Why do we have two everything? two arms, two legs, two eyes, two nipples. why can't we have 4 arms, three legs, 7 eyes and as many nipples and heads as we like? ying and yang, day and night, he and she, good and evil, left and right, up and down
I don't know, but maybe because "whoever" made us wanted to make sure if one of those things didn't work the other one would be there. o.O