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(logo whooshing) (vibrant music) – So I’m going to talk about “Behavior and Settlement Patterns “in Coastal Stone Age Communities: “The Evidence from Stable Isotopes.” And I’m talking about
this because if we look at the long history of our species, we talk quite a lot about
hunting and the role that hunting may have
played in human evolution. We talk a bit about gathering plant foods and the importance of
that, but we don’t talk very much at all about the
importance of coastal resources, and there are interesting questions about when people first began
to use coastal resources, what the implications of this might be, and these questions are interesting because coastal marine areas like this are among the most
productive habitats on earth and in more recent
times, habitats like this have been very important for hunting and gathering populations. Why have they been important? Well, first of all,
coastlines provide abundant, reliable, nutrient-rich
foods like these shellfish. They also provide marine mammals, which are sometimes
washed up on the shore. One doesn’t necessarily
even need to hunt them. You can collect beached animals and when a large animal
like a whale is beached, that provides very large
quantities of food indeed. If coastal communities
have the right technology, they can catch fish. Coastlines provide a range
of stone raw materials and other kinds of raw
materials for making artifacts. Coastlines provide routes for dispersal. So one might expect that
the line leading to humans would have taken advantage of coastal habitats from early on. I have to say that we don’t
have much direct evidence of this, but that’s at least
partly because of issues to do with preservation. So over long time
scales, coastlines shift, sea levels rise and fall, and so globally, we’ve
got very little archeology of coastal areas that date to the earlier periods of human evolution. In South Africa, though, we’re lucky because we’ve got a
relatively stable coastline, at least it’s remained stable over the last several
hundred thousand years, and so we have many
well-preserved coastal sites, which make it a good place to investigate these kinds of questions. So in the latter part of the 20th century, most researchers thought
that aquatic resources only became important
relatively late in prehistory, once populations had already grown and additional sources of food were needed to feed these extra mouths. But today, rather different
perspectives have been offered and some researchers are even suggesting that coastal adaptations
may have played a role in the emergence of our species and that coastal adaptations
may have promoted the particular behavioral patterns that characterize humans. So what evidence do we actually have for early use of marine foods? Some of the earliest comes
from around the Mediterranean, where at the site of Terra Amata in southern France, we’ve got shellfish that date to about 300,000 years ago. At Benzu in North Africa, there are shells dating to about 250,000 years ago, and at the Cave of Lazeret,
also in southern France, slightly younger shells. At Terra Amata, these are associated with acheulean handaxes, but there are some disagreements
amongst archeologists as to the dating of some of these sites, as to what these shells
are actually doing there. Are they really food remains? So we’re not entirely clear what we’re actually
looking at in these sites. I think they probably are food remains because we know that it’s not just humans that collect and eat marine foods. Non-human primates do it too. And this is a troop of baboons that lives very near Cape Town on the rocks, collecting
and eating mussels. This particular troop regularly forages in the intertidal and they
simply pull off the shellfish from the rocks and bite through them. Here are some more pictures
of them doing that, and this makes an important contribution to particularly the protein
component of their diet. But these baboons don’t do this very much. They spend less than 5%
of their foraging time on the rocks, and the rest of the time they are eating terrestrial plants and small animals and so on. Primates do this elsewhere
in the world too. We know that along the Somalian coast, yellow baboons forage for marine foods. In Southeast Asia, crab-eating macaques eat intertidal organisms,
so this kind of behavior may well go back a long
way in the human lineage. And of course, Neanderthals ate shellfish. We know that because they
left the shells in caves in Gibraltar and other places
on the Iberian Peninsula. So I said earlier that coastal
habitats were productive, but we’re only just now
beginning to realize exactly how productive they are. These are some photographs that were taken as part of a research
project in South Africa, where the researchers are
working with local communities who collect shellfish to feed themselves. These are relatively
impoverished, rural communities, and they collect shellfish
as part of their diet. And the researchers were
looking at how long it takes, how much effort it takes
to get a reasonable return, in terms of the quantity of food gathered, and the results, I think, are astonishing. So on average, these collectors can get almost 1,500 kilocalories an
hour by collecting shellfish and under optimal conditions,
so optimal conditions are spring, low tide,
when the seas are calm. They can collect 3,400
kilocalories an hour. And if you think that
a sort of medium-sized, moderately active person
needs about 2,000 kilocalories a day, this is very productive foraging. And it’s not hard. It’s certainly a lot easier than trying to hunt down and kill large game animals. So coastal food resources are rewarding, they’re abundant, but they
are spatially restricted. They’re restricted to the coast, the sort of linear edge
of the land masses. And so some researchers are starting to explore the idea that perhaps foraging in a landscape like this,
where the human groups would have been sort
of aggregated together, might have perhaps promoted the high levels of social interaction that are characteristic of our species. Here are some images of
the site of Pinnacle Point, which is arrowed in the small
map on the bottom left there. Pinnacle Point has become
famous for the evidence that it preserves of marine
foods at 164,000 years ago. So the lower image here,
that kind of bank of material on the left, is a consolidated deposit that has a lot of shells in it, it has a lot of stone artifacts in it, and it’s cemented to the wall of the cave. It dates back to about 164,000 years ago, so we’re now back, sort
of, earlyish in the period of what some people call modern humans. The question is, though,
