TESTOSTERONE . by Joe Herbert . ( OUP £16.99 ) Testosterone doesn ’ t always get a good press . Everything that ’ s unpleasant about male behaviour has been ascribed to the effects of this much maligned hormone . Violence ? It ’ s all testosterone ’ s fault . Sexual assault and rape ? Just blame testosterone . Yet , as Joe Herbert makes clear in his engaging whistlestop tour of the science surrounding it , testosterone is at the heart of human life . ‘ Without our father ’ s testosterone , ’ as he writes , ‘ none of us would exist. ’ It has only one basic function — to enable a male to reproduce , and for that it ’ s essential . Although this is the case and it ’ s impossible to think of ‘ maleness ’ without testosterone , it ’ s also important for sexual behaviour in women . The blood of an adult woman before menopause actually contains about five times more testosterone than oestrogen , the supposedly ‘ female ’ hormone . However , it ’ s as a metaphor for masculinity that testosterone is best known . All that ’ s unpleasant about male behaviour is ascribed to testosterone , yet as Joe Herbert explains , testosterone is at the heart of human life . It begins its influence in the womb as it helps to shape the distinctive characteristics of the male body . This influence continues immediately after birth . That three-month-old baby boy , sweetly smiling at you from his pram , may well have testosterone levels that rival his father ’ s . We don ’ t know why but , starting two weeks after birth and lasting for four to six months , a little boy ’ s testes are producing testosterone in substantial amounts . The hormone ’ s power then recedes , but returns — and how ! — in puberty . Post-puberty , testosterone drives the competition for females . In the animal world , stags lock antlers , elephants enter the aggressive state known as musth and male rhinos go horn-to-horn . Even male giraffes , aroused by the hormone ’ s influence , flail at one another with their long necks . Elaborate colourings emerge in some species , designed to emphasise masculinity and attract female attention . In guenon monkeys the scrotum turns bright blue . They don ’ t seem to mind . They adopt the habit of sitting with their legs apart to show the female guenons just how big and blue they are . We can only be thankful that testosterone ’ s effects on sexual display in humans are not so visually dramatic . Adult human males have varying levels of the hormone in different circumstances . Entirely unsurprisingly , having sex increases testosterone levels . So , too , does talking to an attractive woman and watching pornographic movies . Winning at sports sends the levels racing upwards . Just supporting a winning team can have the same effect . It works in politics as well . A study showed that , during the 2008 U.S. Presidential election , Barack Obama supporters were pumped full of testosterone . Levels fell in the supporters of his defeated rival , John McCain . Testosterone also helps in the City . Another study , on a London trading floor , showed that male traders made more money on days on which their morning testosterone levels were higher than usual . A challenge is obviously stimulating . Surgeons facing difficult procedures often find their testosterone levels shooting up . One would assume that the theatre of war would have the same effect as the operating theatre , if not more so . After all , testosterone is supposed to be the hormone behind violence and aggression . In fact , soldiers in the heat of battle can have testosterone levels not much above those of men who have been castrated . It ’ s the appalling stress that reduces it . Once they leave the front line , however , the soldiers revert to more normal levels . When levels are high , the effects of testosterone on male behaviour are so strong that the human brain has had to find a multitude of ways of regulating and channelling them . The creation of laws , religion and customs has , to some extent , been shaped by the need to do so . In that sense , as Joe Herbert writes , ‘ testosterone lies at the heart of much of our history ’ . His own fascination with the ‘ simple but wondrous chemical ’ that is his subject is clear . His book does a fine job of conveying that fascination to the rest of us .
The male hormone testosterone doesn t cause the body to grow bigger or more muscular All that ’ s unpleasant about male behaviour is ascribed to the hormone . Yet , as Joe Herbert explains , testosterone is at the heart of human life .