Because females are the superior gender. No really. Everyone starts as a female in the womb. "For the first several weeks a developing embryo follows a 'female blueprint,' from reproductive organs to nipples," explains LiveScience . "Only after about 60 days does the hormone testosterone kick in (for those of us with a Y chromosome), changing the genetic activity of cells in the genitals and brain. But by then those mammary papillae aren't going anywhere." Girl power.