A true maverick, Aubrey de Grey challenges the most basic assumption underlying the human condition -- that aging is inevitable. He argues instead that aging is a disease -- one that can be cured if it's approached as "an engineering problem." His plan calls for identifying all the components that cause human tissue to age, and designing remedies for each of them — forestalling disease and eventually pushing back death. He calls the approach Strategies for Engineered Negligible Senescence (SENS).

With his astonishingly long beard, wiry frame and penchant for bold and cutting proclamations, de Grey is a magnet for controversy. A computer scientist, self-taught biogerontologist and researcher, he has co-authored journal articles with some of the most respected scientists in the field.

But the scientific community doesn't know what to make of him. In July 2005, the MIT Technology Review challenged scientists to disprove de Grey's claims, offering a $20,000 prize (half the prize money was put up by de Grey's Methuselah Foundation) to any molecular biologist who could demonstrate that "SENS is so wrong that it is unworthy of learned debate." The challenge remains open; the judging panel includes TEDsters Craig Venter and Nathan Myhrvold. It seems that "SENS exists in a middle ground of yet-to-be-tested ideas that some people may find intriguing but which others are free to doubt," MIT's judges wrote. And while they "don't compel the assent of many knowledgeable scientists," they're also "not demonstrably wrong."