SPECIES OF THE MONTH: JUNE 2013

                                                  

A horse has just taken us further back in time than ever before. The genome of a 700,000-year-old fossil has been sequenced, suggesting we could do the same with other long-extinct creatures – including early hominins like Homo erectus.

Small DNA fragments have survived up to 500,000 years, but until now, the oldest complete genome had come from 110,000-year-old polar bear remains. Pushing that back to 700,000 years is a big jump, says Eske Willerslev of the University of Copenhagen, Denmark.

Willerslev's collaborator Ludovic Orlando, also at the University of Copenhagen, scoured a horse bone found in the permafrost of north-west Canada in 2003 for pockets of collagen. The protein degrades easily, so its presence is a sign that DNA could have survived alongside it.

The team compared the ancient horse DNA to that of five domestic breeds, plus a donkey and the Przewalski's horse. They found that the last common Equus ancestor lived between 4 and 4.5 million years ago, before the last ice age, making the lineage about twice as old as we thought.

They thrived when the ice sheets advanced, but suffered when temperatures rose. The team is now sequencing a more recent species, which lived shortly before horses were domesticated, to figure out how that process changed its genes. The work is a boost for efforts to recover DNA from fossils. 

Link: http://www.nature.com