Abby Tang: You are the first person
to see a bit of Sue's blood vessels.
Jasmina Wiemann: Yes. Abby: That's rad.
Jasmina: And you're going to be the second.
[Abby laughs]
It's this hollow
branching shape. Abby: Yes, yeah!
That Sue in question is Sue the T. rex,
and we're about to see proof that she was warm-blooded.
We went to the Field Museum
to see how they work their magic.
Our first stop was ...
So, here is our dinosaur and oversize collections.
Abby: That's Jingmai O'Connor, and she --
you know what? I'll let her tell you.
Yeah, I would say I'm one of
the world's experts on Mesozoic birds.
Not to brag or anything. Nah, I'm just kidding.
Abby: And one of the key questions she asks
with her research is why birds were the only dinosaurs
to survive the Cretaceous-Paleogene extinction.
We need to look at birds,
and then we need to back up from birds
and look at the dinosaurs closely related.
I think it's kind of funny,
but we have a drawer full of bits of Sue.
When you have the edge of the puzzle,
that's the easiest part to do, right?
The inside of the puzzle is harder to put together.
So these are like the inside puzzle bits.
You can't figure out where they go,
but this is to our advantage,
because these are the type of fragments
that it's OK for us to do destructive analyses on.
Abby: The destruction of these rare
and one-of-a-kind fossils
can involve slicing or dissolving in acid.
Slicing allows the scientists
to study specimens histologically.
You have to cut a piece of the bone, remove it,
grind it down so it's really thin
so that light can pass through it
so you can study it under a microscope.
It's a cost-benefit analysis essentially, right?
What are the questions you're trying to answer?
Is it worth it to damage
this extremely rare, important fossil?
Abby: To show me how it's done,
they demonstrated with a prehistoric bird bone.
Jingmai: You're going to bring it to,
in our case, Akiko Shinya.
She's our chief fossil preparator.
She's amazing.
Abby: Akiko starts by taking
a small slice of the specimen.
Jingmai: You then take your little chunk of bone
that you've removed, and you drop it into resin.
And then this needs to cure for several days.
I mean, can you imagine playing Dungeons and Dragons
with dinosaur dice? Abby: Dungeons and Dinosaurs.
Oh!
Exactly.
Abby: Then you glue your D6 to a microscope slide
and slice it down even more.
I did a terrible job with the saw.
I almost destroyed everything with the saw, actually.
I feel like I'm pushing too hard.
Akiko: It's OK. Abby: OK.
[yelps]
I did it.
Abby: At this point, it's too small to slice,
so Akiko will grind away extra layers.
Abby: We're listening for that "shoog-shoog" sound.
[shoog-shooging]
The slide ultimately needs to be between
30 and 80 microns thick --
thinner than a sheet of paper.
Akiko basically uses finer and finer grinders,
like varying grades of sandpaper,
to slowly shave off extra layers.
Akiko: Straight down. That's the key.
Abby: I will try my best. Akiko: Yeah, I'll show you.
Abby: You scared me now, though.
There's a polishing stage to smooth out
any major imperfections that might obstruct the sample.
You're not getting away from me!
And a second polish for fine tuning.
This one feels like someone is
pulling carpet out from underneath the block.
Even with your naked eye, you can learn about a specimen.
Here's a piece of Sue's rib,
and you can see how Sue grew
almost like rings on a tree.
You see these faint lines?
Yeah.
Jingmai: Yeah, it'll be much -- Abby: It looks like agate.
Yeah, it'll be much clearer
once we get it under a microscope,
but those are the lines of arrested growth.
Do you want to look in?
Jingmai: And here we're looking into
the rib of Sue the T. rex.
You notice that the space between these lines of growth
is becoming smaller and smaller.
So when it was younger and really having to bulk up, right,
it was growing very quickly.
And as it reaches adult size, growth slows down.
Abby: The thinness of these sections was surprising
because it shows a fast growth rate,
a key indicator that Sue had a high metabolic rate,
meaning she was probably not as cold-blooded
as scientists previously thought.
