Cloning, Continued

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Despite grandiose claims, human cloning didn’t materialize in 2003. In January legitimate researchers dismissed claims by the Raelian religious cult that two women had given birth to clones. Skepticism also surrounds rogue scientist Panayiotis Zavos, who in April reported he’d created a cloned human embryo.

Though cloning is on the fast track — this year scientists succeeded with a menagerie including the mule, horse and rat — recent evidence suggests that cloning primates poses unusual challenges. A study published in April by reproductive biologists at the University of Pittsburgh revealed that the current cloning technique strips monkey eggs, and probably human ones, of two key survival proteins. Moreover, many experts believe cloning technology is prone to backfire — studies suggest clones are more likely to suffer from disabling genetic changes — and is thus unethical to perform on humans. Responding to the potential dangers, the U.N. debated a worldwide ban on human cloning (the body ultimately voted to put off the decision for two years).

But for those who consider cloning a medical tool, not a way to make new creatures, the year was fruitful. In an advance that paves the way for transplanting pig organs into human patients in need of new livers, hearts and kidneys, cloning technology enabled scientists to engineer miniature pigs that lack both copies of a gene that causes the human immune system to attack.

THE TOP SCIENCE STORIES OF 2003

• Strike 2, NASA. What Now?
• Discovered! Fame Descended on These Newcomers in 2003
• SARS: A Rehearsal?
• Dark Energy: Cosmic Mojo
• Winners + Losers: Ups + Downs of 2003
• Iraq, Science and the Elusive WMD
• They Die by the Score
• Europe Roasts. Is It Global Warming?
• Obituaries
• Cloning, Continued
• Murder of the Bounty: The Seas Empty
• The New Space Race