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Reintroducing the Lost

Once extinct, always extinct? Maybe not, if cellular DNA can be recovered and embryos transferred to surrogate moms. Joining in assisted resurrection with biotechnicians is uncomfortable for some restorationists.

To Clone a Mammoth

Jarkov, a wooly mammoth, roamed Siberia 23,000 years ago. He's been frozen (or alternately frozen and thawed) ever since. His body, in a cube of frozen ice, has been moved 200 miles from where he was found to an underground tunnel/laboratory. There his DNA will be extracted and placed in an Asian elephant's egg that has been stripped of its DNA. Researchers hope that the Asian elephant will give birth to a complete mammoth. Skeptics say this is a hard task. Adult males are poor sources of DNA even if taken from fresh cells. Male DNA from cells that might have frozen and thawed for 20,000 years may be too damaged.

Resurrect the Quagga

The last living quagga died in an Amsterdam zoo in 1883. The quagga was shaped like the Cape mountain or Hartmann's zebra of South Africa, but its body was chestnut brown and its legs were white. Only its head and neck were striped.

A taxidermist at the South African Museum was remounting its quagga (one of twenty-three stuffed specimens on the planet), and found that the original sloppy job had left behind dried connective tissue, muscle, and blood vessels. Mitochondrial DNA from the quagga turned out to be identical to mitochondrial DNA from the plains zebra. The South African museum staff feels confident that they can "resurrect" the quagga by back-crossing plains zebra specimens most resembling it. In 1987 they captured nine zebras whose flanks, bellies, and legs had very few stripes and crossbred them. The process is long as zebra males start reproducing at five and females at about three years. But, as with the Xerces butterfly (see page 68), the process may yield an extinct species.

The Guar, the Buccardo, and Surrogate Mothers

Advanced Cell Technology (ACT), a biotech firm in Massachusetts, cloned a threatened guar, a cow-like bovine from Asia. It inserted the skin cells of a recently deceased guar into the denucleated egg cells of a dairy cow. A few days later, the cow eggs became "guar" embryos, and were implanted into receptive mom dairy cows. It sounds easy, but the failure rate is high. ACT started with 692 cow eggs with inserted guar cells. Only eighty-one matured to a size that could be implanted into a cow womb. ACT ended up inserting forty-two "ripe" embryos into thirty-two cows, only eight of which became pregnant. Of these, five spontaneously aborted; two fetuses were removed for study. "Bessie" gave birth to "Noah," a baby guar. The embryo-transfer and surrogate mother technique is the same one used for humans with reproductive problems.

ACT will now try their luck with a buccardo, a mountain goat from Spain that became extinct when a tree fell on "Celia," the last known of her kind. Celia's tissue was frozen. If viable DNA can be extracted and put in the eggs of related mountain goats, the buccardo could be reborn as a species. ACT also hopes to create a male from Celia's chromosomes by removing the X chromosome and adding a Y chromosome from a closely related goat. This technology has already been successful with humans. ACT has successfully accomplished interspecies embryo transfers for a rare Indian desert cat into a domestic cat; a bongo antelope into the more common eland; a mouflon sheep into a domestic sheep; and the rare red deer into the common white-tailed.

The Thylacine (Tasmanian Tiger)

This Australian wolf-like marsupial died out in the 1930s. A researcher at the Australian Museum (Sydney) found a pup preserved in alcohol from 1866. That was fortunate, as other preservatives distort DNA beyond repair. Even with the alcohol-pup, scientists will have to reconstruct all the thylacine's chromosomes by stringing together uncorrupted DNA segments taken from the pup.