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Interview with Peter Ungar about diet and diversity in primates

Interview with Peter Ungar about diet and diversity in primates


Peter Ungar is Distinguished
Professor and Chair of Anthropology at the
University of Arkansas in Fayetteville, Arkansas. Peter is one of the
world’s experts in understanding the diets
of ancient primates.>>Peter in
particular studies the microscopic traces of wear on the teeth
of primates.>>And those wear
traces accumulate when primates are chewing on different kinds of foods. Peter talked to me about the ways that he uses living primates to
understand the diets of ancient primates, including ancient hominins. He talked about some of his work on those
ancient hominins, reconstructing what
ancient organisms were eating from the
traces on their teeth.>>Peter, what
do you think?>>That everybody has
some ideas about what they eat and what the role of nutrition
is in their lives.>>And when you
start thinking about what ancient organisms, ate, ancient hominids, ancient primates, and
how that fit in, in the sense
of, if I was to imagine what it was like to be an early hominin. What, what am I
eating day-to-day? What is what is what
does my life like?>>How does food
interact with that? Sure, well, I think
the best way to answer that question is it’s
the, it’s the old joke. What do you feed an
800-pound gorilla? And the answer, of course, is anything it wants.>>Yep.>>I think by and large, if you’re a primate, you are driven to eat whatever’s
available to you. So essentially, diet
is about availability. And when we think about the evolution
of human diet, what we’re really thinking about is we’re thinking
about changing food availability
as the environment in which we’re
living changes. Because in different places there are different
kinds of foods that are available to eat and
our own ancestors, I’ve tracked these
changes related to changes in the environment and found a niche
for themselves. And largely, at least for the last 2.5 million years or so, it’s been about taking a broader and
broader variety of foods, greater
versatility of foods. If you ask me what did a hominid eat on a
day-to-day basis? That’s a really
hard question to answer because it depends where and when
that hominin lived. I could give you some interesting examples if you wanted to from the
primary literature. And there are
basically somewhere, and depending
upon who you ask, between one and three or four
species of gorilla. Alright, the two, the,
the basic dichotomy is between the eastern lowland and the western lowland and
the mountain gorilla. Yeah, but you know what, traditionally we’ve
considered all of them to be leaf-eaters. However, over the
past several years, people have started to say, well, you know what? The lowland gorillas aren’t really leaf eaters, they’re
fruit eaters. But the reality is there aren’t any gorillas
that are leaf eaters. Even the mountain
gorillas are fruit eaters by nature. So why is it that everybody thinks the mountain
gorillas are leaf-eaters? The basic
reason is that the first place
anybody ever went to look for the
diets of gorillas was a place called Karisoke, made famous by
Dian Fossey, a gorilla researcher. Now the site of Karisoke is kind of unusual.>>It’s in the
high mountains of the Virunga volcanic range.>>And the reason that it is up
there is because people have settled
the bases of the volcanoes
where the lands are fertile and it’s
easy to grow stuff. Now what that means is that the
gorillas that had lived there had been pushed up into the high mountains. So there are mountain
gorillas at this site, but they’re living really high in the mountains. They’re eating
nothing but garbage. They’re eating,
they’re eating pith and they’re
eating stems, and they’re eating just leaves in all kinds of nasty stuff that no
self-respecting ape would eat if it
had a choice. Now, there are
other mountain gorillas that live nearby, like in the Bwindi,
Impenetrable Forest. And they eat mostly fruits. They’ll eat fruits
maybe ten months out of the year when there are
fruits available for them to eat, right? But when those
aren’t available, they will switch
their diets to eating leaves
and other tough, nasty stuff like the ones at Karisoke. Now if we start
thinking about this, what’s going on in Karisoke,
it’s not normal. What’s happening
is these animals are perpetually falling
back on the garbage, right, on a, on a, on a low-quality foods that they wouldn’t eat if
they had the choice. All right, so let’s let’s take this back
for a moment.>>Okay.
