Visit https://brilliant.org/scishow/ to get started learning STEM for free. The first 200 people will get 20% off their annual premium subscription and a 30-day free trial.
When caterpillars undergo metamorphosis and become butterflies, their brains melt into goop. Neuroscience says they shouldn’t remember anything about their past lives. So why do studies show that they do?
Hosted by: @TomLumPerson
———-
Support us for $8/month on Patreon and keep SciShow going!
https://www.patreon.com/scishow
Or support us directly: https://complexly.com/support
Join our SciShow email list to get the latest news and highlights:
https://mailchi.mp/scishow/email
———-
Huge thanks go to the following Patreon supporters for helping us keep SciShow free for everyone forever: Toyas Dhake, Reed Spilmann, Gizmo, Garrett Galloway, Friso, DrakoEsper , Kenny Wilson, Lyndsay Brown, Jeremy Mattern, Jaap Westera, Rizwan Kassim, Harrison Mills, Jeffrey Mckishen, Matt Curls, Eric Jensen, Chris Mackey, Adam Brainard, Piya Shedden, Alex Hackman, Kevin Knupp, Chris Peters, Kevin Bealer, Jason A Saslow
———-
Looking for SciShow elsewhere on the internet?
SciShow Tangents Podcast: https://scishow-tangents.simplecast.com/
TikTok: https://www.tiktok.com/@scishow
Twitter: http://www.twitter.com/scishow
Instagram: http://instagram.com/thescishow
Facebook: http://www.facebook.com/scishow
#SciShow #science #education #learning #complexly
———-
Sources:
https://docs.google.com/document/d/e/2PACX-1vS7M8rNbzHS5yCNUStp6h_mxi1m_Iu3Fk-x2ox3eTjIJGiLVuqW5esATiNUD2zZ8IeYAslURSwBCZAo/pub
According to all known laws of neuroscience, there is no way that a butterfly should remember being a caterpillar. It melts into goop when it transforms and loses all its brain connections. The butterfly, of course, remembers anyway, because butterflies don’t care what humans think is impossible.
00:14:…No, this entire episode will not be the script of the Bee Movie… sorry about that. Also We actually do know how bees fly, contrary to what a certain movie might tell you. But there’s a real mystery in the insect world: Some insects that undergo metamorphosis can
00:28:remember things from before they transformed. And that really does seem like it should be impossible. Hi! I’m Tom Lum, and for the next week and a half I’ll be hosting SciShow. Holometabolous insects – butterflies, moths, beetles, flies, bees, and others – go through complete metamorphosis,
01:48:where they undergo a drastic bodily transformation by way of a pupal stage. Much more drastic than my teenage change in music taste… It was never a phase mom! And Metamorphosis is extremely common – more than 80% of animals go through some degree of change throughout their lives.
01:05:For insects, this number is more like 98%. Most scientists think it's an evolutionary strategy used to keep the amount of resource competition experienced between parents and offspring to a minimum, since different life stages generally happen
01:19:in different ecological niches and require different resources. But despite how common it is, metamorphosis is bizarre and difficult to study, and complete metamorphosis is especially enigmatic. Because, to be clear, I wasn’t really exaggerating earlier.
02:35:An insect basically kinda turns into gloop inside its pupa. Virtually everything in their body is melted down and reordered. Digestive enzymes consume the vast majority of the cells, which just rupture into a slurry of the basic building blocks of life --
02:51:proteins, amino acids and other nutrients all sliding around together. Complete metamorphosis is cell death on a massive scale, and you might find yourself questioning whether the snot inside a butterfly chrysalis is even a living thing.
02:05:Essentially, the animal's instructions for being a larva have to be turned off completely in order to make way for the parts of the DNA that tell it to be an adult to be turned on. It's a bit like unplugging a microwave, putting it in a nuclear reactor,
02:19:taking the resulting sludge and rebuilding it into a refrigerator, and then plugging it back in. It's a pretty scorched earth version of puberty. A groundbreaking 2023 study teased out the reason complete metamorphosis should leave no memories
03:32:of an insect's larval stage for the adult to reminisce over. These researchers successfully traced individual brain cells and the connections between them through the process of metamorphosis. The authors scoured the mushroom bodies of Drosophila fruit flies –
03:46:that’s the part of their brains in charge of learning and memory. They found there wasn't a single anatomical hook in the adult's brain upon which to hang a memory formed in childhood. They showed that, although individual larval neurons in
03:58:the study survived the process, the neural connections in the mushroom body were completely dissolved and reconstructed. And those connections, as we understand it, are what memories are made of. Therefore, adult metamorphosing insects should have no memories from their larval lives.
03:15:This was a 5-star, top shelf, roundly celebrated study – everybody agrees! Nice job, scientists! Only one little catch: it certainly seems from past research that adult butterflies and moths can totally remember things from before their metamorphosis.
04:31:But before that let’s take a quick pause to hear from our sponsor Thanks to Brilliant for supporting this SciShow video! Brilliant is a learning platform made by people who have put a lot of thought and design into being as effective as possible.
04:42:Everything you interact with on Brilliant was crafted by teachers, researchers, and professionals from MIT, Caltech, Duke, Microsoft, Google, and more. So they know what they’re talking about. But it’s way better than listening to a lecture from one of them because each lesson is filled
04:56:with hands-on problem solving that lets you play with concepts. You know, active learning. You can start building understanding from the ground up at Brilliant.org/SciShow, the QR code, or the link in the description. That link gives you 20% off an annual premium
04:11:Brilliant subscription. And you’ll get the first 30 days for free. A 2008 paper found that the larvae of tobacco hornworm moths could be trained to avoid the smell of ethyl acetate by giving them a mild electric shock whenever they came close to it. When those larvae matured into moths,
04:27:the adult moths also avoided the smell of ethyl acetate. Seems like they remembered their little adventures just fine. Which begs the question: if they don't even share the same brain, how do the lessons of the juvenile carry over into the understanding of the adult?
05:41:The first question we've gotta ask is, what aren't we seeing? One potential confounder here is called the chemical legacy hypothesis, which says that during a certain period of metamorphosis, if the emerging adult is exposed to odors that its larval self had associations with,
05:56:those associations can carry over into its adult life. However, researchers are generally aware of this and do their best to control for it. The authors of the 2023 paper concede that just because a Drosophila fruit fly's memories could never survive complete metamorphosis, that
05:11:doesn't mean it can't be different for insects with more complex brains and a greater number of neurons – like moths, beetles, and butterflies. Because those insects have more complex brains, it could be they don't get the complete renovation the researchers saw in Drosophila.
05:26:However, a 1994 paper trained Drosophila to avoid a specific smell with electroshocks, and the result seemed to be the same -- they remembered to steer clear of that smell as adults. So, why do adults on the other side of complete metamorphosis have childhood memories?
06:43:According to the extremely rigorous 2023 study, it shouldn't be possible. And yet, nature appears to find a way. The authors of the 2023 paper suggest the possibility that memory for metamorphosing insects looks different than we think,
06:57:and is about more than which neuron is connected to which other one. The rearrangement of their brains might even look different depending on the environment they live in. More research is obviously needed, and it could be a while before someone gets there. There appears to be a limited number of
06:11:neuro-entomologists in the world. Anyway, the answer to the burning question of whether adult metamorphosing insects retain memories from before they pupate is– Sure seems like they can! But do we know why or how? Absolutely not! But hey, that just gives us something to work toward.
06:26:I mean, who wants science to be /done/, right? I can only hope that one day we can play jazz for a pupa and ask the butterfly, do you still like jazz?
Watch Now
