In our culture, adultery is often seen as the ultimate betrayal. Most of put monogamous relationships on a pedestal and hope (at least deep down) that we'll eventually find a nice one for ourselves one day.However, this coupled-up approach to love isn't necessarily how we're meant to live, at least not according to new research on heterosexual relationships.Women have been genetically programmed to have affairs as a "backup" plan in case their relationship fails, said scientists in the US cited by The Sunday Times David Buss, Cari Goetz and colleagues suggest humans aren't meant to be monogamous and have put forward an alternative theory of human relationships. According to the “mate-switching hypothesis”, we have evolved to continually test our romantic relationships and seek out better options. How romantic.The theory particularly applies to childless women because their choice of partner can greatly affect how capable they are of eventually raising children, the researchers said.“Lifelong monogamy does not characterise the primary mating pattern of humans,” the scientists said. “Breaking up with one partner and remating with another — mate switching — may more accurately characterise the common, perhaps the primary, mating strategy of humans.”For early humans, who would mostly not live beyond 30 years old, picking a suitable partner was crucial for ensuring long-term survival, and it was good planning to have someone else in the pipeline in case that person died, the researchers said.These days, women apparently go through a complex set of calculations when they're in a relationship. They compare their partner's "mate value" with that of other single men, and weigh up the “relationship load”, or "the costs imposed by partners who behave badly or fail to provide," reported The Sunday Times Controversially, the researchers also claimed affairs were even beneficial for women in strong long-term relationships. “A regular mate may cheat, defect, die, or decline in mate value. Ancestral women lacking a backup mate would have suffered a lapse in protection, and resources,” they said.Somehow, we don't think this excuse will wash when your long-term SO catches you on Tinder. So it's best to exercise some caution.