Fat of the land: What ancient bones tell us about the origin of the human diet | Jess Thompson ASU


I wanted to just say thank you that was
an amazing introduction I don’t think I was expecting that introduction but
obviously I’m grateful for it and yeah it was my intense pleasure to be a if
you want to call it a product of a ASU, IHO. I arrived there in 2001 it was
actually the very first year that Curtis Marean was there. I was his very first
student. So it’s nice the way these things come full circle because I find
myself now collaborating with him on this project and it’s been an intense
pleasure to be able to kind of go off build my own project in Malawi and if
anyone’s interested in hearing about that I’ve got lots to say about that as
well but tonight I’m gonna be talking to you about the work that brings me home
to IHO and that’s the work that I’m doing with a number of IHO affiliates in
Ethiopia and that is the origins of the human predatory pattern. So it’s — it’s
kind of a mouthful, but what I’m gonna try to do is convince you that it’s a
necessary mouthful because what it is is it’s a signifier of how it is that what
we do as people, and the way we eat, and the way we interact with our environment
is fundamentally different from the way that a chimpanzee does it. In fact the
way that any other primate does it, and maybe even the way that any other
primate has ever done it. So I’m gonna take you through the logic and hopefully
I’ll be able to convince you first of all I’ve got to mention why it
is that I think zooarcheology is probably the best thing you could do. Bill did a great job of starting that but look I mean we all have to eat, right?
So when you’re examining the origins of any kind of significant change in diet
you’re getting right to the heart of what it is that makes the most selective
pressure on every organism to evolve because they have to eat if they don’t
get sustenance they don’t survive they don’t reproduce and they disappear or
never even appear in the first place in the fossil record so we have to
understand diet. It’s fundamentally important to understand diet it equals
survival and also look people like to know about diet we know that you can’t
open the news without seeing something about diet so I’m going to also bring up
why that is relevant as well. I also have to nod to Curtis —
this was an article that he published in Scientific American — but what I want to
point out is that a number of the major milestones that you might think about as
making us fundamentally human a lot of them come down to diet. So this article
is about cooperation, but it’s also about weaponry. Weaponry evolved as a
critical human adaptation in the context of hunting right and hunting
fundamentally comes back to that issue of diet so our unique cognitive
abilities and our enormous oversized brains a lot of that also can be
attributed to diet. So when you really think about it we owe a lot to what it
is that we eat. Diet is essential. Here are some uniquely human traits. So it’s
very difficult when you look at things in the fossil record to try to find
those things that make us totally different from everything else right and
even when you look at other living animals there’s always going to be
somebody who’s like yeah you know language sure but don’t you know don’t
primates communicate with each other in other ways and then you have to start
talking about things like well it’s a continuum right there’s there’s
communication on one side there’s language on the other side there’s
always going to be tool use right there’s tool use on one side and then
there’s the human form of tool use. But I think what we can do is we can actually
pinpoint a few things that are unique that are that are fundamentally
different in humans. I’ll just take the time out here so to say them. First
of all we’ve got these enormous brains and we also very handy with our hands,
and that relates very closely to a very long evolutionary period of tool use, and
of course we’re bipedal right we walk on two legs. So I have to argue to you today
that all of these things are related and I’m gonna say again I think they all
come down to diet. So there’s been a series of stories that have been told
about human evolution over the years and one of the primary ones is kind of this
narrative about these three things. All of these things are things that we would
find important or valuable or or something that’s quintessentially human.
right? Tool making — we think of tool-making as a human adaptation. Yes
other animals make tools and use tools but they do not do it — nobody can argue
that they do it the way that humans do it. We are very different in the way that
we make tools and we can actually see that, the origins of that
behavior, in the fossil record but more importantly in the archaeological record.
