Episode 52. Birgül Öğüt: Phytoliths in west Asian archaeology: transcript

0:13  JT

Hello, and welcome to the Thin End of the Wedge, the podcast where experts from around the world share new and interesting stories about life in the ancient Middle East. My name is Jon. Each episode I talk to friends and colleagues, and get them to explain their work in a way we can all understand.

0:32  JT

Archaeology is not all about the grand scale: landscapes, magnificent architecture, spectacular individual finds. We learn a lot from the mundane as well. And even from finds so small you would never notice them.

0:50  JT

Ironically, these tiny finds that you will never see displayed in museum cases can help us answer some big questions. They teach us about the local environment, and how people used spaces, for example.

1:06  JT

Our guest is an archaeologist with expertise in micro-biological remains. She explains for us what they are and how we can learn from them.

1:16  JT

So get yourself a cup of tea, make yourself comfortable, and let’s meet today’s guest.

1:30  JT

Hello, and welcome to Thin End of the Wedge. Thank you for joining us.

1:35  BÖ

Hello. Hello, Jon.

1:37  JT

Could you tell us please: who are you, and what do you do?

1:42  BÖ

Yes, of course. I’m Birgül Öğüt, a Near Eastern archaeologist. At the moment, I’m mainly working for two projects as a postdoc. Since 2020, I have been part of the Göbekli Tepe project of the German Archaeological Institute. Here I am responsible for the sampling management, and especially the phytoliths and ground stones. In addition, I have been employed as a postdoc in the HighStepLands project in Kohgiluyeh Province in Iran at the Kiel University since 2022. Our third project is my own Şehitkamil survey in northern Gaziantep in Turkey, a province that is now enduring immeasurable suffering as a result of the terrible earthquake. But to get back to your question, these projects also reflect my research interests, which are admittedly very broad. But in general, I’m very interested in subsistence, human environment relations, and the integration of settlements in the landscape. By integrating microfossil analysis, especially phytoliths into the archaeological evaluation, I try to get closer to the everyday life of the people.

3:04  JT

Okay, so we’re going to talk about phytoliths. Maybe we could explain for listeners what phytoliths are?

3:12  BÖ

Yeah. phytoliths are microscopic structures of silica found in some plant tissues that persist after the plant decays. Plants take up silica from the soil, which is then deposited in various intra and extracellular structures of the plant. These deposits which, so to speak, reproduce the imprints of the plant cells have certain shapes, by which they can be assigned to certain plants and plant parts. For example, phytoliths can be easily identified from the influorescence of cereals, in contrast to macro-botany, or archaeo-botanical remains, they are inorganic, and almost indestructible.

3:57  JT

Where do we find phytoliths? And how do we access samples containing them?

4:02  BÖ

Phytoliths get into the soil through the decay of plants. Since they are microscopic, they cannot be seen with naked eye. But by taking soil samples and extracting the phytoliths from the soil sample, it is possible to examine them under a microscope with a magnification of about 400 times. So you don’t really have to pay much attention to take the samples. The bare soil is appropriate. It’s taken from the context that is to be examined. When extracting phytoliths from the soil, first, all components that are not relevant for this analysis were removed. For example, clay, stones, bones and so on. Once the sample contains only soil components, the phytoliths can be separated using various techniques. The most commonly used method is heavy liquid flotation. This involves increasing the density of the solution, so that the phytoliths float on the surface of the solution. This allows them to be collected and later examined under the microscope.

5:14  JT

Ah-ha, so, how does the sampling method affect the questions we can ask?

5:19  BÖ

Very strong! Better said it is like with all samples and examinations, you should be clear in advance what kind of information you want to get. Often colleagues come and bring me a bag full of soil and ask “Can you check if there are phytoliths?” but without seeing the bag and the content, I can say, “yes”, for 90% phytoliths are in there, because phytoliths are usually everywhere and almost indestructible. The more specific the question, the more precisely the context must be documented, and also the very exact location of the sample that was taken. You only need about one gram approximately of the soil you want to examine. Therefore, the sample size does not increase the amount of information one gets about phytoliths.

