Why Do We Have Eyebrows?

From pencil thin arches to bushy caterpillars, eyebrows are something that most humans are born with, and keep forever. But what purpose do they serve beyond framing the face? According to experts there isn't much physical difference between modern humans and ancient Neanderthals, except when it comes to the eyebrows. While our ancestors had heavy brow ridges, modern homo sapiens evolved with smoother foreheads, delicate facial features and softer brow lines.

There are solid arguments suggesting that eyebrows exist to protect the eyes from debris or support facial structure, however the latest study published in Nature Ecology and Evolution claims that they evolved to enhance non-verbal communication. Like a peacock's tail or a stag's antlers, the scientists claim that eyebrows empower humans with a "sexually dimorphic display" that allows them to communicate their emotions and intentions.  

A powerful body language tool

It's no secret that body language plays a pivotal role in human communication. The researchers explored this concept further by studying a homo heidelbergensis skull and Neanderthal jawbone. Using 3D modelling software, they created virtual scans designed to mimic the evolution of eyebrows. While potential theories included supporting the skull structure, improving the mechanics of chewing and protecting the eyes, ultimately, they concluded that eyebrows serve no apparent physical purpose. Instead, they claim that brow ridges evolved as a social tool.

"Sexually dimorphic display and social signalling is a convincing explanation for the jutting brows of our ancestors," explains Paul O'Higgins, senior author of the study and Professor of Anatomy at the University of York. "Their conversion to a more vertical brow in modern humans allowed for the display of friendlier emotions, which helped form social bonds between individuals".

Brows 100,000 years in the making

The study goes on to explain that around 100,000 years ago human social networks began to expand and diversify. At the same time, humans started to develop thinner, flatter brow ridges and the expressive eyebrows that are seen today. O'Higgins and his team maintain that this helped to build the all-important social bonds that helped forge modern society.

"Eyebrow movements allow us to express complex emotions as well as perceive the emotions of others," adds co-author Penny Spikins, a researcher from the Department of Archaeology at the University of York.

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