Network analysis in archaeology, Part 1

The Archaeology Program here at UNCG applied (largely through the suggestion and hard work of our program chair, Dr. Maura Heyn) to host an Ashby Dialogue for the 2016-2017 academic year. The purpose of these endowed dialogues is to bring together students, faculty, and the community to investigate an interesting topic in an informal setting (I was involved in another one of these in 2014). The archaeology faculty thought it might be interesting to explore network analysis in archaeology, largely because none of us had any idea what the heck it really was. Essentially, it gives us an excuse to get together and informally discuss something that is currently hot and that might inform our own research. The official theme: "Exploring Connections in the Past: Archaeology and Network Analysis."

For our first session, held on Friday, Nov. 4, was meant to introduce everyone to network analysis. Dr. Heyn, who moderated the session, chose an article by Tom Brughmans (2010). We had a great turnout, including many students and our colleague Art Murphy, who utilizes network analysis in his work on the responses of contemporary human populations to disasters. We spent a lot of time discussing what network analysis actually is and defining basic parameters like m-slices (apparently, this is a smaller network within a larger network). A couple of key points that arose:

• Network analysis, contrary to what I had originally thought, is not really concerned with space (in the geographic sense). Social networks, shared artifact types, and other data types are more common in the approach.
• It's important to remember that once you throw your data into a network analysis, the resulting pattern is not meaningful in and of itself: what it all means depends on a host of other contextual data.
• Several different types of networks can result from the same data; it all depends on the parameters originally put into the construction of the model. It is up to the researcher to decide which one makes the most sense.
• While it may seem a bit unscientific, it can be valuable to just throw your data into a model and see what emerges. It is certainly possible that otherwise obscure, fuzzy, or unknown relationships may emerge from a so-called "exploratory analysis." 

Looking forward to the next session!

References:

Brughmans, T (2010). Connecting the dots: towards archaeological network analysis. Oxford Journal of Archaeology 29, 277-303.

Ashby Dialogue, Part 3

Our third Ashby meeting was held this past Monday (March 24). The theme for this meeting was disasters, in particular the adaptations of contemporary humans populations to disasters, and was mediated by UNCG's Eric Jones and Art Murphy from Anthropology and Steve Kroll-Smith from Sociology. Another interesting discussion with great student participation. We started off with a veiwing of Trouble the Water, a documentary about the aftermath of Hurricane Katrina. Some of the more salient points that arose:

• Steve argued that the term "natural disaster" is actually a misnomer: including the word "natural," he said, actually furnishes nature with far too much agency and, in doing so, makes culture and human organization less culpable. In other words, and to quote Anthony Oliver-Smith (1994: 74):

...that is, disasters [are] interpreted less as the result of geophysical extremes such as storms, earthquakes, avalanches, droughts, etc., and much more as functions of an ongoing social order, the structure of human environment relations, and the larger framework of historical processes that shaped these phenomena.

Disasters are seen to be far more characteristic of societies than they are of simple physical environments.

• Disasters can also provide an incisive window into capitalist relationships. While it is of course important to make sure that relief makes it to people after a crisis, it is interesting to see which organizations are awarded contracts to do so; oftentimes they have ties to important government personnel or their close friends. 
• Eric Jones made the important point that, in terms of human social adaptation, there is a big difference between expecting a disaster and being prepared for one. One criticism that is often floated around after a disaster is "well, why didn't these people leave the area?" As Eric pointed out, there are several reasons, including (1) a lack of family or friends outside of the area that would facilitate a move; (2) a lack of transportation (public or personal); and, even if the former two are present, (3) fear of theft in peoples' absence. This highlights the fact that an important component of human adaptation to disaster is rooted in social relationships, or, as Eric's research refers to it, social networks.
• In a similar vein, Art made the distinction between preparedness and recovery, arguing further that race and class effects seem to be much stronger in the latter. The structure of social organization (i.e., how we determine the haves versus the have-nots) determines how recovery proceeds. This in turn tends to put certain types of people (usually poorer folks) into more susceptible positions.
• One of our best students, Jessica Haynes, brought up the issue of indigenous knowledge and how it is often ignored at our own peril. Art mentioned that drought conditions in California may eventually cause growers to move their operations to states with climates more conducive to particular crops. Jessica saw this as a case in point−why not grow indigenous plants that are adapted to their respective environments?

