Reconstructing life in an ancient city

Teotihuacan shows off the best archaeological research in the two major approaches to fieldwork at ancient cities: monumental archaeology and social archaeology. Recent and continuing excavations of the main pyramids by my ASU colleague Saburo Sugiyama and by Mexican archaeologist Sergio Gómez are uncovering new information about the ancient religion and politics of the city. This is the monumental approach. I'll talk about this work in a future post.

And current work by David Carballo and Kenneth Hirth in the Tlajinga area of Teotihuacan showcases the advances and accomplishments of the social archaeology approach.

(((WONK ALERT !!!  I use the term "social archaeology" here to describe analyses of ancient social patterns using rigorous methods.  I do NOT use the term in its idiosyncratic postmodern definition that refers to subjective and speculative interpretations of the archaeological record, as exemplified by papers in the "Journal of Social Archaeology" and other works of that ilk. In my usage here, social archaeology focuses on excavation of houses and analyses of the conditions and activities of ancient households, especially non-elites. If you want to know why I don't like the alternative, postmodern meaning of "social archaeology" concept, see this post in Publishing Archaeology)))

Here, I want to point to an excellent description of the current Tlajinga project that focuses on households and obsidian tool production in domestic contexts. Check out the new article, "Lessons from Teo," in the Boston University Research magazine. It is quite good! The artifact analyses of that project are being done in the ASU Teotihuacan Research Laboratory.  I wish we had more university PR departments that produce stories as intelligent, literate, and exciting as this one. My hat is tipped to David Carballo for telling the story of the Tlajinga excavations, and to the Boston University writing and filming crew for doing such a good job communicating that story.

Why do all cities have neighborhoods?

I've been writing about urban neighborhoods for several years now. I have made the claim that all cities have neighborhoods. In fact, neighborhood organization is one of the very few urban universals. There are very few features shared by ALL cities, throughout history and around the world. Besides neighborhoods, other candidates for urban universals include the provision of urban services, and the fact that if a society has an elite class, then many or most of its members live in cities.  See: Do all cities have neighborhoods? (2011), or

I find that I always hesitate a bit when writing that "all" cities have neighborhoods. That is a tough claim to prove. We simply don't have information about all the cities that have ever existed, so a claim for the universality of something like neighborhoods must rest on indirect evidence. Here are the three lines of evidence that make sense to me.

First, every description of a city that is sufficiently detailed and focused to mention the existence of neighborhoods, does in fact mention neighborhoods. This is far from an air-tight argument. But I've been looking at city descriptions like this for a number of years now, and so far this claim has held up. These include ethnographic reports of cities around the world, historical accounts of cities before the modern era, and archaeological reports of ancient cities. Archaeologists started thinking seriously about neighborhoods about eight years ago, and guess what? Since then, many reports of neighborhood organization have popped up. Check some of the works in the bibliography below.

Second, many bin-depth studies of neighborhoods, in the past and the present, have found that neighborhoods are crucial social and spatial units within their city. They are important in many ways for urban residents, and they are important for the overall operation and functioning of the city. Some of my favorite such studies are Robert Sampson's analysis of Chicago neighborhoods today, Abraham Marcus's study of Aleppo in the 18th century, and Eva Lemonnier's identification of neighborhoods at the ancient Maya city of La Joyanca. See: Why are neighborhoods important? (2014).   Or, in Publishing Archaeology, see Archaeological concepts of community confront urban realities today (2015).

Third, I carried out a study, together with a bunch of undergraduates, of neighborhood organization at semi-urban settlements (Smith et al, 2015). The study was based on the assumption that if neighborhoods formed at these rapidly-formed, often chaotic, and sometimes specialized settlements, then they would form at any good-size human settlement. We found neighborhoods did indeed exist at Plains Indian aggregation sites, arts festivale, RV camps, protest camps, shantytowns, military camps and forts, internment camps, company towns (including ancient Egyptian workers villages), and refugee camps. The only kind of settlements where we could not confirm or discomfirm the presence of neighborhoods was disaster camps.  See : Neighborhoods in semi-urban settlements (2011).

So, if neighborhoods really are urban universals, why is that the case? In our 2015 article, we give two types of answers: ultimate causes, and proximate causes. These concepts, borrowed from evolutionary biology, refer to the deep underlying causes of social phenomena (the "ultimate" causes) and to the basic day-to-day reasons for their formation ("proximate" causes). The underlying, ultimate cause of neighborhood formation is that people in cities need, or want, to live their lives on a smaller scale than the entire city. Some studies suggest that this is caused by constraints on human memory; one can only recall so many people, and effective social networks cannot be too large. Other studies suggest that living in cities causes social stress, and neighborhood organization is a way of relieving that stress.

