Counting Phytoliths from Songo Mnara, Tanzania

Right now, I spend my life counting phytoliths – over 3500 phytoliths so far….What’s a phytolith and why does it get me out of bed and into the lab before 7am? How did you not realise this was such an exciting archaeological technique?

© Hayley McParland-Clarke

Phytoliths are a bit like plant negatives; essentially the plant absorbs monosilicic acid (H4O4Si) from its water supply and during transpiration as the water ‘leaves’ the plant, the monosilicic acid becomes solid opaline silica. It has to go somewhere, so it fills in gaps within the cell structure of the plant. These gaps are either within the cells, or surrounding the cells, making silica negatives of the internal cell structure. Not all plants make phytoliths though, just like not all plants preserve well as charred plant macrofossils, and not all pollen grains enter the local archaeological record or preserve well. Plants have to degrade in situ for the phytoliths to be included in the archaeological record, no technique is perfect. But the key is, that phytoliths are well preserved in a variety of contexts and can add to our understanding of plant use; not only on sites with poor preservation of plant macrofossils and pollen, but also in contexts where plant remains may not have entered the archaeological record following charring. For example, organic crafts such as grass or palm matting may not be preserved by charring and therefore might be invisible on archaeological sites without waterlogged preservation. These may be visible through phytolith analysis if they have degraded in situ. To help identify diagnostic phytoliths I collected lots of plant samples from the field and I’m now creating a phytolith reference collection in the lab. It’s not a magic bullet to help us understand plant use in the past, but it is pretty cool!

I’m working on late 14th to early 16th Century samples from Songo Mnara, a Swahili stonetown in Tanzania, part of the  [1] and my PhD project at the University of York. Songo Mnara is part of the Kilwa Archipelago and it’s linked to other settlements and islands along the East African coast through the Indian Ocean Trade network. Songo Mnara has truly amazing preservation of stone buildings!! To get to the site you have to take a Dhow from Kilwa Masoko with a guide and once you arrive on the island you have to wade through a tidal Mangrove swamp, which can be anything between ankle deep and chest high! It’s off the beaten track, for sure.

Songo Mnara © Hayley McParland-Clarke 2013

During the 2013 excavation season, two types of structure were excavated; a stone house divided into rooms and a collapsed wattle and daub structure, which appeared open plan. Initially it was thought that the monumental stone architecture in the town was standing in an open area, but extensive test pitting by Dr Fleisher combined with Geophysical and Magnetometer survey[2] revealed the presence of concentrations of daub within this space. Excavation exposed two wattle and daub structures with comparable finds assemblages to that of the stone structures.

The phytoliths I’m looking at today come from Trench 32, one of the daub structures. Spot samples were taken across the entire packed sand floor surface of the structure on a 1m grid, in order to assess whether phytolith analysis can be used as a tool for spatial analysis and to understand the use of plant materials within the structure. Samples were also taken from the ‘outside’ of the structure in the open area to identify clear differences in the phytolith assemblage between ‘inside’ and ‘outside’ and to see if it was possible to recreate the environment immediately adjacent to and further away from the structure.

Sampling for Phytoliths at Songo Mnara © Hayley McParland-Clarke 2014

Sampling for Phytoliths at Songo Mnara © Hayley McParland-Clarke 2014

I’m really hoping that we’ll be able to see activity areas within the structure through the plant assemblage, for example food preparation areas or areas of matting. It may be possible to identify construction materials such as wood, or roofing materials such as palm thatch. I’m also hoping to see evidence of Indian Ocean Trade through phytoliths from imported edible plants within the assemblage, but as with all archaeology I can hope for lots of things, it doesn’t mean it’s there! We also sampled the stone house, which is really interesting, because it has clear rooms within it, whereas those divisions weren’t clear when excavating the daub structure. Phytolith analysis might enable us to see the limits of the daub structure by providing an ‘inside’ and an ‘outside’ botanical signature.

