Studying change in local and regional economic networks in central Italy Tymon de Haas & Gijs Tol First of all and also on behalf of Gijs Tol, I would like to thank Onno and Mladen for giving us the possibility to introduce to you our research at this workshop. On the outset, we should note that as we have only recently started this research project, we cannot yet present any in-­‐depth analyses. Rather, our aim today is to introduce some recent applications of network analysis in archaeology, and to point out some avenues of study that seem promising for our research. Hopefully, we will also benefit from the input you all provide today. Our paper starts with an introduction to our research project. After this, we comment on recent applications of network analysis in archaeology, highlighting the methodological variation in these applications. We then move on to discuss the ways in which we intend to study the changing economic networks in the Pontine region from geographical, material and social perspectives. The ‘Minor centres’ project The project we discuss is entitled Fora, stationes and sanctuaries: the role of minor centres in the economy of Roman Central Italy. This 5-­‐year project, funded by the Dutch Organization for Scientific Research, aims to study such minor centers, which are often neglected in studies of the Roman economy, as they not easily fit in the opposing categories ‘urban’ or ‘rural’. In terms of the consumer city model the latter is regarded as the place where agricultural surpluses were produced, and the former as the place where such surpluses were consumed.1 By contrast, ethnographic and historical research suggests that minor centres could have an important role as rural markets, and that rural demand could give rise to specialised crafts production in the countryside.2 This in turn could contribute to economic growth and increasing prosperity. Our project therefore intends to critically assess the role of ‘minor centres’ in crafts production and trade, thus examining rural economies in terms of both production and consumption. The research builds on the work carried out by the University of Groningen in the Pontine region, central Italy, where we have over the past 30 years studied rural settlement in relation to urbanization and colonization processes.3 Focus has been the study of the hinterlands of Roman colonies such as Norba, Setia and Antium. However, fig. 1 suggests that in some parts of the region the influence of urban centres is less obvious: following traditional geographic models such as central place theory, in these areas other sites probably performed central-­‐place functions. It is notable in this respect that the road stations marked as minor centers often lie at more than 10 km from urban centres, beyond what is generally considered daily commuting distance. 1
For a discussion see Erdkamp, P., 2001, Beyond the limits of the ‘consumer city’. A model of the urban and rural economy in the Roman world. Historia: Zeitschrift für Alte Geschichte 50-­‐3, 332-­‐356. 2
Smith, C., 1972, Economics of marketing systems: models from economic geography, Annual Review of Anthropology 3, pp. 167-­‐201. 3
Attema, P., 1993, An archaeological survey in the Pontine Region. A contribution to the settlement history of south Lazio 900 -­‐ 100 BC, PhD thesis, Rijksuniversiteit Groningen; Attema, P. & M. van Leusen, 2004, The early Roman colonization of South Lazio; a survey of three landscapes, in Attema, P. ed., Centralization, early urbanization and colonization in first millennium BC Italy and Greece. part 1: Italy, Leuven, pp. 157-­‐195; Attema, P., T. de Haas, & G. Tol, 2011, Between Satricum and Antium. Settlement dynamics in a coastal landscape in Latium Vetus, Leuven. Fig. 1. Towns and minor centers of the Pontine region. To better understand their economic role, the project targets three such centers, Astura, Forum Appi and Ad Medias, for in-­‐depth archaeological study. They will be mapped through on-­‐site field surveys and geophysical prospections, if possible extended with excavations at productive facilities such as pottery workshops. In addition, field surveys within a 10 km radius will be conducted to map rural settlement and to elucidate its ties with the minor centre. An important part of the project are pottery studies, which aim to identify patterns of production, distribution and exchange through typological and archaeometric research. While we already hinted at the usefulness of Central Place Theory to explain the location of minor centers, this theory is less suited to understand changes in settlement patterns and economic exchange. When looking at such changes, a range of social, economic and environmental factors play a role, while in some periods the Pontine region participated in much wider exchange networks. Furthermore, the region is situated less than 100 km south of Rome, and by the late Republican period it was surely incorporated in the Suburbium, which may be regarded as a zone with a high degree of mobility and integration in terms of people, labour and property: in other words, it should be considered as part of a well-­‐connected socio-­‐economic network.4 Network Analysis, archaeology and the Roman economy 4
