Frozen caribou feces collected from the Selwyn mountains of Canada's Yukon and Northern Territories contained only fragments of its depositor's DNA. But the ice-cold poo did contain a 700-year-old virus -- a virus scientists were recently able to bring back to life.

"The DNA of viruses is preserved extremely well under cold conditions," Eric Delwart, a researcher at Blood Systems Research Institute in San Francisco, told NPR. Delwart led the team of researchers responsible for resurrecting the ancient virus.

Though only fragments of the caribou's DNA survived the many years of freezer burn, the virus's genetic material -- which likely lived in a plant before being eaten by the reindeer -- was much better protected, well-suited for a long stay inside a chunk of frozen dung.

"The find confirms that virus particles are very good 'time capsules' that preserve their core genomic material, making it likely that many prehistoric viruses are still infectious to plants, animals or humans," Jean-Michel Claverie, a researcher at Aix-Marseille University School of Medicine in France, told New Scientist. "This again calls for some caution before starting to drill and mine Arctic regions at industrial scales."

The oldest virus ever brought back to life dated back some 30,000 years; it was extracted from Siberian permafrost. Though 700 years may seem short in comparison, the caribou dung-sourced virus originates from a period of time rich in viruses that have since become eradicated. The newly resurrected virus is also a reminder of the reality of global warming -- a reality whereby long-frozen viruses may emerge from the thaw of a hotter climate.

"There's a theoretical risk of this, and we know that the nucleic acid of the virus was in great shape in our sample," Delwart told New Scientist. "But old viruses could only re-emerge if they have significant advantages over the countless perfect viruses we have at present."

The work of Delwart and his colleagues was published this week in the journal PNAS.