Scientists also looked at another indicator
of high metabolism, which is actually color.
More diverse colors in a species
tends to mean a higher metabolism.
Jingmai: Here, we are looking at an SEM image
of a sample from a feather
of a 130-million-year-old bird
called Eoconfuciusornis.
Abby: Pre-extinction.
Jingmai: So the only fossil bird
older than this fossil bird is Archaeopteryx.
Abby: A scanning electron microscope relies on
electrons instead of light to magnify even more detail.
Jingmai: And so if you look closely, you'll see these --
this is literally what we call them --
sausage-looking structures.
[Abby laughs]
They are eomelanosomes.
So eomelanosomes are responsible for the color black.
Abby: Melanosomes are organelles found in animal cells
that are associated with different colors.
When they fossilize, they leave behind distinct shapes.
Jingmai: If they're very nicely aligned with each other,
we can tell it's iridescent black.
If they're kind of a more oval-shaped eomelanosomes,
that's gray, and then if it's a phaeomelanosome,
we call these ones meatballs.
Literally, this is like,
in papers, they're like, Abby: Such a delicious science.
"the meatball-shaped ones."
Like, mm, I'm hungry.
The meatball-shaped phaeomelanosomes are responsible
for a rusty red color.
Abby: Many of the genes responsible for melanosomes
are also linked to things that affect metabolism,
so evolving one most likely evolves the other.
And with both meatballs and sausages,
Eoconfuciusornis shows way more melanosome size diversity
than modern-day cold-blooded lizards.
Jingmai: So we can say that the dinosaurs
that are becoming smaller, that are getting
these large extravagant ornamental structures
that are then able to evolve flight
are also becoming more colorful.
Abby: But these melanosomes can only tell us so much.
They're an indicator of warm-bloodedness,
but not definitive proof.
This is where Jasmina comes in.
Jingmai: Everything that Jasmina is doing,
five years ago that didn't exist.
I'm a molecular paleobiologist.
My passion lies within
the clade of dinosaurs including modern birds.
People tend to think of bones and shells
and these kind of heart tissues
that preserve much more readily.
But if we want to get a complete picture
about the diversity of life on our planet,
we really depend on soft-tissue preservation.
Abby: Soft tissue is the squishy stuff like skin,
blood vessels, and other non-bony materials
that scientists didn't even think
could preserve until recently.
So, about 30 years ago,
a vertebrate paleontologist tried for the first time
to extract soft tissues from dinosaur heart tissues.
Abby: Her name is Mary Schweitzer,
and people did not believe her findings.
It was very critically perceived,
and people thought for a long time
that while these soft-tissue structures
very much looked like the original biological structures,
they could not possibly be related.
Abby: But soft tissues do preserve.
Why do they preserve?
This is absolutely paradoxical
based on what was known scientifically
at that point in time.
Abby: You can actually see traces of it under a UV light.
Jingmai: What we're going to do is just shine the light
and look for things.
It looks like some of these may be scales
that are preserving soft tissue.
Not all of them.
Abby: Once soft tissues are suspected,
demineralization will isolate them if they're present,
so you can see the structures.
This is where I got to try something with Sue's bones
that has never been done before.
So, you mentioned that you would like to dissolve
a Sue fragment and help us look for organics.
Every bone is going to have
the tissues that we're looking for
if they are in fact preserved.
But Sue has exceptional preservation,
so we are quite hopeful.
Abby: We're taking this bit of Sue
and dissolving it in hydrochloric acid.
The acid will dissolve any inorganic rock
but leave behind the organic soft tissues.
It's starting to look like a hazy IPA.
Are you seeing anything?
Jasmina: It's all still in suspension.
Abby: Me too. Jasmina: We'll have to
give it a little bit of time.
Abby: After about 15 minutes,
the precipitate settles
and Jasmina pipettes it onto a slide.
Jasmina: From here we go to the microscope.
Abby: Let's go.
Jasmina: Ooh, this is looking good.
Abby: What are you seeing?
