A review paper on the roles of oxidative stress in aging, both negative and positive: "Oxidative stress is considered to be a major detrimental factor limiting longevity, as originally postulated in the free radical theory of aging. The oxidative stress leads to accrual of damaged/misfolded proteins, increased mutagenesis rate and inflammation. Ironically, due to its ability to accumulate over time (as it was seen in many neurodegenerative disorders), oxidative damage also emerged as a consequence of longevity per se. The human life-span exceeds that of most mammalian species at least 4 times (median life span records across 900 mammalian species is ~16 years). Importantly, anti-oxidative stress adaptations are not subjects of evolutionary pressure at post-reproductive age, which further contributes to the buildup of oxidative damage in aging individuals. Yet, paradoxically, in short-lived Caenorhabditis elegans, oxidative stress might have beneficial effect on longevity by connecting to the nutrition signaling pathways [such as those activated through calorie restriction]. It was suggested that aging is driven by over-activation of signal-transduction pathways such as the nutrient-sensing pathway, while oxidative stress may be both one of its activators and effectors."