So when we actually look at the tools themselves that gives us a sense of when
it all started. But there are some clues we can also get from other things like
hands, right? So as soon as the hand starts to appear in the fossil record
appearing the same way as a human hand you might infer from that that there’s
already been some tool use going on for a long time for that hand form to have
evolved that way and then maybe what you need to do is start trying to find those
tools in the archaeological record and it’s supposed to be connected in this
way, so you start with this. The relationship in the kind of story that’s
always been told is that flaked stone tools, stone artifacts, are used to
cut meat and that that was their primary purpose for why they were invented and
then what you do is you cut your meat you have a higher quality diet — you’ve
got protein, you’ve got fat, you’ve got all of this stuff you didn’t have before
in your diet, and therefore you have an advantage what we might call an energy
surplus and from that you have the emergence of our own genus it comes from
Australopithecus and it’s got a larger brain, and it’s got smaller teeth. And the
reason that it has a larger brain is because it has this energy surplus. And
the reason it has smaller teeth is because it’s now got tools — it can chop
up that meat and it doesn’t necessarily have to rely on these big chompers you
know to get through whatever it was that Australopithecus was eating. So what I’m
going to do today is I’m going to try to tear this down a little bit and I’m
gonna try to tear it down in a way that I lay out in a paper that has been
accepted to Current Anthropology. So it’ll come out in February and I’m gonna
give you tonight a preview of that. So, hopefully I can kind of take you along
of the journey of inference that we’ve been doing in trying to think a little
bit more critically about what I would call a story that we have. I mean, all of
the things we tell our stories, but we want to try to find a way to make
that story test-able so we can actually take that story out into the field and
see if the evidence exists that supports it or doesn’t support it. So the cost of
a big brain. You probably don’t think about this but your brain is an
extremely expensive thing to have — a large, energy expensive, brain and — it
weighs only about 2% of your body mass but it takes up almost 25% of
your of your actual energy. So the amazing thing about this is that
whenever I just kind of feel like maybe I want to lose weight or something I can
just sit you know and just think really hard — really, really hard — and as I’m
thinking I’m going, “yes, yes, it’s working, it’s work…” but I don’t know you can try it and you can
give me feedback and you can be my first experimental subject group. Tell me how it how it works. But it is a very expensive thing right to have and that’s why other
creatures don’t have it they don’t have the extra energy to spend on a giant
brain because they don’t need to have a giant brain for what it is that they do.
So we have to think about the costs and the benefits and we’re going to look at
this from kind of an economics perspective, right? We want to raise the
bottom line of energy in our ancestors and as soon as that bottom line is
raised and they have surplus energy they can start to do stuff with it and they
can start to evolve novel organs like giant brains. Now of course the brain
doesn’t start out giant it’s a slow incremental process, so we want to look
at the fossil record and ask ourselves, “when is the first evidence the brain
size is increasing, even if just a little?” And as soon as we see that we can infer
from that that somehow somewhere there’s an energy surplus and there’s a couple
ways you can do this right you can get an energy surplus by lowering your costs
or you can get it by raising your revenue. In either one of those cases
you’re going to have a surplus that you can put towards something like an
expensive brain. So let’s look again at that issue of food and I hope I’ve
convinced you why it’s important because ultimately calories come down to food.
Whatever’s going into the creature is what’s going to produce that surplus one
way or another and it’s critical for understanding our evolution and it’s
also something that is more kind of know– on the knowable side of stuff, right?
There’s a lot of things we would all very much like to know about Lucy for
example, right? Lots and lots of things. We would like to know about sexual behavior —
that’s very unlikely we’re ever going to know that — there’s an interest factor
there, right? But there’s also an interest factor in things like diet, and diet is
something that’s knowable. Maybe someone in this crowd has really always wanted
to know if Lucy can whistle. Right? Maybe, I don’t know, there could be somebody who really wants to know that. It’s not knowable — I don’t
think it’s knowable — so there are things that are and and fortunately for us if
we have enough data or if we get the right kind of data we can start just
kind of nudge the things we want to know more over to the side of the things that
we can know and I think diet is one of those areas in which we can do both of
those things. For those of you who are maybe needing a refresher on Lucy, I will
talk about her species tonight quite a bit — she lived between about 3.9 and 3
million years ago and this is a time period known as a Pliocene so if you see
that word again that’s referring to the time in which Lucy was alive. She
walked upright it’s very clear that she was a biped her hands were already
adapted for tool use she had a long thumb and short fingers just like a
human hand. It wasn’t exactly the same but the quintessential parts of what
makes us able to manipulate our environment so well were already in
place by the time that Lucy’s species existed and that wasn’t the case for
earlier hominins so something really important happened with Australopithecus
afarensis which is which is Lucy’s species. And, see this, brain slightly
larger than a chimp so it’s already got something going on it’s already a little
bit bigger which means she’s already doing something different with her diet
to be able to give her that energy surplus and give her the boost she needs.
