Okay, hello and welcome back to Ask an
Archaeologist, I'm Sara Kansa the host of
this afternoon's show and Ask an
Archaeologist is a series of live stream
interviews, co-hosted by the
Archeological Research Facility and the
Phoebe A. Hearst Museum of Anthropology that we're putting together for Cal Week
2020, which is this week. Each day this
week at 11:00 and 2:00 we're interviewing
a UC Berkeley archaeologist and
answering audience questions. So before
we start the interview today, I wanted to
let you know how you can ask questions.
If you open a new browser window and go
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type your questions and we will see them
and ask them later on in the interview
and I'll remind you of this part way
through the interview as well. So, um,
afternoon we're happy to have AJ White
with us, who is going to talk with us
about what we can learn from studying
ancient poop. AJ is a third-year graduate
student at UC Berkeley and he uses fecal
molecules to reconstruct ancient
population changes. He's also interested
in how climate change has impacted
people in the past. He has worked in
Egypt, Vietnam, the United States, Jordan
and he is currently working in his
living room,
so welcome AJ, thanks for joining us so
I'm sure the burning question on
everyone's mind is: How did you get into
this particular area of research? Yeah
you know it wasn't something that from
you know day one, you know, I was like
dead set on it. I think in archeology
you kinda have to keep an open mind for, you
know, what opportunities are out there
and when I started grad school at Long
Beach State before coming to Berkeley
for my master's in geology my advisor
there had said "hey, check out this cool
paper that uses fecal molecules to
reconstruct the ancient population
change, um what do you think about it? Do you
think this is something that, you know,
maybe we could do?" and I thought about it
and I was like you know there's like a
huge kind of emptiness
in terms of like what we can do with
poop and archeology. And I mean for a
long time people have looked at coprolites, which is, you know, essentially
fossilized poop or incredibly hardened
poop but there hasn't been a whole lot
done on the at the molecular level and looking at you know what remains when, you know,
everything breaks down except for
a small amount of these incredibly
persistent molecules and I just thought
hey that's like a huge kind of place
that we could go and check it out and
and we tried it out at a place called
Cahokia in Illinois and it worked really
well. I've since then tried it out and
Jordan it's been a little, a little not
as well, but we can get into exactly why
that is, and I think it's good to talk
about, you know, why some thing's work or
don't, but yeah, it's something that kind
of fell into my lap and I'm glad I did
because I think there's a lot of things
that we can do with poop. I think that's
fascinating because you know when we
think about archaeology we think of all
the more, you know, the finds that are
harder like bones, and pots, and that kind
of thing, and we don't think of the
molecular things that you could study
and that's much more recent research
that's being done. Can you talk about how
how do you find these traces, where do
you find them? Do you have to find an
ancient toilet do you have to go to a
place where you know people were going
to the bathroom, or were these
things everywhere, or how does it work? Well
yeah so don't think it's super gross, I
mean the first thing that people think
is that I'm actually going out there and
just like scooping up some poop,  you
know, just getting it. It's not like that,
so we're talking about poop that has
almost completely gone away. The way
to imagine this is that there's a time
before toilets right and there's a time
where people are mostly practicing what
we call open defecation which means just
going out and doing their business like
you're camping. And so when that happens
you know there's poop on the landscape
out in nature and after it rains or
something like that, it'll break it
up into little tiny pieces and a lot of
those tiny pieces will
eaten by microbes, but there are certain
little tiny pieces of poop that microbes
find incredibly unattractive, just like
we find all the poop unattractive,
microbes find a little bit of it, these
very complex molecules that are very
rigid, in particular they're the
breakdown product of cholesterol and as
you all know cholesterol is something
that's hard for us to break down it gets
you know caught in our arteries and
causes big problems so the same idea
it's very difficult to break down and so
they just leave it. And so it's a
molecule, the specific molecule
is called a coprostanol and is something
that, because the microbes don't want it,
it just lasts in nature for a very long
time. Now it's very hard to kind of, if
you were to just go out to an
archeological site, and this is an
area where you know before toilets, which
until, you know, that was actually much of
human history until, like past couple
hundred years really, it'll be hard to
just guess where people went to the bathroom
right? You know you'd be very lucky if
you just put your shovel in and that's
where he found his molecule. So to get
around that, we target areas where these
might have collected after being washed
away by rain and so if you're in
somewhere where there's like a lake
nearby, that's a catchment. That's an area
where stuff naturally just gets
deposited and so we target lakes,
wetlands, low places where the idea is
maybe only a small fraction of what was
originally, in you know, one stool will
make it in, but it's still something and
,you know, we go and meet you know collect big sediment cores, which are, you know,
columns of mud and then you can look at
how much of these molecules are present
any depth and there is, hey you know if
we have more at position X and it's more
than position Y and the problem is there
are more people here. And if you're lucky,
you can tie that into maybe there's a
migration story in the area and like oh
that's, you know, that's when it happened.
