Sign of the Old Times

The universal signs for male/female toilets are so familiar that we hardly think about them. But imagine seeing this sign for the first time. Would you have any clue as to what it means? "Stand here, with your arms slightly spread out"? And looking at men and women today, would it be obvious that men go left and women go right? How many women wear knee-high skirts? Which way would a Scotsman with a kilt go?
The more I think about it, the more I realize that these icons should show what you're actually supposed to do. In detail.