Let me first suggest that there is absolutely no need for you to read this, it’s really just me working through something. Move on to another blog post.
If we are to understand aging and death, the primary question is why should there be aging and death in the first place? What evolutionary purpose might they serve? First let me say that I’m discouraged that I don’t have any formal education in evolutionary biology, I think it’s a fascinating field and I’m frustrated by my status as a dilettante. Yet I proceed in the spirit of an amateur.
Established evolutionary theory holds that genes that lead to the death of an organism would not be adaptive and so aging and death are not part of some program. Current accepted theories fall under two broad categories, both animated by the spirit that aging is a product of evolutionary neglect, not intent.
The first theory is that of “accumulated mutations,” which holds that the organism accrues wear and tear from the processes of life, primarily genetic mutations that compromise function and lead to aging and death. Given the evolving understanding of genetics as well as our new awareness that the hallmarks of aging extend beyond simple genetic mutations, this is theory is now a non-starter.
The second theory that is typically offered is “antagonistic pleiotropy,” meaning that survival to reproduction is prioritized by evolution and the very genes that improve survival to reproductive age lead to aging and death with the passage of time. Or put differently, genes that code to preserve the organism do not improve fitness. This theory is of a different class than the first one—while the first one is mechanistic and has been disproven, this one is teleological, offering an unverifiable story.
Neither of these theories supports the idea that aging and death are evolved and part of some program. I’m suggesting that the field of evolutionary biology is wrong and I want to argue instead that dying is a way to promote evolutionary fitness. Let me just make it clear: I believe that aging is an extension of the same program as development and this program has evolved because it increased iterations of natural selection and evolutionary fitness. Consider the Pacific salmon who swims upstream and suddenly dies.
The only way I can make this point is with a story, so let us consider the example of a nonhuman organism, an early mammal, though we could just as well pick a reptile or something else that is subject to sexual reproduction. Also one presumption–that a given population lives in a particular geography with limited natural resources.
Consider first the non-aging organism. At a certain point, the mature male will be competing for mating partners with males of the next generation. Given the evolutionary imperative to pass on genes, there will be competition, and since our mature male is larger and more experienced than the next generation, it will kill them. Alternatively, it will simply scare them off and prohibit them from mating. But killing them is better as it will prevent them from getting larger one day and becoming a legitimate adversary. Which is to say, those populations that evolve to infanticide will be better off. So now you have an immortal infanticidal creature that continues to mate forever. And if there is an accident or some lethal event, perhaps the accumulation of damage, the younger offspring can finally take his place. But you have a real limit on the amount of natural selection because the population genetics are all deriving from the same male, who is presumably the one mating with all the females.
On the other hand, in an aging organism, the old male always gets weaker with time and is superseded by the young males, who fight it out for the right to mate with the females. Because there is death, this arrangement maximizes iterations of natural selection which selects for better evolutionary fitness. Invariably this population will evolve more rapidly and will likely be better suited to survive in a difficult environment.
So aging and death can be considered an evolutionary advantage. Why couldn’t it be this simple?
Well, the question is what about the cheaters? What I mean is, what about the mutation that codes for long life. The thinking is that if there were some programmatic death, eventually some organism would develop the mutation to live that much longer and thereby gain evolutionary fitness. But what I’m saying is that this would need to be balanced against the evolutionary fitness accrued by shorter lifespans. What I mean is whatever evolutionary benefit of more offspring accrued from longer life would be balanced by better evolutionary fitness from more cycles of natural selection due to shorter life.
This is the end of my brief career as an evolutionary biologist.