Why do humans have eyebrows? It seems that it isn't necessary but only humans have them, correct? So what is the use of them for humans? I hear that they protect our eyes. However, isn't that what eyelashes do? What other functions do eyelashes have?
Eyebrows function to protect the eyes from perspiration and provide shade.
Eyelids function to protect the eyes from foreign objects and sunlight.
Eyelashes function to protect the eyes from foreign objects, produce sebum (a lubriant that the eyelids) and acts as protection for the eyes from tears .
However, note that biologist dont have any concrete reasons for the eyebrow. This is just what many of them agree on I suppose. Here is another resource from sciencefocus.