Most of the time when you hear the word testosterone it is followed by some nonscientific generalisation about anger, adultery or banking (or a near rhyme of that word). As well as making men men, this steroid hormone - which is responsible for reproduction - has come to define men, often in a negative way.In his new book, Testosterone: Sex, Power and the Will to Win, Professor Joe Herbert, of the University of Cambridge's department of clinical neurosciences, opens his reflections on the social and biological function of this much-maligned molecule, which comes mainly from the male testes.Cultural and technological changes, he says, are not matched by physical ones; ergo, testosterone wants us to do things we don't really need to do any more in order to survive.Women call almost all the shots when it comes to conquest and absolutely all the shots when it comes to being fertile and ready to breed. Testosterone is men's way in and, as such, it's little wonder it does all sorts of things to the male body and mind.Does testosterone make males aggressive and brave?Yes, it encourages risk and competitiveness: this is what underlies aggression. Sex doesn't happen in a tranquil world. It's competitive. A male needs to ward off competitors.Are men natural warmongers?I'm afraid so. History teaches us that war is ever present. And it's a male affair. All the attributes that testosterone gives males makes war inevitable. However, as wars become more devastating, the brain is able to moderate the instinct for war.Does more testosterone make us more fertile?No, but you need enough to be.Can testosterone make us attractive?The things that testosterone does to a man's body - increase his height, muscularity, and aggressiveness - are all things that increase his sexual attractiveness.Does more of it make us more well-endowed?No, again, but you need enough, particularly in the womb.Do women have it?Most certainly. It's very important for controlling a woman's sexual drive.Can we control testosterone?Much of society, its laws, customs and traditions are directed towards the social control of testosterone. Males can't behave without restraint, much as they might like to.What happens to testosterone at midlife and beyond?Testosterone does decline with age, but at different rates. It can result in erectile dysfunction, though this is not as common as often believed: erectile problems with age are mostly not dependent on testosterone.Do rapists have more testosterone?No, though rapists need to have enough for an erection. But rape is complex - some rapists might be unusually sensitive to their own testosterone. Also, rape may be more of a dysfunctional, aggressive event than a sexual one in some cases.How can I increase my testosterone level?Get a promotion! Talk to a pretty women (gays: pretty man). Take a supplement, but only under medical advice.Did testosterone lead to the banking crisis?It was said that had there been more women in charge this mess would not have happened. Nonsense. It was lack of control, not too much testosterone. But any risk-taking process (ie financial trading) is going to have a disaster at some point.Men take a lot of stick these days for their testosterone.Should we be proud of it?Absolutely: it makes our world go round and makes life a lot more interesting for everybody. ..