That's when people came here, or maybe
it's the opposite maybe you can see what
people leave. So yeah that's the idea
it's not actual poop, it's very specific
molecules that might accumulate in
specific environments. Great, and so I
know you had a recent paper that came
out in American Antiquity? That's correct yeah.
Yes, that about your work at Cahokia on
this, could you explain a little bit,
about how that looks like?
Sure thing, yeah. So we first went out and
you know went to Cahokia. And by the way
Cahokia, for those who aren't familiar with
it, is like one of the biggest
archaeological sites in this country.
It's home to dozens of these monumental
mounds and to make dozens of monumental
names you need a lot of people. So it's
thought that this area was a city that
you know, maybe, was home to several tens of thousands of people. And what we did
is we went in, right outside Cahokia there's a lake, and we collected sediment from
that lake and did the process I just
explained, you know, identifying where
these fecal molecules are in the mud and
then trying to link that back to the
population in Cahokia and I did
what I think 99% of most archaeology in
the area does, which is I immediately
went to what's called the Mississippian
Time Period, in terms of where my
brain went and that's the time period
where most of those mounds were
constructed, when much the people were
there, there's a whole lot to say about
and there's really great research if
you're interested on on the
Mississippians you're gonna have a lot
of fun learning about this stuff it's
totally fascinating, but the thing is
that there is stuff that happened after
Mississippian Time Period that very few
people have written about. We know for
sure that there were that there's an
Indigenous presence in the area at the
time of European contact because the
French missionaries established a
mission at Cahokia, like actually on the
site and there's almost no
archaeological presence of this very
limited and there's no archaeological
evidence that's been put forward of to
where the people that were living who
were to be associated with this mission
and it must have been enough people to
justify going all the way down there and
building a mission so we know there's a
substantial amount of Indigenous people
around this area but there's very little
research behind it so what we did is we said
hey we don't have archaeology but we do
have this equals stable population
reconstruction and it doesn't just
disappear at 1400 AD, there's 300 years
of additional demographic changes. It
looks like we do hit a low period after
the Mississippian occupation, which is
why everyone talks about
but around starting around 1500 AD the
population numbers from our data seem to
go up, modestly, not a whole lot, but they
go and the idea is maybe that's when we start
to see the movement of this population that was present at the time
of European contact which we think is
probably a group of the Illinois
Confederation who were called the
Cahokia and that's how Cahokia got its
name and so we're able to kind of tie
that into this whole very under
discussed aspect of the local history
I mean it's generated, you know, it's one
of those things we're like "how much can
you say without archaeology?" and I'd
like to say that you can, you know, there
there is a story to be had even if we
don't have stuff that's that our eyes
can see in the ground there's stuff in
the ground that we can't see that still
leaves a record so that was kind of
the fun thing about it. And can you
explain why there is an archeology
during this time when there are
actually people there? yeah I've tried to
it depends on how much you believe me.
What my interpretation of this is that
the two different Indigenous groups that
were present this area at different
times, you know, the Mississippians, under
you know, the traditional period of Cahokia
and then those came after, which are
likely the Kokia which is a member of
the Illinois Confederation it's very
confusing, I'm sorry for that, but they
had very different life styles and so
during the Mississippian period this was
people who were extremely sedentary, so
sedentary that they were building you
know giant mounds that were as big as
the Great Pyramid of Giza, in terms of
their base, it's not their height,
but the point is it's big. And you
compare that to the Illinois peoples and
they were mobile, you know, they
were semi-sedentary so they'd go on
these long bison hunts in the summertime
where the groups would get together and it'd
be this big outing and the point is
they're not where they are for the rest
of the year and so maybe they're big
camps that are being built in the fall
or the spring. In the winter you know
resources are more scarce people would
go off to live in small family groups.
