[♪ INTRO]
Whoa, Squeaks, what are you building?
[Squeaks squeaks]
That’s so cool!
I love dinosaurs, and pretending to visit them
in a time machine sounds like so much fun.
Your time machine is going to have to go back in time really far to see dinosaurs.
Dinosaurs lived on Earth a long time before there were any people,
so we don’t have any photos, or videos, or stories from people.
Because no one ever saw dinosaurs themselves!
Everything we know about dinosaurs,
and the way the world was when they lived here,
comes from special clues that were left behind and lasted until people could
discover them and try to understand what those clues meant.
[Squeaks squeaks]
Fossils are a great example of a clue, Squeaks!
Fossils are created over many years from leftover bones
and other things from animals long ago, like dinosaurs.
Fossils can form from things like bones, shells, or even footprints!
It’s so fun to take clues like fossils,
and try to figure out what life on Earth was like before humans were around.
[Squeaks squeaks]
That’s a really good question.
Squeaks wants to know,
“If dinosaurs lived before people, did anything live before dinosaurs?”
How about we use your time machine
to explore the first known living thing on Earth.
[Squeaks squeaks]
Let’s start our pretend journey back in time.
I’m setting it to send us back 3.5 billion years ago,
way before people or even dinosaurs.
That’s so long ago, it’s almost as far back
as our time machine could take us in all of Earth’s history!
Ready, let’s go!
[Time machine noises]
Whoa, I think we made it!
Ready to see a clue from the first living thing on Earth?
This is a stromatolite.
[Squeaks squeaks]
It does look like a rock, because it is one.
Stromatolites are special rocks made by cyanobacteria,
the first known living things on Earth.
When you look at a stromatolite, you’re looking at the home of
lots of teeny, tiny living things called cyanobacteria.
They’re so small, you can fit thousands and thousands of them in a stromatolite.
There are probably more bacteria in a stromatolite
than there are people in the biggest city you can imagine!
Stromatolite fossils are the oldest fossils anyone has found.
They’re the first clues about early life on Earth.
We find them in places that had shallow, salty water, like near the ocean!
[Squeaks squeaks]
Good question!
The cyanobacteria actually made the stromatolites themselves,
over a long, long time.
Cyanobacteria live in water, and they make their food like plants do.
They gather nutrients around them and energy from sunlight,
and they put those nutrients together in a process called photosynthesis.
As cyanobacteria sit in the water and make their food through photosynthesis,
they also make a bit of rock called limestone.
A whole bunch of cyanobacteria in one place looks like a mat,
and the limestone the bacteria make gets stuck together
with other pieces of rock that wash up onto the mat.
As the cyanobacteria keep growing up towards the sunlight,
the old pieces of rock form a layer, and then another layer, and then another.
Kind of like they are making a lasagna for their home!
We call all of those rock layers together a stromatolite.
[Squeaks squeaks]
Yeah, that stromatolite fossil has some really impressive layers.
Those layers take an extremely long time to form,
much longer than it takes a person to grow up,
so scientists have to use special tools to
help them tell the age of the different stromatolite layers.
And by figuring out the age of stromatolites, scientists can tell that
cyanobacteria were some of the first living things on Earth!
[Squeaks squeaks]
Yes, even before the dinosaurs.
In fact, dinosaurs are much closer in time to us than they are to stromatolites!
Stromatolites are super, super, super old!
What’s truly amazing is that we still have living stromatolites here on Earth today!
Cyanobacteria still live on Earth, and in places like Shark Bay, Australia,
you can actually go see a living stromatolite!
Scientists seek out living stromatolites to study them.
That way, they can understand what the Earth might have looked like
when cyanobacteria were the only things living on Earth.
[Squeaks squeaks]
Oh wow, Shark Bay is like a time machine.
The stromatolites there help us to imagine life long ago.
Life has changed so much since then,
so we’re really lucky to have stromatolites to learn from even today.
[Squeaks squeaks]
I think learning more about Shark Bay sounds like a fun time, too!
Maybe it would give us ideas about
what time period to visit next in your time machine.
Can you imagine what the Earth might
have been like when cyanobacteria first lived?
What time periods do you want to learn more about?
If you want to keep exploring through time with me, Squeaks, and all of our friends,
make sure to hit the subscribe button below.
We’ll see you next time, here at the Fort.
[♪ OUTRO]