>>If you look at the anatomy of their teeth, if you look at
the anatomy of their jaws and
chewing muscles, if you look at the
anatomy of their guts, all of these
things literally scream tough foods, but that’s not what
they would eat if they had the
choice, right? And you know how we
know this? We know this because a researcher
named Melissa Remis did some
work in a zoo where she gave gorillas a choice of different foods, right? She handed them the
choice of mangoes or broccoli, right? Or cabbage. Which do you think
those gorillas chose every single time? Okay, now I’ve got
two little girls, and if I gave them the
choice between a head of broccoli and a Snickers bar? There’s no
question. They take the Snickers bar. You know? They’re yummy. They’re
filled with energy, they taste good.
Like those mangoes do. And that’s what the
gorillas, and in fact, all other apes are
really evolved to eat. We are basically fruit
eaters at heart. Now the gorillas do have this bizarre specialized
anatomy that allows them to fall
back on foods they don’t want to eat,
but sometimes have to eat. And that gives them
an advantage, right? An unusual,
advantage.>>It’s like a survival mechanism.
>>Exactly. And this is a particularly important survival
mechanism in a place where you
have seasonality, in a place where you
have rainy months, where there’s lots of yummy fruits available, and a place where you
don’t have free months, where you have dry months, where things
aren’t very good. So in fact, that’s sort of the adaptation that
we see in gorillas. We used to think
big flat teeth in a hominin told
us a great deal, Oh, it’s a Nutcracker. But–and it may have been– but not necessarily. Certainly having that
specialized anatomy put them at an advantage
when they need it, but they don’t
always need it?>>Yeah. Yeah. So you’ve become known for your
study of the microwear of teeth and looking
at very close detail microscopically at at
scratches and in pits. And and how do you use
that information to go to what the teeth are being used for and what
the diet was like?>>We use something
called the comparative method. In other words, what
we do is we will look at living animals, ones that we
know their diet, and then we’ll look
at their teeth. And it turns out
that in many cases, the pattern of
scratching and pitting on the teeth reflects the diet the different
animals eat. If you eat a lot of
leaves, for example, you tend to have
scratchy surfaces, and the reason is
because the teeth shear or slide
past one another. And when they do, whatever abrasive or are on or in, those leaves get dragged along the surfaces now that causes these fine
parallel scratches. But if you’re a hard
object feeder, like a mangabey, they will crush foods. And when they crush them, then what happens is
the abrasives on or in the food get pressed into the surface and it
causes pitting. Hard object, pit or, sorry. Hard object
feeders typically have very pitted surfaces. Very tough food feeders, those that eat leaves, those that eat meat
which is very tough, sometimes those tend
to have scratches. Ones with very
broad diets have a range of
different features. Ones with intermediate
diets like soft fruits tend to also be
intermediate in their scratching
and pitting pattern. And that reflects maybe a week, maybe two weeks, depending on the diet of what they ate in the past. Because of course, once
you create a scratch, it’ll be replaced
by more scratches as the tooth wears down.
>>Sure.>>Yeah.>>I think that’s
something that people maybe don’t realize
is the extent to which teeth in
most animals and many humans are
really wear over time and you’re looking at a surface that’s
continually evolving? That’s correct. It’s,
it’s changing continually.>>And yet when we look at early hominins, start
with afarensis.>>Here’s a species that we know a lot about
its anatomy.>>We know quite
a bit about what its behavioral ecology may have been in
a broad sense.>>But there are many
unanswered questions about. What do you think
they were eating?>>It’s a very good
question. Afarensis is an enigma to us. On the one hand,
if you look at its teeth and jaws, It looks like it is
on a trajectory. And I hate to use the
word trajectory because evolution is not directional.
