Will mammoths walk the Earth again?
The woolly mammoth, the flightless dodo bird and the quagga, a type of zebra, are all extinct. But the modern techniques of genetic engineering have made it possible to study their genetic make-up - or even to think of giving them life again.vTo do so, scientists would have to obtain a sample of the genetic blueprint needed to re-create an entire creature. This blueprint is contained in the deoxyribonucleic acid (DNA) of the creature's cells. It can be obtained only from flesh that has somehow been preserved since the creature became extinct.
Since most extinct species survive only as fossils, they have left no traces of tissue preserved in its original condition. But some creatures, such as the mammoth, a hairy relative of the elephant, which became extinct about 12,000 years ago, have been frozen solid in the ground in Siberia, Alaska and northern Canada. When dug up, their flesh still contained traces of the DNA. The first step in reproducing a living specimen would be to extract the DNA and copy it. This has already been done for a number of extinct species, including the mammoth and the quagga. The object of the experiments was not to reconstruct the creatures, but to study the DNA and try to learn from it.Half zebra, half horse
For example, pieces of quagga skin kept at the Natural History Museum in Mainz, West Germany, provided DNA for cloning by two scientists in California, Dr Oliver Ryder of San Diego Zoo, and Dr Russell Huguchi of the University of California at Berkeley. The quagga, described by early travellers in the Cape Province of South Africa as 'half zebra, half horse', went into decline when settlers began to fence its territory and introduce their own grazing stock. Uncontrolled hunting killed the last ones in the wild, though the quagga lingered on in zoos until the last specimen died of natural causes in Amsterdam Zoo in 1893. The taxidermists who stuffed the Mainz specimen had left fragments of muscle and fat on the skin, from which parts of the quagga's DNA could be extracted and put into the DNA of a bacterium. By allowing this bacterium to grow, the extinct DNA could be copied.
The DNA showed that the quagga was indeed a subspecies of the zebra, and suggested that its characteristics may still be contained in modern wild populations of Plains zebra. This has inspired an attempt to bring back the quagga by selective breeding. Reinhold Rau of the South African Museum in Cape Town established a group of interested conservationists who went into the Etosha Game Reserve in South West Africa and captured eight zebra with reduced striping on their hindquarters - like the quagga. For the next ten years the scientists will breed the zebra selectively, to try to match the patterns found on the hides of preserved quagga. 'The bone structure of the two animals as far as is known from the skeletons is identical, to quite a minute detail,' says Quintus Hahndiek, a member of the team. 'Some of the zebra only have to lose a few stripes to resemble a quagga.'
DNA samples have also been studied from an Egyptian mummy preserved for more than 2400 years, and from an ancient Briton, whose body, dating from about 2000 years ago, was found well preserved in a Cheshire peat bog in 1984.
Mummy of a baby boy
The mummy - a baby boy less than one year old when he died - is part of the collection of the Egyptian Museum in Berlin, East Germany. A Swedish scientist, Svante Paabo, of the Wallenberg Laboratory, University of Uppsala, took a small sample from the lower part of the left leg and successfully cloned it in 1985. But the DNA fragment he extracted was only about one-twentieth of the total DNA a living person possesses. Reconstructing any creature from such a small sample would be impossible - it would be like trying to rebuild a motor car when you had no more than a diagram of the headlights. But it may make it possible to answer some questions about the ancient Egyptians. Whether, for example, they suffered from genetic diseases, or had any evidence of inbreeding.
Might it one day be possible to go further and reconstruct an entire animal? Suppose the complete genetic blueprint of a mammoth could be recovered from a specimen preserved in the permafrost, cloned, and then inserted into the embryo of an elephant. If the embryo was replaced in the elephant's womb, then the elephant would give birth to a mammoth. Again - at least in theory - the same might be done with quagga genes, or those of the dodo, or even the ancient Egyptians.
So far, it is only a theoretical possibility. Fragments of DNA recovered have provided an insufficient fraction of the complete blueprint, and reconstructing the remainder appears impossible. And this slight possibility does not exist for creatures that survive only as fossils - so the prospect of dinosaurs once ore walking the Earth appears likely to remain science fiction.