Man is the only animal that is always sexually active. Why? Because man is the only animal who is always ambitious. Because you are constantly a seeker, because you are constantly feeling that hollow, because you are constantly feeling inferior, so you are always seeking something from the world. Always.
A byproduct of that is that you are also always seeking sexual gratification. When all the time you are seeking prestige, money, success, it is but obvious that you will also seek sex all the time. These two are one.