Scientists have for the first time created a healthy clone of an endangered species, offering powerful evidence that cloning technology can play a role in preserving and even reconstituting threatened and endangered species.
The clone -- a cattlelike creature known as a Javan banteng, native to Asian jungles -- was grown from a single skin cell taken from a captive banteng before it died in 1980. The cell was one of several that had remained frozen in a vial at the San Diego Zoo until last year, when they were thawed as part of an experimental effort to make cloned banteng embryos.
Scientists transferred dozens of such embryos to the wombs of standard beef cows in Iowa last fall, and the first baby banteng clone was born April 1 after gestating for a standard 91/2 months.
"It let out this big bellow and everybody cheered," said Robert Lanza, a scientist with Advanced Cell Technology, a Worcester, Mass., company that collaborated in the project with the Zoological Society of San Diego and a high-tech cattle reproduction company in Iowa.
"It was so surreal," Lanza said. "There we are, out at this farm in the middle of Iowa, and this beef cow is giving birth to this exotic animal that normally lives in the bamboo forests of Asia."
A second cloned banteng was born two days later to another cow on the same research farm, but was in poor health yesterday and its prospects remained uncertain -- a reminder that scientists still have a lot to learn before mammalian cloning becomes routine.
The only other member of an endangered species ever cloned -- a cattlelike Asian gaur, born in January 2001 -- died of an infection less than two days after birth. By contrast, the first-born banteng "is doing beautifully," Lanza said. "It's a beautiful, adorable creature."
Bantengs, which as adults sport enormous horns and can weigh as much as 1,800 pounds, once roamed in large numbers through the bamboo forests of Indonesia, Malaysia, Burma and other Asian nations. Hunting and habitat destruction have reduced their numbers by more than 80 percent in the past 20 years. Today they have vanished from much of their old range, and only 3,000 to 5,000 remain worldwide.
Most worrisome to conservationists, only a handful of large herds remain, so the animals are at risk of becoming dangerously inbred. That's where the cloners hope to help.
The stored cells were from a male banteng that died at the San Diego Wild Animal Park before it had a chance to mate, depriving the small captive population there of the genetic diversity it could have added.
Lanza and his colleagues combined some of the banteng's preserved skin cells with ordinary cow eggs whose own DNA had been removed, a standard method for making cloned embryos. When the embryos were six days old, the team shipped them by overnight mail to Trans Ova Genetics in Sioux Center, Iowa -- a company that makes genetically engineered cows that produce drugs and other biomedical products in their milk.
Scientists there transferred 45 of the banteng embryos to 30 cows. Two pregnancies made it to term, and the two bantengs were delivered by Caesarean section.
The goal is to ship them to the wild animal park, allow them to mature for six years, then mate them with captive banteng cows.
"This will bring in portions of the banteng lineage that aren't otherwise available for breeding," said Oliver Ryder, chief geneticist at the Center for Reproduction of Endangered Species at the Zoological Society of San Diego, which operates the zoo and wild animal park.
Ryder emphasized that cloning is just one of several "tools" available to conservationists -- none of which is as important, he said, as preserving natural habitat.
"The best way to save species is to save them in their habitat," Ryder said. "This is not to find a shortcut or dispose of the pressing need to save species in their own ecosystems. But it could be used to prolong the persistence of small populations and enhance their ability to be healthy, and ultimately contribute to reintroduction efforts."