Read at the NYT: Researchers at the universities of North Carolina, Michigan and Harvard have found that p16 gradually inhibits the proliferation capabilities of stem cells when they reach certain age. The mechanism is useful to prevent the proliferation of cells that, due to their age, have a significantly increased probability of creating tumours.
The paper reporting the research will be published in Nature. One interesting comment by one of the authors is that in his opinion aging is not random but an anticancer mechanism. I find this observation plausible but having an interest in evolution I cannot help thinking that the reason for aging could also be that once an organism has fulfilled its replication duties, its evolutionary-shaped genetic program does not care much for the long term survival of the individual. In other words, evolution does not favour individuals who are good at surviving for ever but that are good at surviving for long enough as to have lots of equally successful offspring.