How the Squid Lost Its Shell

Published on Apr 17, 2018
The ancestors of modern, squishy cephalopods like the octopus and the squid all had shells. In ancient times, their shell was their greatest asset but it eventually proved to be their biggest weakness.
Special thanks to Franz Anthony for the beautiful cephalopod reconstructions. You can see more of Franz's tremendous work at
And thanks as always to Nobumichi Tamura for allowing us to use his wonderful paleoart:
Produced in collaboration with PBS Digital Studios:
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  • Bringing class to US-tv!

  • Evolution is amazing, probably took millions of years for a mollusk to fart in his hat and become the first cephalopod.

  • The fact that it‘s not nautili but nautiluses makes them very cute.

  • Great episode! Good work. I find it fascinating that even early animal life used blood to transport nutrients etc. around the body. I would really like to see an episode on the evolutionary history of blood.

  • This channel is really amazing. Well made, interesting and with a touch of humor. Along with that, in this video they show baby Cthulhu at christmas time ( plectronoceras). Love it.

  • Gonna go eat some calamari

  • Damn man I never watched a video here and wasn’t expecting to see hank but damn he’s on every science channel.. big fan

  • 635-541 million years ago?! Does anyone else see this imaginary number or am I the only one that thinks that these numbers are overexaggerated?

  • Its the SciShow Guy!

  • Very interesting. You could have touched upon the modern giant squid as an apex predator.

  • Very educational and enjoyable :-)

  • this is very detailed and exact i wonder how people know this

  • How did the one that broke off its shell survive long enough top develop that trait?

  • I'm still waiting for proof of evolution taking "millions of years" to happen.

  • I eat a lot of squid .....but when i see there face i cant help but think there ao adorible and how it would be nice to have one as a pet

  • Do one on the evolution of the different human races and their strategies please

  • i keep learning more from youtube than i ever did in school....boy times have changed. fantastic video. you my friend have a new subscriber.

  • Now I feel like eating sushi

  • Amazing video, thank you!

  • So nice to hear things measured in metric..

  • Hey my house is made of limestone but I found shells like the ones you mentioned in your video

  • And the cuttlefish has a cuttlebone inside. I assume that's the same internal vestigial shell that squid and octopuses have. And now they've evolved the use of electric cars (eg. Elon Mollusk).

  • Didn't realize I was watching scishow, hank.

  • he said octopuses. TRIGGERED

  • The slug stole it. Now thats why snails are slow.

  • Does this apply for Octopus aswell? Since they are considered a Molluscs

  • with how intelligent octopus are, it wouldn't surprise me that they overcome humanity one day. considering the fact that they learn everything from birth since their mother dies before they are born. Heard there was a colony somewhere where the adults are now coming together in groups and teaching their young. How will that impact their misunderstood intelligence?

  • mr.greem

  • Squids must be absent-minded.

  • Nice music underneath!

  • its's thE CAMBRIAN EXPlosion

  • I've always wondered this. Thank you so much!

  • Arms race? C'mon just stick to natural selection, an arms race is only applicable to war mongering humans really.

  • But Mr Green but Mr Green! Wait.....wrong Green.

  • Science is evolving.

  • 6:45 Non-Alien dinosaurs? Were there Alien Dinosaurs? Did I miss something?

  • Octopuses can edit their DNA like any other species in the world, but they are the only ones that can edit their RNA ;)

  • 💜

  • Is... is that John green. I honestly can’t tell?

  • Isnt he also in sci show? 😂

  • I'd like to see something about Eurypterids aka Sea Scorpions.

  • I thought this was going to be a story that explains why squids are the way they are


  • 6:16 octopi

  • Funny, I had always assumed the rise of plant life on land (leading to a sudden spike of oxygen in the atmosphere and a subsequent cooling of the earth) was the reason that there were so few nautiloids and reason squid, octopus, and cuttlefish evolved? At least I read that somewhere else. Can anybody answer definitively if that is also part of what caused this leap in evolution or was it just due to the prey/predator arms/defence race?

  • Wow

  • Im watching PBS on purpose... What happened to me?...

  • why did they develop, or when, they developed the ink mechanism?

  • make a video about Paleobotany


  • siphuncle sounds like if you put simon and garfunkle together

  • Why is it that nothing comparable to megaladon has existed for thousands of years? It seems like a pretty big gap to fill and yet it hasn't been. How come there's nothing that hunts whales on a regular basis?

  • So they made a reverse-weight belt to rise up? that is awesome! like making your own balloon without gas canisters!

  • Funny how I never imagined the molusc --> cephalod transition. After this video it seems so obviou now

  • PBS Eons? What is this?

