A layperson's explanation of the theorized role of mitochondria in driving aging can be found at h+ Magazine: "Aging is a complex process that, by nearly all educated accounts, appears to involve multiple different interacting processes. Aubrey de Grey has sought to break down the causes of aging into seven categories; others have presented different understandings. One perspective on aging broadly recognized as important, however, is the mitochondrial theory - tying aging to changes in the function of mitochondria, the energy powerhouses of the cell. This article reviews the mitochondrial theory of aging, with an aim of describing enough of the science to give the lay reader a real sense of what the theory is about. ... In the mid-1950s, Denham Harman proposed that aging results from accumulated damage inflicted by free radicals - atoms or molecules possessed of a sole unpaired electron in their outer shells. ... In 1972 Harman proposed the Mitochondrial Theory of Aging (MTA), which is considered an extension of the free radical hypothesis. According to this theory, aging is due to the cumulative effects of damage wrought by free radicals on the mitochondrial DNA and function. ... Taken together, data derived from several thousand studies largely supports the MTA. Mitochondrial fee radicals damage the mitochondrial DNA, causing mitochondrial dysfunction with lowered ATP production, cellular energy depletion and death, resulting in aging."