What drives women to cheat is a subject that has been long debated over the years.

And now scientists are suggesting women have been programmed by evolution to pursue affairs in case they decide to leave their partners.

New research claims this 'mate switching hypothesis' particularly applies to childless women whose loved one can affect their ability to raise offspring.

Scientists are suggesting women have been programmed by evolution to pursue affairs in case they decide to leave their partners (file photo)

The theory that affairs are women's natural back-up plan challenges the accepted notion that humans are intended to be monogamous.

It suggests humans have evolved to constantly be on the lookout for better long-term partners that their current ones.

David Buss, Cari Goetz and their team told the Sunday Times: 'Lifelong monogamy does not characterise the primary mating pattern of humans.

'Breaking up with one partner and re-mating with another - mate switching - may more accurately characterise the common, perhaps the primary, mating strategy of humans.'

For our ancestors, disease, poor diet and poor medical care meant few lived past 30 - meaning experimenting to find the most suitable partner may have been key to survival.

Scientists claim people would pick partners with the highest chance of survival, but have someone in reserve in case that person died.

Researchers suggest humans have evolved to constantly be on the lookout for better long-term partners that their current ones, citing the drama Closer featuring a tangled web of affairs among Clive Owen, Natalie Portman, Jude Law and Julia Roberts (all pictured)

Researchers argued that while break-ups have long been characterised as 'failures', in fact, the process of cheating is a mechanism to ditch current partners and acquire new ones at a time or during circumstances that are 'evolutionarily advantageous.'

The research paper mentions the character of Riley Parks that American actress plays in the TV series The Client List.

In the series Riley develops an extra-marital relationship with her brother-in-law and says there's 'no shame' in casting aside her first husband.

The research paper mentions the character of Riley Parks that American actress plays in the TV series The Client List. In the series Riley develops an extra-marital relationship with her brother-in-law and says there's 'no shame' in casting aside her first husband

This casual view of relationships is also reflected in the tangled web of affairs in the 2004 drama Closer, with Clive Owen, Natalie Portman, Jude Law and Julia Roberts.

Mr Buss, professor of evolutionary psychology at the University of Texas, and Mr Goetz, assistant professor of psychology at California State University, San Bernardino, based their ideas stem on combined research and the latest science.

They argued that, in fact, women benefit from affairs as they have a mate to turn to should their partner leave them, die or lose status.

In January 2015 a study also found that men and women react to infidelity differently.

Most men would be more upset if their other half had a sexual affair, but women would be more hurt by emotional infidelity, researchers have claimed.

Scientists asked 64,000 people what would upset them more: their partners having sex with someone else - but not falling in love with them – or their partners falling in love – but not having sex with them.

They found that 54 per cent of heterosexual men were more likely to be more hurt by sexual infidelity than emotional infidelity, whereas just 35 per cent of women would be more hurt by sex than if their partner fell in love with another person.

YOU'RE MORE LIKELY TO CHEAT APPROACHING A MILESTONE BIRTHDAY People who are 29, 39, 49 or 59 are more likely to cheat and make life-changing decisions as they approach a milestone birthday, a study published in November revealed. Researchers analysed the responses of 42,000 adults from more than 100 countries who completed a survey about their values between 2010 and 2014. They found that people with an age ending in nine were more likely to make changes ‘that suggest a search for meaning’ such as taking up marathon running or joining an extramarital dating site. Lead author Adam Alter, from New York University, said: ‘People audit the meaningfulness of their lives as they approach a new decade. 'People tend to either conclude happily that their lives are meaningful or they decide their lives lack meaning. '...some people might struggle to come to terms with the conclusion that their lives lack meaning. They might seek a socially damaging extramarital affair.' The researchers obtained data from an online dating site that targets people who are already in a relationship and found that there were far more 9-ender men - 18 per cent more - than would be expected by chance. Further analysis found a similar, though less-pronounced, pattern of results for women. Advertisement

The results, published in the journal Archives of Sexual Behaviour, were consistent with the evolutionary perspective of paternal uncertainty, the researchers said.

That is, if a man is in a relationship with a woman and she becomes pregnant, he can never be sure if that child is his, or has been fathered by someone else - barring a paternity test - and will therefore fear sexual infidelity more.