6:15  BÖ

For example, if you want to investigate the functional use of floors, it is ideal to do our grid sampling. This means that the floor is divided into approximately 30 centimetre squares, and every second square is sampled like a chessboard. Corners are very good for this, because the floor is swept, residues from use can still be in the corners. In addition, you can also sample objects lying on the floor that may have had something to do with plants, for example, grinding stones. So, I can say whether the floor was clean, if you have for example, a few phytoliths; what plant materials got into this room, when a grinding stone was sampled; for which plants it was used–flour or chaff and so on. And what I myself find most exciting–whether this grinding stone was used in the place where it was found or was it only stored there. This says an immense amount about the function of the objects, the space, the structure of the building, the organisation of the household, everyday life resources, subsistence, and possibly ways of working. This is of course, an ideal case.

7:37  BÖ

Also very interesting are for example, hearths. Here you can find out what kind of fuel was used. In combination with, for example, dung analysis, which are also very exciting, one can make statements about the feed of the animals and about possible herd husbandry, resources, resource use, mobility and so on.

8:02  JT

You wouldn’t be examining dung for phytoliths would you?

8:05  BÖ

Yes and no. When I say dung, I actually mean dung spherulites. These are microscopic particles that are produced in the intestines of mainly herbivores and animals such as sheep, goat or cattle, and enter the soil via the dung. This means that they are then no longer recognisable in that context is dung, and are distributed in the soil. Like phytoliths, these are also not visible to the normal eye; they can only be seen under a certain microscope.

8:41  BÖ

That means for us if we see dung spherulites, there must have been done with there once. Usually this means that the place can we associated with animals. But it does not necessarily mean that at the exact place where the sample was taken, animals have directly produced their dung. It may also be that humans brought the dung at that place. This may sound strange to many people living in the cities today. Why should you touch dung at all? It’s disgusting. It’s bleurgh. But you must not forget that dung is in some places in the world still a valuable raw material. This is because dung consists mainly of plant fibres. It is used as fertiliser, but dried it makes a wonderful heating fuel, especially in areas where there are hardly any trees. It can also be a very good insulation for mud houses. And even for bricks or ceramics dung was and is used as an admixture.

9:49  BÖ

Depending on the amount of these particles, these spherulites, and the place where the sample was taken, one can make many statements. For example, whether it was a stable or a fireplace, since we can see from the dung spherulites that dung has been mixed into the soil. The phytoliths, which also come from the same sample, are very likely to be associated with the dung. That is, the plants came from the dung. This in turn can give clues about the diet of the animals, but sometimes also about the season in which the dung was formed, sometimes also the animal species.

10:33  JT

Is it common for archaeological animal dung to be found, actually?

10:37  BÖ

Yes, it is not uncommon to find dung, even in the form of actual pellets, especially in West Asia or in drier areas. These can rarely even be seen directly during excavation. More often they are found during work for archaeo-botany. For this, seeds and fruits charcoal are separated from the soil. This is usually done by a method called flotation, because these botanical remains float in water. In this way, these remains can be collected and identified under the microscope. Dung pellets are also often found here.

11:17  BÖ

Dung spherulites occur frequently in Western Asia as well. However, they can also decay and do not survive if the soil does not have the necessary properties. For example, the pH value is too low, or these particles are simply washed out of the soil by heavy rain. In Europe, for example, I’ve been told that the preservation is not so good.

11:43  JT

What are the limitations of phytoliths? Where’s that boundary between what it can and cannot do?

11:50  BÖ

I think I have already given some examples on what phytoliths can tell us. But what is very important is that you should not expect too much. For example, phytoliths are not as suitable for determining plants as macro-botany. But they give many, many small clues, which in combination with the archaeological information, and further analysis always yield statements about the life of people. Even for example, in very rare cases, no phytoliths have been preserved. One can ask why: a too high pH value or too little silica in the soil. However, this in turn means that people probably already had to deal with such soil at that time. We can ask then what effects had this to the people’s lives.

12:47  BÖ

There are also for example, some works that want to prove the domestication of plants through phytoliths. This is an immensely important topic in archaeology. But it is just as complicated and in my opinion, cannot be proven exclusively by phytoliths. It is possible to prove the cereal species quite well. Likewise, colleagues are developing methods to distinguish between early forms of domesticated cereals. However, these kinds of investigations require vast amounts of samples and comparative analysis, so that it is impossible to tell from four or five samples from one place, whether the beginning of the domestication of plants lies here.

13:37  BÖ

In general, however, it is almost always possible, especially in Western Asia, to tell by the good preservation conditions, how high the concentration of phytoliths is, whether grass-like plants or tree-like plants occur, what the relation and preservation is, and what components are present. Only through the combination with other information, further statements can be made.

