Rose Eveleth joins the show to talk about chromosome testing in the Olympics. Plus, Claire returns to talk elite tug-o-war, and Rachel talks about the leech that can fly. Listen to Rose's new show, Tested: https://link.chtbl.com/js0J2gTx The Weirdest Thing I Learned This Week is a podcast by Popular Science. Share your weirdest facts and stories with us in our Facebook group or tweet at us! Click here to learn more about all of our stories!  Links to Rachel's TikTok, Newsletter, Merch Store and More: https://linktr.ee/RachelFeltman  Rachel now has a Patreon, too! Follow her for exclusive bonus content: https://www.patreon.com/RachelFeltman Link to Jess' Twitch: https://www.twitch.tv/jesscapricorn -- Follow our team on Twitter Rachel Feltman: www.twitter.com/RachelFeltman Produced by Jess Boddy: www.twitter.com/JessicaBoddy Popular Science: www.twitter.com/PopSci Theme music by Billy Cadden: https://open.spotify.com/artist/6LqT4DCuAXlBzX8XlNy4Wq?si=5VF2r2XiQoGepRsMTBsDAQ Get 20% OFF @honeylove by going to https://honeylove.com/WEIRDEST! #honeylovepod Keep track of what’s important with Tile. Visit https://Tile.com today and use code WEIRDEST to get 15% off all Tiles.  Live it up this summer and make progress towards your financial goals with Chime. Open your account in minutes at https://www.chime.com/WEIRDEST Learn more about your ad choices. Visit podcastchoices.com/adchoices