  • 7:26 Onward my brethren!

  • This makes me want to buy Cthulhu flavored ice cream

  • How did chameleons learn to change color?

  • New favorite channel. Great stuff

  • Any video with one of the Green brothers is a video I'll watch.

  • WAIT. HELLO, HANK. Didn't expect to see you here.

  • how do nautilus survive the bone crushing depth?

  • very interesting stuff, the only issue is the way it's told... It's like the Squid had a choice... "chould i grow the shell inside? what would be better?" thats now how evolution works... and he knows that.. I gess it's just to make the story telling more appeling, but i don't think it's worth it.

  • THANK YOU for saying ''killed the non-avian Dinosaurs'' instead of saying like most ignorant science channels ''killed the dinosaurs''. There's a huge difference and I appreciate that some channels take science seriously.

  • How bout Enantiornithines??

  • Summary: Fish- "You see those cephalopods? They have lame shells, they will never do anything interesting with those." Cephalopods- "Hold my beer..."

  • Good? That's an understatement. This channel is great! Seriously, great content and GREAT presentation.. Just subscribed!!

  • Imagine being the first cephalopod to float. Just minding your own business, pumping your blood. suddenly you start to feel light headed, and the next thing you know, you’re floating away into the sky.

  • I am here because of Splatoon

  • Squids are the cutest

  • Beautiful!

  • Why didn’t the shells offer protection any longer?

    • Instant Win I believe it was because of several factors but at one pivotal point when "they" start to evolve away from the floating shells and the floating shells, they began to curl their shells, or break them off at the end so they won't be so big and easier to maneuver. They accomplished this by coating the end of their shells, with their bodies to soften them.. I believe that's where they started to loose their shells.. I may be wrong but that's what I concluded from watching the video. Anywho. Excellent question. I won't believe the answer can be summed up in a single sentence. Again, I could be wrong. Instep believe every question deserves a satisfactory response so.. I hope this helped! 😂

  • NGYES~!

  • Zoidberg approves this video

  • i'm all for evolutionary adaption; but it just makes me chuckle when credit is given to the the animal.. how they intentionally directed their own change and not just being a passive passenger within their own evolution... What i would like to see is the *science behind evolutionary adaption*. Where's the anatomical physiology mutation for those type of changes to happen. Yes, many many many years have gone by how can animal and plants "do" the changes to their bodies?

  • Open up some random youtube recommendation and surprisingly Hank's there.

  • I scroll down to see if anyone's gonna mention his pronounciation of 'develop' lol xD I like the video tho very informative...but i find it very funny the way he said develop lol anyone?? Edit: well as I progress the video, I realized it wasnt just the word 'develop' , it was the letter L :P

  • 0:27 Excuse me, but where am I on that list?

  • Informative, though you make evolution sound too purposeful. It wouldn't hurt to emphasize that random mutations ended up giving the edge.

  • The narrator kept describing the evolutionary process as if it was something the animals were doing. I realize it's easier to describe that way.

  • good video but lets cut the dialogue that suggests the animals "chose" to evolve such adaptations. they were the subjects of environmental adaptation, not the artists of their own adaptations.

  • Selection bias, we're far more likely to get fossils of creatures with shells than soft squishy creatures. This is all just speculation.

  • So we are assuming we know that this thing evovled. No true evidence, but since it looks like a modern squid- and you cant find specimens to prove this transition than I guess we all have to believe you. Even though there are no animals who are evovlving today we will believe what a man says happened billions of years ago when no one was around. Men cant solve basic world problems, but they are 100% positive that they know this.

  • Do a vid about oarfish pls

  • 6:38 OH NO! Its the asteroid!

  • From hot air balloon to ram jet.

  • It fell off.

  • oh, and give that squid a mirror please.

  • you know, there really hasn't been any real research into seals as in ancient fossils. can you see if it is worth pursuing?


  • Squidward bought his shell

  • But when did the squid become a kid?

  • Science

  • "Octopusses"

  • "Can our D.Va switch to Genji?"

  • Evolution is amazing! I love learning more about it.

  • It’s the cambrian explosion! **KABOOM!!!!**

  • squid have shell but it soft :)

  • I've never been so inspired by a squid

  • I love how these videos never feel rushed. Even from other educational channels it sometimes feels like all the information given is very vague or things are brushed over while other things are repeated more times than is necessary. I especially appreciate that you don't usually do the "this time period happened. Here is an animal from it, we'll give you a name and literally nothing else" thing that a lot of channels seem like they do. I really like that you spare at least a little description for most things its nice