Witcher, R., 2005, The extended metropolis: Urbs, suburbium and population, Journal of Roman Archaeology, 18, pp. 120-­‐138. So in what ways might we study the development of this socio-­‐economic network? Before exploring this question, let us first comment on the use of network analysis in archaeology, and in economic studies in particular. Network perspectives in archaeology and ancient history arose in the 1990s, but have expanded especially over the last decade, with sessions being hosted at conferences like AIAC and Computer Applications in Archaeology. Recent case studies apply elaborate formal analyses, which have come into reach of archaeologists with software packages such as PAJEK.5 Such studies clearly show the usefulness of network approaches to archaeological questions: the configuration of networks strongly influences the exchange of ideas and goods, and changes in such networks may have a profound impact on social, religious, and of course also economic systems: for example, a few well-­‐connected nodes may trigger ‘cascades’ that lead to network-­‐wide changes, while the removal of a few of such nodes may ultimately lead to the disintegration of a system. Whilst a considerable body of research has thus accumulated, there is still little coherence in the concepts, terminology and methods being applied, as Brughmans also points out in a brief review.6 1) Networks may be used merely as metaphors, or quantitatively, using network analysis as a tool to analyse the relations between data. 2) Different network models are used and different terminology is applied to these models: some distinguish small-­‐world networks versus scale-­‐free networks, while others refer to egalitarian versus aristocratic small-­‐world networks.7 3) There are different perspectives with regard to the scale (local, regional and global) and nature (static or dynamic) of networks. 4) There are different kinds of networks that can be studied: not just ‘social’ networks, but also material, geographical and relational networks. There is also variation in quantitative approaches: 5) We can discern between confirmatory and exploratory applications. Examples of the former approach model the rise of settlement networks in order to test archaeologically observed site hierarchies.8 Alternatively, network analysis may be used to explore the structure and characteristics of archaeological data. 5
Graham, S., 2006. EX FIGLINIS The network dynamics of the Tiber Valley brick industry in the hinterland of Rome. Oxford Archaeopress; Sindbaek, S., 2007, Networks and nodal points: the emergence of towns in early Viking Age Scandinavia, Antiquity 81, 119-­‐132; Collar, A., 2008. Networks and religious innovation in the Roman Empire. PhD thesis, University of Exeter; Isaksen, L., 2008, The application of network analysis to ancient transport geography: a case study of Roman Baetica, Digital Medievalist 4. Online, Available from http://www.digitalmedievalist.org/journal/4/isaksen/ 6
Brughmans, T., 2010, Connecting the dots: towards archaeological network analysis, Oxford Journal of Archaeology 29-­‐3, 277-­‐303. 7
For the latter terms see Graham 2006 (supra n. 5), 92. Rihll, T. & A. Wilson, 1991. Modelling settlement structures in ancient Greece: new approaches to the polis, in Rich, J. & A. Wallace Hadrill, City and country in the ancient world, 58-­‐95; Fulminante, F., forthcoming. Social network analysis and the emergence of central places: a case study from Bronze Age and early Iron Age central Italy, Babesch 87. 8
6) Different variables and combinations of variables are used to analyse networks, including closeness centrality that describes how well a node can interact with other nodes, betweenness centrality, a measure of how nodes mediate connections between other nodes, and degree centrality, the number of nodes a node connects to. 7) Finally, when it comes to analysing and interpreting networks, we may distinguish between approaches based on visual inspection and formal statistical ones. On the one hand, the variety in approaches reflects the wide applicability of network analysis: as Isaksen (2008) states, “it is an umbrella term for the evaluation of any of the numerous properties that can be expressed in Graph Theory”. On the other hand, Brughmans (2010) argues that archaeologists have so far used a limited conception of networks, and have not realised its full potential. In sum, while the importance of network theory is beyond doubt, there is not yet a well-­‐defined sub-­‐discipline of ‘archaeological network analysis’. Studying economic networks in the Pontine region This brings us to the use of network analysis in the study of minor centres and the Roman economy of the Pontine region. We intend to use network perspectives on three levels to which we refer as geographic, material and social and which reflect different types of data. While we intend to apply quantitative approaches to these data, today we only point out some qualitative aspects of the changing networks of the Pontine region. 