Biology: genetic search for an equine Eve fails.

A new analysis of horses' genes suggests a different history from that of other domesticated animals.

Dogs, goats, sheep, and cattle each fall into several relatively tidy lineages, explains Carles Vila of Uppsala University in Sweden. Such simple family trees reflect a history of only a few, independent efforts at taming and breeding.

When the researchers checked horse DNA, however, they found unexpected diversity. This probably bespeaks many domestication successes, the researchers say in the Jan. 19 SCIENCE.

For 191 horses in 10 breeds, Vila and his colleagues studied mitochondrial DNA, which mutates relatively quickly and descends through mothers. Archaeological evidence shows that horse domestication began 6,000 years ago. If there had been one maternal progenitor of modern horses--an equine Eve--or just a few co-Eves, then the modern DNA should show less diversity than it actually does, the researchers say.

The genetic historians also compared modern horse DNA with DNA from archaeological remains, such as animals frozen for 12,000 years in Alaska. With old and new genetic data, the researchers traced a horse family tree. Breeds of modern horses turned up on many branches instead of forming one lineage.

So much for finding an equine Eve.

--S.M