Science Says: Cost of Love Is Two Old Friends

"People who are in romantic relationships - instead of having the typical five [individuals] on average, they only have four in that circle," Dunbar told the BBC. "And bearing in mind that one of those is the new person that's come into your life, it means you've had to give up two others."

This may explain why some young males maintain the "bros over h-words" rule—to try to prevent their inner circle from being fragmented. It also explains why the sequel to Sex and The City didn't really work. (Well, that and the whole multiple costume changes in the middle of the desert thing...)

"What I suspect happens," says Dunbar, "is that your attention is so wholly focused on your romantic partner that you just don't get to see the other folks you have a lot to do with, and therefore some of those relationships just start to deteriorate and drop down into the layer below."

Dunbar is noted for previously having suggested that we can only really hold enough space in our brains to have relationships with 150 people, despite what our Facebook pages say. This has come to be known as Dunbar's number.

But evolutionary anthropology is not destiny, as they say in the classics. So even if we have to all roll over and two have rolled out to accommodate our bestie's new flame, nobody's circle is set in stone. After things have simmered down a bit, it's got to be possible to reconnect with good friends again, right? Unless of course, the new lover is unbearable, and there's the only one thing to do.