Tuatara All the Way Down

Hey guys!

Joe here.

I've been thinking a lot about change.

There's a saying: Nothing endures but change.

Of course there's an exception to every rule.

There are some living things on Earth that have been around a really long time and don't seem to have changed much at all.

The Ginkgo tree, platypus, echidna, coelacanths, nautlius, horseshoe crabs... and of course: the tuatara, the sole remaining member of a branch of reptiles that originated 200 million years ago.

[OPEN] And today I'm here at the Dallas Zoo, because I'm gonna meet one.

Let's go find a tuatara.

Hey!

Amber?

Nice to meet you.

Mice to meet you too!

So it's really just your job to hang out with awesome reptiles all day?

All day, every day!

We're here to see one special one.

One special one.

The tuatara.

Take me to the tuatara.

Real quick, some context: During the Project for Awesome livestream, John Green and I said that if we hit a fundraising goal, he'd ride a tiny rocking horse...and I'd make a tuatara video.

So here we are.

Joe is a man of his word.

Back to the zoo... Tuatara?

Tuataaara?

So this is the legendary tuatara.

The plural of tuatara is tuatara.

And they look like lizards but they're not lizards, right?

Correct.

So, way back in time.

Tuatara and its lineage comes off here.

And these all become?

You have like lizards, snakes.

So they're a reptile but not a lizard?

Correct.

When the Gondwana supercontinent split apart beginning 180 million years ago, these lonely survivors were isolated on islands that would one day become New Zealand, which probably protected them from much competition until humans showed up around 700 years ago.

So millions of years ago there would have been a lot of reptiles like this around, but now they're the only ones left?

All your friends are dead!

I'm so sorry.

They have very basal, primitive features that haven't changed in millions of years.

That's why people call these "living fossils"?

Living fossils!

We're gonna have to have a little talk about that word.

"Living fossil"...

I'm not a huge fan of that term.

For starters, it's an oxymoron.

Fossils are dead.

That's how words work.

Unless they're zombies... "Living fossil" implies they're something evolution forgot.

And that couldn't be further from the truth.

Even Darwin realized that natural selection didn't always mean change.

If a species has been molded to be successful in its environment, without a new challenge, it can survive that way for long time.

By this definition, we could be considered a living fossil too, because we don't look all that different from when our species branched off.

And while "living fossils" might be slowly evolving in shape, that doesn't mean they aren't changing on molecular level.

Scientists have found that some tuatara DNA appears to be evolving even faster than most mammals.

Evolution didn't leave these creatures behind or forget about them.

They're a success story!

"Living fossil" doesn't really give them a lot of credit for winning for so long.

But there is one way that "living fossil" is a good name: Fossils, in the ground or surviving on some island in New Zealand, can tell us a lot about how evolution has played out, so we can understand how life came to be like it is today.

But all that aside tuatara are definitely weird, in a TON of ways, which makes sense for something that's kinda been doing its own evolutionary thing for the past 200 million years.

For starters, their teeth aren't really teeth.

They're pointy bits of skull sticking out of their jaw, they even have multiple rows that interlock like little mouth saws...

He looks nice, but you you wouldn't want to get bit by a tuatara... You definitely wouldn't want to get bit by a tuatara.

Since their teeth are never replaced, they wear down as they age.

Elderly tuatara end up eating soft foods like slugs and larvae That's just like people, right?

Our diets get all soft as we get older.

Right!

As we get older we're just like the tuatara.

They don't have ears, but they can still hear.

Their hearts and lungs... super primitive.

They're also the only true diapsids, they have these two big holes right here in their skull... which doesn't sound important, but it's a huge deal to paleontologists!

Tuatara have one really cool feature that nothing else in the world really has.

It's called a parietal eye, and it's kind of on top of its head, if you can see it right there.

There are cornea, there's lens in there, there's even really primitive rod structures.

And there's a nerve that attaches right to the brain.

So it can sense differences in light and shadows.

Yes, you heard that right.

They've got a third eye right smack in the middle of their forehead.

Many other lizards and frogs have them too, but that eye is more developed in tuatara than in any other species.

It might not be easy to see from the outside, but its skull shows right where that nerve feeds into the brain.

This is already cool, but you and I share a small remnant of this extra sensory system.

We think tuatara and other non-warm blooded animals use their extra eye to sense the length of the day.

It communicates with an area of the brain that helps set its internal biological clock: day, night, and seasonal cycles.

Well, deep inside our brain we find the same structure, the pineal gland, which we also use to sense night and day, and tell us when it's time to sleep.

We don't have a third eye, but we do share something just as cool.

What up, cuz?

Semi-related!

And in case you're wondering how you make a baby tuatara... you guessed it.

That's weird too!

They're kind of special in the fact that they don't have outward sex organs.

And the other cool thing about them is they're actually temperature sex-determined.

So females are gonna be produced at lower temperatures, and males at higher temperatures.

Here's a trait where tuatara are joined by many other reptiles, and even some fish.

But it makes creatures like these especially sensitive to climate change.

Shifts in temperature could throw off the whole population ratio... Obviously females are very important in producing... You need both!

You need both to make more tuatara.

Don't worry man, we'll see what we can do.

What all this shows us is while these quote/unquote "primitive" reptiles yes, are very weird, that weirdness has made them winners in the game of evolution.

I mean, if it ain't broke, don't evolve it!

So, spolier: Tuatara are a major character in Turtles All The Way Down, a story about fitting in.

But it's kind of a funny animal to put in the middle of your story So, why'd you do it John?

I think the main reason I chose to write about tuatara is that even though they haven't changed body forms much is 150 million years and they do everything incredible slowly they also have this really fast rate of molecular evolution and I thought that reflected something about Aza she's not changing much on the outside necessarily, but inside there's this constant teaming change Living fossils aren't species that are about to expire.

They aren't leftovers that are just as good dead as alive.

They're important today, for a lot of reasons.

Every living thing on Earth has value.

Because they've all played a part in each other's story, and everything that's ever lived is a success.

But out of all these valuable things, I think a few can teach us something special about life: how it was, how it is now, and how it got to be that way.

Maybe they don't exactly "fit" in.

But they're survivors.

And in a sea of change, they keep shining just a little bit brighter.

Like a tuatara.

Get it?

It's literally change!

Stay curious.