It is interesting to note that neighborhoods can form in two very different ways. The most common path throughout history was the bottom-up approach. People living in an area interact with those around them (their neighbors), and eventually clusters or people, or communities, develop on their own out of the day-to-day actions of people. But in some cases, city or government authorities create neighborhoods. They organize cities from the top down, and people move into ready-made neighborhoods.

In our paper we identify the following proximate causes of neighborhoods: For bottom-up neighborhoods, simple sociality--interacting with your neighbors-- is the primary cause of neighborhood formation. Group preservation and defense also contribute to neighborhood formation in some cases. For top-down neighborhoods, established by authorities, the most common proximate causes are administration (the need to administer the residents) and control/surveillance. Sociality is a secondary consideration; if not present from the start, it quickly develops once people start living in their pre-made neighborhoods.

REFERENCES

 Arnauld, Marie Charlotte, Linda R. Manzanilla, and Michael E. Smith (editors)
2012    The Neighborhood as a Social and Spatial Unit in Mesoamerican Cities. University of Arizona Press, Tucson.



Hakim, Besim S.
2007    Generative Processes for Revitalizing Historic Towns or Heritage Districts. Urban Design International 12: 87-99.

Lemonnier, Eva
2011    Des quartiers chez les Mayas à l'époque classique? Journal de la Sociéte des Américanistes 97 (1): 7-50.

2012    Neighborhoods in Classic Lowland Maya Societies: Identification and Definition from the La Joyanca Case Study (Northwestern Peten, Guatemala). In The Neighborhood as a Social and Spatial Unit in Mesoamerican Cities, edited by Marie Charlotte Arnauld, Linda R. Manzanilla, and Michael E. Smith, pp. 181-201. University of Arizona Press, Tucson.

Marcus, Abraham
1989    The Middle East on the Eve of Modernity: Aleppo in the Eighteenth Century. Columbia University Press, New York.

Sampson, Robert J.
2012    Great American City: Chicago and the Enduring Neighborhood Effect. University of Chicago Press, Chicago.

Smith, Michael E.
2010    The Archaeological Study of Neighborhoods and Districts in Ancient Cities. Journal of Anthropological Archaeology 29 (2): 137-154.

2011    Classic Maya Settlement Clusters as Urban Neighborhoods: A Comparative Perspective on Low-Density Urbanism. Journal de la Société des Américanistes 97 (1): 51-73.

Smith, Michael E., Ashley Engquist, Cinthia Carvajal, Katrina Johnston, Amanda Young, Monica Algara, Yui Kuznetsov, and Bridgette Gilliland
2015    Neighborhood Formation in Semi-Urban Settlements. Journal of Urbanism 8 (2): 173-198.

Are Rural and Urban always very Different?

For most people, the terms "urban" and "rural" conjure up different kinds of places, different kinds of contexts. Urban is cities: dense populations, lots of activity, good access to markets and goods, not much green space, dirty streets. Rural is farms: open land, not many people, boring and tranquil, distant from the busy city. R. Crumb's sequence "A Short History of America" (above) exemplifies this standard view; in this case, a transition from rural beauty to urban ugliness.

But there are other ways of viewing rural and urban. Anthropologist Anthony Leeds, for example, suggested that the terms rural and urban are best used not as opposites, but rather as terms for different settings within a single society:

any society which has in it what we commonly call "towns" or "cities" is in all aspects an "urban" society, including its agricultural and extractive domains . . . the terms "urban" and "rural" come to stand to each other not as opposites and equivalents. Rather, the inclusive term describing the whole society is "urban" while the term "rural" refers only to a set of specialties of an urban society characterized by being inherently linked (under any technology known) to specific geographical spaces. (Leeds 1980:6-7)

Urban house

I like this viewpoint very much, partly because it helps make sense out of some of my archaeological findings at Aztec sites in the central Mexican state of Morelos. My first major excavation project after my Ph.D. focused on "rural" sites: small sites located far from the urban centers of the time. As I described briefly in this blog a couple of years ago, I was initially surprised to find what seemed to be "urban" traits at these sites: an active economy, many imported goods from all over Mesoamerica, complex social and ritual activities, and participation in the current widespread styles of the day. I had expected to find poor, isolated, downtrodden peasants. Instead I found wealthy, prosperous, and well-connected farmers.