The process of counting involves using a high powered microscope at x400 magnification to identify phytoliths, photograph them, measure them and count them. I count around at least 250 per slide, which means that I’ve counted thousands from this site so far, and I’ve a lot more to do! Phytoliths are 3D objects, but when you’re looking down the microscope you only see the 2D image, which means that you have to remember that each phytolith type might look different depending on which angle you’re looking at it from! Phytoliths aren’t always round like pollen, in fact they’re frequently not round at all, they come in all shapes and various sizes!

Although lab work is often thought of as completely different to fieldwork, it’s sort of the same. I search through transects on the slide, much like layers of stratigraphy looking for microscopic evidence in the form of phytoliths rather than artefacts. It can take a long time, it’s systematic and sometimes I don’t find anything of interest. Recording stratigraphy on site tells you a lot about site formation processes and human actions, likewise recording information about the slide assemblage is useful. For instance, lots of phytoliths which are still articulated suggests that there was little bioturbation, or lots of microcharcoal might suggest burning episodes.

© Hayley McParland-Clarke 2014

I’m on my last few slides from this pilot study now, and I’ve started to get an idea of what’s happening in the structure which is really exciting. Each phytolith assemblage has a different character, which suggests that the spatial approach might be working!! I can clearly see a difference between the assemblages from the floor surface ‘inside’ the building and the outside; I can also see variations across the floor surface within the structure.

Future research will focus on the comparison of the stone house and the daub structure to see if there’s a difference between the uses of each structure. I also hope to look at some of the open area samples to try to understand how the urban landscape impacted on the local environment. Follow my progress and find out more about phytolith analysis, archaeobotany and archaeology on my blog, or follow me on twitter @Hayley_McP.

[1] Managed by Dr Stephanie Wynne-Jones and Dr Jeff Fleisher, funded by the NSF and AHRC.

[2] Welham, K., J. Fleisher, P. Cheetham, H. Manley, C. Steele, and S. Wynne-Jones. 2014. Geophysical Survey in Sub-Saharan Africa: Magnetic and Electromagnetic Investigation of the UNESCO World Heritage Site of Songo Mnara, Tanzania. Archaeological Prospection.

The East African Association for Paleoanthropology and Paleontology: 2013 Conference in Mombasa, Kenya

Hi everyone,

We’d like to introduce ourselves – we are the East African Association for Paleoanthropology and Paleontology (EAAPP)!


The EAAPP was officially launched in Kenya on July 18, 2005.  Membership is open to paleoanthropologists and paleontologists working in Eastern Africa (Ethiopia, Eritrea, Kenya, Tanzania, Uganda). The first objective of the society is to bring scholars working in this region together for scientific exchange and reporting on paleoanthropological and paleontological research findings. To this end, we hold bi-annual conferences with an emphasis on making East African and foreign scholars working in East Africa aware of each other’s research, as well as addressing issues affecting all researchers in East Africa such as policy regarding research requirements, collections management, and fieldwork ethics.  The second objective of the society is to raise funds for East African scholars to conduct field and laboratory research within East African countries.


Let us introduce ourselves: the members of the EAAPP Secretariat are —

1. Chairperson: Dr. Emma Mbua (Kenya), a Senior Research Scientist and the Head of Earth Sciences at the National Museums of Kenya, Kenya

2. Vice Chairperson: Dr. Zeresenay Alemseged (Ethiopia), Chair of the Anthropology Department at the California Academy of Sciences, USA

3. Organizing Secretary and Representative for the USA (USA): Dr. Briana Pobiner, Research Scientist and Museum Educator in the Human Origins Program, Department of Anthropology, National Museum of Natural History, Smithsonian Institution, USA

4. Representative for Tanzania: Dr. Jackson Njau (Tanzania), Assistant Professor in the Department of Geological Sciences and Geoanthropology, Indiana University, USA

5. Representative for Kenya: Dr. Purity Kiura (Kenya), Head of Archaeology at the National Museums of Kenya, Kenya

6. Representative for Eritrea: Dr. Amanuel Beyin (Eritrea), Assistant Professor in the Department of Sociology, Anthropology and Criminal Justice, University of Southern Indiana, USA

7. Representative for Ethiopia: Dr. Zelalem Assefa (Ethiopia), Research Associate in the Human Origins Program, Department of Anthropology, National Museum of Natural History, Smithsonian Institution, USA

