Why Couldn't Evolution Delete Sleep?

Tonight you'll switch yourself off for hours: deaf, blind, basically a snack with a pillow. 😴 Evolution took your tail and most of your fur, so why did it never delete sleep? Even jellyfish sleep, and they don't have a brain. We follow evolution's four attempts to delete sleep: dolphins sleeping with half a brain, frigatebirds napping in mid-air, penguins taking 10,000 naps a day, blind cave fish, a teenager who stayed awake for 11 days, and the night crew in your brain that simply refuses to be fired. Your turn: if you could safely delete sleep, would you? Team Delete or Team Pillow? 👇 CHAPTERS 0:00 Why didn't evolution delete sleep? 0:40 Project: Delete Sleep 1:17 Even jellyfish sleep 3:07 Attempt 1: half-brain sleep 4:17 Attempt 2: sleeping in tiny pieces 5:57 Is sleep just rest? 6:53 Attempt 3: the short sleepers 8:17 Attempt 4: no sleep at all 10:03 What sleep actually does 12:13 Recap 12:33 Tonight, remember the jellyfish SOURCES (full details in our research notes; key papers below) • Anafi et al. 2019, Nat Rev Neurosci 20:109 • Siegel 2008, Trends Neurosci 31:208 • Nath et al. 2017, Curr Biol 27:2984-2990 • Jung et al. 2011, J Physiol 589:235 • Vyazovskiy et al. 2011, Nature 472:443 • Shaw et al. 2000, Science 287:1834 • Hendricks et al. 2000, Neuron 25:129 • Raizen et al. 2008, Nature 451:569 • Kanaya et al. 2020, Sci Adv 6:eabb9415 • Lyamin et al. 2008, Neurosci Biobehav Rev 32:1451 • Mukhametov et al. 1977, Brain Res 134:581 • Lyamin et al. 2017, Curr Opin Neurobiol 44:144 • Rattenborg et al. 1999, Behav Brain Res 105:163 • Rattenborg et al. 2016, Nat Commun 7:12468 • Max Planck Society press release 2016 • Libourel et al. 2023, Science 382:1026 • Associated Press 2023 • Kendall-Bar et al. 2023, Science 380:260 • UC Santa Cruz news 2023 • Gravett et al. 2017, PLoS ONE 12:e0171903 • Krueger et al. 2016, Sleep Med Rev 28:46 • Duboué et al. 2011, Curr Biol 21:671 • The Scientist 2011 • North et al. 2025, iScience 28:113940 • Jaggard et al. 2018, eLife 7:e32637 • Nunn & Samson 2018, Am J Phys Anthropol 166:601 • Science News 2018 • Samson & Nunn 2015, Evol Anthropol 24:225 • He et al. 2009, Science 325:866 • Shi et al. 2019, Neuron 103:1044 • Lloyd et al. 2025, eLife 13:RP99191 • NPR 2024 • Gulevich et al. 1966, Arch Gen Psychiatry 15:29 • Guinness World Records 2023 • Vaccaro et al. 2020, Cell 181:1307 • Harvard Medical School news 2020 • Everson et al. 1989, Sleep 12:13 • Rechtschaffen et al. 1983, Science 221:182 • Rechtschaffen et al. 2002, Sleep 25:68 • Newman et al. 2008, Physiol Behav 93:50 • Xie et al. 2013, Science 342:373 • Miao et al. 2024, Nat Neurosci 27:1046 • The Transmitter 2024 • de Vivo et al. 2017, Science 355:507 • Tononi & Cirelli 2014, Neuron 81:12 • Wilson & McNaughton 1994, Science 265:676 • Aguillon et al. 2026, Nat Commun 17:3 • Rasch & Born 2013, Physiol Rev 93:681 • Lesku & Rattenborg 2022, Sleep Adv 3:zpac036 • Lesku et al. 2012, Science 337:1654 • Rial et al. 2023, Neurosci Biobehav Rev 146:105041 Please don't try staying awake for days: it's dangerous, and Guinness stopped tracking that record for a reason. Illustrations made with AI image tools, then selected and edited by hand. Voice-over: CapCut text-to-speech. #science #sleep #evolution