teachnically we do. before humans had evovlved the purpose for our periods was to emit a scent that made the guys go crazy and it would attract them into having with us thus making babies. two things you probably didnt know was that you still have that scent and it still makes guys more attracted to you,but we r civilized ot the point tht they wont just like mount you ahhaha and 2, something you probly allsoo didnt know, when a group of girls to live together thier period cycles will actually change so tht they coordinate with one another. before civilization this was handy cuz the girls would travel in a pack and have one male for the group, then their periods would arrange and well yeah so tht groups season for mating would be the same so any guys they passed were like all and ahhahahah weirddd but this shows just how we are basically just animals, only with bigger brains and stuff. we stil have our instincts and wat not (like how if a baby is crying the mother will splurge milk out... trustt mee i know how thatt onee iss) ahahahha just another instinctt