RE: History And Evolution Of Aging - [Is Aging A Process Of Evolution Or Reverse Evolution?]
Thanks for such an interesting article. Really liked arguments you made. Though, I don't think we need to call ageing as reverse evolution. I see ageing simply from the perspective of - molecules have a lifetime, they degrade. If you think about it for most part biolmolecules or organisms with traits that lead to higher reproductive survival time gets selected for.
- DNA as genetic material over RNA to start with.
- All the DNA repair molecules
- Stem cell niche in multi-cellular organisms.
I don't think there is any active purpose of ageing that comes under any selection pressure. It is a process that occurs and different mechanisms exist to calm it down.
Which gets us to your question, why doesn't evolution makes us immortal, or to be more specific why doesn't it lead to eternal youth? I mean what could be the trouble. Even if ever young people over populated, they will starve to death by resource scarcity. While those fit to survive in that environment carry on. Happens quite often in bacterial colonies, I suppose? I think what limits a lifespan of species is time required by it for reproducing and nurturing enough offsprings. And second being how well the germ cell in that species maintain their integrity. I would assume the high cost of germline maintenance could at least in part explain the constraint.
However, in context of humans this gets even more complicated. Why to we out-live far beyond our reproductive age. I mean if you rather consider lifespan rather than life expectancy(which can be slave to environmental factors and infant mortality rate), we may not find much difference between past and present.. I think our social grouping structure rather contributes to max lifespan. For instance the presence of grandmother may reduce infant mortality rate.
I don't know, I think you initiated a very interesting conversation here. I have so many thoughts running in my head right now. Wonderful post.