This was, overall, another really successful get-together, and we're looking forward to our last session, which will look at human adaptation from the perspective of interior architecture...

References:

Oliver-Smith, A (1995).Peru's five-hundred-year earthquake: vulnerability in historical context. In (Varley, A Ed) Disaster, Development and Environment, pp. 74-88.

Ashby Dialogue, Part 2

So, this past Monday (February 24), we had our second Ashby meeting. This session's theme was Human Adaptation to Sedentism and Urbanism. Gwen Robbins Schug and I moderated the session, although Gwen did most of the heavy lifting. We had a great student turnout this time as well.

As an organizing theme for the session, we used Jared Diamond's Pulitzer Prize winning book Guns, Germs, and Steel (henceforth GGS), which attempts to explain why Europe and her descendants came to dominate today's world. We watched PBS's video adaptation of the book, and Gwen assigned several articles that critiqued Diamond's arguments there and in his other popular book, Collapse. The latter explores the effects of anthropogenic environmental degradation and how this has led to the fall of past societies. One of Diamond's major goals with GGS was to discredit the idea that Western domination was the result of racial superiority. He argued that societies were forced to deal with the hand that geography dealt them and some areas were more conducive to the development of "complex" societies than others based on factors such as the length of the growing season and the presence of domesticateable plants and animals, most importantly draft animals, wheat, and barley. Perhaps unsurprisingly, Diamond has been heavily criticized for what many perceive to be an environmentally deterministic perspective (you can see one of his rebuttals to that charge here).

So, using this as a backdrop, several prominent points arose in our discussions, thanks mainly to Gwen's guidance:

• The first, and probably one of the most infuriating to anthropologists, is that in both GGS and Collapse, Diamond appears woefully out-of-date on his characterization of human societies. His use of terms like "band," "chiefdom," "state," and even the concept of "complexity" are based on decades-old anthropological paradigms. While useful for organizing variation, in practice they unrealistically pigeonhole the vast amount of diversity out there. I wonder how Diamond's definition of "complexity" would change if he were not a Western researcher?
• Collapse also fails to cite the latest archaeological research, which is, after all, the best record we have for the development of past societies. The best example of this comes from his discussion of Easter Island (known to those that live there as Rapa Nui). In Diamond's scenario, reckless Polynesians chopped down thousands of trees in order to transport those iconic stone statues (known as mo'ai). While this story certainly raises the issue of how fragile ecosystems truly are and how destructive humans can be, the archaeology tells a very different version. Gwen had us read a fascinating article by Terry Hunt and Carl Lipo that demonstrates (1) deforestation was largely the result of introduced rats that ate palm nuts and thus prevented forest regeneration and (2) the huge statues were not moved on tree rollers anyway (they were probably dragged, upright, with ropes).
• Diamond's books are attractive because they provide unicausal explanations for very complex phenomena. In GGS, for example, it was all about agriculture: the raising of crops (wheat and barley) created food surpluses, which encouraged the domestication of draft animals, which led to social stratification and, ultimately, to the "complex" state-level societies that came to dominate the world today. However, these sorts of explanations, even when they work for a particular time and place, rarely apply to ALL times and ALL places. The native peoples of North America's Pacific Northwest, for example, developed very complex societies based largely on a fishing, not a farming, economy. 
• This whole issue of societal "collapse" is also problematic. Several people brought up the fact that societies rarely, if ever, fully collapse but, rather, undergo a long decline where people typically move away from the population centers into the hinterlands. 
• We also agreed that, while Diamond's arguments have their flaws, he is doing what many an anthropologist has failed to do: bring these "big picture" issues to a popular audience.  

References:

Diamond, J (1997). Guns, Germs, and Steel: The Fates of Human Societies. W.W. Norton, New York.

Diamond, J (2005). Collapse: How Societies Choose to Fail or Succeed. Penguin Books, London.

Hunt, TL, Lipo, CP (2010). Ecological catastrophe, collapse, and the myth of "ecocide" on Rapa Nui (Easter Island). In (McAnany, PA, Yoffee, N, Eds) Questioning Collapse: Human Resilience, Ecological Vulnerability, and the Aftermath of Empire, pp. 21-44.  