So the obvious question would be well what did she eat then. We don’t know. We
can’t know immediately by looking at all of the creatures that are alive today
because there is nothing like Lucy alive today. If you’ve got a wildebeest you can
look at what it eats and you can say okay in the past they probably ate grass
because we can observe a modern wildebeest eating grass. We can do the
same thing for lions. We know that modern lions eat meat. Let’s find a fossil lion,
okay, it probably ate meat. We’re stuck when it comes with Lucy because we don’t have
a modern-day Lucy that we can look at to try to make this inference. There are
certain kind of tricks that we have though that will help us with this
so we know that at the time that lucy was alive it was a period when
grasslands were expanding across Africa so openings were appearing between the
trees and there were bunches of trees that weren’t necessarily continuous with
one another. There were open spaces and with open
spaces come new resources and with new resources come new opportunities. So
Lucy’s out there exploiting those opportunities and the fascinating thing
about her is you can look at the geochemistry of the teeth of an extinct
organism and you can get a sense of what it ate, to a certain extent, and it’s very
clear that Lucy was not in the trees nor out of the trees she was everywhere so
this is what her species is doing that’s totally different from everything that
had lived before. Her species was the first to really be flexible in this way
and take advantage of all of the opportunities that were around in the
environment. It was the perfect time for experiments, it was the perfect time to
create and invent because you have a smart animal on a new landscape fighting
for survival and whoever gets the most food is going to be the winner, so it
would have been a very exciting time to be able to be around and see things. Now
we have to kind of reconstruct this from dry dead things, right? So let’s look at
the fossil record and what I want to point out is the story’s actually
changed a lot. So this is the importance this is the critical critical importance
of fieldwork. If you look at where we were in 2010 the story would have been
totally different. So, based — this is just an area, let me go back. This was an area —
this is 30 kilometers here so that’s a very short distance, and these are major
hominid fossil sites in the Afar area of Ethiopia and you can see they’re all
very very close to one another. When I first went up there I was actually
shocked because you see all of these names in the literature and then when
you go there you realize you could just drive there, you know, in an afternoon, and
you’d be at the place where the earliest stone tools were found and then you
could drive another day and you’d be at the place where Lucy was found and then
you could drive a little bit further and you’d be at the place where they found
the earliest cut mark bones it’s all in a really small area but that’s because
that’s where the deposits are that are the right age. You’ve got this kind
of — what appears to be an amazing coincidence, right — you can see that
all those numbers are very similar. It appeared in 2010 as though all of these
adaptations arose at the same time. Tool making, meat-eating, and the origin of our
genus Homo — so the extinction of Lucy’s kind, and the emergence of our own kind.
Let’s look at how that’s changed since then. Now, this is what the picture looks
like. Now we know that that homo goes back a little bit further — 2.8 million
instead of 2.4 — we also know that there are earlier cut marks at about 3 and a
half million years old, and then there also are very early stone tools at 3 and
1/2 million years old. That’s a very, very different kind of story. So I’ll
summarize for you here. That story of sharp tools being used or invented to
cut meat and then that gives rise to homo
that’s totally broken down now because those things don’t occur all at the same
time anymore in the fossil record so we have to start asking ourselves did we
construct the story from the evidence we had, or did we construct the story
because we really liked it? And, what do we do now, right? Are we stuck, are we in
this kind of crisis of faith because we don’t know that this, what to do with…?
