Random Thought #202

How is it that the facial hair that grows on your lip (assuming you're a guy) knows when to stop? All of the other facial hair just keeps growing and growing longer and longer but the hair on your lip just seems to stop. How does it know to do that? I mean, assuming it acted like all of the other hair, you'd have to part your  moustache every time you wanted to eat. Interesting isn't it?