Some 86 percent wouldn't even want to clone a pet. But if such tests were available today, animal cloning wouldn't fail so often, say animal cloners. Despite headlines and photographs of Dolly the sheep and cloned cows, pigs, goats and mice, most animal clones still die, usually during embryonic development. Others are stillborn with monstrous abnormalities. Bloated mothers have laborious miscarriages, and occasionally die themselves.
Clones struggle for air in intensive care, only to have to be euthanized.
Even initial survivors remain fragile. Monday, California scientists reported that two recently cloned cows died, presumably because immune-system defects left them unable to fight infection. Nor have scientists yet cloned primates, humans' closest relative. For the first 100 attempts, expect about five live births. Some cloned animals were born twice as large as they should be.