We need a new story, right? And when I say story what I actually mean is a hypothesis. We need something that we can test — that we can actually physically go
out and collect fossils and know that those fossils are going to tell us, one
way or the other, what the answer is to this. The sharp tools and the meat — the
evidence for meat-eating, the cut marks — they occur before homo so they can’t
give rise to homo. It has to have happened with Lucy that places this time
period and these initial very human-like qualities of tool-making and meat-eating
it puts it squarely in Lucy’s arena and it makes it so that she’s really the one
we need to be looking at. Australopithecus afarensis and the
Pliocene is when we got our origins and our start on many of these behaviors
that took us all the way eventually as modern people. So I’m going to look at
this issue of meat eating a little bit more carefully. What we have to do is we
have to develop some kind of theoretical framework so we can test this we can’t
just go blundering around thinking that we’re gonna find stuff and hoping we’re
gonna find stuff — you can’t not find stuff out there, right, you you go to
those fossil deposits you will find something — the question is are you going
to find what it is that you think you need to find to answer your question?
For that you need a plan. So what we’re doing in this paper is we’re
making a plan. We’re presenting a new mode, and a new set of hypotheses, that
we can then use to actually go out into the field and sweat it out and find the
fossils and test that hypothesis and that means we’ve actually got to go do
it. We’re gonna have to do that work and we need to improve our methods in
actually being able to interpret what it is that we find. So these are the three
pieces and here’s what — if you’re going to be at the board meeting tomorrow,
here’s what Jake Harris is going to be talking about, number three — so, I’ll
take you through 1 & 2 tonight. I want to make an argument that this whole meat
eating thing is bogus. So, everyone’s all about meat, meat, meat. I think it’s
actually fat, fat, fat. And you know it’s real — like, you know you like fat. You
don’t want to admit it, but there’s a reason that people like to eat things
with fat in it. And hunter-gatherers love fat, too. These eland are painted
disproportionately on rock art in South Africa because that’s a fatty fatty
antelope. See this lovely fatty dew — look they even illustrated this dewlap right here. That’s just a pure bundle of luscious — no, I mean but seriously, they love it. They
love it and and they love the fat around the organs and they want that
because they know that they can’t really get that. It’s a scarce item and whatever
is rare on the landscape is going to be more valuable, but it’s also it’s like a
concentrated source of calories and we know that when you eat too much raw meat — er, sorry, too much lean meat it can create a problem. Anyone who’s been on the Atkins
diet or it’s you know many associated versions you know it works it actually
does work if you don’t eat your carbs and you and you don’t eat fat you will
lose weight. And that’s because you can’t subsist and continue to gain weight if
you’re just eating lean meat and that’s what many earlier explorers found when
they would find themselves eating a lot of rabbit meat and then they would die
from starvation even though they were eating. So we have to have fat and that’s
why these things right look delicious. You don’t want to admit it, but you’re
all thinking it. They’re tasty, right? And they’re high in fat. So we have to ask
ourselves, “well. when did this start to become something that was craved by our
earliest ancestors?” and then ultimately, “is that what took us all the way?” Is that
what put us on the path to wanting more and more and more so that we’re starting
to hunt big animals now and then ultimately we’re able to find ourselves
in this very sophisticated weaponry large brains and all of the stuff that
goes with that calorie surplus. So let’s rethink meat-eating and think of it more
as kind of fat eating if you want we already know we’ve got to take the
origin of Homo out of this equation at least at the earlier part of this — we
know that a lot of these behaviors have their roots in a much earlier time
period — and now we need to challenge this issue of meat-eating. So what’s usually
happened is people say oh yeah with humans hunt because chimps hunt and look at all
the similarities right humans mostly males hunt chimps mostly males hunt
humans hunting groups chimps hunting groups so people make these similarities
and they draw these conclusions oh well then in fact the last common
ancestor of both must have done it that way but I want to point out to you that
there’s a lot of differences in how chimpanzees hunt and how humans hunt
fundamental differences chimps don’t use stone tools to butcher meat or of course
to acquire meat in the first place right they also won’t scavenge this is a
really important point because chimpanzees are not interested in dead
rotten meat yet we assume that our ancestors were out there scavenging from
these large presumably fragrant elephant carcasses right so it’s unlikely that
that adaptation has a common origin because they are actually very very
different from one another and if we rethink this we can take it a bit
further and I would like to point out that as much as chimpanzees do hunt they