Ashby Dialogue, Part 1

So, this semester (Spring 2014), the Department of Anthropology at UNCG, along with the Departments of Biology and Interior Architecture, are organizing and hosting an Ashby Dialogue, which, through an endowment from the College of Arts and Sciences, "provide the opportunity for informal but focused inquiry into some topic or issue" of interest to university faculty and students. I helped a bit in the planning and organizing, but the lion's share of the work was done by our own Joel Gunn and biology's Malcolm Schug. Our theme for this semester is "Human Adaptation: Past and Future," and you can see the full schedule of events here. This is the first of several posts I'll provide throughout the semester as we progress through our program.

To kick off the schedule, we had hoped to have a talk from Greg Wray, a top-notch evolutionary biologist from Duke University who is interested in the evolution of gene regulation. Unfortunately, the winter storm (defined in North Carolina as a threat of snow or, in our case, an inch or so of snow) we had last week shut down campus and we had to cancel. Nevertheless, we did go forward with our first discussion session on Monday, February 3, and I'll recap that here.

The theme of our first session was How do Biologists Study the Question: What is the Evidence for Adaptation in Humans? There were a total of 10-11 people, including students from both anthropology and biology. We had posted a reading about next generation sequencing of genomes and two videos, one from Evan Eichler (Washington University) about structural variation in the human genome, and another from Sarah Tishkoff (University of Pennsylvania) about variation among modern African populations and evidence for the evolution of lactose tolerance, all of which served to focus our discussion.

We started off with an introduction from Malcolm, who gave us a great overview of the issue of genetic adaptation. He noted first that although "adaptation" can be viewed somewhat differently by anthropologists and biologists, Darwin's theory of natural selection and its focus on reproductive success serves to unite both fields. Biologists traditionally thought that because organisms appeared so well adapted to their environments that very little genetic variation would be present. This idea was blown apart by the work of Richard Lewontin and John Hubby, who in the 1960s documented a surprising amount of inter-individual variation in various proteins (this work was done first with flies and then, later, with humans). Further work by Martin Kreitman found tons of variation in DNA. All of this raised an important question: why the heck is there so much genetic variation between individuals if populations are supposedly well adapted to their environments?

Well, two answers emerged. One, which I'll dub the "adaptationist camp," thought that most of this variation was driven by natural selection (in this sense, inter-individual variation it is actually an adaptation in itself, since this variation will provide natural selection with something to work on). The issue then became to find the specific genes that were being selected for. The other side, which I'll call the "neutral camp," felt that most variation arises by random drift and alleles that have little or no effect on the survivorship of individuals. The debate was pretty acrimonious, but it seems like most folks recognize that both forces are probably at play.

To complicate matters further, Allan Wilson later suggested that perhaps it wasn't the genes themselves that were being selected for, but rather their regulation (i.e., when they are turned off and on, or how strongly they are expressed). Their is, for example, evidence that the human opposable thumb (the length of which permits us to manipulate small objects with ease) evolved not because of some structural change in a specific gene, but rather a change in when (and for how long) the genes responsible for the development of the hand were "turned on."

As Malcolm and our reading pointed out, the rapidly progressing genomic sequencing technology (it took years to sequence the first complete human genome about 15 years ago; we can now sequence entire genomes for everything from bacteria to human in DAYS) now permits huge amounts of data to be mined for evidence of natural selection. Now, geneticists can fish through whole genomes looking for gene that have undergone, or currently are undergoing, selection. I asked Malcolm how one goes about doing this, and he said that, essentially, geneticists scan the genomes of many individuals looking for allele frequencies that are higher (or lower) than expected (this can be determined statistically). I wonder if the technology is outpacing our ability to actually analyze it in a systematic way? Very interestingly, Malcolm told us about a study that simulated the evolution of a fruit fly genome and went back and identified "selected" genes with these statistical methods. Many were found, but the simulation did not include natural selection! So, it is by no means clear in every case whether or not genes have undergone natural selection.

Anyway, the clearest evidence for natural selection among most studies comes from genes identified with pathogen pressure and/or immune function and gametogenesis. Some other genes that appear to have been under selection over the course of human evolutionary history are FOXP2 (development of speech and language areas of the brain) and EDAR (development of several body tissues, including skin and sweat glands). We had additional conversations and discussions over pizza, including the issue of genetic determinism and how we define and analyze "traits."

Overall, a great start to our dialogues. I, along with Gwen Robbins Schug of Appalachian State, will be moderating our second session, which deals with past human adaptations to sedentism and urban life.