I read an interesting theory that humans have periods because our fetuses are so resource hungry . Pregnancy is a very costly process for a human and a lot of women used to die from it before modern medicine . The idea is that periods are meant to weed out the weak . A lot of pregnancies end before they even really begin , if the embryo doesn ' t implant properly and doesn ' t continually excrete the right hormones , it gets eliminated . We can ' t afford to do this pregnancy thing for a baby that might not be healthy . <| sep |> Funnily enough , I googled Satya Nadella ' s address and figured if I emailed that it would probably be filtered and sent to someone else , and it worked haha . Google for his email address and then use that one , I ' ll post it once I get home on my SB , my phone is a bit useless for emails !