You have to think about it from the stance of what is best for the long-term survival of the whole genetic line.
From that standpoint, it makes no sense for individuals to live forever. They need to die to make room for new individuals who will have a different (and possibly better) selection of genes. This might mean new mutations that turn out to be advantageous or it might simply mean a better combinaton of existing genes.
If there is no room for new individuals with new genetic makeups, then the long-term ability of the population to adapt to changes in the environment is decreased. But, from the same standpoint, a lifespan that is long enough to provide for cultural continuity is also advantageous to the population. At least for creatures that have culture. Bacteria probably don’t fit into this idea.
So you have two competing forces, one requiring death, the other favoring a long life span. Add in the idea of limited resources keeping populations at or below a certain size. These forces, through the process of natural selection tend toward the equilibrium which is of maximum benefit to the genetic line. The point of equilibrium may vary according to shifts in these forces, but it is always present.
This reasoning depends on selection at the population level, rather than the individual. While this is possible, it is not necessary to invoke population selection to understand why individuals don’t live forever.
Within any population, there will be a certain amount of attrition due to reasons that have nothing to do with aging. Individuals will die due to accident, disease, predation, etc. For this reason, each older age class will be smaller than the one before it, and even if individuals reproduce they will contribute less genetically to the population as a whole. By the time you get to very old individuals, they are so few that they are contributing very little genetically to the overall population. Selection against genes that promote long life span will thus be comparatively weak.
mattdillon87, General Questions is for obtaining factual answers to questions. If you want to make arguments from a non-scientific perspective, then take it to Great Debates. The existence of genes is a well-established fact that is not disputed even by most creationists.
I’m not saying my “postulated conditions” are typical (I said they were ideal). But they should be. I’m not trying to draw evolutionary conclusions. I don’t believe in evolution. The thing is, none of us, not you or I, know if evolution is true. Nobody can possibly know how humans originated, because none of us were there. Unless someone built a time machine.
The way I look at it is this: the time she should give birth is the time she becomes fertile. So she should give birth in her mid teens to early twenties, prior to the 35-40 age range you mentioned. Well, at least, that’s the way it should be.
mattdillon87, this forum is not for discussing what “should be.” I’m instructing you to stop posting in this thread, and start a new thread in Great Debates if you wish to pursue this argument any further. Additional posts by you in this thread may be subject to a warning.