The aging of bacteria grants us insight into the very earliest evolutionary origins of aging: "When a bacterial cell divides into two daughter cells and those two cells divide into four more daughters, then 8, then 16 and so on, the result, biologists have long assumed, is an eternally youthful population of bacteria. Bacteria, in other words, don't age - at least not in the same way all other organisms do. ... [But] not only do bacteria age, but [their] ability to age allows bacteria to improve the evolutionary fitness of their population by diversifying their reproductive investment between older and more youthful daughters. ... Aging in organisms is often caused by the accumulation of non-genetic damage, such as proteins that become oxidized over time. So for a single celled organism that has acquired damage that cannot be repaired, which of the two alternatives is better - to split the cellular damage in equal amounts between the two daughters or to give one daughter all of the damage and the other none? ... bacteria appear to give more of the cellular damage to one daughter, the one that has 'aged,' and less to the other, which the biologists term 'rejuvenation' ... In a bacterial population, aging and rejuvenation goes on simultaneously, so depending on how you measure it, you can be misled to believe that there is no aging. ... We ran computer models and found that giving one daughter more the damage and the other less always wins from an evolutionary perspective. It's analogous to diversifying your portfolio."