So, I was just reading a book about evolution, and I had a thought about why we aren't immortal. A person who is immortal won't have changing DNA. Every time he has a child, he will essentially be a relic of the past that is constantly tearing down any evolution that has happened since his birth. He will be stopping the evolution of the species on an order of magnitude parallel to how long he ends up living compared to his mortal peers. It is in the best interest of any species to forbid immortality. The only exception I can think of that wouldn't damage the species is a person who never has children after he reaches the average age of death of his species.
People almost always die from either atherosclerotic disease(heart attack etc), general wear and tear(kidney failure, congestive heart failure etc), cancer, or self harm(alcohol and cigarettes etc). Or injuries and infection of course. Death from "old age" is a meme.
Probably not. Why would it be?
We can't counter the old age diseases because they have no effect whatsoever in evolution. And that is because we reproduce long before we are afflicted by those diseases. Old age diseases is not a factor that determines how reproductively successful we are.
What about how men are fertile until death? Surely, an old man who lives longer has a higher probability of having more children than his competitors that die younger. This makes me think we've hit the "sweet spot" in our lifetimes.
Men are fertile until death because they continuously produce sperm. They need a lot of sperm to maximise the chance of impregnating a woman, because only a small fraction of the sperm cells are able to reach the egg. There's never a reason to shut down the production of sperm.
Still, most men have their children waaaaaay before they are afflicted by old age disease. Thus, these diseases are not a factor in natural selection.
I might have misinterpreted your question. Do tell me if that is the case.
Our expected life span is continuously increasing, and there's no reason to think it will stop. Medical treatments and awareness of healthy behaviour is improving, and at this time it is impossible to say if there really is a maximum life span or not. Time will tell.
I read an interesting paper discussing what one might call "suicide genes," or pre-programmed organism death. In this theory, aging and death are intentional, rather than a side-effect of living past a reproductive age.
In layman's terms, our genes literally conspire to kill us so as to eventually make way for the next generation. Think of the selfish gene theory: once the gene has spread to descendants, and the descendants no longer require nurturing, the parents are now consuming resources needed by the younger generation. They are a burden, and if they lived forever the species would evolve much slower and be more likely to fail (extinction). Enter "suicide genes"
Think about it: the longer the previous generation continues past their reproductive age, the more they consume resources from the younger generation for no gain. A species without the natural death "feature" (it's not a bug, it's a feature) would stagnate genetically and be less-equipped to deal with change than a species that did die off.
The author went on to explain that this may be why no species has every achieved a state of evolutionary "perfection", i.e. a state where the species lives in total harmony with its environment and any change, however slight, would make it less-equipped.
That explains exactly the idea I was trying to articulate! Thanks! So, a natural question from that is are we damaging our ability to adapt in the future by using medicine to extend our lives? I suspect that the answer is an uncomfortable yes.
Yes probably. Our old ones are an economic burden. Whether or not it is okay to stop medical treatment of elderly to improve the advancement of mankind is a moral question that I dare not answer...
Agreed. I think it's also important to keep in mind that the massive human population and the relative stagnation in evolution we are experiencing as successful adaptations help a smaller and smaller percentage of the population possibly makes the worry about stagnation irrelevant. After all, why worry about changing when we are already unchallenged masters of our domain?
True. And if something is going to help mankind advance, it is not evolution, as it is a very slow process(unless we control it). It is our own minds, and using them with total focus on our goals.
Or priorities depend on the situation. Right now, our situation is very safe. In an apocalyptic scenario, we will do anything to ensure our survival as a species. I don't doubt the capabilites of the human race.
If our environments never changed then sexual reproduction would no longer be selected for by the evolutionary process, and there would be a stronger selection for long-life genes.