Scientists Think They’ve Cracked The Eyebrow Code

As humans evolved from their prehistoric forebears, one noticeable change was that they had prominent, bony browlines, and modern humans don't. Instead, we have flatter foreheads and emotive eyebrows.

In a new study published in Nature Ecology & Evolution, a trio of researchers say they now know why: it all comes down to making friends.

Believe it or not, scientists have puzzled over this change for years -- proposing that early man needed the beefier brow for protection, or to aid their larger jaw muscles with chewing tougher grub.

Ricardo Miguel Godinho, Penny Spikins and Paul O’Higgins tested -- and tossed -- those long-held hypotheses and instead say they've gotten to the bottom of the strips of hair atop our eyes.

"Conversion of the large browridges of our immediate ancestors to a more vertical frontal bone in modern humans allowed highly mobile eyebrows to display subtle affiliative emotions."

Simply, our flatter foreheads acted as a billboard to display our more mobile eyebrows -- which were needed to express more subtle emotions than early man needed to convey. Non-verbal communication is essential to social interaction.

Being able to communicate between others that way gave humans the chance to get to know, at a glance, what others are thinking, even if they've just met, instead of just clubbing the new guy.