Is network science useful for Roman studies? What’s so great about it, and what’s not? In January I gave a keynote talk on the topic at ‘Finding the limits of the Limes’. The talk was caught on film, so you can judge my arguments for yourself. It starts a bit negative but ends on a hopeful note (spoiler alert: I LOVE networks). Talk abstract below the video.
Roman studies are all over network science! In particular the team behind the ‘Finding the limits of the Limes’ project at the VU Amsterdam. They’ve been doing some really cool network analyses of Roman socio-economic and transport networks. Next month they will be hosting a major conference. The program is available on the project website, and it includes a whole session on networks. A few seats are still available so don’t hesitate to sign up and attend.
Where? VU Amsterdam
When? 26-27 January 2017
Thursday 26 Jan 2017, 09:30 – 17:30
Welcome and opening lectures
Nico Roymans (Vrije Universiteit Amsterdam): Setting the scene: characterising Batavian society at the edge of empire in the Dutch river area
Philip Verhagen (Vrije Universiteit Amsterdam): Modelling the cultural landscape of the Dutch Roman Limes: approach, results and prospects
Session 1: Modelling subsistence economy
Session keynote: Wim Jongman (University of Groningen): What did the Romans ever do for us?
Jamie Joyce (Vrije Universiteit Amsterdam): Simulating the Roman farm
Tilman Baum (University of Basel): Models of Land-use in the Neolithic Pile-Dwellings of the Northwestern Pre-Alpine Forelands (4400-2400 BC)
Antoni Martín i OIiveras (University of Barcelona): The economy of Roman wine. Productive landscapes, archaeological data, quantification and modelling. Case Study Research: “Regio Laeetana-Hispania Citerior Tarraconensis” (1st century BC-3th century AD)
Tyler Franconi (University of Oxford): Cultivating change: Roman agricultural production and soil erosion in the Thames River basin
Maurice de Kleijn (Vrije Universiteit Amsterdam):Simulating land-use for the Lower Rhine-Meuse delta in the Roman period
Eli Weaverdyck (University of California, Berkeley): Farmers and Forts in Moesia Inferior: Modelling agricultural strategies on the Lower Danubian Frontier
Session 2: Modelling demography
Session keynote: Isabelle Séguy (Institut National des Études Démographiques, Paris)
Philip Verhagen (Vrije Universiteit Amsterdam): From population dynamics to settlement patterns. Linking archaeological data to demographic models of the Dutch limes.
Wim De Clercq (University of Ghent): The Disastrous Effects of the Roman Occupation!? Population dynamics and rural development on the fringes of the Roman Empire: theories and models.
Chris Green (University of Oxford): Modelling evidence densities: past population variation or modern structuring affordances? The case of England from the Iron Age to the early medieval period.
Antonin Nüsslein (École Pratique des Hautes Études, Paris): A different vision of ancient settlement dynamics: creation and application of a model of evolution of theAntique habitat of the Plateau Lorrain
Friday 27 Jan 2017 09:30 – 17:30
Session 3: Modelling transport
Session keynote: Dimitrij Mlekuž (University of Ljubljana): The archaeology of movement
Mark Groenhuijzen (Vrije Universiteit Amsterdam): Diverse movement in a dynamic environment: modelling local transport in the Dutch part of the Roman limes
Rowin van Lanen (University of Utrecht/Cultural Heritage Agency of the Netherlands):Shopping for wood during the first millennium AD: modelling Roman and early-medieval long-distance transport routes in the Netherlands using a multi-proxy approach
César Parcero-Oubiña (INCIPIT, Santiago de Compostela): Postdicting Roman Roads in the NW Iberian Peninsula
Katherine Crawford (University of Southampton): Walking Between Gods and Mortals: reconsidering the movement of Roman religious processions
Session 4: Modelling socio-economic networks
Session keynote: Tom Brughmans (University of Konstanz): Network science in Roman studies: the potential and challenges
Mark Groenhuijzen (Vrije Universiteit Amsterdam): Possibilities and challenges in the use of networks to study socio-economic relations in the Dutch part of the Roman limes
Pau de Soto (Universidade Nova de Lisboa): Network analysis to model and analyse Roman transport and mobility
Angelo Castrorao Barba (University of Palermo), Stefano Bertoldi (University of Pisa), Gabriele Castiglia (Pontifical Institute of Christian Archaeology): Multi-scalar approach to long-term dynamics, spatial relations and economic networks of the Roman secondary settlements in Italy: towards a model?
