Palaeontologists are piecing together the complete genome species of long-dead species such as the woolly mammoth and the Neanderthals in an effort to bring them back to life, much like billionaire John Hammond resurrected the extinct dinosaurs in Steven Spielberg's Jurassic Park.
A team led by Stephan Schuster and Webb Miller at Pennsylvania State University, US, and Tom Gilbert at the University of Copenhagen, Denmark, is working on the genome of woolly mammoths preserved in the Siberian permafrost.
Scientists have already deciphered the complete gene sequences - or genomes - for many living species, including humans, dogs, and mice. However, they are divided over how they should do it in the case of long extinct species, and whether it's even feasible.
Max Planck researcher Svante Paabo, who together with colleagues, is aiming to assemble a Neanderthal genome from bones preserved in arid caves, in a paper appearing in this week's Proceedings of the National Academy of Sciences (PNAS) said only certain types of errors appeared in ancient DNA.
As such, its not that difficult to piece together much of the original genetic instructions.
However, he is unsure whether the animals can be resurrected completely.
'Resurrecting these animals is for the most part science fiction,' said Paabo.
'Retrieval of DNA from ancient specimens is relatively easy now,' said Alan Cooper, of the University of Adelaide in Australia.
'I think it's definitely feasible to assemble these genomes. But it's going to be extremely hard work,' National Geographic quoted Eske Willerslev of the University of Copenhagen in Denmark, as saying.
According to Cooper, the basic problem is that living animals package their DNA with proteins that help it wind up into chromosomes. This packaging is crucial to making the DNA work properly, and this is something absent in these fossils.
Willerslev however, believes it is possible to bring back an extinct species like a mammoth only if an extremely well-preserved cell is found.
'That's extremely unlikely to happen, because all parts of a cell break down over time, even in mammoths that have been encased in ice since they died. But, researchers working on cloning have contacted me wanting to get a hold of mammoth tissue so they could try to clone a mammoth,' he said.
According to Hendrick Poinar of McMaster University in Canada, 'it's theoretically possible' to recreate a woolly mammoth.
'I think it's going to be done at some point. Once you have the genome of a mammoth, you could compare it with the genome of its closest relative, the Asian elephant. Then you could genetically engineer the elephant DNA, point by point, so that it matches the mammoth DNA,' he said.
'Then, by inserting this modified DNA into an elephant's egg cell, and implanting it in an elephant's womb, you could create a modified elephant that's nearly identical to the original mammoth. Or it could become possible to make entire chromosomes from scratch. I wouldn't be surprised if, in ten years, you'd be able to synthesize chromosome-length DNA,' he said.
'Five years ago everybody was saying you'd never be able to sequence the genomes of extinct animals ... but here we are. We're not that far away now,' he added.