14:07  JT

How do we get from the micro-scale to the big picture of life in the ancient world?

14:14  BÖ

That’s a wonderful question. I’m convinced that without the micro-scale we are not able to get sound knowledge about the big picture at all. Phytoliths are an excellent proof of this, as also described in the previous examples. I can perhaps illustrate this again with another example. In a project with my colleague Doğa Karakaya, who is an archaeo-botanist working on macro-botany, we asked ourselves exactly this question and chose an area where the Syro-Hittite kingdoms in south-eastern Turkey are in the Iron Age. These selected sites are Zincirli Höyük, Tell Tayinat, Sirkeli Höyük, Dülük Baba Tepesi. All sites are relatively close to each other, but have either temporal or geographical differences. For example, they are embedded in a different environment. The classic Syro-Hittite city contains an upper city, where the elite live, and a lower city, which is inhabited by the non-elite population. Our idea is to compare the everyday with the monumental special, both within each settlement and then compare these settlements with each other to see if there are differences and what they are. Is it organisational differences? Is it all dependent on the environment and resources? Can we assume, for example, that all settlements have a general similar structure? If so, what is the reason. Is the political elite so well networked that they even use similar organisational structures? Or have previous structures been adopted? So admittedly, these are really big questions, and we don’t know if we will ever be able to answer them.

16:18  BÖ

But how are we going to get to these answers via plants? Using samples that come from the same context to get to the basis for comparison. For example, we takes samples in each place not only from the same spatial structures like dwellings, or palaces and so on, but from the same contexts like pits, floors, grinding stones, ovens, and so on. By analysing hundreds of samples and embedding them in their archaeological chronological historical context, we try to arrive at the big picture with very small steps.

16:59  JT

So how does evidence from phytoliths fit with other archaeological and scientific evidence?

17:05  BÖ

As already mentioned, phytoliths live from multi-proxy analysis. In my opinion, phytolith analysis alone can hardly make statements, especially in archaeology. In combination with dung spherulites, macro-botany, diatoms and other analysis, however, very exciting results can be achieved. Always in the archaeological context, of course. Take phytoliths, dung spherulites, animal bones, macro-botany in one example. Here phytoliths say that there were a lot of shrubs. Dung spherulites say there was an extreme amount of dung. The archaeological context does not speak against a stable. The animal bones say there were a lot of sheep and goats. From the combination of all of them, if all goes well, of course, it could come out that goats were probably kept in this place. Because they prefer eating shrubs, and sheep more grass. They could probably freely graze in the immediate vicinity, and chose their own food and were kept in the site at a certain time. For example, at night.

18:30  BÖ

One good method to determine micro-histories is micro-morphology. In this method, blocks of soil are cut out. From these blocks, a fine layer is cut out and attached to a glass slide. In this way, we can see from a block from the floor, for example of a house, how often the floor has been renewed, because each layer of floor is recognisable as a fine line under the microscope. Or you can find out what the floor was made of. Or it can tell us about the use and whether the room was kept clean. But this method gives only a very small gaze into approximately 20 by 10 centimetre window in the soil for each slide. Therefore, the combination of different methods can give information in different scales.

19:32  BÖ

Combining these methods, we can describe the biography of houses, maybe settlements, and actually also part of the people’s biography. The more analysis, the more possibilities of course. However, one should think carefully about which analysis make sense.

19:53  JT

Do you think that all excavations should study phytoliths, then? How should this kind of work be incorporated into the project plan?

20:01  BÖ

I would say, yes, of course. All the excavation should add phytoliths into their project plan. But it really depends on the question of the excavation. The big question. If you’re not interested in microscale information, of course, it makes no sense. And if very large scale excavation is being done, the samples are too large scale to give specific answers. And sometimes there are actually places where no phytoliths are preserved. So I would always suggest before planning a big project with phytoliths, that you study over two or three samples, how the phytolith preservation is. It is best to discuss sampling with a phytolith expert, and draw up a sampling plan depending on the budget and questions of the project.

20:59  JT

Would you say that the study of microbiology is something that will always be specialist work? Or should the next generation of archaeologists learn how to do this as a part of their training?

21:10  BÖ

As an archaeologist who learned phytolith analysis through additional training, I would say that it depends on the field you want to work in. But definitely, I would say that while studying archaeology, you should have the opportunity to at least get an insight. Not every archaeologist has to be an expert in the field later on, but should at least know that these kinds of analysis exist, and what they can be used for. A good example is 14C dating. We archaeologists know what they are good for. Many can integrate 14C results in their work, but very few of us can analyse them themselves.

