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.
