Any past animals, if evolved protected against chromosome ends shortening during somatic cell reproduction, (thus by this not aging greatly), then due to not needing to produce new young very often (with some occasionally evolving better), then they would have long ago ultimately ended up getting competed out of existence by the more often reproducing, thus somewhat faster evolving species usefully having superior evolved aging. Thus they would have long ago gotten genetically left behind, due to their species evolving too slowly, too infrequently, to thus have finally gotten rendered extinct. So having all age to death is good, advantageous for more successfully evolving competing species!
Some aging is good, on some rare occasions giving time needed for some reproductive cells to become slightly randomly chemically altered. A rare few such alterations may happen to contribute to genetic evolutionary advances for new babies, maybe helpfully slightly advantageous against some other competeting also very slowly randomly evolving species.
Some genetically revised humans could now overcome any natural cell aging problem within their reproducing somatic (body) cells, and then maybe sometimes also nicely incorporate into their chromosomes ever better modifications in some DNA sections regulating genes, or incorporate good favorable modifications into actual genes, or add suitably regulated new genes, to thus intelligently creatively make themselves very rapidly evolve much better. So it will be fine for such modern DNA altered folks to genetically carefully halt and limit any such past evolved needed animal aging beyond too old adulthood.
Sexual reproduction had been much helped in animals, including mammals, thanks to important evolved useful sexual pleasures. This protectively helped limit reproduction if between less compatable pairs, such as if one of the two had poor health or had some visible bad mutation, or seemed not good as a future child raising parent, or was now unattractively aging too old. Then if a male wasn't gaining sufficient enjoyment of sex long enough with some female, orgasmic ejaculation of sperm might become unlikely. Or if the female wasn't gaining good pleasure or not enjoying it long enough, she might break out of any attempted sex early, and thus not get impregnated.
But sexual reproduction between more compatable good healthy younger couples would succeed more often, increasing their numbers of good inheriting young. Thus bad matched maybe unhealthy couples had no or fewer young, while good younger healthy couples, which much more enjoyed more frequent more extended extra sexual pleasures, normally produced more young, to most importantly continue their surviving species evolution. Good strong sexual pleasures had thus been a most helpful important key successful evolved natural feature.
Thus good rich enjoyment of pleasures from extended lengthy sex wasn't some strange bonus. It had become quite useful to assist healthier quicker improving evolution. Enjoying sex thus had importantly become very helpful for Earth life, much helped in animals by good pleasures from sexually stimulating a favored partner to fully engage in reproductive sex. (Then having a fond close partner often also helped humans while raising their new young.) All this had been very good to help advance our successful species evolution.
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