When you're in the winter and a small
family group, it's just, you know,
maybe eight people
I'm gonna guess you know a small number
of individuals. You're not
producing as much archaeology, you know,
the less people that are in any sort of
spot you're not going to be leaving as
much stuff behind it's gonna be a lot
harder to see and so Mississippian stuff
is obvious it's a it's a giant mound you
know you're gonna find it. Stuff from the
later time period might be a little more
subtle, and I think it either is stuff
that hasn't been found, it's stuff that's
been destroyed by a fair amount of post
1900, just, expanse. This is right outside
the city of St. Louis so there's been a
lot of just highway building, housing
development, stuff like that and finally
I wonder if some stuff that might be
from this time period has been dated
Mississippian just because. If you don't
have diagnostic artifacts and you find
like a, you know, a small scatter of chipped
stone you might think "oh well everything
else is Mississippi, and I'm going to
checkbox Mississippian" and go on with
your survey. I mean, that's super, I can't
master speculative but I wonder if there
might be a little bit of this kind of
little recording bias go on. So yeah I
mean I could I could go on with my
theories, but I hope that gets the idea across. Well let's pause for a sec to remind listeners on YouTube that
you can ask questions by going to Sli.do.
S-L-I- dot D-O and typing in askarf and
you can pose your questions there, and
we'll see if AJ can answer them, but in
the meantime, can you talk a little bit
about how animals, do they produce this
too and can their poop get in the mix
and mess things up? Absolutely so the
what I just told you about, you know, this
whole method is relatively new, in terms
of using these molecules for population
estimates, and there's always a
point where you know the methods looking
great and then everyone kind of realizes
"Okay here are the imperfections, here the
the places where it kind of has a fair
amount of limitations" is one of them, is
what you just mentioned, is that humans
aren't the only ones that make these
molecules. Now for everything that I've
seen in the literature, humans make way
more coprostanol than anything else. On
the average of, you know, ten times as
much. But there are certain animals, they
tend to be large domesticated animals
that we've tested, things like sheep and
pigs, cows make a little bit too, will
produce a little bit and so the point is
how can you tell whether they're dealing
with a city of cows in the past or a
city of people? And there's certain kind
of ways around this, and Cahokia we were
able to kind of make the argument that
okay this is before European contact
there's no large draft animals in the
area, the only domesticated animal is
probably gonna be a dog, and dogs we know make almost they don't make any actually.
so carnivores don't really seem to be
making this molecule so we could say
humans are the big animal on this
landscape and, you know, whatever is being
produced we can be, there might be a bear
that goes by occasionally that makes a
little bit of it, but we can be pretty
sure that this whatever controls the
changes is people. Now if you're an
area, where there's a lot more animals
that are present, that are, you know,
particularly domesticated animals, like
those I just mentioned, then it becomes a
lot harder to pull apart the human and
the animal signature. There are ways of
doing this in terms of looking at more
molecules, particularly bile acids, and
looking at various ratios of these
different molecules to each other to say
if you have this number here and this
number there, it's probably a pig, you
know, and so there's ways to get more
specific, but you can't completely be a
hundred percent certain that you know
everything you're seeing is human. And
we ran into this problem a little bit
more in recent work I'm doing with my
adviser Lisa Maher
and we tried this out at her site,
which is in Jordan, and it's very old,
it's about twenty thousand years old, it's amazing archaeological site it
seems like there's a lot of people there,
however since there's been a lot of
people there twenty thousand years ago
there's also been a lot of camels there
that have just been going across the
desert and so we were wondering does,
you know this camel, poop contains some
of these molecules too, and could that
contribute to what we're seeing in the
sediment. So we tested camel poop and it
turns out, like cows, they make a little
bit too, so you know, it's what we think
is happening is that over time they're
their poop is broken up and kind of
percolated downward into archaeological
sediment and it makes it really hard to
distinguish, you know, what's going on
with people and animals, it's a real mess
and so what I hope to do now is
kind of go out and say "Okay here are
some limitations, here are some of the
places where I think it works really well."