Yes, there are similarities between my work and things that people actually want to spend time listening to. But you really have to look hard for them. I’ve given a lot of presentations over the last few years and noticed that one of the best ways of getting a difficult idea across is to use a movie analogy. I also learned I was very bad at preparing my presentation in time to think up movie analogies. So here’s a blog post to make up for it, inspired by a new paper I wrote that just came out in Journal of Archaeological Method and Theory. My work is a bit like Lord of the Rings and Mulan.
But not in the way you hope it is. There is nothing near as exciting in my research as the cavalry charges in both those movies, and I definitely never experienced a ‘montage’ moment that provided me in a ridiculously short timespan with the crazy skills needed to destroy the baddie.
What my work has in common with both Mulan and Lord of the Rings are fire signals. This video shows the memorable scene from Return of the King when the fire beacons in Gondor are lit, triggering the lighting of a chain of other beacons. The message is clear and reaches its target quickly: Gondor looks to Rohan for help.
The opening scene of Disney’s Mulan is similar: when the bad guys attack, beacons are lit all along the great wall of China to warn the Chinese people of the coming threat.
These scenes are not completely unthinkable fantasy scenarios, but are inspired by early communication systems that actually existed in the past. In times before telephones and telegraphs, signalling systems using fire, smoke, sound or light could have been used to spread messages over very long distances.
Archaeologists studying the Iron Age of Spain believe such a communication system might have existed in some regions. And it is easy to understand why. The settlement pattern in much of Spain during the Iron Age was dominated by large fortified urban settlements on hills, hence they are sometimes referred to as hillforts. These large urban settlements were surrounded by smaller rural settlements. The surrounding landscape could be visually controlled from many of these hillforts, and the hillforts were visually prominent features that could be seen from far away.
Now what scene of Lord of the Rings does this remind me of? That’s right: the Eye of Sauron perched on top of the massive tower of Barad Dur, scanning the surrounding landscape for his enemies, and to his followers acting as a visible reminder of who’s boss.
Many archaeologists believe these large urban settlements were located on hills on purpose, and not just because a hill was easier to defend but because of the views it offered: visually controlling the landscape, being visually prominent from its surroundings and acting as a good link in a fire signalling network.
And this is where networks come in! If archaeologists argue that settlements might have been located with visibility in mind for the three reasons mentioned here, then we should approach these statements as hypotheses that need testing. And we can do that in three ways using network science:
1) visualise the network of inter-visible settlements using our knowledge of the settlement pattern;
2) explore its structure to see whether it would function well as a communication network, or whether some settlements are more visually prominent;
3) simulate a process where places are settled so that a well-functioning communication network and/or a few more visually prominent settlements is established, and compare this simulated settlement pattern with the observed one.
This is what I do. The first approach uses network data representation and network layout algorithms to show a network of inter-visible settlements, and explore this pattern in a new way by extracting it from its geographical context and focusing just on its structure for a change. The second approach then uses exploratory network analysis techniques that tell us something more about individual nodes in the network and about the network as a whole (e.g. identify most visually prominent settlements, identify chains of inter-visible settlements). The third approach is in my eyes the most interesting one because it is totally new: using simulation models we generate millions of networks according to the process we hypothese might have taken place and we compare the simulated networks with the oberved ones using the same exploratory network analysis techniques as in the second approach.
This new approach to simulating our hypotheses about visibility networks is called exponential random graph modelling for visibility networks. A pair of papers just came out in which we introduce this method and apply it to Iron Age and Roman Southern Spain. The results are really interesting: there is no evidence for a well-functioning communication network, but there is definitely reason to believe that the pattern of visually prominent settlements that visually control surrounding rural settlements was purposefully established in the Iron Age. The importance of visibility as a factor determining settlement location then gradually decreases throughout Roman times.
Our recently published paper in Journal of Archaeological Method and Theory tells you the full story. The method is explained in detail in our paper in Journal of Archaeological Science. Both are available through my Academia.edu page or my bibliography on this blog. Enjoy!
