But this focus on biological interventions may be wrongheaded. After all, some argue, we don't fly because we sprouted wings, so neither will we live longer because we've fiddled with our genomes. Why not make machines that hunt down harmful disease organisms and repair damaged cells? That is the ambitious aim of nanomedicine.

Proponents of medical nanotechnology -- such as Ralph Merkle, a former research scientist at Xerox's Palo Alto Research Center and now a fellow at the Texas nanotech company Zyvex -- outline an ambitious vision. "Nanotechnology will let us build fleets of computer-controlled molecular tools much smaller than a human cell and with the accuracy and precision of drug molecules," Merkle declared in the Winter 1999 issue of the Anti-Aging Medical News. He added, "These machines could remove obstructions in the circulatory system, kill cancer cells or take over the function of subcellular organelles." Robert Freitas, author of the 1999 book Nanomedicine, foresees a day when oxygen-carrying red blood cells could be supplemented by artificial respirocytes made of carbon that would be 200 times more efficient.

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