barely rely on it for nutrition it seems to be a very social kind of activity
that they do and there might be some trace nutrients that they get but they
don’t rely on it for filling their bellies they it’s not a primary source
of nutria for them in terms of calories but for
humans it’s very much a source of nutrition in terms of calories and those
calories are mostly coming from the fat so humans are actually the only primate
and this is one thing within which we are actually very very very different
we’re the only one that will take down something that’s larger than ourselves
we will hunt it down and we will and we’ll kill it
even without the biological equipment of sharp claws or large canines or any of
that stuff that other carnivores have we do it with tools and chimpanzees also
have large canines that they use when they do it so humans lack all of that
and yet and yet we still manage to take down the largest game on the landscape
so this is what I’m calling the human predatory pattern and this is why I
think we have to have a new name for it we can’t call it meat-eating because
it’s not meat-eating it’s it’s meat and fat and all of the nutrients that are
bound up with that and it is really about the uniqueness of going after
something that is larger than yourself taking it down and consuming it that is
a fundamental difference between humans and other primates so this is an amazing
thing that I found when we were doing our survey it was a an action this is a
fossil bone from Hadar and in it it’s like a geode you know the the crystals
have actually formed inside the marrow cavity so it was this beautiful specimen
that was just broken on the surface and I thought I got to take a picture of
that I don’t know when it’ll be useful but I’ll take a picture and then I
remembered that picture because it really is the kind of wealth of the
Pliocene bone marrow is like a stick of butter on a landscape where there’s no
fat right it’s inside the bone it’s encased it’s not gonna rot there have
been experiments believe it or not in my field where people have tested that it
doesn’t rot it can sit around and remain fresh for days and days and days as long
as nothing else gets inside of it what can get inside of it not many things but
you can access that if you have a rock so if you’ve got a rock and you’re
willing to use a rock you can get inside the bone marrow so you don’t necessarily
have to invent a sharp-edged stone tool to cut the meat to eat the rotten meat
you only have to have a rock and a dead animal and you can get all of the fat
that your competitors don’t have axe – the only other thing that can get
inside this is hyenas so let me take you through the different costs and benefits
of going after small prey and why it is I think Lucy didn’t do this – bitumen
process um without tools that’s nice you also are likely to encounter fewer
predators because if you go out on the landscape and you’re putting yourself
out there in proximity to a dead animal you are putting yourself in proximity to
whatever killed it as well but we know Lucy was already out there because we
know from the geochemical signatures of her teeth she was eating something out
on that open landscape and the question is was she eating seeds and things like
that that are out there or she eating the animals that ate the grass that are
out there and either one of those would create the same signature so there’s
lots of reasons why humans are not or especially humans but but Lucy’s kind
also are not well adapted for eating small prey and then large prey they
become something that makes sense that you would eat only if you’ve got tools
so as soon as you start having access to a basic hammerstone finding yourself in
proximity to large carcasses now you have a reason to be able to going after
that be going after these large animals and you can share them and that’s
another important human behavior you can share the surplus and they also provide
these kind of fat reservoirs on this landscape so let’s look at
Australopithecus and here’s what kind of got me thinking about this is I’m
imagining the last common ancestor being something like Australopithecus but more
like if you’re familiar with our Topeka something that was more if I could put
it I guess the awkward then Cosi right longer arms longer fingers a little bit
shorter legs much smaller brain that kind of template for a common ancestor
whatever grave gave rise to Lucy that might have been a creature that was more
adept in the trees but it’s not a particularly well adapted form for
chasing small prey around in the tree canopy chimpanzees can do it because
they’re quick they have large canines to tear it apart and they have adaptations
to be moving through the trees quickly and Australopithecus quite frankly
didn’t have she was something that again was
flexible she could be in the tree sometimes or she could be on the ground
but she wasn’t particularly stellar at either of those things so putting her in
a position where she’s got to hunt down her prey doesn’t work very well putting
her out on the landscape with a hammerstone works a lot more so here’s
this kind of contrasting view it’s subtle right it’s a very subtle
difference but what I’m doing is I’m taking the emphasis away from the flake
stone I’m taking the emphasis and putting it on a hammerstone a regular
old rock you don’t necessarily have to make a stone tool to have a stone tool
