From The Scientist, a challenge to the details of the mitochondrial free radical theory of aging: "Point mutations in mitochondrial DNA do not cause signs of aging in mice ... The data, which contradict a prominent theory that mitochondrial mutations drive the aging process, show that mice with mitochondrial mutations 500 times higher than normal levels do not show signs of premature aging. ... mutation frequency in mouse mitochondria is more than 10 times lower than that reported in previous studies, suggesting earlier work overestimated the rate of these mutations. 'The technique we are using is much more sensitive' than previous assays, which had very high background levels ... Since their assay examined point mutations only, it remains possible that large deletions in mitochondrial DNA could still underlie aging." The article contains further caveats on what this all means - we shall see where it all goes as researchers continue to hold up a light to mitochondrial biochemistry and its role in the aging process.