While men tend to cheat more, women do have their fair share of infidelity, and a new study claims to know why.

Researchers have found that females are unfaithful because they want 'good genes' for their offspring, known as 'dual-mating theory.'

Women tend to seek out more attractive affair partners for their genetical material, but stay with a long-term mate who would make a better parent.  

However, some participants reported straying out of boredom or a lack of investment from their current partner, saying the simply wanted to have their cake and eat it too. 

The study was conducted by Australian and UK researchers who surveyed 254 heterosexual people, 116 of whom were women, and asked them to measure their physical physical, personal and parental attraction to both partners.

Participants were asked to rank the physical attraction stating: 'He was very sexy looking,' 'I didn't like the way he looked,' or 'He was somewhat ugly,' among others.

Questions about their parental attraction to their affair partner included: 'I thought he had good fatherly qualities,' 'I thought one could depend on him to care for a child' and 'I believed men like him made bad fathers.'

The study, published in the journal Evolution and Human Behavior, found women ranked their affair partner's physical attraction as 1.93 points higher than their primary partner while the parental attraction was 3.33 points lower.

Their findings backed up what's called the dual-mating theory - where women cheat to obtain 'good genes' for their offspring while relying on their primary partners to be good co-parents.

However, the researchers reported that they found no evidence that the participants preferred their affair partner over their long-term mate. 

'Infidelity is a tactic that serves a variety of evolutionarily coherent strategies, including obtaining additional resources, switching to a new primary mate, and, especially in our study, acquiring genetic benefits for offspring,' Macken Murphy, a PhD student at the University of Melbourne told Psypost.

'However, while humans evolved to cheat, that doesn't mean we should, and most people don't.'

These findings mirror past studies that have also indicated that whether your partner cheats could come down to how good-looking they are, according to researchers at Harvard University. 

In the new study, researchers also speculated that infidelity could be caused by the mate-switching theory - when a woman has an affair while searching to replace their current partner with someone better.

Although some women did report this as the reason for cheating on their boyfriend or spouse, the findings said this wasn't the main reason.

The researchers reported that some women said they cheated because they were 'bored,' suggesting a drive for new sexual or romantic partners and experiences and others said they wanted revenge in response to their partner's infidelity to retain a sense of justice and balance in the relationship.

A significant number of women did mention being unsatisfied with their relationship including experiencing feelings of neglect, unhappiness and a lack of emotional support.

'It might sound funny, but the evolutionary drivers of female infidelity in humans is an area of vigorous debate in my part of academia,' Murphy told Psypost, adding: 'In a way, there are too many good explanations for it!'