A compelling investigation into the potent influence of testosterone, from our physical bodies and the way we behave to its explosive impact on our politics, sport and culture.

Through riveting personal stories and the latest research, Harvard evolutionary biologist Carole Hooven shows how testosterone drives the behaviour of the sexes apart and how understanding the science behind this hormone is empowering for all.

The biological source of masculinity has inspired fascination, investigation and controversy since antiquity. From the eunuchs in the royal courts of ancient China to the booming market for 'elixirs' of youth in nineteenth-century Europe, humans have been obsessed with identifying and manipulating what we now know as testosterone. And the trend shows no signs of slowing down. Thanks to this history and the methods of modern science, today we have a rich body of research about testosterone's effects in both men and women.

The science is clear: testosterone is a major, invisible player in our relationships, sex lives, athletic abilities, childhood play, gender transitions, parenting roles, violent crime, and so much more. But there is still a lot of pushback to the idea that it does, in fact, contribute to sex differences and significantly influence behaviour.

Hooven argues that acknowledging testosterone as a potent force in society doesn't reinforce stifling gender norms or patriarchal values. Testosterone and evolution work together to produce a huge variety of human behaviour, and that includes a multitude of ways to be masculine and feminine.

Understanding the science sheds light on how we work and relate to one another, how we express anger and love, and how we fight bias and problematic behaviour to build a fairer society.