Study Traces Cat’s Ancestry to Middle East

Some 10,000 years ago, somewhere in the Near East, an audacious wildcat crept into one of the crude villages of early human settlers, the first to domesticate wheat and barley. There she felt safe from her many predators in the region, such as hyenas and larger cats.

The rodents that infested the settlers’ homes and granaries were sufficient prey. Seeing that she was earning her keep, the settlers tolerated her, and their children greeted her kittens with delight.

At least five females of the wildcat subspecies known as Felis silvestris lybica accomplished this delicate transition from forest to village. And from these five matriarchs all the world’s 600 million house cats are descended.

A scientific basis for this scenario has been established by Carlos A. Driscoll of the National Cancer Institute and his colleagues. He spent more than six years collecting species of wildcat in places as far apart as Scotland, Israel, Namibia and Mongolia. He then analyzed the DNA of the wildcats and of many house cats and fancy cats.

Five subspecies of wildcat are distributed across the Old World. They are known as the European wildcat, the Near Eastern wildcat, the Southern African wildcat, the Central Asian wildcat and the Chinese desert cat. Their patterns of DNA fall into five clusters. The DNA of all house cats and fancy cats falls within the Near Eastern wildcat cluster, making clear that this subspecies is their ancestor, Dr. Driscoll and his colleagues said in a report published Thursday on the Web site of the journal Science.

The wildcat DNA closest to that of house cats came from 15 individuals collected in the deserts of Israel, the United Arab Emirates, Bahrain and Saudi Arabia, the researchers say. The house cats in the study fell into five lineages, based on analysis of their mitochondrial DNA, a type that is passed down through the female line. Since the oldest archaeological site with a cat burial is about 9,500 years old, the geneticists suggest that the founders of the five lineages lived around this time and were the first cats to be domesticated.

Wheat, rye and barley had been domesticated in the Near East by 10,000 years ago, so it seems likely that the granaries of early Neolithic villages harbored mice and rats, and that the settlers welcomed the cats’ help in controlling them.

Unlike other domestic animals, which were tamed by people, cats probably domesticated themselves, which could account for the haughty independence of their descendants. “The cats were adapting themselves to a new environment, so the push for domestication came from the cat side, not the human side,” Dr. Driscoll said.

Cats are “indicators of human cultural adolescence,” he remarked, since they entered human experience as people were making the difficult transition from hunting and gathering, their way of life for millions of years, to settled communities.

Until recently the cat was commonly believed to have been domesticated in ancient Egypt, where it was a cult animal. But three years ago a group of French archaeologists led by Jean-Denis Vigne discovered the remains of an 8-month-old cat buried with its human owner at a Neolithic site in Cyprus. The Mediterranean island was settled by farmers from Turkey who brought their domesticated animals with them, presumably including cats, because there is no evidence of native wildcats in Cyprus.

The date of the burial far precedes Egyptian civilization. Together with the new genetic evidence, it places the domestication of the cat in a different context, the beginnings of agriculture in the Near East, and probably in the villages of the Fertile Crescent, the belt of land that stretches up through the countries of the eastern Mediterranean and down through what is now Iraq.

Dr. Stephen O’Brien, an expert on the genetics of the cat family and a co-author of the Science report, described the domestication of the cat as “the beginning of one of the major experiments in biological history” because the number of house cats in the world now exceeds half a billion while most of the 36 other species of cat, and many wildcats, are now threatened with extinction.

So a valuable outcome of the new study is the discovery of genetic markers in the DNA that distinguish native wildcats from the house cats and feral domestic cats with which they often interbreed. In Britain and other countries, true wildcats may be highly protected by law.

Female Shark Reproduced Without Male DNA

A hammerhead shark that gave birth in a Nebraska aquarium reproduced without mating, a genetic analysis shows.

This form of asexual reproduction, called parthenogenesis, has been found in other vertebrate species, including some snakes and lizards. But this is the first time it has been documented in a shark.

Researchers from the Guy Harvey Research Institute at Nova Southeastern University in Florida and Queen’s University Belfast in Northern Ireland found no male DNA in the female baby shark, which was born in December 2001 and died shortly after birth, apparently killed by another fish. The mother was one of three female bonnetheads, a small hammerhead species, that had been captured in Florida and kept without male sharks for three years in the Henry Doorly Zoo in Omaha.

At the time of the birth, many scientists thought that the female had mated with another species, or that it had used sperm obtained years before. Female sharks are capable of storing sperm, although none have been known to store it as long as these sharks had been isolated.

But through the analysis “it was pretty clear that there was no male contribution,” said Mahmood S. Shivji, director of the Guy Harvey Research Institute and author of a paper on the finding being published online today by the journal Biology Letters.

Instead, the female shark’s own genetic material combined during the process of cell division that produces an egg. A cell called the secondary oocyte, which contains half the female chromosomes and normally becomes the egg, fused with another cell called the secondary polar body, which contains the identical genetic material.

Robert E. Hueter, director of the Center for Shark Research at the Mote Marine Laboratory in Sarasota, Fla., said the finding helped fill a gap in understanding of parthenogenesis, which has been found to occur in most vertebrate lines except mammals and, until now, cartilaginous fishes like sharks.

Dr. Shivji said that after the bonnethead birth was reported, keepers at the Belle Isle Aquarium in Detroit reported similar virgin births by white spotted bamboo sharks. While those births have not been proved to result from parthenogenesis, Dr. Shivji said, it is reasonable to assume they did. And if it is found in these two species, “it seems not unreasonable to think this is probably more widespread in different shark lineages,” he said.

Gordon W. Schuett, an adjunct professor at Georgia State University who discovered parthenogenesis in a snake in 1997, said it would probably be discovered in more species “because we know to look for it.”

Previously, Dr. Schuett said, zookeepers and others tended to discount evidence of virgin births precisely because they were so out of the ordinary. But in recent years it has been found in Komodo dragons, other lizards and snake species.