Monogamy is defined as having a single mate (aka sexual partner) during a certain period of time; sometimes it refers to marriage. On the flip side, polygamy means having more than one partner at the same time. In the USA, the number of monogamous couples has increased significantly since the 1970s[4][5]. Perhaps surprisingly,marriage rates across the USA have actually decreased in the past few decades (2.1 million Americans were married in 2009, the same number as in 1970, although the national population has increased by about 100 million people in the last 40 years). But, in 2008, Americans were 10 percent more likely to say lipstick on the collar was wrong than they were in the 1970s; one study estimates about three quarters of married people today stay faithful to their spouses. There are plenty of possible theories to explain the increasing rates of monogamy in the USA. Potential reasons range from economic factors to differences in mates’ childhood environments, and some suggest natural selection is pushing us toward tighter-knit family units. Some scientists have looked into the potential health benefits of sticking to a single mate. Research comparing the health status of monogamous and polygamous couples is pretty scarce, but studies suggest pairing off has benefits for our health and happiness that flying solo doesn’t[6].
Turns out there’s little reason to lose a guy (or girl) in 10 days. In many cases, people in relationships live longer than single ladies and gents. Intimacy between two is also linked to lower rates of depression, higher immunity, and better heart health[7]. Married folks may even be less likely to get cancer than unmarried people[8]. And relationships aren’t just about the honeymoon feeling. In one study, participants looked at photos of their sweeties and results indicated lovebirds in long-term partnerships showed levels of pleasure-boosting hormones similar to people in new relationships[9]. In fact, people in long-term relationships also produced attachment hormones (like oxytocin) that people in short-term relationships didn’t have[10]. (Of course, it’s unclear if the participants in any of these studies who said they were in a monogamous relationship really were faithful to their partners.) Still, monogamy may not be for everyone — to each his/her own?