning, coloring, hair length, etc. Despite the people-friendly evolution and domestication of the cat, the domestic cat still retains many features of the wild cat. However, a couple traits have evolved to fit the domestic cat’s new lifestyle: shorter legs, smaller brain, and, as Charles Darwin observed, a longer intestine adapted to digesting kitchen scraps.

1 comment:

chickenpox said...

Here is a lucky picture of an African wildcat (Felis silvestris) taken near Moremi NP in Botswana

It looks pretty much like a house cat.

I guess this is the original "Sylvester the cat".