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Body Language

Why Do We Have Eyebrows?

The evolution of human eyebrows holds lessons for communication today.

Photo by Andrea Piacquadio from Pexels
Source: Photo by Andrea Piacquadio from Pexels

When you’re talking anthropogeny, it can be hard to tease out cause and effect: Did we humans evolve a bigger brain as cause or effect of our development of language and other advanced functions, for example? Hard to know. Correlation, as careful scientists are fond of saying, doesn’t necessarily imply causation.

With that in mind, a study by researchers at the University of York in the UK set my communications-fixated pulse racing. It turns out that one of our ancestral precursors, Homo heidelbergensis, who lived roughly 300,000 years ago, had a thick brow, even thicker and scarier than the Neanderthals'.

The question is why: Why did we start out with such a prominent brow, and why did we lose it over the eons as we evolved from caves, campfires, and grunting to condos, boilers, and sonnets? The researchers used a clever computer simulation to eliminate the need for the brow to keep our heads from caving in. So it wasn’t a structural issue. Then, they looked at food: Did the stresses of chewing require a massive eyebrow bone? Apparently not; we can chew just fine without one.

So why the brow, and why did we lose it? The researchers figure that the loss of the brow allowed us to begin to use our eyebrows (and a more mobile face) to communicate a wider, more expressive array of emotions to our fellows. With the unibrow, all you could do is threaten, with perhaps the occasional glower thrown in. But with a thin forehead bone and wiggly eyebrows, you can go to town, metaphorically speaking, and start expressing all your inner sapiens feelings.

Now, recall my mention of the difficulty of determining cause and effect. We don’t know if people needed more expressive brows as they began to get along better and in more sophisticated ways than the Neanderthals, or if the brows produced the greater range of expression. But either way, one correlated with the other: We became better communicators, and we got expressive brows. That’s what the study can tell us.

Why should you care about this early mystery of causal anthropogeny? Because it’s a great reminder of how important the eyebrows are to human interaction and communication.

One of the results of stage fright or nerves is a tendency to gesture less with your face. You freeze up and your brows go mute. But because we use our eyebrows to show that we recognize someone when they first come into view (with the eyebrow "flash" – a quick up and down) from roughly 12 feet away, eyebrows are important to connection. And when we raise our eyebrows and leave them up for a little longer, we show a desire to hear from the other person – body language for, "What do you think?" That also strengthens connection, because the implicit message is, I care what you think.

On the negative side, we bring our eyebrows down in anger and suspicion – two important emotions in the human repertoire. Thus your eyebrows, flexible thanks to 300,000 years of evolution, signal your emotional state and receptivity to other people. They are essential to good communication.

Don’t leave home without them.

Facebook image: Iryna Inshyna/Shutterstock

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