I think if you're like on an island
somewhere where you know exactly what's
coming in and out, I think if you're in
the Americas in a pre-contact setting it
might be a pretty good way to do, but in
in the Old World it's a little more
complicated, so yeah, that's where we're
getting at that, there's a lot of
limitations to be discovered and we're
kind of getting into that. Mm-hmm,
and so how old is this approach? I mean
like what is your research community
look like? What's the size of, do go to
conferences for people who just do this
or is this really emergent? It's just the
men's restroom, you know, in any
conference, you know. Anyway, so what
we do is, where this all started was in
the 1960s or so, people started
using coprostanol for sewage
contamination studies and they still do
this today, you know, like if a pipe
breaks near a port or something, or
somewhere where people go swimming,
they'll go out and test the water and if
they find coprostanol, it's like okay
no one goes swimming in this water, there's been a sewage leak. And so that's where
it started, and then archaeologists
beginning around the 90s realized that
this molecule doesn't just indicate
modern sewage and modern human waste but
also is a molecule that can persist
for a long time and so they started
first using it as like an indicator of a
human presence, so particularly
for pooping, so you know, people used ,
okay let's say you've got an ancient fortress
and you want to know where people went
to the bathroom, you find an area where
you just find a ton of these molecules
then you've found your bathroom. And so it's
stuff like that, so there's, you know,
studies from Roman forts that we're
finding where the the privies were, it
was used to try to find out where, you
know, fields were manured and other
fields were not, but in terms of using it
as a population indicator, that didn't
really start until 2012, as far as I know,
that's the first paper that went out
and said "Hey, we can use these as a way of
tallying how many people were here in a
kind of relative sense" so in terms of
the population it's less than a decade,
but the whole thing has been around and
there's a kind of cool history to it, and
yeah and the fact that it still is used
for finding sewage pollution, it still
goes up, just as it has been for 50 years.
Cool, so when you talk about like finding
it in different parts of the site, say, I
know this is necessarily the research
you do, but if we were a Roman fort or
something, what kinds of tools would you
use to sample areas, I mean like what
kind of controls need to happen during
the excavation to allow you to do your
work? Yeah, I always joke that it's good to
wash your hands, yeah, you never know what
sort of contaminants you might be
bringing, you know, we're dirty people, as
this whole, you know, outbreak has shown
us, you know, you can never be too sure
about what you're carrying with you but
yeah.
The first thing is, yeah, you don't want
to contaminate anything, you don't want to be
eating anything that has cholesterol and,
you know, be touching anything with that.
So if you just had like a pepperoni
pizza, not a good idea to go out and do
your sample. But let's say that, you know,
you got, I wear gloves on when I'm in the
field, and if you're not doing it in the
approach we talked about before, which is
you go to a lake, right, it's so if you're
in an archaeological site, it's the way
we've done is pretty much like any sort of
excavation, where you have your
profile, you know, your
sidewall, or what have you, and you can
pick depths that you want to sample and this isn't anything you can see, right, so you
just need sediment. Typically we fill up,
at least for what I do, is fill up one
of these. It's about, you know, maybe fifteen milliliters, or a volume of sediment and
from that, we don't need a whole lot
because we're gonna take, what the
sediment is, and we're gonna go take it
back to the lab, and we do what's called
"a solid and liquid extraction" and so you
take the dirt that was in here and you
want to get it into a a solvent that
will will strip out the molecules you're
interested in and now it's out of a you
know it's out of the mud and it's into
something liquid that machines can deal
with and then you do several controlled
chemical reactions to further isolate
the molecules you want and then you put
that in a mass spectrometer, which is
an extremely sensitive instrument that can
tell you how much of these molecules are
present to the nanogram, so you
don't need a whole lot. And in terms of
the sampling procedure, it's pretty
simple. The analytical procedure is a little
more involved. That's the part that takes
the time. I see, and so it sounds like
carnivores don't produce any trace of
this sort of, but herbivores and
omnivores do, and so can you, is it
refined enough to be able to tell like
if there's a human population that is
eating more of one type of food or, you
know, more meat or more plant material?
