[Neithan]

I think that both the feminine and the masculine were just different parts of Eru's mind, which I think is part of what Ka was getting at.
Just a note on feminine roles in mythology, the very first primitive civilizations often worshiped women figures (often times a women leader of the tribe) for fertility. Women are the symbol of fertility so from this came the concept of "Mother Earth". In those times these mother figures were the most important in mythology because people needed crops to survive. Later mythology was largely taken over by men (in Greek mythology mother earth's husband and later her male children gain power over her, this was probably the Greek's way of shifting from the female dominated religion to a male dominated one). In most mythologies there was still a remnent of that "mother figure" representing fertility (Demeter). In Tolkiens mythology Yavanna seems to fill this role. Of course that is not the only role in mythology for women, but it is the one role that is almost always played by a women.