Jasmina: We have a couple of
extracellular matrix pieces,
blood vessels, large blood vessel fragments.
Abby: You are the first person to see
a bit of Sue's blood vessels.
Jasmina: Yes.
I was the second person
to see Sue the T. rex's veins.
Right now, take a look.
Abby: OK.
Jasmina: Do you see the blood vessel structures
right in the focus center?
It's this hollow
branching shape. Abby: Yes, yeah!
Jasmina: That is definitely one of the
bone vascular canals.
Abby: [gasps] Oh, I see it real good now.
Hold on.
They've just been in there the whole time!
Jasmina: They've been sitting there
for 65 million years. Abby: Just floating around.
[Abby laughs]
That was rad.
Because we can look at this
of course fascinated by the fact that,
you know, soft tissues preserve in the time,
but there's actually a lot of information
in the molecular composition
of these materials. Abby: Yeah, what can we see?
Demineralization shows us that
there are soft tissues present in a specimen,
including the proteins, lipids,
and sugars that indicate a high metabolism.
But to concretely say
what soft tissues are present
and prove that this vein is really a vein
and that these metabolic stress markers are actually here,
we need to study the chemicals found in the tissues.
This requires a brand-new method:
an application of Raman spectroscopy
developed by Jasmina and her team.
Jasmina: It's the brightest, purest green
that you will ever see.
Yeah, why the green light?
We're using a green light that is exactly 532 nanometers.
That is particularly good for characterizing organics
with many unsaturated carbon bonds.
Abby: It's a nondestructive technique,
so you can stick entire specimens under the laser
without having to prepare them at all.
We popped in a piece of Sue taken from her femur core.
Jasmina: We want to make sure that we're looking at a spot
where we don't have too much surface texture,
where we have a lot of carbonaceous material preserved.
Abby: The laser excites
the different materials in the sample.
And so these chemical bonds, they start to vibrate
in direct response to their chemical environment.
And these very specific little wiggles
are then detected in form of a spectrum.
Now, if we want to, for example,
learn something about the metabolic rate of Sue,
we collect the spectrum for Sue
and for all other kinds of dinosaurs
that have this mode of preservation.
I can show you basically what it looks like
when you compare these different spectra.
Abby: This is Sue's Raman data
compared to data Jasmina got from other dinos.
Jasmina: So every individual line basically represents
evidence of the total composition
of one of the fossils we've looked at.
So these numbers are sort of different wiggles.
Yes.
So you get a different wiggle
at each of these different wave numbers,
and that then evidence is
a different kind of molecular bond vibration.
So a different kind of chemical compound
present in the sample.
Abby: Different compounds tell us different things
about the dinosaur we're looking at.
For example, thioethers,
sulfur heterocycles, and nitrogen heterocycles
in the soft tissues signal high metabolic stress.
We have very high amounts
of these metabolic stress markers
in warm-blooded animals,
and we have very low amounts
of these metabolic stress markers in cold-blooded animals.
This peak here in combination with this peak here
and this one here tells us if we're looking
at a warm-blooded or a cold-blooded extinct animal.
Abby: This wiggle here is proof
that Sue the T. rex was truly warm-blooded.
And it once again changes the story of evolution
that scientists have been telling
and retelling since the early days of paleontology.
It has been suggested that the high metabolism of birds
eventually helped them to better adapt
to the changing environments, the changing conditions
right after the mass-extinction event.
What we basically realized here once we start putting
these new physiological data into context
is that this incredibly high avian metabolism
is actually not an avian innovation.
Abby: It's not just Sue either.
Jasmina's work has definitively found
that most dinos were warm-blooded,
practically upending what was once common knowledge.
I have been coming to the Field Museum
since I was a little kid.
Oh, the Tully monster!
This is my favorite fossil!
I won't get distracted.
Being able to come to the Field Museum
and see how the Field Museum works
was like a dream come true for tiny paleontologist Abby.
The Ab-B-roll.
Producer: Got 'em.
Jasmina: I cannot do inches. I'm European.
[Abby laughs]