In my madness series of posts published a few months ago I mentioned I was looking for a method to study processes of emerging intervisibilty patterns. I can finally reveal this fancy new approach to you 🙂 Here it is: introducing exponential random graph modelling (ERGM) for visibility networks. In previous posts I showed that when archaeologists formulate assumptions about how lines of sight affected past human behaviour, these assumptions imply a sequence of events rather than a static state. Therefore, a method is needed that allows one to test these assumed processes. Just analysing the structure of static visibility networks is not enough, we need a method that can tackle changing networks. ERGM does the trick! I just published a paper in Journal of Archaeological Science with Simon Keay and Graeme Earl that sets out the archaeological use of the method in detail. You can download the full paper on ScienceDirect, my Academia page or via my bibliography page. But in this blog post I prefer to explain the method with LEGOs 🙂
Social network analysts often use an archaeological analogy to explain the concept of an ERGM (e.g., Lusher and Robins 2013, p. 18). Past material remains are like static snapshots of dynamic processes in the past. Archaeologists explore the structure of these material residues to understand past dynamic processes. Such snapshots made up of archaeological traces are like static fragmentary cross-sections of a social process taken at a given moment. If one were to observe multiple cross-sections in sequence, changes in the structure of these fragmentary snapshots would become clear. This is exactly what an ERGM aims to do: to explore hypothetical processes that could give rise to observed network structure through the dynamic emergence of small network fragments or subnetworks (called configurations). These configurations can be considered the building blocks of networks; indeed, LEGO blocks offer a good analogy for explaining ERGMs. To give an example, a network’s topology can be compared to a LEGO castle boxed set, where a list of particular building blocks can be used to re-assemble a castle. But a LEGO castle boxed set does not assemble itself through a random process. Instead, a step by step guide needs to be followed, detailing how each block should be placed on top of the other in what order. By doing this we make certain assumptions about building blocks and their relationship to each other. We assume that in order to achieve structural integrity in our LEGO castle, a certain configuration of blocks needs to appear, and in order to make it look like a castle other configurations will preferentially appear creating ramparts, turrets, etc. ERGMs are similar: they are models that represent our assumptions of how certain network configurations affect each other, of how the presence of some ties will bring about the creation or the demise of others. This is where the real strength of ERGMs lies: the formulation and testing of assumptions about what a connection between a pair of nodes means and how it affects the evolution of the network, explicitly addressing the dynamic nature of our archaeological assumptions.
More formally, exponential random graph models are a family of statistical models originally developed for social networks (Anderson et al. 1999; Wasserman and Pattison 1996) that aim to scrutinize the dependence assumptions underpinning hypotheses of network formation by comparing the frequency of particular configurations in observed networks with their frequency in stochastic models.
The figure below is a simplified representation of the creation process of an ERGM. (1a) an empirically observed network is considered; (1b) in a simulation we assume that every arc between every pair of nodes can be either present or absent; (2) dependence assumptions are formulated about how ties emerge relative to each other (e.g. the importance of inter-visibility for communication); (3) configurations or network building blocks are selected that best represent the dependence assumptions (e.g. reciprocity and 2-path); (4) different types of models are created (e.g. a model without dependence assumptions (Bernoulli random graph model) and one with the previously selected configurations) and the frequency of all configurations in the graphs simulated by these models is determined; (5) the number of configurations in the graphs simulated by the models are compared with those in the observed network and interpreted.
My madness series of posts and the recently published paper introduce a case study that illustrates this method. Iron Age sites in southern Spain are often located on hilltops, terraces or at the edges of plateaux, and at some of these sites there is evidence of defensive architecture. These combinations of features may indicate that settlement locations were purposefully selected for their defendable nature and the ability to visually control the surrounding landscape, or even for their inter-visibility with other urban settlements. Yet to state that these patterns might have been intentionally created, implies a sequential creation of lines of sight aimed at allowing for inter-visibility and visual control. An ERGM was created that simulates these hypotheses. The results suggest that the intentional establishment of a signalling network is unlikely, but that the purposeful creation of visually controlling settlements is better supported.
A more elaborate archaeological discussion of this case study will be published very soon in Journal of Archaeological Method and Theory, so stay tuned 🙂 Don’t hesitate to try out ERGMs for your own hypotheses, and get in touch if you are interested in this. I am really curious to see other archaeological applications of this method.
