Whales are majestic, awe-inspiring animals. Some species can reach up to 150 tons and take in a living room-sized volume of water in one gulp. They can even dive thousands of feet into the ocean while holding their breath all the way down. It’s hard to imagine that the earliest ancestors of these graceful creatures of the deep were four-legged dog-like animals that lived on land. In his book Spying on Whales: The Past, Present, and Future of Earth’s Most Awesome Creatures, paleontologist Nick Pyenson examines their evolutionary story.

Plus: Think back to your sex ed class in school. Chances are you were introduced to lots of new jargon too: Terms like spermatozoa, oviducts, chromosomes, germ cells and gonads. It was that last word, gonads—and a researcher who referred to them as “magical organs”—that sent Radiolab producer and host Molly Webster on a quest to respark our fascination with embryonic development, X and Y chromosomes, and reproduction. The first few episodes of the limited-run series called Radiolab: Gonads are out now, and Molly joins Ira here to talk about it.

And Sophie Bushwick, senior editor at Popular Science, joins Ira to talk about the James Webb Space Telescope and other news from the week in science, including the FDA’s approval of a marijuana-based medicine,  the discovery of a nursery for manta rays, and research into just how wiggly the tongue of a T. rex actually was.