In fact, in contrast to the obviously negative influence of celibacy on fecundity and thus Darwinian fitness, it is not a priori certain that reproductive disadvantage is strong for drug use. Direct comparisons of fertility/fecundity between affected and nonaffected individuals may be faulty because of inability to ensure whether any differences observed are due to the factors acting pre- or post-initiation of substance use. In addition, drug use may be not so strongly related to fecundity as to be subjectively perceived as threatening it, and thus is even less under selective pressure than celibacy, which selection has not been able to preclude. Notably, inasmuch as pleasure in humans has evolved to become substantially detached from its likely original evolutionary goal of signaling a fitness benefit and becoming a goal par excellence instead of being a means, pleasurable sensations, including those drug-induced, may override and erode what remains from that original connection and related perceptions. Risky sexual behavior and promiscuity associated with drug abuse also make it difficult to ignore a potential direct fitness benefit due to drug abuse that may