So, "rural" Aztec sites had "urban" traits. I then went on to excavate at an urban Aztec site, Yautepec. My initial expectation there was that if the peasants were prosperous and successful, the urbanites would be fabulously wealthy and well-connected. But instead, the urban households were almost identical to the rural households in many respects:

• The houses were virtually identical in materials and size
• The basic kinds of domestic artifacts were virtually identical. Each area had its own styles of painted pottery, but everyone used obsidian blades, everyone had some fancy serving vessels, and the same kinds of domestic rituals took place in the urban and rural houses.
• Rural and urban households all had ceramic vessels imported from several distant areas, they all had bronze tools and ornaments from the enemy Tarascan territory hundreds of miles away.
• Rural and urban households all participated in extensive Aztec style networks in goods like ceramic vessels, ceramic figurines, and ritual implements.
• And the kicker was that the basic population density in urban neighborhoods was very similar to the density within the ritual sites. There was quite a bit of open land within the city of Yautepec, and at least some of it was dedicated to agriculture.

From the standard view of rural and urban as opposites, these findings are simply bizarre. But from the view of Anthony Leeds, they make more sense. There is no inherent reason why urban residents could not practice agriculture, or why rural residents could not be wealthy and well-connected to the outside world.

Rural house

I am not saying that rural and urban contexts were the same in Aztec central Mexico. Yautepec had more elites running around, and there was a royal palace. Yautepec almost certainly had a tall pyramid dedicated to the patron god where victims were sacrificed periodically. There were more economic specialists in the city. But still, rural and urban life were just not all that different in this part of central Mexico.

Why was this? Well, I am out of space here and can't go into the details. But here are three quick reasons: (1) Aztec commoners in this area belonged to an organization called a calpolli that structured rural and urban life in similar ways. (2) The Aztec marketing system was extensive and efficient, bringing goods, ideas, and styles to rural as well as urban people. (3) These particular farmers (both urban and rural) had a big advantage over their cousins in other areas: they could grow cotton, which could be woven into money (literally).

I discuss Aztec rural and urban contexts in my book, Aztec City-State Capitals, and in an article with Christian Isendahl. And I provide a longer answer in my new book, At Home with the Aztecs: An Archaeologist Uncovers their Domestic  Life (due out in February 2016).

So, the next time you see some nonsense about how rural and urban  are complete opposites (as in this photo; or rather, as in the text that labels it), think about the perspective of Anthony Leeds. Rural and urban are two different sectors of an urban society. Life in thees contexts may be very different, or it may be very similar.


Isendahl, Christian and Michael E. Smith
2013    Sustainable Agrarian Urbanism: The Low-Density Cities of the Mayas and Aztecs. Cities 31: 132-143.

Leeds, Anthony
1980    Towns and Villages in Society: Hierarchies of Order and Cause. In Cities in a Larger Context, edited by T. Collins, pp. 6-33. University of Georgia Press, Athens.

Smith, Michael E.
2008    Aztec City-State Capitals. University Press of Florida, Gainesville.

2016    At Home with the Aztecs: An Archaeologist Uncovers their Domestic Life. Taylor and Francis, New York.

Collapse or Longevity? Failure or Success?

When many people think of the ancient Maya, the term "collapse" often comes to mind. The Mayas were a group that were around for a while, but then collapsed. Archaeologists have spent a lot of time (and a lot of fieldwork and publications) trying to figure out how or why (or sometimes, whether) the Maya collapsed. If they collapsed, there must have been something wrong with Maya society, right? But the Maya cities lasted for some seven centuries before they were abandoned. Think about it. Seven hundred years. Were the Maya a failure (they collapsed), or were they a spectacular success (they lasted 700 years).

