A team has pieced together an almost complete genome for the woolly mammoth, which throws up the possibility of one day bringing the prehistoric animal back to life, writes Dick Ahlstrom
A DEFROSTED hairball has helped an international team of scientists to piece together an almost complete genome for that pre-historic behemoth, the woolly mammoth. This is the first near-complete DNA sequence assembled for an extinct animal, and raises the notion of bringing the animal back to life using the sequence to produce a clone.
Teams from the US, Germany and Russia participated in the work, which involved decoding the sequence based on DNA samples recovered from different mammoth species preserved in the permafrost.
They believe the sequence is about 80 per cent complete, and they were able to match up genes the animal shared with modern Asian cousins. Details of their work are published this morning in the journal Nature.
The mammoths weren't really as big as their name suggests, weighing in at about 5.5 tonnes and not much bigger than an Asian elephant.
One of the largest was four metres at the shoulder, but there were also dwarf versions of the mammoth and these may have survived in the Alaskan wilderness up to about 3,800 years ago.
Most, however, disappeared by about 10,000 years ago, having first arose about 150,000 years ago. Predation by humans, along with climate change, which led to a loss of ice and hence suitable habitat, served to bring an end to the mammoth lineage.
The team sequenced about four billion DNA base pairs or steps, although they estimate that the actual mammoth genome is only about 3.3 billion base pairs long, the remainder being contamination confounding the data from sources such as bacteria, fungi and other material.
"Previous studies on extinct organisms have generated only small amounts of data," stated Prof Stephen Schuster, Penn State's professor of biochemistry and molecular biology and one of the team leaders. "Our dataset is 100 times more extensive than any other published dataset for an extinct species, demonstrating that ancient DNA studies can be brought up to the same level as modern genome projects."
The challenge in studying ancient DNA is to be able to recover intact fragments, but this was made easier with the woolly mammoth because of the toughness of its hair.
The researchers extracted hairs from two mammoths found in Siberia, one 20,000 and the second 60,000 years old. The hair shaft encapsulates the DNA, keeping it intact and protecting it from degradation. It also protects the genetic material from contamination by other sources.
Researchers have long been interested in recovering DNA from mammoth carcasses, given they are not fossils but full animals that have been well-preserved in the permafrost. Modern techniques allow researchers to sequence the DNA very quickly once it has been extracted.
Nature also includes a "how-to" feature about how to clone your own woolly mammoth. The step-by-step guide discusses the technical challenges and the methods that might be used to achieve such a goal. It would involve creating a reconstructed sequence, a huge and uncertain challenge, and then fusing this genetic material with a harvested elephant egg and later reimplantation.
While such an ambition lies well beyond our current capacities, holding an accurate sequence means that, as the technology improves, it brings closer the day when we might once again see woolly mammoths grazing the permafrost.
"By deciphering this genome we could, in theory, generate data that one day may help other researchers to bring the woolly mammoth back to life by inserting the uniquely mammoth DNA sequences into the genome of the modern day elephant," said Prof Schuster.
This means that genetic information lost to science would once again become available in a living animal. It could give insights into why animals go extinct and could also support the "future-proofing" of threatened animals.
The Tasmanian devil could go extinct because of its susceptibility to a deadly form of face cancer. Having its DNA sequence now would at least provide some way back to the original animal should the worst happen.
Not resting on its laurels, the Penn State team is already making plans to reconstruct the DNA sequences of other extinct species.