Humanity: The Remix

Researchers first reported finding stem cells in human embryos in 1998, noting their chameleon-like ability to become any number of the body's specialized cells as they matured. Since then, stem cells have been touted as a source of possible regenerative treatments for spinal cord injuries and many diseases, including diabetes, Alzheimer's, and Parkinson's.

"Therapeutic" cloning is one among several ways to produce stem cells for research. In both therapeutic cloning and reproductive cloning -- the technique that could lead to cloned babies -- the nucleus of a human egg is removed and replaced with the genetic material from another cell. But instead of implanting the doctored egg in a womb and letting it grow, researchers harvest the newly formed stem cells that bud within it after just four or five days. In theory, therapeutic cloning could provide tissues and whole organs for transplant patients, in a sense turning them into their own donors: Stem cells derived from their genetic material could be coaxed to grow into spare parts their bodies wouldn't reject.

Any tampering with the human embryo is a problem for many abortion foes like Bush, but it's also an issue for those hoping to thwart a posthuman future. They particularly dread the idea of "germline genetic engineering" -- that is, giving humans new genetic traits they're able to pass on to future generations. To block that, they hope to stop the nascent technology today with a ban or a moratorium on therapeutic cloning. That means breaking ranks with the many liberals who support such research. It can also mean parting with those who worry about altering the human species but who see the campaign against abortion as a more immediate fear. Indeed, for some liberals, the stem cell debate has triggered a very real philosophical struggle -- with others, and with themselves.

"What we can all agree on, whether we're pro-life or pro-choice, is that embryos are potential unique human beings at the early stages of development," Rifkin says. "Nobody can say that's not true. To my mind, the idea that we would propose legislation in the U.S. Congress to clone embryos specifically for the purpose of experimentation, or as research models, or to harvest spare parts and then destroy them, opens the door to a commercial eugenics era."

In late 2001 a Massachusetts biotech company announced it had been the first to clone a human embryo. Around that time, Rifkin floated a petition, signed by Fukuyama and other conservatives as well as liberals, in support of a law that would ban all cloning. In 2002 McKibben and others signed a different petition that called for a ban on reproductive cloning and a moratorium on cloning for research purposes. Other unlikely alliances emerged. In Chicago, for instance, progressive tech skeptic Lori Andrews and conservative tech skeptic Nigel Cameron founded the Institute on Biotechnology and the Human Future. Together they hoped to forge new ties between the anti-biotech left, the Christian right, and secular conservatives.