we know this from the way chimpanzees do it so if you’re already using poundings
tools and you find something new to pound and it opens up this whole world
of possibilities for you in terms of nutrition now you’ve got something that
everyone else doesn’t have and now you have the opportunity to get the calorie
surplus your brain gets bigger and now you’re smarter and you can start doing
other things like inventing flakes stone tools so I’m talking now about the very
very very origins of the human predatory pattern and how it is that I think it
happens so this pounding is a very important component to that the reason
is because percussion is something it shows up in a lot of primates it’s
convergently evolved it’s a very simple technology it doesn’t have to have a
common ancestor that use pounding tools lots of different primates do it and
what you find is that because all of these different primates do it you can
you can assume that something smart like Lucy would have been able to do it we
also know and this is critical that that kind of behavior leaves traces that you
can find in the fossil record okay so this is what I’m talking about what do
you want to know versus what can you know we can know this we can know that
something was smashed open with a hammer stone because it leaves a microscopic
trace on the surface of that bone that preserves in the fossil record which you
can identify and you can find and these are called bone surface modifications so
I should credit bill with this picture this was a this was us and had our in
2012 so you can see we’ve already started this work and I’ll take you just
real quickly through the work we’ve done so far on this you might be asking well
okay oh if this is so obvious why hasn’t anybody
this evidence yet right well it could be that maybe this kind of scavenging using
percussive tools was just rare maybe at the very beginning or the very very very
origins of something you shouldn’t expect it to be all that common also it
could just be we’ve been looking for the wrong things with our obsession with
flake stone artifacts and our obsession with meeting at cut marks and the things
that come from the use of flake stone maybe we just simply haven’t opened our
eyes to what’s right there in front of us and the solution then therefore would
be to go back to the same places that we’ve already worked we already have
established context and we already know what there is to be found in terms of
hominins and find the archaeology that goes with it so it’s also possible that
these kinds of behaviors have already been found or at least hints of
behaviors so we know that Lamech we three in Kenya there are the earliest
flakes own artifacts but what’s really cool about these flakes stone artifacts
is there like big right there pounding stones as well as little flake stone
cutting stones these are not delicate cutting tools these are giant things
that have been produced through the action of pounding and percussion and
there are three and a half million years old they emphasize heavy-handed
percussion and I’ll just show you as well that the cut marks from the DES
kike site also show a very heavy pounding kind of behavior so it is
possible that this stuff is out there and I’ll point out that both of those
discoveries were big news discoveries they were amazing discoveries but they
were not found through systematic work they were found on accident both of them
they were found when people were out there looking for other things and
somebody opened their eyes and said the right thing and saw the right thing so
can you imagine what must be out there that we haven’t found that we are
equipped and poised to find as long as we know what it is now that we needs to
be looking for that’s what’s so exciting because we can go back to the same
deposits that have been so productive so far for iho in terms of hominins
and we can now learn things about their behavior that we couldn’t have imagined
knowing before because we didn’t think they had an archaeological record we
didn’t think they were producing anything that would be called a trace of
Behe we just simply had their body fossils
and now it’s possible that we may have just been overlooking it this is a paper
that was published this year and mind you our papers not out yet so these
people didn’t know about our hypothesis and what they found is that smashing
open marrow produces a handshape or seems to be the most parsimonious
explanation for the human hand shape so very early on
percussive behavior in the context of nutrient extraction was most likely
critical so there’s independent lines of evidence and everyone’s kind of
converging on this idea right now and I’m going to very quickly just show you
or summarize for you what I think is going on here so the key arguments are
this hominids didn’t have large canines they weren’t equipped biologically to
take down and kill prey they just weren’t well-suited for it so therefore
I don’t think that’s a good model for the origins of the human predatory
pattern secondly we know ancient habitats were becoming much more open
and that small prey or scarcer or at least quicker when they’re out in the
open so there’s more opportunity there right there’s more opportunity to
exploit these marrow and brains that are inside carcasses big carcasses that only
live out mostly in the open habitats and of course large mammal carcasses are
