It is a regular recurrence in the sports news that various athletes are disgraced due to their having taken drugs that were intended to improve their athletic performance (known as PEDs for short). All of the world’s most prestigious sports organizations have banned the practice. And, to enforce this ban, expensive and intrusive testing regimes have been put in place. Taking a drug like this is broadly considered among the most grievous sins a sportsman can commit, ranking in severity alongside engaging in a conspiracy to throw a contest to the opponent for gambling purposes. Accordingly, disgraced individuals are routinely retroactively stripped of their honors and chased out of their sport.

Furthermore, these drugs have been placed on the list of strongly controlled substances alongside drugs intended for more recreational purposes by most every advanced society. This means that illicitly taking a drug intended to improve one’s athletic performance can possibly get one thrown in jail and branded a felon. The basis for restricting recreational drugs is the belief (whether well-founded or not) that they are addictive and will lead the user to destroy their lives and the lives of those around them. But, to my knowledge, no one makes that claim for PEDs. At worst, some of these drugs are claimed to make a person wrathful and violent, but that’s very a different situation than the cycle of despair and degradation that people fear from the other drugs on the controlled substance lists.

So, the question arises: why are PEDs so reviled? What exactly makes them bad enough that being caught taking them is grounds for stripping an Olympian of his gold medals? Or taking away seven Tour de France titles from the greatest cyclist of his generation? Or hounding the all-time home run leader out of the game of baseball and preventing him from being enshrined in the sport’s Hall of Fame?

The answer most people would give is that it’s cheating. There were rules against it and the rules were broken. So it’s not fair to the PED-user’s competition that they were doping (the official term for using PEDs illicitly). But that’s not really enough to explain the vehemence of the reaction. After all, there are lots of other rules bound up in athletic competition that people break in an attempt to gain an edge on their opponents. To take baseball as an example, the PED-users are reviled by many of the same people who consider a pitcher openly admitting throwing illegal spitballs (a baseball with a foreign substance added to it to make it harder to hit) to be charming.

Perhaps a look at the history will help make some sense of it. The first PEDs to get popular were anabolic steroids, which when taken by otherwise healthy individuals allow for the generation of significantly increased muscle mass. These drugs are how modern bodybuilders and ’80s action stars were able to achieve physiques akin to comic book heroes. It’s worth noticing that this is a stark difference from what people were able to accomplish before these drugs came along, and has considerably changed the conception of what an athlete can and should look like.

It turns out that the primary way these steroids help build muscle is by enabling a person to recover more rapidly from working out. The user is then able to train harder; to work out more intensely. And these workouts then build unprecedented amounts of muscle. A secondary effect of this mechanism is that it prevents the user from losing as much of the benefit of their exercise routine to injury or age. The drugs help the user’s body to respond to exercise as it did in the user’s healthy youth. This is why many athletes who have been caught using PEDs have reported that they only turned to them after a catastrophic injury.

The early steroids had some nasty side effects. Users would sometimes contract strange cancers. There were fertility implications, as the hormones generated by flooding the body with testosterone-like molecules led to the body’s negative feedback loops kicking in. And people using them unwisely could develop a wildly unbalanced physique that led to unusual injuries.

But from an ethical perspective, there doesn’t seem to be any obvious difference between PEDs and any other technique used to train modern athletes. Both can require expensive equipment, provide benefits in competition, and carry with it some risk of significant injury or death. If allowed by the rules of the sport, they quickly become mandatory among anyone who wishes to compete at a high level. And, like any other training technique, PED use doesn’t directly effect what happens on the field of competition. A person taking PEDs really does run the world record track time. It physically happened; it’s not like the runner hacked the electronic stopwatch to show a faster time or something.

Along those lines, it’s also interesting to note that athletes who are willing to risk their health for the sake of victory or of their teammates are commonly lauded. For instance, in basketball a player who bravely takes a charge from a bigger rival to draw a foul is praised. Similarly, in baseball a player who constantly hustles, even on plays that have a very low chance of success, is considered worthy of special praise. In contact sports like football or rugby, playing through severe pain to earn a victory gets a player all sorts of credit from fans and opponents alike.

It seems to me like virtually everyone actively wants athletes to put their futures at risk in the search of glory. Looked at coldly, it seems pretty clear that by taking a PED, a player is risking his health to some degree to enable him to sacrifice more of his life in the gym and, thus, triumph over his opponents on game day. This decision is commonly labeled selfish and beyond the pale. At the same time, the decision to play a championship game on a broken leg or with a torn hamstring is often considered the height of heroism, even when that can turn the injury into a lifelong source of agony.

Why the difference? Looking at the pattern of the people who are upset and those who don’t seem to care so much, it seems pretty clear that the opponents’ real problem with doping doesn’t stem from some idea of harm being done to the participants. For some reason, PEDs are considered a purity violation. It’s disgusting to take steroids to win an athletic competition. And those people with a strong sense of disgust recoil from the practice, while those who put little weight on classic purity issues tend to believe that PED use should not invalidate what actually happened on the playing field. But where does this disgust come from? What’s the real purity violation?

I contemplated this problem for a long time. And I think I finally figured it out. To cop a formulation from Robin Hanson: sports aren’t really about victory; sports are about sex.

The cliche about the high school sports star pairing off with the prettiest girl on the cheerleading team isn’t incidental. Nor is the NFL quarterback ditching his actress girlfriend to marry a supermodel. Or the stories of NBA stars with thousands of conquests. In this way of thinking it’s really the entire point of the endeavor.

This also explains the great disparity between the popularity of men’s and women’s sports leagues. Victory is especially sexy to girls, so everyone cares about who the champion of the men’s league is. This drives interest, which leads to money, which leads to professionalism and a constantly improving standard of play in a virtuous cycle.

Women’s sports leagues, on the other hand, commonly find to their chagrin that their most popular players are the prettiest ones. And classical female beauty is not terribly conducive to athletic performance. So the very most popular female sports are the ones that combine artistry and grace with athletic prowess. Women’s gymnastics, figure skating, and women’s tennis are examples of the form. But unless they take careful steps to prevent it, the competition for victory will tend to bring relatively unattractive but highly skilled athletes to the fore, which will erode public interest in the league.

So the most important part of the appeal of athletic competition is that it displays the athlete’s attractiveness to onlookers of the other sex. Think of it as a demonstration of one’s genetic value as a mate. And, therefore, the most attractive sports to most people are the ones that require the athletes to demonstrate attributes that would be highly prized in the sexual marketplace. This model implies that soccer is the most popular sport worldwide in large part because success in soccer demands excellent endurance along with good body control and coordination, ability to work on a team, and individual creativity in setting up rare scoring opportunities.

Bringing this back around to the original discussion, I contend that the purity violation stems from the fact that PED-fueled accomplishment is uniquely uncorrelated with the athlete’s genetic endowment. The “natural” player who barely needs to exercise in order to triumph is looked up to as a hero. The same goes for the genetic “freak” who combines rare size and strength with extreme agility and coordination to physically dominate his opponents. Those athletes would pass down their excellent genes to strengthen future generations.

From this perspective, the PED-powered sports hero really is cheating in the most pernicious way. A man who cheats on the field of play so cleverly as to not be caught is at least demonstrating the superiority of some of his inborn attributes. In the real world, cleverness can be as valuable a trait as strength. But the PED-user is unfairly taking the adulation belonging to the true champion. And, therefore, the women who naturally flock to the victor. That is the real source of the disgust at the “unearned” strength, speed, and endurance stemming from the drugs.