Are men meant to be monogamous?

By: Hugh Wilson

New research suggests we are, but the wider evidence is mixed

There are two schools of thought when it comes to men and monogamy. One says men are meant to stay with a single partner for life, and the other says that men are biologically predetermined to spread their seed as widely as possible. George Clooney, for example, is a famously eligible bachelor with no shortage of women interested in spending time with him, but as yet he remains unmarried.

Followers of the second theory explain the predominance of monogamous relationships - marriage, cohabiting, settling down and so on - in modern society as a consequence of religion and social convention rather than evolution. Men aren’t meant to be monogamous, they say, but are forced to be so by prevailing societal norms.

Now new research challenges that view, and suggests monogamy may have been part of human evolution after all. But can it really answer that thorny old question: are men meant to stay with the same partner for life?

The new research

The new research, conducted by scientists at the Universities of London, Oxford, Manchester and Auckland, found that the macabre practice of infanticide (the killing of children) may have driven the evolution of monogamy.

It discovered that, in non-monogamous monkeys, infants of other males are often killed by males wanting to mate with females more quickly. Female monkeys typically delay mating when nurturing young children.

But the research, which looked at the mating habits of 230 primate species, found that multi-mate societies often evolved into monogamous ones to stop males killing infants that weren’t their own.

Instead, males settled with one partner and stayed to protect the children from attack, before further evolving to take some part in childcare. By having two parents to protect and nurture it, a child is more likely to survive, prosper and even develop a bigger brain. Our complex, intelligent brains may be the direct result of monogamy, the researchers say.

This evolutionary trait in primates can also be assigned to humans. Dr Susanne Shultz, from the University of Manchester, said: “What makes this study so exciting is that it allows us to peer back into our evolutionary past to understand the factors that were important in making us human.

“Once fathers decide to stick around and care for young, mothers can then change their reproductive decisions and have more, brainy offspring.”

So why all the infidelity?

So according to the new research, monogamy has given us survival advantages, and maybe even the mental wherewithal to become the primary species on the planet.

And yet monogamy is not always the popular choice, even in our advanced society. In fact, studies suggest that anywhere between 10% and 30% of people in western societies - and more men than women - pay lip service to monogamy while also seeking extramarital relations on the side.

It’s also known that monogamy is not the norm in the animal kingdom. Only 3-5% of mammal species form lifelong monogamous bonds.

Taken together, facts like these suggest to some experts that humans, and human males in particular, are not naturally monogamous.

Pepper Schwartz, a professor of sociology at the University of Washington in Seattle, has pointed out that compared to geese - which bond for life and never mate again even if a mate is killed - humans are hardly monogamous at all.

According to Schwartz: “Monogamy is invented for order and investment – but not necessarily because it's 'natural’.”

Christopher Ryan, PhD, co-author of Sex at Dawn: The Prehistoric Origins of Modern Sexuality, is blunter still. He writes:

“Human beings are clearly evolved for sex lives featuring multiple simultaneous sexual relationships.

“Men, especially, are designed by evolution to be attracted to sexual novelty and to gradually lose sexual attraction to the same partner in the absence of such novelty.”

Monogamy without fidelity

So on one side, men have evolved to hang around and protect the children, and even lend a hand in bringing them up. That way we stop other males killing them, and we produce strong, intelligent kids who are more likely to pass on our genes to the next generation successfully. In a nutshell, monogamy does us a great big evolutionary favour.

But on the other, that pesky testosterone means we soon get bored with the sexual menu on offer from one partner, and yearn for sexual novelty. The urge is sometimes so strong that it brings into question the idea that men are naturally monogamous at all.

So which side wins out? Are we meant to be monogamous or not?

To square the circle, experts talk of social and sexual monogamy. Social monogamy means that we stay with one partner and help to bring up the kids. Sexual monogamy means we never sleep with anyone but that partner. Far more of us do the first than the second.

The splitting of monogamy into two coexisting parts helps explain everything from the prevalence of infidelity and pornography to lap dancing clubs and prostitution. Men hang around in committed relationships, but seek sexual novelty on the side.

At the same time, the majority of men in committed relationships don’t have affairs. Is that reticence to philander among a large group of men just down to social pressure, convention, religion, or what have you? Or is it simply a lack of opportunity.

Evolutionary biologists say it may be down to something else. They say that both men and women have a flexible mating strategy, which they can modify depending on circumstance. Men in particular are more likely to embrace both social and sexual monogamy if they have what’s called 'paternity certainty', which means they can say without much doubt that the mother of what they assume to be their children or future children has been and is likely to remain faithful to them.

Or we could put it more simply. If men feel they’ve met the right woman, they may well mate with her for life.

So are men meant to be monogamous? It seems the only sensible answer on current evidence is a bit of a fudge: sometimes we are, and sometime we are not. Both evolution and social convention seem to accept the possibility of both.