fatter so they’re marrow and brains are concentrated source of calories they’re
desirable and they open up an opportunity for these hominids if they
can be the ones to exploit it and remember nobody up to that point could
get inside the bone marrow cavity of a large animal except for a hyena so as
soon as the hominin can do that that puts them in a position to be able to
access nutrients that nobody else could before and there actually is a
paleontologist who’s been arguing for a long time that as soon as hominins start
to acquire the ability to get into that carnivorous niche that they start to
actually impinge upon the carnivores territories and the carnivores start to
decline around this time in terms of their abundances on the landscape in
terms of their diversity so it does actually look like in terms of the long
game in fact this is what one of the commentators said on our paper which the
comments will be published with it he said it was a marvelous quote he said
something like we although hominins may have lost the
game in short one-on-one confrontations with predators they would have been the
losers right we can imagine that little Lucy saber-tooth cat predictable outcome
right but in the long term hominins were the winners because they’re the ones
that are getting into this niche and taking away food from the Predators and
you do see a decline in predator diversity after this time and then
furthermore it’s an easy technology it’s a bridging technology you don’t have to
jump to the assumption that flake stone tools which are actually pretty
complicated to make I don’t know how many of you here have tried but it’s
harder than it looks and getting an ice flakes own artifact
takes practice you have to also be thinking about okay well what kind of
rock is the right kind of rock how does it break how do I hold it how do I turn
it how do I not smash my finger with this oh I just smashed my finger if I
was a hominin I wouldn’t do that again right so it’s a complicated thing it’s
much more complicated than you think and a hammer stone to break open a nut is
not so complicated so you just have to take that thing and put it against a a
bone instead of a nut and you have the same outcome but but even better because
more calories so here’s what we’re doing new field methods we’ve done a few
different things where we’re actually collecting data the way archeologists
collect data so instead of walking and looking for hominid fossils we’re
walking and we’re looking for traces of behavior but it’s harder to find traces
of behavior because they’re very small so what do you have to do you have to
collect everything and then you have to look at everything under a microscope
and then the stuff that you don’t think is going to be relevant to the question
instead of ending up with 40,000 new bones taking up space in the museum we
do what’s called catch and release so send them back so fossils go back except
for the ones that have marks on them and the ones that have marks on so we record
data about them but then they go back and then the ones with marks get kept
and that way people can go and they can study them any researcher in the future
could go and have a look and confirm what it is that they think we found and
what have we found well we found some hominids that was kind of cool nobody
was expecting to find hominins necessarily because these are areas that
had been well looked over and we went up the hill we went back
down the hill and you put all the things that you find in a bucket like this and
then you take them back to the camp sort them analyze them record data about them
and put them back and in the course of doing this we actually found a nice
hominid jaw which was published a couple years ago so it actually has these kind
of side benefits as well adopting this new strategy and it’s not a new strategy
for archaeologists who are used to looking for tiny little micro traces of
human behavior but it is a very new strategy for people who are used to
doing paleontology which is looking for like very large diagnostic bones it’s
it’s a it’s a new way of thinking about how to approach the problem in the field
and here’s what we find shot fragments are the fragments of long bones that are
left behind when you access the marrow and shaft fragments is where you’re
gonna find the evidence for marrow extractions so you want shaft fragments
paleontologists don’t want shaft fragments because shaft fragments that
are not informative about what kind of animal it is so you’ve got this kind of
problem where paleontologists want nice complete bones and archaeologists want
they’ve really smashed up nasty bones so what we have to do is we have to try to
compromise right and so you can have both of those things going on at the
same time people looking for the the more complete elements at the same time
a smaller program that’s doing the archaeological work and what we’re
finding is shaft fragments are concentrated in these hotspots so
they’re not evenly distributed all across the landscape here where’s redder
there’s more shaft fragments and look at this
the stars are hominins so shaft fragments are actually concentrated at
least in this sample near where we’re finding new hominids so that’s kind of
interesting it does imply that these are the kinds of environments in which maybe
were seeing some activity or or ancient behavior from Australopithecus and what
