Without any direct evidence (although it's an idea I picked up from attending various immunology lectures), it seems like aging/death is at least partially linked to immunity.

Our ancient ancestors had to make a tradeoff in order to combat the extremely high mutation rate of their microbes, by increasing their own rate of genomic diversity (through sex, and through adaptive immunity) including in the receptors which detect microbes.

Sexual reproduction https://en.wikipedia.org/wiki/Sexual_reproduction

V(D)J recombination https://en.wikipedia.org/wiki/V(D)J_recombination

Evidence of G.O.D.’s Miracle: Unearthing a RAG Transposon https://www.sciencedirect.com/science/article/pii/S009286741...

However, nothing is free, and with the ability to generate this extreme genetic diversity comes a higher risk of making mistakes including un-programmed DNA breaks, etc.. All these little mistakes add up as aging, and sometimes cancer, when the repair pathways are not able to keep up with the damage.

Also, by having an adaptive immune system you're constantly breeding tougher and tougher microbes, which could be considered harmful.

The acquired immune system: a vantage from beneath https://pubmed.ncbi.nlm.nih.gov/15539148/

Not pc anymore but a lot of humor and insight. I got a kick out of why he thinks hungry animals run. Pretty sure he is wrong (there are often unexploited niches and opportunities) but it made me laugh.

> I used to think that way, too, but I don’t any longer. You see, every creature alive on the earth today represents an unbroken line of life that stretches back to the first primitive organism to appear on this planet; and that is about three billion years. That really is immortality. For if that line of life had ever broken, how could we be here? All that time, our germ plasm has been living the life of those singlecelled creatures, the protozoa, reproducing by simple division, and occasionally going through the process of syngamy -- the fusion of two cells to form one—in the act of sexual reproduction. All that time, that germ plasm has been making bodies and casting them off in the act of dying. If the germ plasm wants to swim in the ocean, it makes itself a fish; if the germ plasm wants to fly in the air, it makes itself a bird. If it wants to go to Harvard, it makes itself a man. The strangest thing of all is that the germ plasm that we carry around within us has done all those things. There was a time, hundreds of millions of years ago, when it was making fish. Then at a later time it was making amphibia, things like salamanders; and then at a still later time it was making reptiles. Then it made mammals, and now it’s making men. If we only have the restraint and good sense to leave it alone, heaven knows what it will make in ages to come.

>I, too, used to think that we had our immortality in the wrong place, but I don’t think so any longer. I think it’s in the right place. I think that is the only kind of immortality worth having -- and we have it.

If you take that line of reasoning, you might as well go further. The protons of the hydrogen atoms in your body are from seconds after the Bing Bang. They were there at the formation of gas clouds, and galaxies, and stars, and novae, and supernovae, and, the formation of our sun and planets. They were present even before the single celled organisms in the water, the methane, the precursors of nucleic acids and organic molecules. And, with an estimated half-life of 10^34 years, these protons will be around long after the all life on Earth is gone. Compared to them, the germline, is but a drop in the bucket.

Very fascinating read. Reminds me of a recording of a stream I was listening to recently where the person talks about the idea of death being given in a deal to biological life.

A great read, fascinating stuff