That's not necessarily true. While I agree that the production of these chemicals takes a lot of energy/resources which may not be worth the tradeoff within the

That's not necessarily true. While I agree that the production of these chemicals takes a lot of energy/resources which may not be worth the tradeoff within the human body, there is no reason to believe such benefits cannot be achieved through externally produced drugs. Also, evolution is a game of chance, and the required mutations may not have occurred in humans yet.