The topography of teeth

Ancient human teeth can tell us a lot. Hidden inside each set of teeth are clues about their owner’s behavior and ancestry as well as what really made up the paleo diet. Shara Bailey, Associate Professor of Anthropology at New York University, reads the topography of teeth to better understand the origins and lineages of humans.

TRANSCRIPT

Ancient human teeth can tell us a lot.

Hidden inside each set of teeth are clues about their owner's behavior and ancestry, as well as what really made up the Paleo diet.

Shara Bailey, Associate Professor of Anthropology at New York University, reads the topography of teeth to better understand the origins and lineages of humans.

Our partner, 'Science Friday,' brings us the story.

Who are we?

Where do we come from?

What makes us human?

Shara Bailey looks to answer those questions by peering into the mouths of ancient humans.

My specialty is in the dental morphology or the bumps and the grooves and the shape of teeth.

I'm interested in when we get the teeth that we recognize as being distinctly Homo sapiens.

Locked inside our teeth are secrets of our past.

Teeth are 98 percent mineral in content already.

Teeth are basically fossils in your mouth.

A lot of what we know about evolution of organisms is based on the teeth.

Sometimes, it's the only thing that preserves.

And the information Bailey and other researchers uncover from looking at pearly whites pieces together the origins of early humans going back to when humans and chimpanzees split from a common ancestor around 6 to 8 million years ago.

One key difference is recorded in the fangs or canines.

They become more diamond-shaped.

Other clues are more subtle.

In reading the topography of teeth, Bailey can reconstruct details of their owners' lives like behavior, location, and even their last meals.

If you run your tongue along your molar teeth, you'll feel little bumps.

Those are called cusps.

In leaf-eating primates, their cusps are very high, and they shear against one another, right, like scissors.

Flat cusps work more like a mortar and pestle, and pointed teeth used for grinding nuts or seeds.

Counting cusps can give indication about origin.

Most people have five cusps on the lower molars.

Four cusps point to places with a long history of agriculture like Europe and India.

Six cusps are often counted people with Asian ancestry, and an extra cusp on the tongue side, cusp seven, may point to Sub-Saharan African ancestry.

Now move your tongue behind your top two front teeth.

Do you feel deep ridges?

That could indicate northeast Asian or Native American ancestry and could also be accompanied by ridges on the front of the teeth.

That's called double shoveling because it looks like a coal shovel, and that's where they get the name.

And a link between Native Americans and Northeast Asians is very clear when you look at the teeth.

Zooming in closer, a scanning electron microscope reveals fine scratches and gives clues on a month of meals.

And going deeper, you can look at the growth lines of the enamel, which researchers can read like tree rings.

You can tell how fast an individual grew their teeth, which some people think reflects how fast they grew in general.

Bailey looks at how all the bumps, scratches, and features combine to piece together information about early humans, and her work can put her in the middle of debates about our origins.

We like to think that we're really special, and so it's like... Because we're here, and Neanderthals aren't, right?

So why is that?

Was it diet?

Was it that we killed them off?

Were we smarter?

When archaeologists discovered a site in Southern Italy from 41,000 years ago, around the time Neanderthals went extinct, containing some of the earliest art and tools, there was a debate about the culture that created them.

Was it Neanderthals or modern humans?

It's, like, one of these transitional tool industries, and so the question is -- what were Neanderthals capable of?

What were their minds like?

And the only way you can get in a Neanderthal mind, because we don't have brains, is by what they left behind, what they were doing.

Scientists didn't have many remains to go by, just a few teeth.

We looked at all the teeth, and they're all, you know, they're modern human.

Not Neanderthals.

The cultures that created the earliest art and tools represent a shift in human evolution and likely led to the demise of Neanderthals in the area.

And Bailey was called again when researchers found a site with remains of a specimen nicknamed 'The Hobbit.'

The question was -- Is this a new species, Homo floresiensis?

I was called in to go look at the teeth.

I did, and be honest to you, I looked at the molars, and I'm like, 'They look kind of modern.'

I mean, they have four cusps.

You know, there's nothing really remarkable about the upper molars, but there's the lower-third free molar.

There's your first bicuspid.

That's what the dentist would call it.

It's like nothing I've ever seen in all, you know, all the modern humans I've looked at, even the fossil hominids.

It has, like, three roots.

It has an extra weird cusp.

The shape of it is, you know, kind of odd, but it's really just the whole way it's put together is completely unique.

The teeth support this as being a different species.

Recently, Bailey examined a set of baby teeth which helped determine that remains found in 2015 were from a new species, Homo naledi.

But despite so many differences, early human and Neanderthal teeth have one surprising thing in common.

They'd get a good report from dentists today.

You know, I look at all these fossil teeth, right?

There's no dentists back then, and they're perfect.

They're beautiful.

You start looking at teeth after agriculture gets adopted, and their teeth just, you know, go to hell in a handbasket.

There are cavities.

There's abscesses.

They're just... They're disgusting. [ Laughs ]

Now that's some history you can sink your teeth into.