The idea that something must have been wrong with ancient cities or civilizations to make them collapse is a popular notion. And while it is a valid question to ask how or why a society like the Classic Maya collapsed, any such question should be paired with a consideration of just how long they managed to thrive. This collapse bias surfaced again today in a paper just posted in the Proceedings of the National Academy of Sciences:  "Human domination of the biosphere: Rapid discharge of the earth-space battery foretells the future of himanking" by Rohn R. Schramski, David K. Gattie and James H. Brown. This is a fine paper, about the global chemical energy supply on earth, and how it is being depleted at an incredibly fast rate right now. But they had to throw in a dig at ancient societies:

At local and regional scales, many multiple past civilizations (e.g., Greece, Rome, Angkor Wat, Teotihuacan) failed to adapt to changing social and ecological conditions and crashed catastrophically

Let's take a different look at those four ancient societies in comparison to contemporary nation-states:
 

So, which of these societies seem successful, and which ones seem too young to judge? I am dating the start of the European nation-states to 1648, the signing of the Treaty of Westphalia which created the modern system of nation-states. If European nations manage to survive another half century or so, they will have matched the longevity of ancient Greece (I am using the Classical and Hellenistic periods here). And if they last another 350 years they will match those failed collapsers, the ancient Maya.

I am the last one to deny the significance of the Classic Maya collapse. I think the revisionists who claim that they didn't really collapse are just plain wrong (see some of my posts on Publishing Archaeology about this, such as this one about Jared Diamond and his critics). But if the Maya managed to thrive in the jungle for seven centuries, maybe that fact should outweigh their eventual collapse. They spent centuries doing many things right, and then they got trapped for a few crucial decades and collapsed.

I will just chalk up the collapse quote above to the fact that scholars outside of history and archaeology tend to be clueless about ancient societies. I think the authors of the new paper are correct when they claim that ancient collapses "are of questionable relevance to the current situation." Much as I'd like to believe that the sustainability (or lack thereof) of ancient societies might have lessons for us today, in fact the technological, energetic, and demographic situation today is radically different from that of ancient societies like the Maya. I do think that ancient cities and societies have lessons for us today, and that is a major theme of this blog. But the nature of overall societal sustainability may not be one of those lessons.

Can we decipher the "meaning" of ancient buildings?

Many people wonder about the "meaning" of ancient buildings and sites. Why was the Pyramid of the Sun at Teotihuacan built? Was it dedicated to a specific god? What meaning did it have to the people who built it, and those to witnessed ceremonies there for centuries afterword? I am a skeptic about talk of ancient "meanings" of this sort (see a previous post about high-level meanings.) I agree with my colleagues Kent Flannery and Joyce Marcus (1993) that this kind of religious symbolism and meaning cannot usually be deciphered without written texts that explain ancient myths and beliefs. There are no such texts from Teotihuacan, so it is unlikely that we can figure out just what this pyramid meant in ancient times. But we do have some clues. This position is explained in general terms by architectural theoretician Amos Rapoport, one of the top scholars on wide urban topics and one of my heroes.

Amos Rapoport

Rapoport developed a very useful scheme of how architecture communicates information. He identifies three levels of communication in the built environment: high-level meanings, middle-level meanings, and low-level meanings (see Rapoport 1988, 1990). High-level meanings communicate messages of symbolism, cosmology, and religion. In ancient societies, these high-level meanings are typically understood by only a small number of specialists and elites; many commoners know little of them. High-level meanings are culturally-specific; for example, Egyptian symbolism is completely different from Mayan symbolism. Today, scholars can reconstruct high-level meanings only if there are explicit written texts, or in some cases, very rich archaeological finds.

Middle-level meanings communicate messages of power, control, stability, wealth, and other positive values that rulers and elites want their subjects to receive. These meanings are more general and widespread than high-level meanings. Big buildings signal power, whether in ancient Mesopotamia or Classical Rome. Because these messages are valid across cultures (and not culturally specific), archaeologists can often interpret them from the mute remains of ancient architecture.

The Aztec Templo Mayor in Tenochtitlan

Finally, low-level meanings concern the specific ways that people interact with buildings. They provide cues for how to behave appropriately, where to enter or exit, and other messages concerning movement, privacy, accessibility, and the like.

The Coyolxauhqui stone

The birth of Hutziliopochtli

I will illustrate Rapoport's scheme with the Aztec major temple, the "Templo Mayor" in their imperial capital Tenochtitlan (today the ruins are in the middle of Mexico City). It turns out that we have a good idea of the high-level meaning of this temple, mainly because of a key find of a stone monument, coupled with written evidence of Aztec creation myths. The monument, a stone slab some 10 feet in diameter, depicts the Aztec goddess Coyolxauhqui, who has been dismembered. It was excavated in front of the main front steps of the Templo Mayor. This monument illustrates the birth of the Aztec god Huitzilopochtli, whose first action after birth was to kill his sister Coyolxauqui (yes, that sounds odd; if you want the whole story, check one of the many books on the Aztecs, such as my book, The Aztecs). We know this myth from written sources, and from some early Spanish pictures (see the illustration from Sahagun's Florentine Codex). In terms of religious symbolism (high-level meaning), the Aztec main temple was a model of Serpent Hill, where their god Huitzilopochtli was born and killed his sister Coholxauhqui. The human sacrifices that took place on top of the Templo Mayor were re-enactments of Huitzilopochtli's birth.

