We place unreasonable trust in biological explanations of male behavior. Nowhere is this truer than with testosterone. Contemporary pundits invoke the hormone nicknamed T to prove points about maleness and masculinity, to show how different men and women are, and to explain why some men (presumably those with more T) have greater libidos. Yet, despite the mythic properties popularly associated with T, in every rigorous scientificstudyto date there is no significant correlation in healthy men between levels of T and sexual desire.

Beginning in the 1990s and really picking up steam in the 2000s, sales of testosterone replacement therapies (TRTs) went from practically zero to over $5 billion annually in 2018. This was either because there was a sudden outbreak of Low T when a major medical epidemic was finally recognized, or because T became marketed as a wonder drug for men thrown into a panic when they learned that their T levels declined1 per cent annually after they hit 30.

The answer is not that mens bodies changed or that Low T was horribly underdiagnosed before but that, in the minds of many, T became nothing short of a magic male molecule that could cure men of declining energy and sexual desire as they aged.

Whats more, many have been taught that, if you want to know what causes some men to be aggressive, you just test their T levels, right? Actually, wrong: thesciencedoesnt support this conclusion either. Some of the famous earlystudieslinking T and aggression were conducted on prison populations and were used effectively to prove that higher levels of T were found in some men (read: darker-skinned men), which explained why they were more violent, which explained why they had to be imprisoned in disproportionate numbers. The methodological flaws in these studies took decades to unravel, and new rigorousresearchshowinglittlerelation between T and aggression (except at very high or very low levels) is just now reaching the general public.

Whats more, it turns out that T is not just one thing (a sex hormone) with one purpose (male reproduction). T is also essential in the development of embryos, muscles, female as well as male brains, and red blood cells. Depending on a range of biological, environmental and social factors, its influence is varied or negligible.

Robert Sapolsky, a neuroscientist at Stanford University in California,compileda table showing that there were only 24 scientific articles on T and aggression 1970-80, but there were more than 1,000 in the decade of the 2010s. New discoveries about aggression and T? No, actually, although there were newfindingsin this period showing the importance of T in promotingovulation. There is also a difference between correlation and cause (T levels and aggression, for example, provide a classic chicken-egg challenge). As leading experts on hormones have shown us for years, for the vast majority of men, its impossible to predict who will be aggressive based on their T level, just as if you find an aggressive man (or woman, for that matter), you cant predict their T level.

Testosterone is a molecule that wasmislabeledalmost 100 years ago as a sex hormone, because (some things never change) scientists were looking for definitive biological differences between men and women, and T was supposed to unlock the mysteries of innate masculinity. T is important for mens brains, biceps and that other word for testicles, and it is essential to female bodies. And, for the record, (T level) size doesnt necessarily mean anything:sometimes, the mere presence of T is more important than the quantity of the hormone. Sort of like starting a car, you just need fuel, whether its two gallons or 200. T doesnt always create differences between men and women, or between men. To top it all off, there is evenevidencethat men who report changes after taking T supplements are just as likely reporting placebo effects as anything else.

Still, we continue to imbue T with supernatural powers. In 2018, a US Supreme Court seat hung in the balance. The issues at the confirmation hearings came to focus on male sexual violence against women. Thorough description and analysis were needed. Writers pro and con casually dropped in the T-word to describe, denounce or defend the past behaviour of Justice Brett Kavanaugh: one commentator inForbeswrote about testosterone-induced gang rapes; another, interviewed on CNN, asked: But were talking about a 17-year-old boy in high school with testosterone running high. Tell me, what boy hasnt done this in high school?; and a third, in a column inTheNew York Times, wrote: Thats him riding a wave of testosterone and booze

And it is unlikely that many readers questioned the hormonal logic of Christine Lagarde, then chair of the International Monetary Fund, when she asserted that the economic collapse in 2008 was due in part to too many males in charge of the financial sector: I honestly think that there should never be too much testosterone in one room.

You can find T employed as a biomarker to explain (and sometimes excuse) male behavior in articles and speeches every day. Poetic license, one might say. Just a punchy way to talk about leaving males in charge. Yet when we raise T as significant in any way to explain male behavior, we can inadvertently excuse male behavior as somehow beyond the ability of actual men to control. Casual appeals to biological masculinity imply that patriarchal relationships are rooted in nature.

When we normalize the idea that T runs through all high-school boys, and that this explains why rape occurs, we have crossed from euphemism to offering men impunity to sexually assault women by offering them the defense not guilty, by reason of hormones.

Invoking mens biology to explain their behavior too often ends up absolving their actions. When we bandy about terms such as T or Y chromosomes, it helps to spread the idea that men are controlled by their bodies. Thinking that hormones and genes can explain why boys will be boys lets men off the hook for all manner of sins. If you believe that T says something meaningful about how men act and think, youre fooling yourself. Men behave the way they do because culture allows it, not because biology requires it.

No one could seriously argue that biology is solely responsible for determining what it means to be a man. But words such as testosterone and Y chromosomes slip into our descriptions of mens activities, as if they explain more than they actually do. T doesnt govern mens aggression and sexuality. And its a shame we dont hear as much about theresearchshowing that higher levels of T in men just as easily correlate with generosity as with aggression. But generosity is less a stereotypically male virtue, and this would spoil the story about mens inherent aggressiveness, especially manly mens aggressiveness. And this has a profound impact on what men and women think about mens natural inclinations.

We need to keep talking about toxic masculinity and the patriarchy. Theyre real and theyre pernicious. And we also need new ways of talking about men, maleness and masculinity that get us out of the trap of thinking that mens biology is their destiny. As it turns out, when we sift through the placebo effects and biobabble, T is not a magic male molecule at all but rather as the researchers Rebecca Jordan-Young and Katrina Karkazis argue in theirbookTestosterone(2019) asocialmolecule.

Regardless of what you call it, testosterone is too often used as an excuse for letting men off the hook and justifying male privilege.

Matthew Gutmannis professor of anthropology and faculty fellow at the Watson Institute for International and Public Affairs at Brown University. His latest book isAre Men Animals? How Modern Masculinity Sells Men Short (2019). Follow him on Twitter @MCGutmann

A version of this article was originally published at Aeon and has been republished here with permission. Follow the site on Twitter @aeonmag

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Viewpoint: Time to stop thinking of testosterone as a 'magic male molecule' - Genetic Literacy Project