As humans, we have a ton of relationship options open to us — millennials especially are starting to take notice of this fact. So, why is monogamy still so popular? Well, let this new BritLab video explain. As the video points out, human society definitely tends to prefer pairing up exclusively. But, that doesn't mean animals aren't up for it, too. In fact, 90% of bird species are monogamous, just like most of us silly humans. Non-human monogamy doesn't always look the same as the main human variety; instead, it's often more like serial monogamy. Even then, animals are still "sneaking around" in search of a little extra fun. Nevertheless, monogamy has its upsides, especially since humans are a heck of a lot of work to raise. Of course, monogamous relationships aren't perfect (nor are they all heterosexual, like the ones this video focuses on). But, it's nice to know human society isn't alone in the monogamy game — and that we're not totally crazy for trying to keep it up.