Where Is My Woolly Mammoth?
|CREDIT: Stephan Shuster Lab, Penn State|
Compared with the idea of cloning a Tyrannosaurus rex, bringing back a gentler giant like the woolly mammoth sounds like a much safer bet. Cloning a prehistoric cousin of Asian elephants is the goal of a team of researchers at Kyoto University, who hope to produce a woolly mammoth within five years.
Bringing extinct animals back to life is a common theme in science fiction, most notably in the popular "Jurassic Park" books. Now, with advances in DNA sequencing and cloning in the past five years, some scientists feel they are on the verge of actually resuscitating animals that have not walked the earth for thousands of years.
Even with the technological advantages, however, there are serious hurdles to successfully cloning any extinct animal, including the woolly mammoth, which disappeared about 10,000 years ago.
If it was purely the situation that it was only genes that mattered, that would be one thing, but unfortunately all of these complicated parts are important, said Thomas Gilbert, a professor at the University of Copenhagen who has worked on the DNA sequence of mammoths and other elephantids. Just getting the DNA isn't quite enough.
To even get the DNA, researchers use high-throughput sequencing, which has allowed for much faster genome sequencing than in the past. However, getting the chunks of genes that make up chromosomes is not the same as having the full picture, said Gilbert. He said that the sequence is the equivalent of shredding a book into phrases, then trying to reassemble them into the right order. For a mammoth, that means looking toward living relatives for clues on how the pieces go together.
Japanese scientists are planning to take intact nuclei from muscle and skin cells from a well preserved woolly mammoth that was found frozen in Siberia. They will then implant the nuclei into an egg of an African elephant. (The Asian elephant is a closer genetic relative but is extremely endangered.)
The use of frozen cells for cloning is a relatively recent development. In 2008, Teruhiko Wakayama produced a clone from a mouse that had been frozen for 16 years. But 16-year-old mouse cells from a freezer are different from cells that have been sitting in minus-80-degree Fahrenheit temperatures (-62 Celsius) for a few thousand years, said Gilbert.
Once the egg is inserted into a living elephant, no one knows just how different the chemical cues inside the womb will be, compared with inside a mammoth's womb. It would be like trying to put a human embryo into a chimpanzee, said Gilbert, who noted that elephants and mammoths split genetically about 5 million years ago, the same as chimps and humans.
He suggested it might be worthwhile to try to clone a mouse using a rat to test the hypothesis, since the mouse and rat diverged about 12 million years ago. Until we actually understand the environment the egg has to develop in, we're going to have a lot of trouble, Gilbert told InnovationNewsDaily.
For other species, researchers are trying to bring them back the old-fashioned way, by breeding. The quagga, which went extinct in the late 19th century, looks like a cross between a horse and zebra. Researchers in South Africa are using the plains zebra, of which the quagga was a subspecies, to try to recover the genetic traits that produced the quagga. It's a cheaper way to get to a result if the desire is to reproduce an animal that is almost but not completely like its predecessor.
Given that cloning an extinct animal means having it gestate in another species, there is a good chance that the product of the Kyoto experiment will not be identical to a mammoth. Scientists might end up with just a hairy elephant. Since many elephant species around the world are endangered, some critics say the research money might be better spent maintaining habitat for what is still roaming the earth.
However, Gilbert was careful to note that technological breakthroughs can open new doors for species both living and extinct.
What sounds really damn difficult today, who knows what will come next week or next year? he said. We should never forget how fast technology is moving.