8. Representative for South Africa: Ms. Andrea Leenan, Chief Operating Officer, Palaeontological Scientific Trust (PAST), South Africa

9. Representative for Europe (Germany): Dr. Christine Hertler, Scientific Researcher for Paleobiology, Research Centre ROCEECH (The Role of Culture in Early Expansion of Humans), Senckenberg Research Institute, Frankfurt, Germany

10: Representative for Asia: Dr Masato Nakatsukasa (Japan), Associate Professor, Laboratory of Physical Anthropology, Kyoto University, Japan

11. Representative for South America: Dr. Rene Bobe (Chile), Associate Professor, Department of Anthropology, George Washington University, USA


Right now we’re in the throes of gearing up for our 4th bi-annual conference, which will begin in two days! It’s being held at the Leisure Lodge Resort in Mombasa, Kenya, from July 28th – August 2nd. The conference is organized by the secretariat of the EAAPP in coordination with the National Museums of Kenya (NMK). We’re very excited to have 52 presentations planned by researchers from all over the world. The archaeology talks range from discussions of the characterization and chronology of the earliest Acheulean at Konso, Ethiopia to characterization of obsidian sources and provenience of Middle Stone Age artifacts in the Kenyan Rift Valley, to the implications of ostrich eggshell strontium isotope analysis for reconstructing prehistoric exchange systems in the African Late Stone Age, to recent findings of multidimentional features of megalithic monument centers in southwestern Ethiopia. There are also papers on case studies of cultural heritage management such as conservation of the paleoanthropological record with limited resources: the case of Olduvai Gorge, Tanzania and oil exploration in sensitive cultural landscapes: the case of Tullow Oil in the Lake Turkana Basin, Kenya.


We invite you to visit our website: http://www.eaapp.or.ke/ and Facebook page: https://www.facebook.com/pages/East-African-Association-of-Paleoanthropology-and-Paleontology/167166840038050, and we’d love for any of you to attend our conferences! Email us at eaapp.committee@gmail.com if you’d like to be put on our email list to get updates about future conferences.

A Day at Olorgesailie, Kenya

The Smithsonian’s Human Origins Program is excited to participate in the Day of Archaeology 2013!

Our research scientists conduct field research at prehistoric sites in Africa (Kenya: Olorgesailie and Ol Pejeta Conservancy; Tanzania: Engare Sero) and Asia (China: Nihewan Basin and Bose Basin; Indonesia: Flores).  Today we’ll bring you into a day in the life of Dr. Rick Potts, the Director of the Human Origins Program. Today Rick is in the National Museums of Kenya, studying fossils and artifacts excavated at the site of Olorgesailie in southern Kenya.  But to give you a flavor of what fieldwork at Olorgesailie entails, we’ll be going back in the past — just two years, to July 26th 2011, when the excavations were going strong. Here is a modified version of Rick’s blog entry for that day from our Olorgesailie field blog: http://humanorigins.si.edu/research/east-african-research/olorgesailie-field-blog/olorgesailie-2011-field-season/day-31-july-26

Rick says:

One of the big-picture studies we do at Olorgesailie focuses on how the landscape changed over time, all the way back to the beginning of the sediment record more than 1 million years ago.  This area of the southern Kenya Rift Valley has the most precisely dated record of archeological and fossil remains in the world for the past 1 million years.  There is only one major gap in the time sequence, between the Olorgesailie and Oltulelei Formations – a gap that resulted from widespread erosion in the region between about 490,000 and 340,000 years.  But other than that, Olorgesailie presents a pretty continuous record from the handaxe era up to and beyond the time of the African origin of our speciesHomo sapiens.