The middle-level meanings of the Aztec Templo Mayor were messages of power and wealth. No other Aztec city had a pyramid this big, with such sumptuous offerings. The Aztec emperors were powerful, and the city and empire were wealthy. Visitors to the city from foreign lands may not have known the myth of Huitzilopochtli's birth, but they could clearly understand the middle-level messages being sent deliberately by the Aztec emperors through their main temple. The low-level meaning of the Aztec Templo Mayor concerned access to the temple: who could approach it, who could climb the steps, and what were people expected to do when they approached the building.

Feathered serpent temple, Teotihuacan

Let's return to Teotihuacan to see if we can glean any information about high-level meanings from the main temples. We lack the myths of the Aztecs, in written and painted form. But one of the main temples, the "Feathered Serpent Temple", was covered elaborate carved images. One of the key images is the feathered serpent, a major deity at Teotihuacan. So in this case we can suggest that this temple was dedicated to a particular god. But we can't say much more than that about it's high-level meanings.

A recent discovery at the Pyramid of the Sun at Teotihuacan furnishes a clue about possible high-level meanings at this largest temple. Archaeologists have known for some time that another major god at Teotihuacan was the "Old fire god," whose stone sculptures are often excavated in houses. A very large example was excavated a couple of years ago in the Pyramid of the Sun; the photo here shows archaeologists Alejandro Sarabia and Nelly Zoe Nuñez working on this find in the lab. While we are a long way from being able to show that rituals at this temple reenacted key myths (as at the Aztec case), this find does provide a clue about the possible symbolism (high-level meaning) of the Pyramid of the Sun. So while we are not "clueless" about the ancient symbolism of this structure, we really know very little about its high-level meaning. But its middle-level meanings are much clearer, as anyone who has approached the building from the west can attest. We can understand the power and wealth and stability communicated by this building, even if we know almost nothing of the culture, language, or myths of Teotihuacan.

If you want to learn more about the three levels of communication, the place to start is with Rapoport's publications. I discuss them in several papers, and Flannery and Marcus discuss very similar ideas. There are several levels of meaning in the wide urban world, and some are more accessible to us today than others.


References:

Flannery, Kent V. and Joyce Marcus
1993    Cognitive Archaeology. Cambridge Archaeological Journal 3: 260-270.

Rapoport, Amos
1988    Levels of Meaning in the Built Environment. In Cross-Cultural Perspectives in Non Verbal Communication, edited by Fernando Poyatos, pp. 317-336. C. J. Hogrefe, Toronto.

1990    The Meaning of the Built Environment: A Nonverbal Communication Approach. rev. ed. University of Arizona Press, Tucson.

Smith, Michael E.
2007    Form and Meaning in the Earliest Cities: A New Approach to Ancient Urban Planning. Journal of Planning History 6 (1): 3-47.

2011    Empirical Urban Theory for Archaeologists. Journal of Archaeological Method and Theory 18: 167-192.

2012    The Aztecs. 3rd ed. Blackwell Publishers, Oxford.

How do big cities differ from small cities (in the ancient past and today)?

Are big cities different from smaller cities mainly in their size? Or do they differ in other ways that go beyond simple population size? Recent research on urban scaling has answered this question definitively for contemporary cities. Large cities ARE different from smaller cities in ways that transcend their size. They aren't simply larger. Yet many of the changes that come with size turn out to be linked systematically to population size.

For example, large cities of course have more miles of roads and and electrical cables than smaller cities. But when we look at roads or cable per person (miles per capita), the quantities are smaller for the biggest cities. This makes sense: if you have twice as many people in a city, you don't need twice as many roads, since some of the new people can use existing roads. While this much is obvious, quantitative research in urban scaling reveals a surprising finding: the way that the miles of roads per person changes with city size is extremely regular. The same quantitative relationship holds if you are studying cities in the U.S., in Europe, or other parts of the world. There is a basic underlying regularity to the quantities of urban infrastructures that get built and used, in cities all over the world.

