Towards a million-year-old genome

Abstract

The sequencing of a complete horse genome from a bone dating to around 700,000 years ago sheds light on equine evolution and dramatically extends the known limit of DNA survival. See Letter p.74 A low-coverage draft genome sequence has been obtained from a horse bone recovered from a permafrost site in the Yukon Territory, Canada, dated to around 560,000–780,000 years before present. This is by far the earliest genome sequence so far determined. The data were compared to draft genome sequences for a Late Pleistocene horse, those of five contemporary domestic horse breeds, a Przewalski's horse and a donkey. Comparative genomics suggest that the Equus lineage that gave rise to all contemporary horses, zebras and donkeys originated about 4.0–4.5 million years ago — much earlier than previously suspected. The data support the contention that Przewalski's horses — an endangered subspecies native to the Mongolian steppes — represent the last surviving wild horse population.