My geologist colleague, Kay Behrensmeyer, and I have been studying landscape change in the region throughout the entire time period recorded in the Olorgesailie sedimentary layers.  Kay’s short visit draws to an end tomorrow, as she heads back to Nairobi and flies home to her family.  So we spent the morning going over the evidence for landscape change in the younger beds, the Oltulelei Formation, which includes the oldest Middle Stone Age excavations at BOK-2 and nearby sites.  Let me provide a couple of images that can help clarify what I mean by ‘landscape change’.

a river gorge wall with horizontal bands of grey, white, and tan. Green trees and round dark grey river stones in the foreground

Deep erosion along the river unveils many stratigraphic layers. Studying these layers helps us reconstruct how the Olorgesailie landscape changed over hundreds of thousands of years.For example, in the first image, you can see thick white bands and gray bands – where the upper layers were laid down on top of (and thus after) the ones below.  The white layer just above the line of rocks and trees is a thick layer of diatomite (look forward to me talking about diatoms tomorrow!).  The diatoms in the diatomite show that a large lake once existed at that point in time in the Olorgesailie area.  The gray band above it is a thick volcanic sand, which show two things – that there was a volcanic eruption in the vicinity, and that the debris from the eruption filled up wide stream channels that had cut across the region after the lake dried up.  So, count ‘em up:  that’s three major landscape changes.  First, the lake was present and then dried up.  Second, the dried-out landscape was eroded and water channels crossed the area.  Third, after a nearby volcano erupted, the ash and pumice and gravel was carried into the Olorgesailie region and it filled up the channels to form yet another, different kind of landscape.

One thing I’m especially interested in is how early humans responded to these big transitions in the environment.  Stone tools were the early humans’ version of a business card – they left the tools behind as if to say ‘We were here!’  Thus we use the stone tools to indicate whether our early ancestors were very successful or not in surviving the major shifts in the landscape, or perhaps repopulating the landscape after an especially difficult time.  Just think, 10 centimeters of volcanic ash blanketing the ancient terrain would have killed all the grass, forcing the abundance of grazing (grass-eating) animals to depart.  That’s a big drop in opportunities for obtaining meat from those animals.  So every landscape change affected the plants and animals – in fact, the entire ecosystem – and thus the early human toolmakers as well.

Now consider this next image:

Aerial view of the Olorgesailie landscape with white and reddish brown sediment layers and deep channels and ravines cutting through them

White and gray layers reflect the gradual build-up of the Olorgesailie Formation layers. They indicate many shifts between lake and land from about 1.2 million to 490,000 years ago. The darker brown sediments are ancient river sediments.  The narrow brown bands across the present-day landscape represent the erosion of large river channels, which were eventually filled up with silt and sand of the younger Oltulelei Formation. A big question:  What caused the repeated cutting of river valleys, followed by silting up of those river and stream channels?

After 490,000 years ago, the largest landscape changes we see were caused as river valleys were cut by erosion into the underlying Olorgesailie Formation.  These valleys were then filled up with brown silt and sand.  The filling was followed my more erosion as a new river valley formed.  This process happened at least 3 major times, and several minor times.

Aerial view of the Olorgseailie basin with green trees dotting the landscape of winding gorges with white and light brown and grey striped walls

The beautiful landscape of Olorgesailie – exposing layer after layer of landscape change, which could have resulted from climate shifts and earthquakes. Kay and I discussed two main causes:  Earthquakes or climate?  Earthquakes could have caused uplift of the Olorgesailie region, with rain and wind then carving out channels and creating valleys in the high ground of the uplifted landscape. The other possibility is climate.  That is, during dry times, the water levels across the region would have dropped, causing the occasional rain storm to carve the landscape down further and further over many years to reach the lower levels.  During wet times, as the regional water levels rose, the rivers and streams would have backed up and slowed, which caused the silt and sand in those flowing waters to be dumped within the channels.  In other words, cycles of erosion and deposition, over and over again as climate shifted over time.

At present, Kay and I are pretty certain that these big fluctuations of the landscape in the younger geological beds reflect strong climate cycles – that is, big shifts between dry times and wet.

The work continues as we keep seeking better clues to see whether we are right or not…


A Nevada CRM Archaeologist

This is my first post for the Day of Archaeology event.  I’d like to begin by thanking the organizers, advisors, and sponsors for conceiving of and making this event happen.  It’s important that we discuss archaeology across the world and get our work out to a broad audience.  All most people know about archaeology is what they see on the Discovery Channel or from Indiana Jones.

