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Speaker 1: Welcome to brain Stuff from house stuffworks dot com where

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Speaker 1: smart happens. Hi Am Marshall Brain with today's question, why

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Speaker 1: do human beings have eyebrows? Scientists aren't entirely sure why

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Speaker 1: we kept this hair, but they have a pretty good guess.

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Speaker 1: We know that eyebrows help keep moisture out of our

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Speaker 1: eyes when we sweat or when we walk around in

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Speaker 1: the rain. The art shape diverts the rain or sweat

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Speaker 1: around to the sides of our face, keeping our eyes

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Speaker 1: relatively dry. The most obvious advantage of this is that

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Speaker 1: it lets us see clearly when we're sweating a lot

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Speaker 1: or when we're out in the rain. Without eyebrows, getting

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Speaker 1: around in these conditions is a little more difficult. Diverting

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Speaker 1: this sweat away is also good because the salt and

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Speaker 1: sweat irritates the eyes, making them sting a little. Eyebrows

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Speaker 1: are a very significant aspect of our pearance. They are

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Speaker 1: one of the most distinctive features that make up our faces,

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Speaker 1: and we pay a lot of attention to them. We

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Speaker 1: think of some types of eyebrows as attractive and some

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Speaker 1: is unattractive, and many people spend as much time preening

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Speaker 1: their eyebrows as they do applying makeup to their eyelashes

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Speaker 1: or lips. Eyebrows are also one of our most expressive

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Speaker 1: facial features. One of the clearest ways to tell somebody

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Speaker 1: what you're thinking is to simply move your eyebrows up

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Speaker 1: or down. We all know what different eyebrow positions mean,

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Speaker 1: so eyebrows obviously serve a lot of functions for our faces.

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Speaker 1: There's beauty, nonverbal communication, distinctive appearance, the whole water shedding thing.

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Speaker 1: But most scientists are inclined to believe that if we

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Speaker 1: didn't have eyebrows, something else would have evolved to help

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Speaker 1: the situation. For example, humans could have developed incredibly thick

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Speaker 1: eyelashes to shield out excess sweater rained or our skulls

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Speaker 1: could have continued to protrude so that they formed a

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Speaker 1: ledge above our eyes. Rain or sweat would then drop

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Speaker 1: from that ledge, straight away from our faces without going

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Speaker 1: into our eyes. For more on this and thousands of

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Speaker 1: other topics, visit how stuff works dot com and don't

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Speaker 1: forget to check out the brain stuff blog on the

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Speaker 1: how stuff works dot com home page. You can also

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