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THE famous Przewalski’s horse, a conservation icon, is less closely related to domestic horses than we thought. The finding suggests that the two lineages split long before humans domesticated horses.

Przewalski’s horse, or takhi, went extinct in its native Mongolia in the late 1960s. Around 150 animals existed in captivity and an intensive breeding programme was mounted to increase their numbers for re-release. The first 16 animals were returned to the wild in 1994 and the herd now numbers over 100.

The charismatic breed’s stick-up punk mane makes it easy to distinguish from domestic horses, but whether it is really a separate species is controversial. The wild horse’s two extra chromosomes suggest that it is, but the two animals have virtually identical mitochondrial DNA, implying they are simply different breeds.

Now Mathias Müller and colleagues at the University of Veterinary Medicine in Vienna, Austria, have compared mutations in Y chromosome sequences of domestic and Przewalski’s horse with seven species of wild equid. They estimate that the two populations diverged between 120,000 and 240,000 years ago (Animal Genetics, vol 34, p 453).

So the takhi can’t be the domestic horse’s ancestor, since domestication happened around 6000 years ago.