Other types of regularities have been found by the urban scaling researchers. First, big cities have denser populations than smaller cities. One way to view this is that the areal extent of cities grows more slowly than does the population. The result is an increasing population density in larger cities. But again, this patterns is extremely regular and predictable mathematically. Second, the most remarkable regularity identified by urban scaling has to do with socioeconomic outputs. Whether you measure income, wealth, innovation, crime, poverty, or the number of rock bands, these features all increase more rapidly than does the population size. Big cities not only have more rock bands than smaller cities, but they have more rock bands PER PERSON than smaller cities. Furthermore, the mathematics are predictable. The rates of rock bands--or poverty, or patents--per person follow a very regular quantitative pattern.

Why is this? The basic idea is that as city population grows, so too does the number of social interactions among the residents and visitors to the city. But the number of potential  social interactions can increase at an exponential rate. And these interactions generate information and change. One basic metaphor is to say that cities are social reactors. They magnify the benefits (and negative consequences) of social interactions.

So far, I have been describing urban scaling research on modern cities. See the works of Luis Bettencourt and his colleagues listed below for more information, or see my earlier post on this research. But what about cities and settlements before the modern era? A new paper, published today, provides new evidence that similar predictable quantitative patterns are found in ancient cities. That is, Precolumbian settlements in central Mexico exhibit the same quantitative regularities in population density and social outputs as modern cities. Of course the society, the economy, and the nature of cities were very different back then. But still, the same quantitative patterns are present. To me, this is a remarkable finding.  The paper is:

Ortman, Scott G., Andrew H.F. Cabaniss, Jennie O. Sturm, and Luís M. A. Bettencourt   2015    Settlement Scaling and Increasing Returns in an Ancient Society. Science Advances 1(1).

This is an update and extension of their prior paper:

Ortman, Scott G., Andrew H.F. Cabaniss, Jennie O. Sturm, and Luís M. A. Bettencourt   2014   The Pre-History of Urban Scaling. PLOS-one 9 (2): e87902.

The authors analyze settlement size and other data from the Basin of Mexico Archaeological Survey Project  (Sanders et al, 1979), and find that the quantitative patterns match those predicted by models of urban scaling that were first worked out for contemporary cities (Bettencourt 2013). I find this line of research fascinating, to the extent that I have been measuring cities and the sizes of their central plazas to investigate the quantitative pattern. It turns out that the size of the central plaza relates to the overall city size in a quite regular pattern, but the form of the equation does not match any of the quantities measured for modern cities. Hmmmmmmmm. I'll write more on this later.

For now, the new paper by Ortman et al is important for several reasons:

1. It provides new data on quantitative patterns in the ancient cities and settlements of the Basin of Mexico.
2. The results compare rather precisely to the predictions of the models and to the data on modern cities.
3. This work shows the value of archaeological data for answering interesting questions about cities and urbanism in the past and the present. This only works when the original fieldwork was done well, and when the data are published and made available to other scholars.

Here are some publicity and news items about today's new paper:

An article by Emily Conover in Science Online

An article by Megan Gannon in LiveScience. 

Press release from the Santa Fe Institute

Bettencourt, Luís M. A.
2013    The Origins of Scaling in Cities. Science 340: 1438-1441.

Bettencourt, Luís M. A., José Lobo, Dirk Helbing, Christian Kühnert, and Geoffrey B. West
2007    Growth, Innovation, Scaling, and the Pace of Life in Cities. Proceedings of the National Academy of Sciences 104: 7301-7306.

Bettencourt, Luís M. A., José Lobo, Deborah Strumsky, and Geoffrey B. West
2010    Urban Scaling and its Deviations: Revealing the Structure of Wealth, Innovation and Crime Across Cities. PLoS One 5 (11): 1-9.

Sanders, William T., Jeffrey R. Parsons, and Robert S. Santley
1979    The Basin of Mexico: Ecological Processes in the Evolution of a Civilization. Academic Press, New York.

Three days in Teotihuacan

Big pyramid, little pyramid

I am posting from the Arizona State University archaeology facility in San Juan Teotihuacan, Mexico. I've just spent three days at the site of Teotihuacan, exploring the outer neighborhoods of the ancient city and learning about geophysical techniques applied to archaeology. I am considering using geophysics at Teotihuacan, so I came down to see Luis Barba and his team at work. Luis is collaborating with David Carballo, who has been working in the southern Teotihuacan neighborhood called Tlajinga, exposing apartment compounds by both excavation and geophysical prospecting. Check out his project website.

