TOEFL Quiz 6: Tracking Ancient Diseases Using Plaque
Quiz by: Danielle_BIA

Have you ever wondered 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.


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.


Thank you.

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