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Science File

Ancient Wanderlust Key to Cat Family Tree

January 07, 2006|Thomas H. Maugh II | Times Staff Writer

Cats are notorious for roaming far from home, and it turns out that trait played a very important role in their evolutionary past, spreading new lineages around the world as the cats roamed from continent to continent with apparent ease, researchers said Friday.

The 37 modern species of cats evolved from a single ancestor in Asia 10.8 million years ago and spread by crossing land bridges connecting the continents -- often several times in each direction, according to the first comparison of DNA from each of the species.

Biologists have previously had a difficult time establishing a family tree of cats from the fossil record because the fossils of different cat species all look very much alike, differing primarily in size.

Geneticists Warren Johnson and Stephen O'Brien of the National Cancer Institute in Frederick, Md., compared both mitochondrial and nuclear DNA from all 37 species, and were able to show not only how all the "great roaring cats" are related, but also how the domestic tabby fits into the picture.

They reported in the current issue of the journal Science that ancient cats ultimately evolved into eight main lineages that diverged in the course of at least 10 migrations from continent to continent. Those migrations occurred across the Bering land bridge, which connected Asia and North America throughout much of the past, and over the Panamanian land bridge between North and South America.

The Panthera lineage, which includes the lion, jaguar, cloud leopard and tiger, emerged first. It was followed rapidly by a group of three Asian species, three African species, and the lineage that led to the New World ocelot.

The youngest of the eight lineages, which led directly to the domestic cat, branched off 6.5 million years ago from a line that had migrated to North America and back to Asia.

The team estimated that 60% of modern species arose in the last million years.

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