There's no evidence, seemingly, but intuition tell us that the black burka is a symbolic statement. A symbolic statement does not have a functional purpose, meaning the burka doesn't have a functional purpose, such as keeping the Sun off the body. Black burka's attract ultraviolet sun rays so they should be very hot in a very hot land. No, this is not it's symbolic meaning.

It's meaning seems to be an analogy to black space, that virgin, female purity which the Creations male principle impregnated, to create matter. So the black burka "represents" the dark, black, virgin, pure, hidden void of outerspace. So today, Muslims demand that the hidden female wear it to represent empty, black, pure space.....kinda stupid if you ask me.

As for the mens headdress? I don't exactly know but it probably stems from the ritual of covering the head when entering the "Holy Places" as a symbolic sign of respect and honor for the unknown spirit, or before reading from a silly book.