21:56  BÖ

Micro-biological analysis are, of course different from 14C analysis. You basically don’t need an extremely well-equipped laboratory, and extremely high budget or many years of training to be able to do the analysis at all.

22:12  BÖ

Unlike for example, macro-botany, archaeo-botany, which is a subject in its own, and where it is essential to know the plant world and systematics, one can work very well in archaeology with the analysis of quantities and determinations of phytolith types, even without knowing the exact circumstances why plants produce phytoliths. I would even argue that knowledge of the archaeological context is indispensable for the statements that can be made afterwards.

22:48  BÖ

I myself only learned how to analyse phytoliths after my studies in archaeology during my PhD, through extra training with experts and through self study. I can integrate the analysis into the archaeological context. Whereas when results come from an external biological laboratory, many archaeologists who have nothing to do with the subject find it difficult to integrate the results into their work.

23:18  BÖ

So I would say that every archaeologist should at least know what phytoliths are, how to take sampling during fieldwork. That should be part of the training. Doing the analysis yourself, should be offered maybe as a part of postgraduate degree. For example, as part of a master’s program in scientific archaeology.

23:45  JT

I wonder if you’d like to say something about the training materials you’re producing?

23:49  BÖ

Training students is in this part, very important. As I said, phytoliths are not so well-known. We are doing with some colleagues special trainings for students to get them used in phytoliths analysis. What I exactly explained that they know what phytoliths are, and especially how to take samples in the field. Because the specialists can’t be at the field during the fieldwork there often to take the samples, it’s very important that the archaeologists or the students working in the fieldwork, get the samples. And how to analyse the samples is the next step. So we are beginning to train students, for example, in Turkey, and we are preparing an actually a handbook for our archaeo-metric sampling. This is for archaeo-botany, for example, isotope analysis and phytoliths and so on, so that the students have a basic knowledge about these analyses. And maybe if they are more interested in these analyses, they can find more possibilities later to study or to get involved in these analyses.

25:13  JT

Do you see yourself becoming a dedicated phytoliths specialist offering this expertise to a range of projects? Or do you prefer to keep it as just a part of your archaeological skillset?

25:26  BÖ

Although I’m working more and more intensively with phytoliths and analysing them for many projects, I would not see myself as a pure phytolith specialist. I am more of an archaeologist who has learned this method and can evaluate the results with the archaeological context. That is why I would not for example, evaluate phytoliths from geographical surveys, from the landscape in their geographical contexts. So I’m not the expert for this. Or I’m not a biologist who could explain the exact processes in phytolith formation. My focus is also not the exact determination of plant species, which is important for our archaeo-botany. Even though the work in the lab is a lot of fun, and the evaluation on the computer brings very interesting results, I can’t do without excavations.

26:27  JT

You mentioned earlier that you were involved in a number of projects. Could I ask you to say just a few words about what these projects are and what your contribution to them is?

26:37  BÖ

Of course.

26:38  JT

So the first one is Göbekli Tepe. I imagine many people have heard of it, but perhaps associate it really with standing stones rather than phytoliths. So what work are you doing there?

26:49  BÖ

Göbekli Tepe is a site in south-eastern Turkey, in the province of Sanliurfa settled about 11,000 years ago. This site is particularly known for its round oval buildings with T-shaped pillars, and sensational representations of scenes of many animals. These buildings have often been referred to as the first temples of mankind. Although more recent research has called these superlatives and especially the term of “temple” into question. Temples have always played an immensely important role in research, with the rituals being a major attraction for a wide variety of interpretations. Since we have no written sources from this period, we have to try to explain the use of these buildings in other ways. Not only the use but also the construction and abandonment of this place is fraught with different, sometimes very contradictory opinions.

27:56: BÖ

The spectacular and thus popular opinion, very simplistically summarised, is that men from hunter gatherer societies of the region erected these buildings as a kind of temple, and to use this place as a gathering place for regular cultic feasts. Beer, bread, and other dishes were made for these feasts. This is inferred from the stone troughs and many grinding stones found here. In this context, plants play a decisive role. If beer and bread or other food containing cereals were produced, does this mean that the transition to sedentism can be guessed here? The cultivation of plants is one of the factors that has so far been linked to or with sedentism.

