Why Don't Humans Have Tails?

Every mammal you've ever loved has one. Your dog. Your cat. The monkey you laughed at in a documentary. And for the first nine weeks of your life, before you were even born, you had one too. In this video, we dig into the genetic science behind why humans lost their tails — covering the 2021 NYU study that identified the exact genetic mutation responsible, the CRISPR mouse experiments that proved it, the surprising hidden cost that came with the trade, and the physical evidence still sitting at the base of your spine today. ⏱️ TIMESTAMPS 0:00 – Every Mammal Has One 0:40 – The Nine-Week Embryo Reveal 1:00 – Back to 25 Million Years Ago 2:15 – The Genetic Mutation (Bo Xia, NYU 2021) 4:00 – The CRISPR Mouse Experiment 5:30 – Why the Tail Became Expendable 7:15 – The Hidden Cost (Neural Tube Defects) 8:45 – When the Tail Doesn't Disappear 10:00 – Apes vs. Monkeys: The Evidence 11:30 – The Barbary Macaque Exception 12:30 – The Proof at the Base of Your Spine 📚 SOURCES Xia et al. (2021), New York University — genetic study identifying the Alu element insertion in the TBXT gene responsible for tail loss in apes and humans, including CRISPR mouse-model validation. Comparative primate genetics research on ape vs. monkey tail morphology. Documented medical literature on vestigial human tail cases. 🔔 New videos on human history, behavior, and the science behind everyday things — every week.