All over the web today is the story that scientists have cloned mice from animals that had been frozen for more than a decade. The work raises the possibility of cloning extinct species - such as woolly mammoths preserved in the permafrost. This picture shows one candidate - a perfectly preserved baby mammoth found last year, after it had lain frozen in Siberian permafrost for 10,000 years.
I'm a biologist by training and I'm fascinated by what genetic material can tell us about the past (hence the post on Ötzi the ice man last week). Researchers have already managed to resurrect extinct virus strains - most dramatically in 2005 they recreated the deadly 1918 flu virus from the cells of a flu victim preserved in Alaskan permafrost.
But to clone an animal you usually need living cells, whereas freezing kills cells because of the ice crystals that form. In this latest work, Teruhiko Wakayama and her colleagues from the RIKEN Center for Developmental Biology in Kobe, Japan, got round the fact that cells in the frozen mice had ruptured by extracting only the cell nuclei, which contain almost all of an animal's DNA, and using that for the cloning process.
The mice Wakayama used were frozen at -20 C (roughly the temperature of permafrost, or a kitchen freezer) for 16 years, without any protective chemicals. The fact that it worked means cloning other animals that have been frozen for longer periods might not be so far-fetched after all - DNA is pretty stable at low temperatures. Doing this for ancient species such as mammoths is still a stretch though because the DNA will degrade slowly over time, especially if the ground they're in has ever defrosted and refrozen.
Of course creating a clone would only be the start of biologists' problems - they'd need living relatives for the clone to breed with, and they'd have to find somewhere for it to live (tricky for mammoths, as all the permafrost is melting!) But I still think there's something magical about the possibility of seeing an ancient animal brought back to life, even if it's not such a great idea in practice.