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« on: May 07, 2023, 07:01:29 PM »
This is a very complex question that involves genetics, physiology, and evolution. Most species have a lifespan more or less delimited by their size, larger animals require more time to make sufficient cells to create the adult animal, hence they reproduce later and live longer. Smaller animals tend to reproduce more quickly and live shorter lives.
Some might point to telomeres, the repeat sequences that form the end caps of our DNA. In humans these are put on embryonically, your cells don't make the requisite proteins or nucleic acids to reinforce them, hence they shorten as you age. Then again, mice do express the proteins and nucleic acids to make telomeres, yet they peter out after just a few years. There's more to it than that.
We could point to the build up of mutations as the driving force behind aging, and there is some evidence to back it up. Animals with long life spans relative to size, like tortoises and psittacines have insanely good DNA repair, but still there's more to it.
Almost 20 years ago the Japanese scientist Yamanaka discovered a method to turn boring old somatic cells into exciting pluripotent stem cells. Further research has shown that not only are these cells pluripotent, but they're also young. Yamanaka found a veritable fountain of youth. Aging is complex. That said, there are only two certain things in life, death and taxes.