>>Right. But it seems to be on a trajectory looking across human evolution
towards the ability to eat more and
more hard foods. Okay, its jaws
are a little bit thicker and wider
than yours or mine. Its teeth, cheek teeth, back teeth are a
little bit larger than yours or mine. Its incisors are also,
believe it or not, a little bit larger
than yours or mine. The enamel on those
teeth is fairly thick. Overall, this
would lead us to suspect that unlike, say, a chimpanzee today, they would not have focused mostly on soft fruits. They would’ve taken a broader variety of foods, including some
hard objects. The evidence from
the isotopes, the chemistry of the teeth, suggest that they
had a fairly broad diet because some of them show that there are
grassland products. Others show that there
are forest products. Microscopic,
wear on the teeth, though very
strange. They’re dominated by fine
linear grooves, or scratches. So these fine
linear features, these fine scratches, suggests that they were doing something other than necessarily smashing
hard foods. They suggest
perhaps grinding tough vegetation
because the scratches aren’t all aligned
like a leaf eater. That’s the thing.
Leaf eaters will usually have very
aligned scratches, but these ones
are, maybe because the teeth are flattened,
the teeth move more. They look like
whatever it is they’re eating,
they’re grinding.>>Yeah.
>>If you if you asked me to guess
what they’re eating, I would say they probably had a fairly broad diet, perhaps including some
soft leaf material, maybe even some, some
grass related material. Although not much. Not much because
there is not a dominance of chemistry that would support
that at that point. They were not yet hard
object specialists, though that’s pretty clear.>>So when we move
to later hominins and we enter the phase where we have these species called robust
australopithecines. And then we have
these other species that are not robust.>>They’ve maybe
ancestors of Homo. There may be other kinds of australopithecines, but they do not have the, the massive, especially
post canine teeth.>>What do you
think is going on?>>I mean, you describe a situation
where there’s multiple species that are eating
the same foods.>>I wonder what
is going on in the Late Pliocene
with these species.>>Well, it seems, based on what we can tell, that round about 2.5
million years ago, there’s this major
change globally. The world’s climate or the world’s temperatures, average temperature drops, it becomes somewhat drier, and the savannas of
Eastern Africa and the veldt of Southern
Africa began to spread. We used to think
that that happened five or 6 million years ago with the origins of our own biological tribe. But we now think that that happened a bit later, starting around 2.5
million years ago or so. It’s an effect and evolutionary fork
in the road. And this evolutionary fork in the road really did mark two different
approaches, two different ways
of dealing with the changing
resources associated with the spreading
savannas.>>Sure.>>Now what’s
interesting is If the two species
that we commonly recognize as the two later
Paranthropus species, boisei and robustus from two different
parts of Africa, one from Eastern
and the other from southern Africa, are
closely related. And many of us believe that they’re just too similar, to not be closely related.>>They’re
anatomically really much, very much alike.
>>They are.>>But what’s interesting
is if you look at the chemistry of their teeth and the pattern of
scratches on their teeth. They don’t look like they ate the same things. They were both
very specialized. These big dish-like midfaces, these big crests on
top of their heads. Chewing muscles, the,
the big thick jaws, big flat cheek teeth, these things, people have asked me what they were. And my initial response was there
Paleolithic Cuisinarts they could eat anything they want.
They ate very different things, it seems, which
again extremely surprising because the
shapes of their teeth, the size and shape of their jaw, their
chewing muscles. Those are all
quite different.>>Yeah. I’m sorry, I mean quite the same.
