From Spock to “The Rock,” arched eyebrows can speak volumes. Now researchers suggest that communicative eyebrows may have proven key to the evolution of modern humans, a marked advance over the prominent brow ridges of early humans.

Modern humans possess smooth foreheads with expressive eyebrows. In contrast, early humans had sloping foreheads with thick brow ridges.

“There have been many explanations over the years for why early humans had these huge bony ridges,” said study co-author