It isn't completely clear exactly how many longevity genes affect our biochemistry. For example: "The researchers studied a family of transcription factors called FoxO known to be involved in proliferation, differentiation and programmed cell death. FoxO genes are required for the extreme longevity seen in some strains of laboratory roundworms, and a single mutation in the FoxO3 gene has recently been associated with long life in Japanese, German, American and Italian populations. ... We wanted to know if FoxO3 could be involved in regulating the pool of neural stem cells ... researchers examined laboratory mice in which the FoxO3 gene was knocked out. ... the few stem cells found in the adult mice without FoxO3 more rapidly churned out neural cell precursors - those cells destined to become new neurons - than did the mice with normal FoxO3 levels. In fact, the brains of the mice that lacked FoxO3 were heavier than the control group, perhaps because they were burning through their pool of neural stem cells by making too many new nerve cells. ... It's intriguing to think that genes that regulate life span in invertebrates may have evolved to control stem cell pools in mammals. ... [researchers] are working on creating a mouse in which FoxO3 levels are artificially elevated. If their theory about the function of the protein in the brain is correct, it's possible that the neural stem cell pools of these mice will be protected from the ravages of time. ... We're very interested in understanding how everything unravels during the aging process."