Good morning, John.

This is kind of a dream come true for me.  Recently, we started a residency at SciShow for newer science communicators.  The idea, basically, is for four or five months, you get paid to be a part of our editorial team,  pitching and writing and editing scripts. And then, at the end, we fly you out to Missoula  and you host those episodes.

It's always a little bit scary to do new things,  but our first resident, Jaida Elcock, finished her residency recently  and absolutely everyone loved working with her and I loved hanging out with her.  I also had an idea for something I wanted to do while she was in town because I am obsessed  with what makes a good fact. Unsurprisingly, probably. I've been writing facts for, like, 20 years now, and it used to be that I just went by feel,  which is, of course, fine, but the same way you can dissect a punchline and understand  what makes something funny, you can dissect a fact to try and figure out  why it's working on people and what makes it good.

Now, a good fact doesn't really have to be  anything more than interesting. Of course, what adds up to interesting  is very complicated and probably worth discussing at some point, but interestingness does not make  for a great fact on its own.  A great fact is both interesting and it uncovers something true about the world or about the person  learning the thing, something that is complex and hard to either understand or internalize,  or that changes how you see the world after you know it. So combining that thought with the fact that I am so lucky that I get to hang out  with lots of science communicators, I wanted to start asking people  what their best fact is.

And so here it is, Jaida's best fact,  followed by my best shark fact. You may never see the world the same way again.

Hank: What's your best fact?

Jaida: I think my best fact, which of course, is going to be a shark fact.

Hank: I should have said,  Jaida is a shark scientist.

Jaida: Yes.

Hank: What is that? A thresher shark on your earrings?

Jaida: Thresher sharks on my earrings, because thresher sharks are my favorite.

Hank: I wore a fish shirt.

Jaida: I do appreciate the Fish Drip™.  Something that I think  people find very shocking is,  you find out that the largest fish on the planet is a shark. It is the whale shark.  The largest one ever recorded, I think, was somewhere around 61 feet long.

Hank: What's that in, like, bowling alleys?

Jaida: Bowling alleys?

Hank: Like a lane.

Jaida: How long is a bowling lane?

Hank: I don't know! You don't have stored in your head the length of a bowling lane?  60 feet.

Jaida: Oh, okay, so a bowling lane! Think of a bowling lane and that is the largest shark.

Hank: That's a long way.

Jaida: Ever recorded, though. The average is closer to, like, 35. Still, yeah,  not a small shark. You find  out that the largest fish  on the planet is 40 feet long and a shark, and that is immediately terrifying to people.  People have, like, a very healthy fear of sharks, like, I understand that healthy fear.  I always say, we cannot  let the fear get in the way  of the respect, though, that we need to have.

Hank: I will say, I also have an unhealthy fear of sharks in addition to the healthy fear.

Jaida: Wait, why? What? How so?

Hank: Because I just, I'm in a lake and I'm like, what if there's a shark?

Jaida: Well, bull sharks swim in freshwater, so.

Hank: I don't think they got to Montana.

Jaida: However, one has been found  so far up the Mississippi,  like, it was in Illinois.

Hank: What? There's Illinois sharks?

Jaida: There was at one point.

Hank: They should name a minor league baseball team after that guy.

Jaida: You see this huge  shark. It is a filter feeder.  Its teeth are no more than  a couple centimeters long  and it can't swallow anything bigger than, like, a grapefruit, maybe even a quarter,  because all they eat is phytoplankton. Also, the whale shark being—

Hank: Phytoplankton meaning “plant plankton”.

Jaida: Sorry. No, no, I meant zooplankton. But they do also eat sargassum,  which is like a seaweed, so they are the second identified omnivorous shark species on the planet.

Hank: Oh! After?

Jaida: The bonnethead shark.

Hank: I'll put a picture of that there.

Jaida: Your smallest hammerhead species, they eat seagrass and they, like, actually digest  and get nutrients from it.  They thought in both cases  that it was just like,  incidentally ingesting something  while they're eating other things and like, oh, they'll just pass it,   it's fine. But no, they're actually breaking it down and getting nutrients from it,  so they're considered omnivores. The thing that comes with this fact is, the more knowledge  you have about something, the  less typically you fear it.

Hank: Right.

Jaida: Understandably, a lot of people are afraid of sharks. If you've seen Jaws—

Hank: They're very mysterious.

Jaida: Yeah! Jaws jumping out of the water and eating seals and stuff and you're like,  I don't want to be that  seal, and I totally get that.  But then you learn that there are sharks that are omnivores or filter feeders that,  even if they wanted to,  physically cannot swallow you,  and I feel like that kind of  eases the fear just a little bit.

Hank: So you get in the water with whale sharks?

Jaida: Yes.

Hank: Have you ever been worried that you might accidentally get into one of their mouths?

Jaida: No, I just don't swim  directly in front of their face.

Hank: Do you want to know my best shark fact?

