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Wherein we explore tiny skeletons and adaptive evolution.


The Brain Scoop is hosted and written by:
Emily Graslie

Created By:
Hank Green

Directed, Edited, and Scored by:
Michael Aranda

Assistant Editor:
Stefan Chin

Francisco Balzarotti, Katerina Idrik, Martina Šafusová, Hervé Saint Raymond, Tony Chu, John-Alan Pascoe, Seth Bergenholtz, and Kelleen Browning helped provide transcriptions for this episode! Guys, you're awesome.


Michael Aranda: This episode of The Brain Scoop is brought to you by a wondrously generous contribution from Heather Hsu.

(Brain Scoop intro plays)

Emily Graslie: The Chicago Field Museum is one of the largest and most respected natural history museums in the world.  Join me as we go behind the scenes!  Dun dun dun!

Bill Stanley: Because of the nature of the collection that we have, all of these old, wild-caught specimens, and you can put a zoo specimen of the same species in amongst the wild-caught and it stands out like night and day.

Emily: Yeah, yeah.

Bill: In terms of shape and excess bone and all of these weird-

Emily: Oh.

Bill: Missing teeth.

Emily: Yeah, abscesses.

Bill: Yeah, it's ick.

(Transitional music.)

 Numbering Specimens

Bill: Andria is our go to person for numbering bones. We would love to give you a demonstration on how fine she puts a six digit number on a skull that's about that size.

Emily: I would love to know because I have demolished a couple pygmy shrew skulls.

Andria: So these are not numbered yet.

Emily: What?

Andria: For something this small, I would do-

Emily: gracious!

Andria: The pelvis and the limbs.

Emily: What?

Andria: And the scapula. What's usually the most important things to number are each side of the mandible and the skull. Researcher's most likely going to look at the skull first.

Emily: Mhmm. Wow.

Andria: So.

Emily: Feels like watching magic happen.

Andria: And if the pen's working fine, then it just takes that. But if- Also if the bones are really greasy, using a larger pen where the ink will flow out a little bit quicker works better. And usually, with, uh, something that's pretty greasy, I'll write the number out once and it will be really diluted and you won't be able to read it very well and then I'll write over it again.

Emily: And what do you do if you screw up?

Andria: I'll use a scalpel and scrape the ink off once it's dry or I will use alcohol and like a Q-tip.

Emily: Ok, rub it.

Andria: I can wash it off and just let the bone dry. Um, and so for the skulls, our rule of thumb is to put the skull facing to the left.

Emily: Mhmm.

Andria: And imagine it as a- a grid with four quadrants and we put the number in the lower right.

Emily: But you just put it in a little pill capsule.

Andria: Yeah. So little pieces that are just going to get lost, like under the piece of paper, end up going in a little pill capsule. Um, and then the pill cap will get numbered.

Emily: I swallow things bigger than that.

Andria: And this guy's-

Emily: You're not gonna-

Andria: Legs are-

Emily: You're not even going to do that.

Andria: His legs are being-

Emily: I don't even believe you right now.

Billy: Hey, look at those nails.

Emily: I know, it's wonderful. It's like you were anticipating this.

Andria: Other systems of writing are different than ours, so sometimes the numbers are always on the other side or they're always written at an angle or-

Emily: Oh, weird. Yeah.

Andria: Or stuff that you don't really think about until you see it.

Emily: Yeah! No, I thought about that too. When I first started numbering, I was like "What? Where do you write the number on a femur?" I'm sure if you came to our collection, you would be horrified because sometimes I'm just like "Eh! 26835 or whatever!" and just shoof! Wherever!

Andria: Well, especially when the bones are, like, big-

Emily: Yeah.

Andria: You could theoretically write it anywhere you want, but having like a system of like always writing in the same place-

Emily: Consistency is key.

Andria: Is nice. Like, it's not always going to look the same from one animal to the next.

Emily: Yeah. It's amazing. You've got some skills. I'm really impressed. That was really sweet.

(Transitional music.)


Emily: So many cabinets! What are these? What's in here? I'm so excited.

Billy: What's in here?

Emily: Seals! Are these seals and sea lions?

Billy: Seals have multiple cusps on each tooth, right?

Emily: Yeah.

Billy: You see like three or four points on each of those teeth?

Emily: Mhmm!

Billy: This is a harbor seal and this, uh, these points, these cusps, uh, would allow this seal to grab a salmon and grip it and it wouldn't get away. Like a tight end has little points on his gloves so he can catch the football. And that's a characteristic that's found throughout all the phocids, uh, they have cusps on each tooth.

Emily: Mhmm.

Billy: But there is one particular phocid that has those cusps, but evolution has left them with a morphology that makes them use those cusps in a completely different fashion than the harbor seal. Ready?

Emily: Mhmm. It's happening. Oh, what? Is this a crabeater seal? That's awesome. They have the weird Christmas tree teeth.

Billy: And? What do they do with them?

Emily: They filter for krill.

Billy: Emily, you're the best.

Emily: That's amazing! You can see all the details on all the- urg, why? How can this happen?

Billy: So they, they take a mouthful of water, close their teeth, and then squeeze the water out through their teeth and filter out all the krill, all the the small, microscopic quote unquote "crabs." They're actually invertebrates. But, uh, and that can sustain them! And it's the most popular seal in the world.

Emily: That's amazing!

Billy: Found only in Antarctica.

Emily: Yeah.

Billy: So the same thing that sustains hundreds of thousands of these guys also sustains the one hundred foot long blue whales.

Emily: Wow.

Billy: All in Antarctica.

Emily: That- I can't even- I don't even know how this happens.

Billy: Lobodon carcinophagus. Lobed tooth, crab lover.

Emily: That's a pretty accurate name for these guys. I want teeth that look like that.

Billy: Yeah.

Emily: How long- How long would it take for me to, like, adapt and grow a pair of those?

Billy: So, I don't know. But if I come back next week, and these teeth are gone? If I see the next episode of Brain Scoop and you're wearing some necklace with crabeater teeth on them?

(Closing theme.)

Emily: It still has brains on it.