Interesting, I've seen the symbols for Mars and Venus being used to represent genders, but not a square or triangle for male.

As for zero/circle/woman and one/vertical line/man.. I guess in my mind, they couldn't be more obvious, universal and simple - to put it crudely: the hole and the stick.

But also: off and on, dark and light, absence and presence.

(So far, I have found no historical evidence that supports the above theory, no basis in logic or fact. I'll leave it as idle speculation on a possible primordial/mythological way of thinking in pictures, with perhaps two of the most primitive symbols.)