Like can you actually distinguish that
from know..? So there's, I'm gonna bring
your question into two parts: the first
one is that I don't think we have enough
data yet to make, and this is kind of
my fault cause earlier I said that all
carnivores don't do this. The problem is
we've only sampled, as far as I can tell, perhaps under 50 animals
specifically for this, that I'm aware of.
A lot of them are ones that we can
easily get our hand on, so stuff if you
go to a farm, just sample everything
there so there needs to be, I think just
a lot more
survey of just, you know, what the
difference of the animal kingdom to find
out, you know, okay well is it true that
we can say carnivores in general or am I
just basing that off of the dog, you know,
which in that case I want, so I think we need
to expand the amount of animals that
we're studying, but then let's say that
it does pan out where there are
differences based on these kind of diets
right. Yeah, it might be possible to look
into that, and I think would be difficult
because it would be a trade-off between,
let's say you had someone who is
ingesting very little cholesterol, so
conceivably they would produce less coprostanol,
right, the byproduct of the
cholesterol breakdown in our guts.
However, that might look like, if you had
a hundred of, you know, that kind of
people, would that just look like fifty
people who were eating, you know, more
cholesterol, right, because it's not like,
there are multiple variables here and so
it would be difficult to pull apart
whether it means more people or a
different diet. At the moment, you know,
the assumption I make when I do these
studies is that people have a similar
diet through time. Of course there's
gonna, you know, differences in there, but
you have to kind of choose some sort of
assumption in order to make
interpretations, otherwise they're just
going to say "Ah, there's too many
variables" and leave it there, but one
thing I've joked about doing and
actually might want to seriously do this
is actually try that out myself and you
know have like these different diets and
then just, you know, test what comes out
 to see what if there are noticeable
differences because one thing that's
good to keep in mind is that we produce
cholesterol as well, so no matter how
vegan you are there's still cholesterol
in your body, otherwise you'd be just a
bunch of jello because you need
cholesterol in yourselves to have
structure so we make cholesterol
anywhere, so it's complicated. I'm not sure
if I completely answered it. No, it's
fascinating to hear about this new area
of research and I love the idea of being
able to see beyond what's actually in
the ground, what's being excavated, and to
be able to do these types of analyses.
A listener
has asked "What your favorite
project so far, working in this field?
Gotcha.
Well I've been very fortunate to do
these fecal stable analyses in multiple
places. In Vietnam we did a really cool
project on an island and looked at
sort of the the timing of when the
greatest populations were there. In
Jordan we've learned a lot in terms of
the method, but I'd say that in terms of
what has, I'd say, produced to me the most
interesting findings is from Cahokia, as I
was talking about earlier, and one thing
we haven't talked about is that you know
from the Cahokia Study we were able to say
"Okay, in our sediment core, here's what's
happening with the fecal molecules," but
we're also going to say "Okay, well what's
happening within the environment based
on what we have in this lake mud" because,
you know, we can see things that were
going on in the  environment just by looking at the mud with our eyes, there's like a
very obvious flood and it looks like
this real gray pulse of silt that just
shows up and right after that, our fecal
molecules start to be in decline. Now in
addition to that, we sampled the mud for
oxygen isotope analyses, which is a way
of getting what rainfall was like in the
past and we also find that around the
timing of that flood, it seems like rain
started to change and it became drier
during the growing season in the summer,
which would be a big problem if you're
making, you know, if crops are what's
feeding your people, and so it seems that
climate change was happening, and it was
having some effect on people living in
this area in addition to what was
happening, you know, in their society and,
you know, completely cultural realms as
well. So what I really love about that is
that I think we've been able to make a
really clear, sort of argument for how
the environment and people go together
through this method and I think it can
be quite powerful and I hope to
encourage people to try this method out
for, you know, among other reasons, just
that, that you can really connect,
you know, the climate and people in a way
that it's hard to do otherwise so I
really enjoyed you know making those
interpretations
being able to be pretty confident about them. Well then that leads nicely to another question
about what, um,
if people on archaeological projects
want to, should they, all be doing this,
should they all be collecting these
samples even if they don't have someone
like you on their team and how would
