Many societies throughout history and around the world today have cultivated strong pressures to stay married.

In the absence of societal pressures to maintain pair-bonds, O'Sullivan suggests that romantic love has increasingly come to be seen as the factor that should determine who we stay with and for how long

If you believe that you have found true romance, and your culture tells you that this is what a long-term relationship should be based on, there is less need to rely on social or family pressures to keep couples together, O'Sullivan argues.