Endangered-species clone inspires hope, concern
Birth of rare banteng calves from a cloned cell is a landmark, but its future role in conservation is uncertain.
A small calf stands in a cattle stall on a farm outside Sioux Center, Iowa, and peers outward with the doe-eyed charm that would make it a natural poster pet for a local 4-H Club.
This calf, however, is unique. Native to the island of Java, the week-old banteng calf is the longest-surviving clone of an endangered animal. It represents the most successful attempt yet for efforts to see whether cloning - a deeply controversial technology for human-related research - can become a feasible tool to help save endangered species.
Yet it also is a field of research where success is still measured in days. The calf is one of two cloned banteng born last week. The second, born at twice a banteng's typical birth weight of 40 pounds, was euthanized on Tuesday. Two years ago, researchers cloned an endangered wild ox they named Noah, only to lose the calf two days later to an unrelated illness.
Still, the fact that the two banteng arrived at all is a landmark, researchers say.
"I was absolutely astounded when I saw the picture of the living animal that came from one of these cells that came out of our freezers," says Oliver Ryder, a geneticist at the San Diego Zoo's Center for Reproduction of Endangered Species, which supplied the genetic material to clone the calves.
For years, Dr. Ryder and a group of colleagues have argued that researchers should begin building DNA "banks" where tissue and other sources of genetic and reproductive material from endangered species would be archived. San Diego Zoo began to store samples in its "frozen zoo" in 1976 and now has collections of viable cells from more than 3,200 mammals representing 355 species and subspecies - all preserved at liquid-nitrogen temperatures.
The zoo shipped banteng cells preserved since 1980 to Advanced Cell Technology, a Worcester, Mass., biotech firm. There, technicians took DNA from the samples and transferred it to domestic cow eggs that had been stripped of their DNA. ACT fertilized the modified eggs and shipped the resulting embryos to another biotech company in Sioux Center, Iowa, where they were implanted in 30 cows. Sixteen cows became pregnant; two came to term.
The procedure's inefficiency and the loss of the second banteng calf clearly indicate that conservation cloning is not ready for prime time, researchers acknowledge, noting that the banteng experiment was designed to help assess the technique's feasibility.
Others acknowledge that such cloning experiments may be of scientific value. But the notion of cloning, at least on its face, sidesteps the real issues behind declining species.
"People have been fantasizing about cloning for quite a while," says Karen Baragona, deputy director of the World Wildlife Fund's species conservation program in Washington, D.C. "But it doesn't get at the root causes" of species loss, such as loss or fragmentation of habitat, disease, poaching, or competition with humans for food.
As if to underscore her point, a research team led by Princeton University ecologist Peter Walsh reported in the journal Nature's online service Sunday that during the past 20 years, the number of gorillas and chimpanzees in Gabon has plunged by more than half. Gabon and its neighbor, the Republic of Congo, are believed to host 80 percent of the world's gorillas and most of its chimps. The team attributed the drop to hunting, logging, and disease.
"Without aggressive investments in law enforcement, protected-area management, and Ebola prevention, the next decade will see our closest relatives pushed to the brink of extinction," they conclude.
Cloning as a conservation tool also raises broader questions, she continues.
"We can't save genetic material from every species, so who decides which to clone?" Clones likely would end up in zoos, she says, while the objective for species conservation should be to ensure viable populations in the wild.
Others, such as Washington University geneticist Alan Templeton, foresee a limited role for conservation cloning - if the biological hurdles to the approach can be overcome. "The main rationale I can see is stopping the erosion of genetic diversity," he says. "In that sense, it could play a positive role."
But, he adds, there are less-expensive and less-extreme ways to reach that goal.
Indeed, the issue of genetic diversity is a key driver behind Dr. Ryder's efforts to encourage biologists to establish a network of DNA repositories. The material would yield immediate benefits to ecologists and conservation biologists using powerful genetic tools by providing insights into the range of habitats a species can inhabit or their evolutionary relationships to species, he says.
In the long run, the archives would provide a rich source of genetic material for cloning, should it ultimately find a place in the conservation biology's toolkit.