Good morning, let's keep talking about Island colonization and
this time in Madagascar.
My name is Kristina Douglass, I'm a Buck Postdoctoral Fellow
in the Department of Anthropology and in the Department of Vertebrate Zoology.
So as many of you may know Madagascar was colonized
recently in human history relative to other parts of the world.
Some estimates place initial arrivals of people in Madagascar to the first
Millennium A.D. but there's emerging evidence that an early forager phase
may be present in Madagascar.
We're not sure exactly who the first Malagasy were in terms of
where they were coming from and so many questions remain to be
answered both about the precise timing and location of first arrivals.
Madagascar is incredibly biogeographically diverse as I'm sure you all know.
In the late Holocene, Madagascar also experienced tremendous
environmental change and so many research questions from
archaeologists and paleontologists and paleoecologists are concerned
with the link between human arrival on the island and some of these changes.
Famous among these changes are the extinction of megafauna
in Madagascar and other endemics.
Here you see reconstructions of some of these megafauna
species that included giant lemurs, pygmy hippos, and these
giant elephant birds.
The elephant birds in particular are a mysterious case of extinction
because we have very limited evidence from archaeological
and paleontological sites of elephant bird remains.
Very few, if any, elephant bird bones have been recovered from
any archaeological sites and the purpose of my research is to look
at eggshell which I have found in abundant quantities at archaeological
sites in Southwest Madagascar as an alternative means for understanding
extinction of these animals.
To give you some context in terms of where we are in addressing
some of these questions, we have very large gaps in our data
sets concerning human impact on the environment in Madagascar.
Here for example you see that of the many invasive plants and
animals that were introduced to the island in the late Holocene
we have limited knowledge of the precise timing
and location of their introduction.
So the arrows are essentially pointing to places where we
know rice, cotton, and cattle were introduced and some suggestions
of the timing of those introductions but for the vast majority of invasives
in Madagascar, we have almost no data to time their introduction.
We also have a fairly limited archaeological sample in terms
of a geographic representation of the different regions in Madagascar
and in terms of timing.
The map on the left hand side if you turn your attention to the
orange boxes those represent sites with this potentially very
early forager component going back as far as 4500 BP.
The other sites that you see, the other phases that you see
highlighted in those boxes are all from the mid-1st Millennium AD and onward.
On the right hand side, if you look at that map, you'll see that
paleontological sites are concentrated very heavily in the southwest which is
why I focus my research there to link archaeological signatures
to paleontological remains.
Why ratites? I'm interested broadly in human ratite interaction as these
birds have gone extinct from much of their former ranges.
Famous examples include New Zealand and Mauritius which I'm
sure you're all familiar with where moa in the case of New Zealand
and the dodo in the case of Mauritius went extinct relatively recently due
to human pressures.
So ratites are very interesting because all of the materials that
people are interested in have multiple lives and iterations
in human life, eggs as something to be consumed, as containers for
liquids, as material for crafts and so on.
So for the first time I've documented that people in Madagascar were in fact
exploiting nests of elephant birds. They were doing this for many reasons.
I found evidence of worked eggshell for the first time. Along the top row
you'll see eggshell fragments that were worked and are essentially
the remains of perforations that were created to extract liquid from eggs and
then presumably to be able to use eggs as containers for other liquids
after they were consumed.
I found evidence of beads and other artifacts associated with eggs.
But the question of timing is still very pertinent.
Are the eggs that I have found that have been worked extensively
by human communities coming from active nests? And this is
where is microstructure work comes in.
The main picture in the center of the screen is showing you
an ontogenetic time series of changes in eggshell microstructure,
this is the interior portion of eggshell as the embryo develops.
This was done on turkey eggshell and applied to the archaeological
record of the American southwest. I'm now using similar techniques and
developing them further to look at extinct taxa, in this case the elephant
bird and as you see on the upper right hand side these are SEM images
of elephant bird eggs showing the degree of erosion, so as the embryo
develops and here again in the main image, the top left corner that is an
undeveloped egg embryo and in the far bottom right that is a fully
developed embryo and a fully eroded egg. So I'm using this
to track whether eggs that I'm looking at from the archaeological
record were in fact harvested from active nests and had living embryos in them.
So by using these techniques we'll be able to use eggshell
to understand human use of eggs, we'll be able to potentially distinguish
better between the different species of ratites in Madagascar and learn
a little bit more about their reproductive ecology and finally better be able to
address this question of human driven, or not, extinction of the elephant bird.
Thank you.
[applause]
You're not finding elephant bird bones in archaeological
sites. What about other large sub-fossil remains? Are you
finding other sub-fossil taxa represented in archaeological sites?
That's a great question.
One of the main problems I would say is that we have
a sampling bias because most of these sub-fossil sites in
Madagascar are concentrated from what we can tell in the
southwest but aside from my excavations which cover
a 20 kilometer x 2 kilometer area, there have been no other systematic
archaeological studies. So it's not clear, you know we don't have
a very good sample of sites in the southwest to be able to say
whether or not, you know, a lot of other sub-fossil remains do
show up. For the moment though it doesn't seem to be the case and
these sub-fossil sites that I mentioned are taphonomic traps and so one of the
priorities for field research is to go out and survey those areas,
so survey around these sub-fossil sites and look
more carefully for archaeological signatures.
Why elephant birds?
Well, I'm interested in environmental change and particularly in how humans
contribute to environmental change.
Islands in particular are interesting and Madagascar among them I would
argue is the most interesting because of its tremendous biogeographical and
cultural diversity and the fact that it was settled relatively late
in human history. It's a huge land mass, you know, a little bit bigger
than California to give you some context and it's only approximately
250 miles off the African mainland.
So why was it settled so late and there's a huge debate about
anthropogenic influence and things like the extinction but
we still have relatively sparse evidence to ...
say exactly how people may have contributed to environmental
change in Madagascar.
I know what taxonomy is, I don't know what taphonomy is. Thank you.
So taphonomy is the study of how things change once they've
been deposited into … in my case into the archaeological record.
And so this is important with the eggshell in particular
because I'm trying to disentangle erosion due to development of the
embryo so that I can know when these eggs were potentially harvested
and then erosion that occurs on the surface of these microstructures
through action like wind, sand erosion, and etc., so trying
to disentangle those factors.
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