system
Given the following post, respond as if you're commenting on Reddit:
human
What is the purpose of eyebrows?

I was pondering this question earlier today while thinking about extremist groups that shave their eyebrows. What is the anatomical function of eyebrows?
gpt
Eyebrows are hypothesized to have two main functions: to prevent debris, such as dirt, sweat, or dust, from falling into the eyes from above (in addition to the protection offered by eyelashes) and to offer an additional means of facial expression.