what role did shellfish play in people’s diets at this time? So were the people who lived in this cave collecting shellfish just occasionally, like the baboons do, or were they focusing on these marine foods like more recent coastal hunter gatherer populations do? Here are a couple of sites
from the same part of the world that date to the last 12, perhaps even more recent than that, the last several thousand years, and you can see that those
are huge shell middens. In the upper photograph,
all of that gray area that you’re looking at
on the ground there, all of that is shell. That’s hundreds of thousands of shells. On the bottom image, you can see very densely packed shell middens. And this is typical of the kinds of sites that we see in more recent time periods. In older time periods, many of the sites don’t look as dense as this, don’t seem to preserve this kind of
evidence of intensive use of marine food, but it’s often unclear whether that’s because people
were doing something different further back in the past, or perhaps, whether the evidence is just
often not so well preserved. So in order to answer that question, in order to answer the
question of how intensively were people back 100-plus
thousand years ago focusing on marine foods, we might turn to a different
way of investigating this question, and that
is the kind of thing that I do a lot of, which is to measure the stable isotopes in
the bones and the teeth of consumers in order to try to assess what they were eating. So the way this works is
that we measure the ratios of carbon-13 to carbon-12,
nitrogen-15 to nitrogen-14, and those, the two isotopes in the pair, the heavier and the lighter isotope, progress at slightly different rates through the reactions that
make up the global carbon and nitrogen cycles, and that
happens somewhat differently on land and in the sea, so we can measure these isotope ratios in
the bones of consumers, including humans, and assess more or less whether they were heavily
dependent on marine foods or heavily dependent on terrestrial foods. And these pictures were taken
in our lab in Cape Town. So we’ve done a lot of work like this on more recent coastal populations, because we’ve got a lot more
evidence from more recent times and it makes sense, I think, to use that more recent evidence that we can interrogate more closely and then try to see
whether we can reflect back on earlier time periods. So here are the results of
some work that’s been done on communities, coastal communities dating to the last few thousand years. And we have skeletons of people who died and were buried in the area
marked by the yellow ellipse. They have somewhat unusual bone chemistry, indicating very intensive use of high trophic level marine foods. Their bone chemistry is
different from the bone chemistry of the people who died and were buried at the sites marked by the yellow star, although that yellow star is
only about 14 kilometers away. The bone chemistry is
sufficiently different that we can infer that there
was a territorial boundary between the two. Those two groups were separate, because we see different
chemical signatures in their bones, reflecting
diet over many years, probably several decades of their lives. Similarly, on the right, people who died and were buried in caves marked
by the inland green star, the uppermost green star,
had a different diet. They ate very little seafood, whereas people who died and
were buried on the coast, marked by the lower green star, were eating a lot of seafood. So there was another territorial boundary between those sites, over
very small areas of ground. In the middle, we haven’t
got so much evidence, so that’s why there’s
a question mark there. We can do even better than this. We can look at diet through life by comparing teeth and bones. So teeth form in childhood
and record the diet that the person was eating as a child, whereas bones continue
to resorb and reform throughout life, so they
give a longer term average. And by comparing teeth that
form relatively early in life, like the first incisor
and the first molars, shown here, those teeth complete
their formation pre-puberty so we can look at a childhood diet and compare it with an adult diet and we can tell whether people were living as children in the same
area where they died and were buried as adults. In other words, we can tell whether people were bringing marriage partners in from outside their own territory, or whether they were
getting marriage partners from within their own group. And in this case, the people
with the unusual bone chemistry in the yellow ellipse
were marrying partners from within their own group. So what we’ve got here,
in recent time periods, are societies that were living out very specialized coastal adaptations. They were specializing in
collecting marine foods and they had a social and a
kind of group organization that supported that way of life. And this kind of intense
coastal specialization is, of course, documented in many other coastal hunter
gatherer societies elsewhere in the world, here in
California, amongst other places, in other parts of North America,
in Europe, and elsewhere. So one of the things we’d like to know is how far back in time does this go? How early in human development
can we see this kind of intensive use of coastal resources and what might that tell us about the way that coastal resources may or may not have factored into human development. So we’re only just starting to do this, but we now have some
results from Klasies River, where we’ve, excavators have uncovered a number of human remains. The work that I have done on these has been on the teeth, not on the bones, because the teeth preserve
better over long time periods like 110 or so thousand years. The teeth are more chemically stable and so we can have more confidence in the measurements that we make on them. What we found in our analysis
of the teeth from Klasies, is that back at about 110,000 years ago, some individuals were indeed
specializing in marine foods. Other individuals were not. And we’re seeing a wide range of variation that pretty much spans
the range of variation that we see in populations dating to the last couple of thousand years. So it’s clear from this that we can push the beginnings of significant
reliance on marine foods back beyond 100,000. We don’t know quite how far back yet, but towards the earlier period of the development of modern humans, and we wonder whether, if
there were marine specialists back then, does that mean
that populations back then were territorial, as the same way that the coastal hunting
and gathering populations were in the last few thousand years? Does that mean that
we’ve got the same sort of anthropological correlates that we see in more recent time periods? I don’t know what the answer to that is. We’re working on it, and
perhaps in a few years, we will have some answers. Thank you very much. (audience applauding) (vibrant music)