I have just read on the internet that the basic reason why we die in say 80-85 years is because of evolution. Yes, our bodies have just been designed to reproduce the genes to the next generation. So, after 50-60 years, when the reproductive phase ends, then the evolution doesn’t have anything to do with us. Why should evolution prevent us from dying when we do nothing to pass on genes and in fact use up resources which can be used by other organisms for reproduction. That is why we die. After the reproductive phase, we do not do any good as far as preserving genes is concerned, so evolution lets other use the resources.
See, let us imagine that we have a gene called TOTAL_AGE and another gene called REPRODUCTIVE_AGE. And now, if there is a mutation in TOTAL_AGE which shoots up the age to say 200 then REPRODUCTIVE_AGE being the same, won’t make any difference to the fitness of an individual. That’s because another individual with same REPRODUCTIVE_AGE but having TOTAL_AGE of 100 is equally like to produce as many offsprings as the previous one. Thus, from an evolution’s point of view, they both are equally fit, hence no selection pressure.
But, on the other hand, if some mutation doubles the REPRODUCTIVE_AGE then the individual is fitter and he is more likely to be selected by the natural selection.
Hence, if we somehow, manage to increase the reproductive age of an
animal, then in the long run, animals with longer life spans are likely to be selected.
One way to prevent natural death from aging is to keep reproducing indefinitely. This will certainly help evolution to select populations with larger life-spans. Thus, in long term, we can increase the life span of humans. I don’t know what restricts the humans to keep on reproducing, but if can be possible, then we might live indefinitely (well almost)…
UPDATE (7th Jan, 2006)
I am/was having a discussion on this same topic on Google groups.
Few interesting points from the discussion are worth mentioning in this context:
1. Two ways to increase reproductive age can be Genetic Engineering of Humans and Eugenics
2. “”People should know that such experiments have already been done by Michael Rose on fruit flies. By selecting eggs from females at
progressively later dates in their reproductive cycles, he was
eventually able to breed flies that lived twice as long on average. And
as a nice illustration of the coupling between age of reproduction and
lifespan, these Methusalah flies bred much later in life than normal flies. “”
Wow, this means my proposal can be correct actually.
3. “”Life span and the age range of reproduction are inextricably linked in a balance that does not allow for a master/slave relationship. If you evolve increased life span, you will also get increased age of reproduction as a correlated response, and vice versa.””