It's a topic that's taboo in many cultures, yet it's also something nearly every woman experiences – on average upwards of 400 times throughout her life: menstruation.
Responding to a flood of questions from our CrowdScience listeners, Marnie Chesterton seeks to unpack how periods affect women physically, mentally and societally.
Why did humans evolve to have periods when fewer than two percent of mammals share our experience of menstrual cycles? Is it really a good use of our limited energy reserves? What can the little Egyptian spiny mouse teach us about PMS symptoms? We hear why periods may reduce the number of faulty embryos that implant and how more menstrual cycles may even increase our chances of developing certain types of cancer.
Finally, as the number of periods a woman has over the course of her life has more than quadrupled since the pre-industrial era, Marnie asks: Do we really still need to have them? Contributors: Dr Nadia Bellofiore, Hudson Institute of Medical Research at Monash University Dr Deena Emera, Buck Institute Lameck Kiula, Jambo for Development Sally King, Menstrual Matters & King's College London Dr Diana Mansour, New Croft Centre & Newcastle University
Presented by Marnie Chesterton Produced by Sam Baker and Melanie Brown for the BBC World Service