Geophysical prospecting is one of the "magical" tools available to archaeologists. We can see what lies beneath the ground surface without excavating.

Luis Barba with the gradiometer

Luis Barba (Instituto de Investigaciones Anthropológicas, Universidad Nacional Autónoma de México) is the leading archaoemetry specialist in Mexico (I can't get blogger to insert accents! Aaarghhh). He does geophysical research, archaeological chemistry of soils and artifacts, and other scientific studies. He and David spent the whole week doing geophysical work in the Tlajinga area, and I arrived Wednesday to see the fieldwork first-hand. Luis's team includes two members from his lab at UNAM: Jorge Blancas and Agustín Ortiz. Also, Meztli Hernandez Grajales of the Escuela Nacional de Antropologia e Historia, and Ashley Krauss of Yale University joined the crew for the week.The goal was to locate the outlines and some inner walls of apartment compounds in the Tlajinga area.

Me measuring electrical resistivity

Luis uses three main methods. The fastest method is magnetometry (see photo). They grid off a 20 by 20 meter square, and carry the instrument down the grid lines, taking four readings on the gradiometer per meter. This generates quantitative measurements of the magnetic properties of the subsoil, which is useful for archaeologists because the magnetic signatures of buried structures and features often contrast with the surrounding soil. The second method is electrical resistivity. Two probes are placed in the ground away from the sampling area, and then two metal probes are inserted into the ground at set intervals, again following the grid lines. Luis let me try this for a few passes (see photo). For these techniques, the data are uploaded, and maps can be generated very quickly to serve as guides to further steps.

Jorge Blancas & Ashley Krauss with the GPR unit

The most sophisticated and complicated geophysical technique is ground-penetrating radar ("GPR"). The device is dragged along the ground (the orange box in the photo), and a wheel records the distance traveled. The instrument sends radar waves into the ground, and registers the waves when they are reflected back up. GPR is far more sensitive and precise than the other methods, but it requires a large amount of processing and analysis after fieldwork is complete. While we could look at the day's magnetometry maps each evening, it takes much longer to make the GPR results available.

David, me, and Jorge with the GPS

The 20-meter survey blocks are aligned with the Teotihuacan grid, which means that they are aligned with the orientation of the ancient structures. The team uses a differential GPS unit to fix the precise location of the survey blocks. See the photo, with David and me standing around while Jorge works the unit.

I have always been fascinated by geophysical prospecting, but I haven't had the opportunity to use the methods in my research, and I didn't have up-close experience with the fieldwork. This was a great experience, and I am considering a possible fieldwork project with Luis and David, to expand their approach to other parts of Teotihuacan.

Street of the Dead in Tlajinga

Close-up showing the Moon pyramid

The Tlajinga neighborhood includes the central avenue at Teotihuacan, the Street of the Dead. In the main INAH archaeological zone, which is open to tourists, the street is paved, and lined with ceremonial structures. Down in Tlajinga it was evidently not paved, and was in fact a channel dug out of the underlying tepetate bedrock. This photo is looking north up the Street of the Dead from the Tlajinga area. You can just see the Moon Pyramid at the upper end of the street; I include a close-up from the center part of this photo with arrows pointing to the outline of the pyramid.

Reconstructed murals from Tetila

I also saw the excellent new museum,the Beatriz de la Fuente Museum of Teotihuacan Mural Paintings. In addition to having many of the actual wall paintings on display, several entire painted rooms are reconstructed at the museum. Also, the museum is integrated with a 3-temple group that was excavated a number of years ago (see the photo at the top of the post). These were probably neighborhood temples. The photo shows one of them, with the huge Pyramid of the Moon in the background.

I have been staying at the ASU archaeology facility in the town of San Juan Teotihuacan. This is a major storage facility, with many important artifact collections from Teotihuacan and nearby sites. There is space for artifact analysis, and living quarters for people using the lab or doing fieldwork.

Arizona State University lab facility at Teotihuacan

In the photo the two-story storage/analysis building is at the left. On the right are three small cabins with beds and bathrooms (I am staying in one of these). The doorway at the end of the driveway leads to the "Casa antigua," an old house that has bedrooms, a kitchen and common space, in addition to technical workspace and some storage. The tree behind the doorway is in the yard of the house.