The road I took to get to a career in archaeology involved several u-turns and a few speed bumps.  Here is a quick history.  When I was a kid I wanted to be an astronaut, an airline pilot, or an archaeologist.  Since my family didn’t have the money for me to realize any of those goals I did what I thought was the next best thing and joined the Navy right out of high school.  I spent the next four and a half years working on EA-6B Prowlers as an aviation electronics technician.  During that time I went on a cruise on the USS Enterprise for six months in the Mediterranean and in the Persian Gulf.  We saw some great cities with great archaeology and history.  At this time, archaeology was something you saw on TV and included crusty old PhDs working in universities.  I never considered it as a career.

Near the end of my time in the Navy a random phone call landed me in commercial flight training at the Spartan School of Aeronautics in Tulsa, Oklahoma.  While there I received my private pilot’s license and finished the training for a few other licenses.  After a year and a half I transferred to the University of North Dakota to continue my flight training at the nations largest and most advanced collegiate flight training school.  UND Aerospace has an amazing program with state of the art aircraft and flight simulators.  It was a great experience.

While I was taking aviation classes I filled up my general education requirements with anthropology classes.  I still loved the science of archaeology, in particular paleoanthropology, but still didn’t see it as a career option.  I’m not sure why.  I think it was still just one of those fantasy fields that you never think you are capable of performing.

After a couple of years I started to lose my desire to fly commercially.  I just didn’t think I would get any satisfaction from shuttling people around the country for the rest of my life.  Sure the pay is good but there are a lot of things you can do that involve less stress if all you want is money.  I need a job that makes me feel good at the end of the day and that I look forward to going to everyday.  Since I still didn’t see archaeology as an option, even though I had taken most of the classes offered, I spent the next couple of years taking photography and math classes just for fun.  I know, I like math.  I’m probably the only CRM archaeologist that has used SOHCAHTOA to determine the exact angle for a transect.

During my penultimate year in college my professor, Dr. Melinda Leach, told me that I could graduate in one year with a degree in anthropology.  I just had to take all of the upper level classes and that would be it.  With no other direction I decided to go for it.  I had to take 18 credits during the fall and 15 credits during the spring and write, I think, five or six research papers during the year but in the end I graduated.  After graduation I went back to Seattle and worked with my brother’s father in law’s home remodeling company.  I hated it.

In the fall I went back to North Dakota to help with the big event that the department had planned the previous year.  We had Jane Goodall coming to speak to a packed house.  One day, while sitting in the student lounge, a former student, and friend, came up to me and said hi.  He was visiting because hurricane Katrina had destroyed his apartment in New Orleans and his company laid everyone off for a little while.  He asked what I was doing.  At the time I was getting ready to go on an Earthwatch expedition to dig in Olduvai Gorge in Tanzania.  After that I had no plans.  He asked if I had checked Shovelbums.  Shovel what?

I educated myself on shovelbums.org, prepared my CV, and started on a job in Minnesota a week after I returned from Africa.  That was in October of 2005 and I’ve been in CRM ever since.  I’ve worked at all times of the year, on all phases of field archaeology and in 13 states.

In August of 2009 I began a one year MS program at the University of Georgia.  The program was intense but I received my Master of Science in Archaeological Recourse Management in July of 2010.  I’m currently working in the Great Basin of Nevada and love every minute of it!

So, I guess that wasn’t too brief.  My fiancé will tell you that brevity is not a trait that I possess.  Hopefully someone will get out of this that it’s never too late and you are never too old to get into the dynamic field of anthropology.   There are many paths that you can take to get to anthropology and there are just as many that you can take along your career.

My Chief in the Navy once told me how he decides whether a job or a position is right for him.  He said to look around at the people that have been doing your job and are at the ends of their careers.  Are they happy?  Are they doing what you would want to do?  My favorite thing about archaeology is that you can’t really tell what the future will bring.  You could be running a company, teaching at a university, or hosting your own show on the Discovery Channel, if they ever get back to science and history shows and away from reality shows.  The possibilities are nearly endless.

In my next post I’ll talk about the project I’m on right now and the wonders of monitoring.


Written northeast of Winnemucca, NV.