Tuesday, August 15, 2006

Bring back the mammoth
Stories about Japanese or Russian geneticists who think they might be able to bring back the woolly mammoth are becoming something of a staple of science journalism. Every couple of months we get a new story about it. Basically, there are only two stories. The first, is the scientist who hopes to recover intact mammoth DNA from a frozen mammoth to use in cloning experiments. So far no one has recovered any intact mammoth DNA. The second story is about a scientist who wants to recover sperm cells (with intact DNA) from a frozen mammoth to use in artificial insemination or in vitro fertilization. Both approaches then use an Indian elephant as a surrogate mother to carry the mammoth fetus to term. Today's story is one of the latter type.
Descendants of extinct mammals like the giant woolly mammoth might one day walk the Earth again.

It isn't exactly Jurassic Park, but Japanese researchers are looking at the possibility of using sperm from frozen animals to inseminate living relatives.

So far they've succeeded with mice--some frozen as long as 15 years--and lead researcher Dr. Atsuo Ogura says he would like to try experiments in larger animals.

"In this study, the rates of success with sperm from 15 year-frozen bodies were much higher than we expected. So the likelihood of mammoths revival would be higher than we expected before," Ogura said in an interview via e-mail.

There is a big difference between mouse testes stored fifteen years under laboratory conditions and mammoth testes left outside for fifteen thousand years.
Less enthusiastic was Dr. Peter Mazur, a biologist at the University of Tennessee who has worked with frozen eggs and sperm and is a past president of the Society for Cryobiology.


"The storage temperature of frozen mammoths is not nearly low enough to prevent the chemical degradation of their DNA over hundreds of thousands of years," he commented. And "even if the temperature were low enough to prevent chemical degradation, that would not prevent serious damage over those time periods from background radiation, which includes cosmic rays."

While Ogata and Mazur might be great biologists in their own fields, neither is much of a paleontologist. A spokesman for Ogata's team refers to frozen mammoths as millions of years old and Mazur refers to them as hundreds of thousands of years old. All of the frozen mammoths ever dated fall into an age range of fifty thousand to twelve thousand years old--an order of magnitude younger than Ogata and Mazur's references.

Both methods for bringing mammoths back face monstrous obstacles. While the cloning method is less discriminating in its source of DNA it depends on implanting ancient DNA from one species into another. Simple cloning with the best materials from the same species is still quite difficult. The mammoth plan adds additional levels of complexity with additional barriers to success. While artificial insemination and in vitro fertilization are methods with a far higher rate of success than cloning, the odds of finding mammoth sperm cells with intact DNA are much smaller than those of finding any old cell with intact DNA.

Assuming they do find intact DNA and accomplish fertilization, both methods need to get an Indian elephant to carry the baby mammoth (or mammoth hybrid) to term--another difficult task. Finally, if we can overcome all of these obstacles, the baby mammoth is going to be an orphan like no orphan has been--the only member of its species. There will be no adult mammoth available to teach it how to be a mammoth; it will have to learn to be an elephant. In time some uniquely mammoth behaviors might emerge. If we produce a whole herd, they might get more mammothy over the course of a couple of generations. Since we don't have any mammoth to compare them to, we wouldn't know if this was authentic mammoth behavior or if our orphans were inventing new behavior in response to the new environment in which we have placed them.

So many questions. So many problems. As much as I'd like to see a mammoth stomping around on a healthy mammoth steppe, it might be better if I held out for time travel to show me one.

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