When the Penn researchers questioned almost 1,000 people in two subject populations, one undergraduate and one Internet-based, [they found that] … differences in reproductive strategies are driving individuals’ different views on recreational drugs.  While many items predict to some extent whether people are opposed to recreational drugs, the most closely related predictors are people’s views on sexual promiscuity. While people who are more religious and those who are more politically conservative do tend to oppose recreational drugs, in both study samples the predictive power of these religious and ideological items was reduced nearly to zero by controlling for items tracking attitudes toward sexual promiscuity. …

According to the researchers’ evolutionary model, people develop complex differences in their sexual and reproductive strategies. One key difference that creates strategic conflict arises in people’s orientations towards casual sexual activity. The relationships of people following a more committed, monogamous reproductive strategy are put at greater risk when casual sex is prevalent. On the other hand, people pursuing a less committed lifestyle seek to avoid having their choices moralized, forbidden and punished. The researchers cite prior work showing that recreational drug usage is often associated with promiscuity. The results of the study imply that attitudes against recreational drugs are part of a larger attempt to advance the cause of committed, monogamous reproductive strategies. (more; source; HT David Pearce)

OK, it is plausible that the main thing folks fear from drugs is that drugs lead to promiscuous sex.  But if so, then why does the US pay a terrible cost to (poorly) discourage drug use, and yet allow great promiscuity with only weak punishments.  We even prevent blackmail that would naturally tax illicit promiscuity.  Perhaps we don’t like to admit that sex is our concern?

Added 4:30p: OK, maybe there are three main types: 1) abstainers – those who don’t want promiscuity, 2) stoners – those who do want promiscuity, are willing to admit it, and use drugs to help get it, and 3) cheaters – those who want promiscuity, but aren’t willing to admit it, don’t use drugs to get it, and compete with stoners for partners.  Groups 1&3 together support anti-drug laws, while groups 2&3 together keep punishments of promiscuity weak.  I’m suggesting the survey used in this study measured willingness to admit to liking promiscuity, not willingness to actually be promiscuous.