Ancient DNA has been recovered from some sources. The record for survival of DNA suitable for sequence analysis is 700,000 years. A horse skeleton buried in permafrost has provided bones with some DNA surviving. The sequence was only 70% complete, but it was enough for researchers to say "It would not look like a horse as we know it... but we would expect it to be a one-toed horse". For comparison, researchers had access to DNA sequences of modern horses, donkeys and Przewalski's horse.