And evolutionary biologists, sociologists, anthropologists, psychologists, economists and geneticists have been puzzling over it for more than a century."It's the most common mating pattern globally," Queensland University of Technology (QUT) behavioural economist Stephen Whyte says."You see it in every single culture, in every single country The broader societal ramifications are still playing out but in the US, researchers have estimated that up to half of the increase in income inequality is linked with increased couple matching on earnings.The effects carry across generations, since parents tend to pass advantages to their children, entrenching inequality and further reducing the chances of intermarriage.Lastly, the question of who we share our lives with is a key measure of how deeply different parts of any society have truly accepted and integrated with one another."[Marriage is] really the ultimate connection between people within a society," says sociologist Darren Sherkat, from Southern Illinois University in the US."It's the real test of whether or not groups of people within a multicultural society are connecting with one another."Georgia Brazier, 29, says it's definitely an "opposites attract" situation with her partner Pat