A group of scientists at Kyoto University are currently working on resurrecting the woolly mammoth.
The method is simple in principle; they will use tissue from a frozen mammoth carcass found in Siberia. Nuclei will be removed from cells in the tissue, and those nuclei will be inserted into the egg cells of an elephant which have had their own nuclei removed. The engineered egg cells will be inserted into the uterus of a female elephant, and if all goes well, the elephant will give birth to a baby mammoth.
Of course, in practice, it's quite a bit more difficult than that. Differentiated tissue (i.e. just about all the tissues in an adult organism) has undergone genetic changes that have to be undone, returning the cells to totipotence -- the state of then being able to re-differentiate into all the kinds of tissue the animal produces. Put simply, if this isn't done, skin cells can only produce more skin cells, muscle cells more muscle cells, and so on. The trick is to return the cell to the capacity it had very early in development.
It's been done before, not that it's easy; consider Dolly the Sheep, the first animal born that was the result of adult-tissue cloning. Some animals have proven very difficult to clone -- to my knowledge, monkeys have never been cloned from adult tissue, although my source for that particular piece of information is two years old, and in this field things change nearly on a daily basis. And the idea of using cloning to produce animals that are endangered (or extinct) has already been done; a gaur, an endangered species of water buffalo, was produced that way in 2001, but the baby only lived two days.
And this brings us to the risks.
First, there's the risk of it being a big waste of money, and I hope my readers know me well enough by now that I'm not saying this from any sort of anti-science stance. The gaur that only lived two days died of dysentery, but some scientists believe that it was felled by the cloning process itself. Recall that Dolly the Sheep lived only half the lifespan of a normal sheep. Cells seem to retain a "memory" of the age of the animal they were taken from, and so if someone cloned me (heaven forfend), the baby thus produced would be normal in all respects except for two -- first, it would look like me, which is unfortunate but not fatal; and second, its cells would very likely retain the genetic memory of having been taken from a fifty-year-old, and therefore the cloned Gordon would probably die of old age by age thirty or so. So one has to wonder if a mammoth born from this process would live long enough to make it worth it.
Second, of course, there are the vaguer fears of resurrecting extinct animals, which of course have only been made worse by Jurassic Park. Many folks seem to be reacting to the mammoth-cloning project by saying, "Don't you people ever watch science fiction movies? Inevitably, the scientists plunge right on ahead with their experiments, ignoring the people who are worried about the risks, and then next thing you know there are herds of giant, malevolent mammoths destroying Tokyo."
Well, maybe. I think the former problem -- that it will be unsuccessful, and therefore something of a waste of time, effort, and money -- is far more likely. Nevertheless, I think it should proceed. There's just the coolness factor of getting to see, finally, what an animal looks like that went extinct long ago. Myself, I'd love to see them bring back a few others -- how about the dodo? Or the moa? (For those of you who don't know what a moa is, picture a badass ostrich on steroids, and you have the idea.) The Tasmanian wolf would also be near the top of my list, as would the saber-toothed tiger, although I suspect that last one went extinct long enough ago that it might be impossible to find intact cell nuclei. All animals with high awesomeness factor, however.
I recognize the fact that even if the cloning project is successful, it is a long way from producing a single individual that way to producing a large enough number of them to generate a self-sustaining population, that is capable of reproducing faster than their death rate -- what ecologists call the "minimum viable population." The question comes up, of course, of where we would put a herd of mammoths once we got one -- heaven knows I don't want them around here, we have enough trouble with deer eating our gardens. But that's a question to be resolved later.
In any case, we'll keep our eye on the team at Kyoto University, which is predicting success within five years. Whatever happens, they are sure to learn a great deal about the cloning process from this study. All Jurassic Park-style fears aside, it's a pretty amazing thing to attempt, and I wish them success in this mammoth undertaking.