Why some Indian Buddha statues depict the Buddha having a moustache?

Thank you for the input, it has clarified many things to me, really.

Indeed, I have just looked at the images from Mathura and they appear to be much closer to what I in general see today in Korea or Nepal. A couple days ago I read that the moustache might have been added in order to show the high social position, which the Buddha had in his lay life.