we can do is we can map bone surface modification across this paleo landscape
this hasn’t been done before in paleoanthropology it’s a new approach
this is what we find lots of little things the stars represent places on the
bone where there are marks of some kind and our job is to try to figure out what
those marks are are they crocodile marks are they carnivore marks are they
organic root fungus marks or are they hominin marks so if we can
answer that question we can answer the question of when did this behavior begin
because we do it systematically if we don’t find it we can actually say with
some confidence it probably wasn’t there right whereas if we’re just wandering
around the landscape accidentally finding wonderful discoveries we’re not
going to necessarily know what it is that we’ve that we’ve missed so we have
to approach this more systematically it’s kind of a new way of thinking about
it and if I return to this original question I do think that we have a
connection right between stone tools the human predatory pattern and the origin
of Homo but I think what we’re dealing with is two different thresholds of
behavior and biological evolution so you have an initial threshold in which you
have the very very first stone tools there pounding tools you have the origin
of the human predatory pattern and then eventually you position Australopithecus
to evolve ultimately to emerge as Homo but then you have later homo you have
regular predatory patterns this would be like when you’re actually hunting
animals not just scavenging and then complex tool-making like like actually
flaked stones so I think that there is likely to be a connection between these
three things biological evolution behavioral evolution and also diet but
they we have to start thinking about them in a little bit more of a subtle
way and so what we’re interested in here is this origin point we want to know
about the origin origin origin of all of this stuff all right
more data right that’s what we need so the future is we need new tree article
framework I have that now I think I hope I hope I’ve convinced you we have that
so we will be looking for specific things and we have a methodology by
which we can do this that means systematic survey that means more
fieldwork and then we also have to be able to figure out what it is we’re
looking at when we find it and that’s what Jake’s working on with his bone
surface modification work and he’ll be talking about that tomorrow I mentioned
that the at the board meeting I couldn’t cover everything so you have to have to
wait if you’re gonna be in that room you’ll hear all about it and I just want
to say that this will be published in February so
you’ll be able to read all of it you’ll be able to read the reviewer comments
you’ll be able to read our reply to the reviewer comments and you know it’s a
it’s a fundamentally different way of thinking about the emergence of I guess
these very unique human qualities and thinking about it not as just some sort
of extended version of a chimpanzee but thinking of it in its own unique
ecological context for which we can actually test if we have the right kinds
of data and move it over more into that side of the knowable and I have a lot of
people obviously who’ve helped me think my way through this I’m collaborating
with Curtis and I’m also collaborating with somebody who was affiliated with a
night show for a while that’s suryya lemp’s again and Susana Carvalho also is
a co-author on that paper where is she there she is and she studies ape
behavior so she’s actually looking at pounding tools in modern Apes so we all
kind of bring our perspectives from archaeology from paleontology also from
from ape behavior and we had a lot of good input from the reviewers too so
you’ll be able to actually read that that’s the nice thing about current
anthropology you can see all of the criticisms that they have and I’ll just
give you kind of a spoiler alert they didn’t have many criticisms right I was
like I have arrived my career because I’m going to have lots of people
criticizing me publicly but in fact no they actually were very interested in
what it was we were saying and they liked the subtle twist that we put on
the kind of old tired story and especially like the fact that it’s
testable so I should also say thank you all of you for being here and watching
me talk about this the opportunity to talk about this if you’ve got any
questions at all please ask me and I think we’ll be kind of mingling around
for a while I’ll also be at the board meeting tomorrow if I happen to see you
there so thanks again so much you you you

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Reader Comments

  1. seeWemm

    It's difficult to imagine hominins carrying pounding tools weighing a kilo or two predating savannah animals. It's also difficult to imagine today's Kalahari Bushmen – large-brained and all – obtaining sufficient calories from animal fat, if only equipped with pounding tools.

    Scavenging, when 'true' predators provided the kill and after scavenging hyenas and wild dogs had had their pick of the meat, would seem the only way to access carcasses, in the absence of 'fighting tools'. Might fighting tools show up as co-evolutionary along with improved dexterity, pre-Homo? Then, more calories, protein and fat –> big brains?

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