The news that researchers have used cloning to make human embryos for the purpose of producing stem cells may have some people wondering if it would ever be possible to clone a person.
Although it would be unethical, experts say it is likely biologically possible to clone a human being. But even putting ethics aside, the sheer amount of resources needed to do it is a significant barrier.
Since the 1950s when researchers cloned a frog, scientists have cloned dozens of animal species, including mice, cats, sheep, pigs and cows.
In each case, researchers encountered problems that needed to be overcome with trial and error, said Dr. Robert Lanza, chief scientific officer at the biotech company Advanced Cell Technology, which works on cell therapies for human diseases, and has cloned animals.
With mice, researchers were able to use thousands of eggs, and conduct many experiments, to work out these problems, Lanza said. "It's a numbers game," he said.
But with primates, eggs are a very precious resource, and it is not easy to acquire them to conduct experiments, Lanza said.