Anderson, C. J., Wasserman, S., & Crouch, B. (1999). A p* primer: logit models for social networks. Social Networks, 21(1), 37–66. doi:10.1016/S0378-8733(98)00012-4
Lusher, D., Koskinen, J., & Robins, G. (2013). Exponential Random Graph Models for Social Networks. Cambridge: Cambridge university press.
Lusher, D., & Robins, G. (2013). Formation of social network structure. In D. Lusher, J. Koskinen, & G. Robins (Eds.), Exponential Random Graph Models for Social Networks (pp. 16–28). Cambridge: Cambridge University Press.
Wasserman, S., & Pattison, P. (1996). Logit models and logistic regressions for social networks: I. An introduction to Markov graphs and p*. Psychometrika, 61(3), 401–425.
We are pleased to announce the Call for Papers for the third series of the Digital Classicist Seminar Berlin . This initiative, inspired by and connected to London’s Digital Classicist Work in Progress Seminar , is organised in association with the German Archaeological Institute and the Excellence Cluster TOPOI. It will run during the winter term of the academic year 2014/15.We invite submissions on any kind of research which employs digital methods, resources or technologies in an innovative way in order to enable a better or new understanding of the ancient world. We encourage contributions not only from Classics but also from the entire field of “Altertumswissenschaften”, to include the ancient world at large, such as Egypt and the Near East.Themes may include digital editions, natural language processing, image processing and visualisation, linked data and the semantic web, open access, spatial and network analysis, serious gaming and any other digital or quantitative methods. We welcome seminar proposals addressing the application of these methods to individual projects, and particularly contributions which show how the digital component can facilitate the crossing of disciplinary boundaries and answering new research questions. Seminar content should be of interest both to classicists, ancient historians or archaeologists, as well as to information scientists and digital humanists, with an academic research agenda relevant to at least one of these fields.Anonymised abstracts  of **300-500 words max.** (bibliographic references excluded) should be uploaded by **midnight (CET) on 01 August 2014** using the special submission form . Although we do accept abstracts written in English as well as in German, the presentations are expected to be delivered in English (when submitting the same proposal for consideration to multiple venues, please do let us know via the submission form). The acceptance rate for the first two seminar series was of 41% (2012/13) and 31% (2014/15).Seminars will run **fortnightly on Tuesday evenings (18:00-19:30)** from October 2014 until February 2015 and will be hosted by the Excellence Cluster TOPOI and the German Archaeological Institute, both located in Berlin-Dahlem. The full programme, including the venue of each seminar, will be finalised and announced in September. As with the previous series, the video recordings of the presentations will be published online and we endeavour to provide accommodation for the speakers and contribute towards their travel expenses. There are plans to publish papers selected from the first three series of the seminar as a special issue of the new open access publication from TOPOI . The anonymised abstract should have all author names, institutions and references to the authors work removed. This may lead to some references having to be replaced by “Reference to authors’ work”. The abstract title and author names with affiliations are entered into the submission system in separate fields.
The Digital Classicist has become a bit of an institution, offering great examples of how and why classicists should not necessariy be afraid to use modern technology. The series is gearing up for another year of seminars, the call for papers is now open with a 9 March deadline. The organisation, audience, venue and presenters are generally awesome, so I can only recommend submitting an abstract. More info below or on their website.
The Digital Classicist London seminars have since 2006 provided a forum for research into the ancient world that employs digital and other quantitative methods. The seminars, hosted by the Institute of Classical Studies, are on Friday afternoons from June to mid-August in Senate House, London.
We welcome contributions from students as well as from established researchers and practitioners. We welcome high-quality papers discussing individual projects and their immediate context, but also accommodate broader theoretical consideration of the use of digital technology in Classical studies. The content should be of interest both to classicists, ancient historians or archaeologists, and to information specialists or digital humanists, and should have an academic research agenda relevant to at least one of those fields.
There is a budget to assist with travel to London (usually from within the UK, but we have occasionally been able to assist international presenters to attend).
To submit a proposal for consideration, email an abstract of approximately 500 words to firstname.lastname@example.org by midnight UTC on March 9th, 2014.
Further information and details of past seminars are available at: http://www.digitalclassicist.org/wip/index.html
You can watch the show on BBC iPlayer.