The Victorian era (1837–1901) delivered explosive progress in technology and agriculture, transcendent changes in art and literature, and profound growth in rational and progressive thought. Important foundations of modern utilitarianism, feminism, socialism, and democracy were laid in Victorian England. And Charles Darwin’s great works on evolution forever changed human understanding of what it means to be alive. Nonetheless it is not a time that is known for an equally freethinking and liberated attitude to sex.

Today, Queen Vic and the time of her reign evoke stultifying prudishness. Biology has been lugging Victorian baggage for the last 150 years, only recently entering its own sexual revolution. While Darwin’s books transformed scientific thinking about reproduction, the stuffiness with which his fellow gentlemen naturalists thought about sex lingers today, distorting the ways in which people understand love, sex and reproduction.

The euphemistic view that sex is a necessary act that happens for the ‘perpetuation of the species’ prevails in scientific papers and nature documentaries alike. Elsewhere, we wallow in the sanitised view that sex is a happy and co-operative event, best discussed discreetly, seen in soft-focus and not too close up.

But for most animals, mating involves one part co-operation and several parts exploitation. Consider the various plant bugs and bedbugs in which the male inserts his hypodermic penis straight through the female’s body wall during mating, inflicting great trauma on her. Or the male spiders for whom a successful date involves becoming his mate’s dinner. What is good for the goose is very seldom good for the gander.

Compared with most of the animal kingdom, human mating is remarkably co-operative and mutually satisfying, most of the time. Human families are a true marvel of nature, rife with co-operation. But they are always stalked by the conflicting interests of the two partners.

In Sex, Genes & Rock ‘n’ Roll: How evolution has shaped the modern world I explore some of the many insights which modern evolutionary biology provides to illuminate our modern lives. One such insight, and the reason that affairs of the heart fascinate us so wickedly, is sexual conflict; the idea that even a mommy and daddy who love each other very much can be in a perpetual tug-of-war between co-operation and conflict.

Intriguingly, in recent decades, as biologists have been waking up to sexual conflict, economists have enjoyed a similar epiphany. Until recently, economists modeling household decision-making always assumed that couples work together to maximise their combined benefits. 

Adrienne Germain, the inspirational head of the International Women’s Health Coalition, recalls how in the 1970s, as a young sociologist working on family planning and development programs, she struggled to get economists to incorporate the differences in interests between men and women within households in their models. From her fieldwork in places like Peru, Germain knew that ‘every household has two decision-makers, not one’. It took a young field sociologist to persuade the best economic minds that ‘household decisions are a negotiation’.

Nobel-winning economist Amartya Sen coined the wonderful expression ‘co-operative conflicts’ to describe the complex push and pull at the heart of even our most loving relationships. The economic understanding of co-operative conflicts quite literally changed the world. Development agencies now know that educating, empowering and extending credit to women, particularly mothers, generates the most effective improvements in the lives of families and the communities where those families live.

But economics can only take us so far. The embryonic science of evolutionary economics is making important steps toward understanding the links between our evolved biology and our economic behaviour. Sex, Genes & Rock 'n' Roll repeatedly illustrates how evolution generates the tension between co-operation and conflict, both biological and economic.

Understanding sexual conflict can help societies mitigate the damage when love or lust goes wrong: from spiteful divorces to sexual harassment. But we can achieve so much more when we understand that conflicts colour even our most loving and apparently harmonious relationships, and that partners can be in furious co-operative agreement and simultaneously have conflicting agendas.

I argue that a mature grasp of sexual conflict and evolution can help us to understand why educating girls is the most effective way of slowing population growth and curing poverty, why polygynous societies suffer such enormous violence, why marriages last longest in societies like the Inuit that inhabit harsh environments, why there is no such thing as the ideal family, why societies are better off when women have cheap and safe access to contraception and abortion, why rock stars and sportsmen are so obnoxiously promiscuous, and why we erupt in indignation at both the stars and the women with whom they dally.

Rob Brooks is the author of Sex, Genres & Rock 'n' Roll: How evolution has shaped the modern world, published by NewSouth.