they go about that is that, is something
they could do? Yeah, so what I feel like
I'm learning now, is that this isn't
necessarily a method that should just be applied
universally to, you know, every single
archaeological site due to the way that
this molecule preserves and due to how
other animals can affect its
interpretation so I think that if you're
an archaeological site and you've got a
nice, like wetland, nearby, that's an area
that, you know, go get a quorum and, you
know, sometimes that requires specialized
equipment and training to do, but if you
have like a nice sedimentary archive
right by your site, that's a main area
where you can be pretty confident that
the stratigraphy is is real intact, there
hasn't been a lot of disturbance, things
are going to be in there. The problem of
the archaeological site is that it's
porous sediment a lot of the time, right,
if you're getting with sands or silts
even, where stuff can mix around
you know, what I think was happening at
our site in Jordan is that modern or
near modern molecules are percolating in
to archaeological sediments which makes
it it makes a real problem, so if you
have somewhere where it's nice and tight
and like a waterlogged area I'd
recommend it, and you also have to
consider the archaeological context as
well. Are there a lot of the animals that
might produce this in the area, you know,
are you in Africa, Europe, or Asia, or are
you in somewhere where there might
not have been as many large animals in
that area. That would perhaps be a
better option so so I'd say, yeah, think
about the context and if it checks those
boxes then yeah, you can. There's
plenty of people who are starting to do
this when you can you know collect the
samples and you know give someone an
email who's published on this and say
would you be interested in analyzing
this. It is an expensive method
I might say, so per sample, it can be
pretty pricey.
It's not something that you can just say
"Oh well, you know, we'll just throw it over there, it does
take some money. And does
the sample have to be sent to a lab and
processed by someone like you, or do you
send it out somewhere to be analyzed?
Yeah, it depends on how comfortable you're with chemistry. I'm not I'm not a chemist
I'll just go ahead and just say that, so to me
what I feel, what I'm doing the lab, feels
sophisticated. To a real chemist they're
like "Oh that's that's you know undergrad
chemistry, that's not a big deal." If you
 know your way around a
lab you can perhaps do the the
extraction procedure in, I imagine that,
any sort of university campus will have
some some sort of way to have this solid
to liquid lipid extract which is what
you're doing, that's what you're making.
Now, once you get to that part you need
to run it on a gas chromatography mass
spectrometer. That's something that you
know I don't do that part because that
requires a fair amount of training and
understanding of a very delicate and
expensive piece of equipment, so I'd say
that at that point you almost
certainly need to send it out to a lab,
but you might be able to do the
extraction point and then send them the
 sort of the final project before it
goes in. As I'm saying this though, I
think it is best to perhaps send it out to
someone who specializes in this, even
though theoretically could you could
take care. Good, so along those same lines
then in these and doing this work to do
look at actual poop is another question
that came in. I've seen it before.
I do not look at actual poop, you know,
and that's something that I get asked a
lot and there's a whole tradition of
looking at coprolites in archaeology
that is much older than what
talking about here and there's a lot of
great things that can come from looking
at actual poop. Looking at the stools, in
terms, of looking at diet and looking at
macro remains inside of it, as well as
looking at parasites and looking at how
people's health was like in the past. But
what we're talking about here is all at
the micro-level. This is all stuff where
it just looks like dirt, and that's
what's kind of fun about it too. Is it's
like in any sort of volume of dirt
there's all sorts of stuff, and it is
crazy dirty, you know, that's another problem
running this on the mass spec, because
they're just so much stuff in dirt and
it has so many sources and it's just
it's totally its own little world and it
blows my mind.
Yeah, well it's so great to hear about
this from you and it's fun to learn
about something totally new and I'd like
to thank you so much for joining us
today for this session of an
archaeologist, so thank you for coming AJ,
 it was fascinating and thank you to the
listeners, the people who joined us
online, I'd like to invite you all to our
next Ask an Archaeologist, which it will
be tomorrow Tuesday at 11:00 a.m. and
it's gonna be with Scott Byram who'll be
talking about how archaeologists use
ground-penetrating radar to map buried
artifacts and ruins before they begin an
excavation so another chat about
archaeology without actually looking at
artifacts. So I hope you're able to join
us tomorrow and again thanks so much AJ
for joining us, it was fascinating. Thank
you.
*This event was recorded on April 20th, 2020*
