Monogamy, explained.

In 2016, more than 2.2 million couples got married in America, but more than 800,000 got divorced. Why?

Cheating and breakups cause grief and heartache every day. Yet some historians and evolutionary biologists say monogamy is a relatively new, self-imposed system. Their evidence suggests humans lived without it for more than 250,000 years. And we only started marrying for love in the 1700s.

So if monogamy is so hard, why do most of us, all around the world, make it a central goal of our lives?

Vox tackled this question in the first episode of their new show with Netflix, Explained.