28:54 BÖ

But more recent research at Göbekli Tepe assumes that the site was used, at least not exclusively for special purposes. Numerous rectangular rooms have been discovered around these round oval buildings, which were probably used domestically. In addition the singularity of Göbekli Tepe has been abolished for some years. There are more and more sites where similar buildings with T pillars are found. And some of them even seems to be older. Highly interesting is the interpretation that these are not the beginning of sedentism, but possibly the last remnants of hunter gatherer societies that might have used these places as their last retreats. As you might guess, wherever plants come into play, phytoliths play an important role, especially when as in Göbekli Tepe the archaeo-botanical remains are not well preserved. So, what were the troughs and grinding stones used for? Was cultivated grain actually used? What are stored in the troughs? What can be found on the floors? Can phytoliths provide answers? So, some initial investigations have already been made, but the real work is still to be done. Using various methods, we’d like to get to the bottom of this question in the coming years. For example, we are working on an article about the floors from Göbekli Tepe, which we are investigating architecturally, geo-chemically, mineralogically, and for phytoliths and lipids, so it remains very exciting.

30:47  JT

Okay, the second one, then, the HighStepLands project. That’s rather different, isn’t it? What about that one?

30:56  BÖ

Yes, it is. So the HighStepLands is a project that is about reconstructing long-term social, cultural and environmental dynamics in the Zagros Mountains in southwestern Iran. In particular, settlement dynamics and the mobility patterns of people in the past, and the strategies of past societies, and their response to changing ecological and political conditions will be identified in this project. So it’s a highly topical subject. We are concentrating on the small province of Kohgiluyeh-e Boyer Ahmad, which has received little attention so far, and is situated in a crucial position between the main cultural zones of southwestern Iran and Mesopotamia. Phytoliths can be used, for example, to compare the use of plant resources in the settlements of the different landscapes, and perhaps even to investigate the question of why people chose this site. Since at the moment, it is not possible to conduct excavations, the team is working on compiling previous work on the Neolithic in this area, a somewhat outdated assumption is that neolithisation, sedentism, agriculture and so on, in the southwestern Zagros arrived later from the west along the Zagros, because hardly any sites in the region have been dated to this period so far. In our opinion, however, this is only a research gap.

32:43  JT

And then I can’t really let you go without asking about the third project, your own one, your survey. Could you tell us about that one, please?

32:51  BÖ

Of course. The Sehitkamil survey is in northern Gaziantep in southeast Turkey, and is my own project which started in 2022 with a very small team. In this work, the main focus is on the village of Dülük. On the one hand, it is a significant palaeolithic site. And on the other hand, the sanctuary of the storm god Jupiter Dolichenus dating to the Iron Age, was located in the vicinity. In Hellenistic Roman times, the sanctuary became a cultic centre of super-regional importance. Later, a medieval monastery complex was built there. Contemporary settlement to the temple has so far only been excavated from the Hellenistic period at Keber Tepe/Doliche, and seems to be a new foundation with no traces of older periods. The settlement structures and settlement network in the immediate vicinity before the Hellenistic times are unknown, as is the need for a new foundation.

34:00 BÖ

In general, the periods between the palaeolithic and the Hellenistic in this area have only been superficially researched. In the following years, we would also like to include palaeo-environmental and landscape archaeological research, to see what influence the environment and landscape may have had in the dynamics of past societies. A first article will be published soon. And we are working on the evaluation of the results of the first campaign. How and whether our work can be continued is unfortunately impossible to assess at the moment, as the exact extent of the destruction caused by the earthquake is not yet known. But we hope to be able to work in the region again as soon as possible. Not because archaeology is more important to us than human lives. On the contrary, we are constantly asking ourselves, “How can we as archaeologists help the people in the areas where we are working?” Of course, we donate to many aid organisations, which can help acutely in the region in the most professional way.

35:17  JT

I’d like to add a short editorial note here. As Birgül mentioned, people need help to recover from the effects of these devastating earthquakes. If you’d like to make a donation and aren’t sure where to do that, there are some suggestions in the show notes.

35:34  BÖ

What we do in addition is to contribute to the people’s living, even if it’s very little through work, and especially train local students and support them. In this way, we hope that these places will continue to be alive and remain as places of interaction and cultural exchange as they have been for millennia.

36:04  JT

Well, thank you very much indeed.

36:05  BÖ

You’re welcome.

36:07  JT

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37:14  JT

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37:52  JT

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