Until recently, scientists assumed humans were the only species in which females went through menopause, and lived a substantial part of their lives after they were no longer able to reproduce. And they had no idea why that happens, and why evolution wouldn’t push females to keep reproducing right up to the end of their lives. But after a close look at some whale poop, and a deep dive into chimp life, we find several new ways of thinking about menopause and the real purpose of this all too often overlooked second act of life. Special thanks to Danielle Friedman, Rachel Gross, and Kate Radke. EPISODE CREDITS: Reported by - Heather Radke and Becca Bressler Produced by - Sarah Qari and Becca Bressler Fact-checking by - Emily Krieger and Edited by - Becca Bressler EPISODE CITATIONS: Books - Check out everything Heather Radke writes, including Butts: A Backstory, cause it’s all that good, here: Heather Radke ( www.heatherradke.com ). It includes short essays, recommendations, and details about other ways to interact with the show. Sign up (https://radiolab.org/newsletter)! Radiolab is supported by listeners like you. Foundational support for Radiolab was provided by the Alfred P. Sloan Foundation.