Jaida: Yes.

Hank: This is gonna sound  like the fact on its own:  sharks are less related to  bass than bass are to humans.

Jaida: Mm-hmm.

Hank: So, like, humans and bass have a closer common ancestor than bass have with sharks.

Jaida: Yep.

Hank: I don't know. There's,  Osteichthyes is the bony fish.  Do you know what the cartilaginous…?

Jaida: Chondrichthyes.

Hank: Chondrichthyes.

Jaida: Mm-hmm.

Hank: Okay. Of course you know that. There's more to being a bony fish than just being  a bony fish, and one of those things is scales.

Jaida: Right.

Hank: So just like mammals have, like, a four-chambered heart and they have hair  and they have placentas. Many  of them, not all of them.  What else do mammals have? They—

Jaida: Mammary glands.

Hank: They have—that's the big one. *laughter*

Hank: So there's all these, like, things that  mammals have in common, and there's also lots of things that bony fish have in common,  and they have scales. Cartilaginous fish don't have fish scales.

Jaida: Right.

Hank: They have something else.

Jaida: Mm-hmm.

Hank: But they do have scales, kind of. They're not called scales. They're called dermal  denticles. Dermal means “skin”.

Denticle means “teeth”—

Jaida: Yeah.

Hank: It means, like, little teeth thingies. And that's not because they look like teeth  or they function like teeth, or they're, like, smooth like teeth. It's because they're teeth.  Our fingernails and our skin and our hair are all made of the same stuff. It's all made of keratin.  In the same way, sharks, when faced with the need for, like, a protective skin covering,  instead of evolving a separate thing, used the same biochemical mechanisms  to create skin teeth that have, on the inside,  they have dentine, and on the  outside, they have enamel.  It's just teeth.

Just like our teeth, chemically, they're made of the same stuff.

Jaida: Yes. They have skin teeth. And I love saying that to people   and watching them completely panic.   They're like, what does that mean? I'm like, allow me to explain.

Hank: And they also, like, they grow new ones.  Just like, they would, like,  replace their mouth teeth,  they replace their skin teeth.  And once they get bigger,  they have to make more of  them to fill in the gaps.

Jaida: And also whale sharks, another whale shark thing, they have them on their eyeballs.

Hank: What?!

Jaida: I believe that this was discovered in 2020, somewhere around there.

Hank: Recently, somebody was like, has anybody put a whale shark eye under a microscope ever?

Jaida: My hypothesis, it's probably for protection of their eyes as well. Protecting from,   like, pathogens and parasites and whatnot.

Hank: The reason this is my best fact of the day, it shows two things about evolution.  One, you can solve the same problem in different ways. Oftentimes, evolution converges.  So, like, scales, they are  both kind of like scales  in that they're these little  skin protective things,  but it arrives at the solution very differently. But also, evolution reuses stuff.  So in the same way that  our skin is made of keratin  and our hair is made of keratin, that seems kind of normal to me  because I'm exposed to that idea. I'm aware of it.  But it seems very unusual that you could do the same thing with something as specific as a tooth.

Jaida: As teeth, yeah.

Hank: And that, like, skin teeth could happen,  but it's just reusing a bunch  of mechanisms it already  had to build a specific structure, but build it in a different way to achieve a different purpose.

Jaida: Yeah, oh, my gosh, wow. Evolution just,  she impresses me every day. I don't know, sharks are just the coolest,  and there's so many of them, they fill so many different niches. There's some in the tropics,  there's some in the Arctic, there's fast ones and slow ones and big ones and little ones.

Hank: And there used to be one that could eat an orca in five bites.

Jaida: Yeah.

Hank: And a person in half a bite.

Jaida: I want the megalodon to still be alive.

Hank: You're the only one.

Jaida: Probably. Jaida, thank you so much for letting the team at Complexly experiment on you,  it's been a delight to get to know you. Complexly, which is our educational media  company, is always trying to figure out how to do cool new things in the world  and also how to invest what we can in the next generation of science communicators.  If it's not clear, we take the responsibility of making educational content very seriously.  Like my shirt says, good information is worth it.  And you can get this shirt if you support Complexly during the Learn-a-Thon.  Also, I'm doing a trivia night on the last day of the Learn-a-Thon, but in order to participate,  you have to donate $15. You can find out more about that and other Learn-a-Thon events  at complexly.com/learn.

John, I'll see you on Tuesday. Also, report from today! This video has now been filmed on three  different days, and now it's Friday, and I gotta get this video uploaded.  But Jaida, I said at the beginning of this video, doesn't have a YouTube channel, but she does!  She started one and has a video of the two of us answering fish questions on it right now!  I'll put a link in the description or maybe on the end screen.

Is that a thing?  God, I never use the end screen. Is it there now?  Maybe. Okay, bye.

Jaida: Channel my Inner Furby.

Hank: Uh-huh. *laughter*