A red open car blasts past you, exhaust and radio blaring, going at least 10 miles faster than the speed limit. Want to take a bet on the driver? Well, you won’t get odds. Everyone knows the answer. All that exhibitionism shouts out the commonplace, if not always welcome, features of young males. Just rampant testosterone, you might say. And that’s right. It is testosterone. The young man may be driving the car but testosterone is what’s driving him. And it’s not only testosterone coursing round his body, rushing into his brain that’s responsible. Testosterone has played a subtle role even whilst he was in the womb, enabling his genitals to develop properly, and preparing his brain for later hormone-driven activity. It might even have influenced whom he finds sexually attractive. For in adulthood, this apparently simple hormone has only one function: to enable males to breed. Nothing else. So, why the car, the noise, the machismo? Because breeding isn’t that simple.
The testis has two functions: to make and deliver mature sperm and to secrete testosterone. Making sperm needs testosterone. But testosterone also prepares males for the rigorous and competitive events of reproduction. For a man to want sex, testosterone must go to work on his brain. And other males want mates as well, so there’s competition in a rough and tumble world. Which can be dangerous, so males need weapons. And there you go again. It’s testosterone that provides them – causing the growth of muscles and, in some species, teeth, horns, claws.
And testosterone does other things to the masculine brain. A male needs the motivation (some would say courage) to take risks – to confront other males, and to fight his corner. But this is no good if a male is unattractive to females. So testosterone makes him look attractive, that is, ‘male-like’. It doesn’t end there. Males need resources, like access to food or shelter, in order to attract females and provide for them and their young. Sometimes males need to cooperate rather than compete: so attempts by males of other groups to steal his resources (and those of his group) are repelled.
In short, to to be effective, testosterone has to do a great many things: it must influence physique; act on the brain; and inflame sexuality. But this hormone also makes males enjoy taking risks, resorting readily to competitiveness and aggression to obtain what they need, seeking domination over other males, resenting and repelling invasion of their territory. The extraordinary fact is testosterone does all this, and more.
It’s an ancient hormone, evolved way back in vertebrate history. Testosterone is so powerful that every animal species has developed ways of controlling its action. In humans it has to operate within our modern world, a world very different from the ancient one. How do we cope with this primeval force? Humans have developed unique ways of regulating the primal actions of testosterone. Ethics, laws, social and religious prohibitions – all have been developed to control what it does. These controls have not been devised by the parts of the brain on which testosterone acts, but by more recently evolved areas, responsible for the amazing inventiveness and flexibility of human behaviour. The two domains work together, sometimes in synchrony, at other times in opposition.
Yet testosterone’s imprint is still with us in male competitiveness, risk-taking, and the tribal behaviour shown by gangs and football supporters. And, all too often, in war. War has been a constant feature of human history, and much of the propensity for humans to go to war can be attributed to testosterone. But the technology of war has evolved as well, and this greater potential loss of resources and life may be altering the decision as to whether or not to wage war: a judgment made by more recently developed parts of the brain (not always successfully). And controlling testosterone sometimes fails in other ways: rape is depressingly commonplace in humans, though rare in other species. Is this one penalty of a brain evolved for a more primitive world but carried forward into a modern one?
Testosterone is also important for women. Not just because what men do affects their lives, but because this hormone acts on female brains as well. Thus we see the tendrils of testosterone everywhere. Not just in sexuality, but also in business (e.g., in finance); in the way we behave towards others; in sport; in politics, and in the organization of society; even in the frequency of pub brawls on a Friday night. So to understand the true impact of testosterone, and its central role in our history, we need to consider the gamut of humanity, and how we got to where we are, and how successfully we have been able to adapt the ancient, powerful force that is testosterone to our modern world.
Featured image credit: Red Ferrari. Public Domain via Pixabay.