Why do female symbols “wear” skirts?

Symbols for woman and man, pictographs or pictorial symbols existed long before the progress of writing and typography started. There are consistently efforts of people to communicate more comprehensive and unique by pictures.

This work looks at gender stereotypes in symbols. I did this project during my internship at Designalltag Zürich. It's mainly about the question: Is it really necessary to picture a womans pictograph with a skirt, to differ assuredly from the man's pictograph?