what is inside your dental plaque?

Probably not, but people like me do.

I'm an archeological geneticist

at the Center for Evolutionary Medicine

at the University of Zurich,

and I study the origins and evolution of human health and disease

by conducting genetic research

on the skeletal and mummified remains of ancient humans.

And through this work, I hope to better understand

the evolutionary vulnerabilities of our bodies,

so that we can improve

and better manage our health in the future.

There are different ways to approach evolutionary medicine,

and one way is to extract human DNA

from ancient bones.

And from these extracts,

we can reconstruct the human genome at different points in time

and look for changes that might be related to adaptations,

risk factors and inherited diseases.

But this is only one half of the story.

The most important health challenges today

are not caused by simple mutations in our genome,

but rather result from a complex and dynamic interplay

between genetic variation,

diet, microbes and parasites

and our immune response.

All of these diseases

have a strong evolutionary component

that directly relates to the fact

that we live today in a very different environment

than the ones in which our bodies evolved.

And in order to understand these diseases,

we need to move past studies of the human genome alone

and towards a more holistic approach

to human health in the past.

But there are a lot of challenges for this.

And first of all, what do we even study?

Skeletons are ubiquitous; they're found all over the place.

But of course, all of the soft tissue has decomposed,

and the skeleton itself

has limited health information.

Mummies are a great source of information,

except that they're really geographically limited

and limited in time as well.

Coprolites are fossilized human feces,

and they're actually extremely interesting.

You can learn a lot about ancient diet and intestinal disease,

but they are very rare.

(Laughter)

So to address this problem,

I put together a team of international researchers

in Switzerland, Denmark and the U.K.

to study a very poorly studied, little known material

that's found on people everywhere.

It's a type of fossilized dental plaque

that is called officially dental calculus.

Many of you may know it by the term tartar.

It's what the dentist cleans off your teeth

every time that you go in for a visit.

And in a typical dentistry visit,

you may have about 15 to 30 milligrams removed.

But in ancient times before tooth brushing,

up to 600 milligrams might have built up on the teeth

over a lifetime.

And what's really important about dental calculus

is that it fossilizes just like the rest of the skeleton,

it's abundant in quantity before the present day

and it's ubiquitous worldwide.

We find it in every population around the world at all time periods

going back tens of thousands of years.

And we even find it in neanderthals and animals.

And so previous studies

had only focused on microscopy.

They'd looked at dental calculus under a microscope,

and what they had found was things like pollen

and plant starches,

and they'd found muscle cells from animal meats

and bacteria.

And so what my team of researchers, what we wanted to do,

is say, can we apply

genetic and proteomic technology

to go after DNA and proteins,

and from this can we get better taxonomic resolution

to really understand what's going on?

And what we found

is that we can find many commensal and pathogenic bacteria

that inhabited the nasal passages and mouth.

We also have found immune proteins

related to infection and inflammation

and proteins and DNA related to diet.

But what was surprising to us, and also quite exciting,

is we also found bacteria

that normally inhabit upper respiratory systems.

So it gives us virtual access to the lungs,

which is where many important diseases reside.

And we also found bacteria

that normally inhabit the gut.

And so we can also now virtually gain access

to this even more distant organ system

that, from the skeleton alone,

has long decomposed.

And so by applying ancient DNA sequencing

and protein mass spectrometry technologies

to ancient dental calculus,

we can generate immense quantities of data

that then we can use to begin to reconstruct a detailed picture

of the dynamic interplay

between diet, infection and immunity

thousands of years ago.

So what started out as an idea,

is now being implemented

to churn out millions of sequences

that we can use to investigate

the long-term evolutionary history of human health and disease,

right down to the genetic code of individual pathogens.

And from this information

we can learn about how pathogens evolve

and also why they continue to make us sick.

And I hope I have convinced you

of the value of dental calculus.

And as a final parting thought,

on behalf of future archeologists,

I would like to ask you to please think twice

before you go home and brush your teeth.

(Applause)

Thank you.

(Applause)