Importance of Natural Resources

The ecology of early human scavenging

Hi, I’m Briana Pobiner and I’m a
Paleoanthropologist in the Smithsonian’s Human Origins Program and I’ll talk to
you today about the ecology of early human scavenging, a study I’ve done
within the larger context of my interest in the origin and evolution of meat-eating. We know that early humans were eating
meat back at least 2.6 million years ago, as in the reconstruction you can see on
the left, we know they were eating meat from large animals like this giant extinct
elephant and we know that because we have fossils of those animals with butchery
marks like you can see in the top right. Right around that time we also have evidence
of the earliest archaeological traces, stone tools, simple cores and sharp flakes
dating back to right around that time. But we don’t have evidence for hunting
technology until about half a million years ago, that’s the age of the earliest
spear points that we have right now. So early humans were eating meat
from big animals 2 million years before they were hunting them, so how
were they getting that meat? One hypothesis is that
they were scavenging it. There are two main types of scavenging
that have been hypothesized for early humans. The first is called “confrontational” or
sometimes “power or aggressive scavenging” and that’s reconstructed
on the left, the idea is that early humans would have gone in, chased carnivores
off of carcasses and potentially gotten a lot of meat and marrow from this. They
also would have put themselves in direct competition with these large carnivores
and potentially become prey, like you can see on the right, with a leopard dragging an
early human carcass away and we do have fossils of early humans with bite
marks from carnivores that indicated that this happened not infrequently. The other hypothesis is called “passive
scavenging.” That’s basically waiting until carnivores are completely done with their
kills, going in and getting the leftovers. A main criticism of the passive scavenging
hypothesis is that there may not have been enough meat to make it
worth an early hominin’s while. So I decided to go out and answer
the question. Do lions leave leftovers from their lunches? So I’m interested
in figuring out if there’s anything left over by simulating passive scavenging
in a modern ecosystem similar to those kinds of ecosystems where our
earliest meat-eating ancestors lived. So, this study was done actually as
a part of my dissertation at a place called Ol Pejeta Conservancy, which
is a game reserve in central Kenya, you can see the location
in the map on the left. I spent nearly 7 months here and this
place is a savanna ecosystem, the predator community is dominated by
lions and the herbivore community is dominated by zebras as well as
warthog, buffalo, baboon, and impala. After finding out about carnivore kills
I would wait until the carnivores were completely finished, you can
see there’s a very happy lion in the top right with a distended belly full of
meat, wait ‘til things were safe, come and document what was left over and
unlike my earlier ancestors, I had a four wheel drive vehicle which you
can see on the bottom right and I had an armed guard with me at all times
when I was out of the car hopefully ensuring that I was less likely to
become part of my own sample. [ laughter ] So, I collected information on 24 kills
over this time you can see the species of carnivore on the left
hand column in the table, I’m only going to talk about the lion sample today that’s
my biggest sample and I separated the prey into two basic categories
standard categories, larger prey or large prey with your over 250
pounds, things like zebras and larger antelopes, smaller prey less than
250 pounds usually warthogs and smaller antelope. The top right picture
is a picture of a zebra torso or a zebra rib cage with a lot of meat left
on it as one example, and the bottom right picture is a picture of part of a
limb of a young gazelle which has practically nothing left on it. So how much meat could an early
human scavenger eat? It turns out quite a lot and I’ll walk you through
this graph. So the X or the horizontal axis is skeletal elements or bones and
the number of bones in my sample are in parentheses above each one,
but I’ve grouped them into four body size categories. So all the way on
the left are two bones of the hind limbs, next to that are three bones
of the forelimb, next to that are five bones of the torso and then all the
way to the right are three bones of the head and neck. The y-axis is the proportion
of flesh divided into 3 categories for the entirety of those
bones in the sample and they’re coded basically like a traffic light,
where green is bulk flesh, yellow is flesh scraps and red is no flesh.
And… it turns out that in large kills you see a lot of flesh left, you see a lot
of green in here, you see a lot of yellow and so … 95% of those larger
of those kills, larger kills of lions had at least some flesh left on them and
50% had bulk flesh. And actually I will define what those mean. Bulk flesh
is more than 10% of the original muscle mass is still there, flesh
scraps are defined as, flesh scrap is less than the size of your hand but at least
2 to 3 centimeters and probably more than the third of a pound.
Smaller kills different story, mostly flesh scraps on half of them and then
hardly, and then basically no flash on half of them. But if we try to quantify this if you
use a fully-fleshed wildebeest on the left, zebra on the right, adult hindlimb
you can get about 19 pounds from a wildebeest, 50 pounds from a zebra
hindlimb but if we’re going to model a defleshed carcass then less than
10% of the weight, you’re talking about up to two pounds from a wildebeest,
maybe five pounds from a zebra but that’s only a single hindlimb. Potentially
a defleshed wildebeest can give you 19 pounds of meat and defleshed
zebra can give you 34 pounds of meat. And an estimate of 4 calories
per gram, that’s about 2200 calories from a defleshed wildebeest, and
over 6100 calories from a defleshed zebra, that’s over 11 Big Macs and
I think this guy probably thinks that was worth it. So have I solved this question?
Probably not but I’ve contributed some data to it. I think early humans thought
that meat taste great and I would say that early human scavengers
also thought it was more filling. Thank you. [ applause ] Briana, presumably the passive
early hominid scavengers had competition from other carnivores and
how are you going to factor that in? The hyenas, the jackals, the vultures,
and everybody else who was hanging around the kill. That’s a good question. So how
would I factor in the fact that early human scavengers would have had
competition from other scavengers like hyenas and vultures and jackals?
Well one thing I did was I actually had some kills that were initially killed
by lions and then eaten by hyenas to see if I could make that comparison,
they certainly had less flesh on them but they still had some, so that
means that even kind of a secondary passive scavenger potentially would
have had maybe some worthwhile meat left to go in, but, but
that’s a very good question. Thank you. So this is a question Briana, was there
any evidence of them cooking their scavenger meat or is it more
like zebra tartar kind of stuff? [ laughter ] The question was if there evidence
for cooking the scavenged meat. Not for a while, the earliest evidence for
cooking and fire, goes back to about 800 thousand years, so, still not that
much earlier than actual hunting technology. We’re still million and a
half years of zebra tartar. As a follow-up fior Briana, I also
have a question about the hunting technology and when it appears and
not finding it so much earlier and I guess there’s always the question
of taphonomy and preservation and are you just not finding it. If it did
exist at that time, if they did have that technology, what would you
expect it would look like and where would you expect to find it?
Or how would it appear and how would you know if
you saw it, basically. So the question is, how would you
know earlier hunting technology if you saw it and where would
you expect it to appear? So we have spear points have
very particular morphology and shape so I feel like if we see stone
hunting technology it would not be hard to recognize. I think the
problem is with preservation of wood. So I suspect that there would have
been wooden spears back much earlier. We, the oldest wooden spears that
we have go back to about 400ish thousand years old. A very special
preservation case in Europe where things tend to preserve a bit
better, this was in a kind of bog environment. … So I suspect
that they were potentially thrusting spears at least with just sharpened,
basically big sharpened sticks. I don’t know how you’d find that in the record
though. It’d have to be a very special case.

Reader Comments

  1. This makes lots of sense – meat was probably only a small amount of their diet. But scavenging could very well give them a taste for meat, and as intelligence increases the ability to get more, fresher meat increases. Tool making could have been partly driven by wanting to get more meat in a shorter time, and to drive off competition. That's why some animals develop bigger teeth and horns; we humans just saw a way to skip that painfully slow step. After all, humans are still the king of the arms race…

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