Then why don't we reproduce like dogs? Like flies? Why doesn't the female have more eggs? If we didn't get old, we could reproduce more. IOW, the higher animals should be better at reproduction and the lower should be less efficient. If all that is necessary is to pass on the genes, why do we live beyond 20?
Here's another puzzle for youse:
The Egyptians held that the ideal age was 120. That was over 3500 years ago.