>>Right.>>Right. Yeah.>>But the pattern
of wear on their teeth and the isotopes are
quite different. In eastern Africa, isotopes suggest
grasses or sedges. Isotopes being the chemical signatures in the teeth. The microscopic wear
is scratchy, again, suggesting perhaps
grass like structures that’s
the most, either, either grass seeds, perhaps on occasion
grass blades, you can’t say for certain, but those are entirely internally consistent. South Africa, we get
a different signal. We get a signal more like what we would expect. We get a mixed
diet based on the isotopes and we get more pitting
in the teeth, right, suggesting
the consumption of hard brittle foods. So are we looking at an example like
our gorillas, where in some cases they use the same anatomy for a very different diet. Perhaps, perhaps that’s
what’s going on.>>I think what, what strikes me as
you describe it is that when you look
at the anatomy, you know your first
reaction when John Robinson studied the
anatomy and he said, look, you’ve got
these big toothed ones, you’ve got small toothed ones, it’s obvious what’s going on. And the big toothed
ones are eating big toothed things and the small toothed ones are
eating like chimps. And, and to come to
where we are now, where we appreciate that
each of these forms, It’s quite flexible in the actual foods that
were part of its diet. And, and that the
same anatomy might be related to
different kinds of diets in different places, different ecologies. But another key point is the role that we see in living primates of
climate fluctuation, climate variability, and, and how species must be adapted to the
extremes, in a sense, is there anything
we can learn about that sort of context for, for understanding how
our own genus arose.>>Sure. What we see in terms
of the anatomy with early Homo is we see
very subtle changes. The teeth become smaller, believe it or not, they become slightly
crestier. The enamel on those
teeth becomes thinner. And these are
changes we would expect of something that is not driven to a
specialized diet. In the same way that the contemporary
Paranthropus was driven to a
specialized diet. Some might even argue that these would be
considered adapt, adapted to the consumption of some tougher foods, potentially including
things like meat because crestier teeth and thinner enamel really good for sharing
through things.>>Yeah.>>So it may be that the strategy
that early Homo took was instead of
broadening out the diet, or ultimately, even
in the case of Boise, specializing
on the savanna resources which
are the grasses. We’re looking at
something that, that itself had a
fairly broad diet. in another way, including not just the vegetation, but perhaps the
meat and whatever else in could get
into its mouth and the archaeological
record comes in and begins to support the
consumption of meat at this time.>>How did you get into
this line of work?>>Get into this
line of work?>>I don’t know.>>I’ve always
been fascinated by human evolution. Yeah, probably when I was six or seven years old, my father took me to see 2001: A Space Odyssey. One of these late night. I’m not old enough
so that this was when it first came out, one of these sort of
late night shows. I just, I just fell
in love with the idea of understanding
where we came from, how, how we came to
be the way we are, why we’re different, sure, from the other apes. And I really, I really enjoyed that very much. And then of course, little trips in
elementary school to the Museum of Natural
History in New York.>>Oh, yeah.>>That was another
another big one for me.>>Yeah. Yeah. So you were really looking
for this field?>>Yeah. A lot
of people go. a lot of my own
students went into college with
no idea what they wanted to do for a living when they grew up. And there are a lot of very successful
anthropologists that came late to the idea that they
wanted to do this. I think I kinda knew by the time I was five or six.>>Awesome. Yeah.>>Yeah. If you are going to give
advice to students, says, as I’m sure
you often do, you want to pursue
anthropology, you wanna pursue
understanding evolution or biology. What advice do you give?>>Depends on the
level you’re talking.>>You’re talking an
undergraduate level.>>In that case, I would say a couple of things. First, go into
it with an with an open mind and
go into it with the understanding
that there are more people interested
in doing it and there are jobs out
there, it’ll be done. Be realistic. And if it’s something
that you love, something that you
definitely want to do, that’s great. If you’re not certain, you need to think
really long and hard about it because it is
a long and hard road and they’re a
lot more people interested in there are
positions for that. But yeah, because I can tell you from
personal experience, I did not have a tenure track
permanent professorship when I got out of
graduate school, I had a couple of post-doctoral fellowships
with some very, very good people that kept me employed while I
was on the market. And and and that stick-to-it-ness, it
took three years? Yeah. But that
stick-to-it-ness, I think was sort of
what got me through it. But I would say, I would say if you’re
passionate about it and take as many different
courses as you can. I wish that that that I had been able
to take more courses and things like
geology in things like genetics gives broad and education at the undergraduate
level as possible. It will serve you well
as you go forward.>>All right. Well,
thank you so much. I really appreciate you spending the time with us and I know that everybody
else is going to appreciate it too,
so thank you.>>Thank you, John.

Author Since: Mar 11, 2019