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Have you ever been in a museum, staring down a mounted T. rex,
and feeling incredibly grateful that it’s not around any more
because each of those teeth are the size of a banana?
I’m asking for a friend.
Fossilized teeth have way more value than just inspiring awe,
and sometimes terror, in museum visitors.
They can tell paleontologists a lot more than you’d think
about the evolutionary past, from a creature’s diet
to when humans started to develop tools.
So, here’s what makes teeth a paleontologist’s best friend.
Teeth are hard, compact, and already have a layer of mineralized
tissue called enamel on the outside.
This makes them an almost perfect specimen
for preservation in the fossil record.
In fact, tooth enamel is one of the hardest biological substances around.
And enamel isn’t just protecting a tooth during an animal’s life,
it’s preserving its history for millions of years.
Part of that history lies in the shape and size of all the little nooks
and crannies that make up a tooth’s shape.
There are the big differences between teeth, like how square,
smooth molars help some animals munch all day on grass
while sharp fangs help others bring down prey.
But there are also more subtle similarities
and differences in tooth anatomy between closely related species.
These anatomical features are passed down
or evolve through generations, meaning paleontologists
can map tooth surfaces like a landscape to start building family trees.
In some cases, teeth might be the only fossils researchers have to
work with in figuring out who’s related to whom, since teeth keep so well.
And if they look even closer, scientists can see more signs
of how an ancient creature lived.
Because, if you think about it, teeth are the only parts
of our skeleton that interact directly with the environment!
Every time an animal munches on, say, a leaf,
tiny bits of silica from the plant’s cells are dragged
across the tooth’s surface leaving a trail of microscopic scratches behind.
Or, if it’s gnawing on a nut, the hard chunks pound
microscopic pits into the tooth.
Paleontologists call this a foodprint, and it tells them what an animal ate,
at least in the weeks leading up to its death.
But that’s still a really valuable source of dietary info.
Sometimes, researchers might find tiny micro-fossils or bits
of preserved food that got stuck on the teeth,
which helps them confirm their suspicions.
And teeth can tell paleontologists more than just
what was going on in the mouths of ancient animals.
They can give us clues about other parts of their bodies, as well.
Take ancient humans for example. Like the rings of a tree,
scientists can count the growth lines in their enamel
to get a sense of a person’s age or health.
See, as teeth mature and develop, new layers of enamel are laid down
through a process called amelogenesis.
As that process speeds up or slows down, it leaves bands in the enamel.
And because this happens in a 24 hour cycle,
those growth lines can show how old a prehistoric human was
when they died. Kind of like tree rings, but for days instead of years.
Since your teeth stop growing eventually,
it tells us the most about an individual’s juvenile years.
/Defects/ in that growth can also show that a person was sick,
stressed or malnourished during a particular time of their lives,
since those things affect how well teeth can lay down new enamel layers.
In 2022, scientists used teeth from primates in the fossil record
to model how early humans grew during pregnancy.
The big brains of anatomically modern humans take some time to grow.
The researchers showed that the proportions of a species’ teeth
are related to both its brain size, and how long it takes
to develop in the womb.
So by studying the proportions of teeth from different primate species,
researchers could predict when early human brains
started to evolve to be bigger.
And that’s not the only way our teeth changed as we evolved.
As early humans started to develop tools and cook with fire,
that was reflected in their teeth.
For example, teeth evolved to become smaller
as we started cooking with fire,
since the heat was doing a lot of the food
breaking down for us, not our chompers.
Teeth from early humans like Australopithecus are relatively large teeth,
whereas those from Homo erectus onwards were much smaller.
Which lets you guess who’s cooking.
Plus, you can see the evolution of tool use
in the wear patterns on ancient humans’ teeth.
Neanderthals, for example, used their teeth basically
like an extra hand to hold onto hides as they cut them.
Or they softened wood by chewing on it,
or used their teeth to hold onto leaves while weaving.
And all that grasping and biting left different patterns of scratches
and scrapes on their teeth, which paleontologists can now decipher
to get a glimpse of prehistoric life.
Early humans continued to use their teeth
as a kind of extra tool for a while,
but as their hand-held tools became more advanced,
they used teeth less and less,
and the teeth even shrunk as a consequence.
So ancient teeth are pretty darn amazing for reconstructing not
just what happened in the mouths of prehistoric animals,
but what their lives and interactions were like.
And that makes them the perfect fossils for
researchers to sink their teeth into.
Now, if researchers had only found teeth from animals
that cooked their food, they wouldn’t know about all of this tooth evolution.
And that would have just come down to a sampling problem.
But, luckily for us, there are resources on the internet, like Brilliant,
that teach us more about sampling bias.
Their course on Sampling is a great place to start drawing
more accurate conclusions about a population.
This course starts with an intro to sampling and estimation,
and by the end, you’re learning about the nuances of error and bias.
In just 9 lessons, you’ll know what makes a truly representative sample
that reduces bias and helps draw more
broadly informative conclusions about the world around you.
To get started today, head to Brilliant.org/SciShow
or click the link in the description down below.
That link will give you a free 30 day trial and
20% off an annual premium Brilliant subscription!
And thanks for thinking critically with Brilliant and SciShow.
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