Actually it's about 40. That's when your immune system starts to shut down, because it's not needed anymore, as it no longer matters whether you live or not.
I seem at 54 to have beat the odds then, along with most adults across the developed globe. Odd. Yes, I know you were elliptically suggesting something about procreation. Males however seem to be able to do that too past 40. It must be some sort of evolutionary gender discrimination. Sue the evolutionist. He is not PC.
Hmmm,...come to think about it,.., that's also one aspect of a possible intelligent design applicable to those who are gay.