1) Geographic networks With geographic networks we refer to settlement patterns and infrastructural data, which we will use to model the rise of central places. As we have seen, Central Place Theory to a certain extent explains the location of minor centers in niche locations in the region; however, infrastructural improvements and changes in the nature of the geographic network help explaining their rise. th
th
Fig. 2. major sites and roads of the 5 and 4 centuries BC in the southern ager Romanus and the Pontine region. and Fulminante that In fig. 2 you see the major sites of the 5th and 4th centuries BC in the southern ager Romanus and the Pontine region. In this period, the region formed the scene of repeated struggles between Rome, Latins and Volsci. From an archaeological perspective, we do not know much about the size and character of the sites, and it seems that this period is characterised by a loose settlement organisation with little central control. The geographic network is fairly homogeneous in terms of degree centrality, with many sites having two or three connections. Velitrae forms an exception, having more connections than any other site. Its position in the network explains why the site is of particular strategic value and why historical sources describe it as being one of the most contested sites in the region: for Rome, it formed the gateway into the Pontine region, and loss of control over the site also obstructed communication and exchange with the region. rd
st
Fig. 3. major sites and roads of the 3 -­‐1 centuries BC in the southern ager Romanus and the Pontine region. After Roman rule had been established in the mid to late 4th century, changes take place in the geographic network (fig. 3). Velitrae lost its central position within it and new routes developed, including the via Appia through the Pontine plain, a road from Signia through the Lepine mountains and a road from Rome directly towards the coastal town of Antium. The network shows a higher degree of connectivity with Rome, and reflects an increasing integration of the region with Rome in both economic and social terms. With the construction of the via Appia, the position of the towns on the Lepine margins within the geographic network changed: they were marginalized, as they were no longer necessarily nodes in the communication between Rome and the northern part of the region with Tarracina. This could explain why Norba, after being destroyed in the Civil War, was never rebuilt. At this time, the minor centers that developed along the via Appia could take over functions of Norba, but also Setia, as a market and administrative center. For example, Forum Appi as a forum had market rights and administrative and juridical functions. In economic terms it occupied a highly attractive position on a crossroads and at the start of the so-­‐called Decennovium canal that ran along the via Appia towards Tarracina. It may therefore have become a transit point in distribution networks. st
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Fig. 4. major sites and roads of the 1 -­‐3 centuries AD in the southern ager Romanus and the Pontine region. The network underwent a further important change in the Imperial period: the coastal route known as the via severiana gained importance, and road stations developed along it (fig. 4). This reflects an increasing importance of the coastal part of the region with an increased connectivity of Antium and Tarracina. This is also clear from the construction in the early Imperial period of harbours at these towns. The effects of this change in economic terms were fundamental: the harbours allowed the region to directly tap into supra-­‐regional exchange networks, as is clear when looking at the pottery data from our field surveys. As illustrated in the diagram, these show an enormous increase in the volume of imported fine wares from northern Africa, mainly Tunisia, at this point in time (fig. 5). Fig. 5. Fine ware consumption trends based on field survey data. Note the Increasing numbers of imported fine wares after the st
mid-­‐1 century AD. With the construction of harbours at Antium and Tarracina, we may also witness a change in the nature of the network itself: the tapping into Mediterranean-­‐wide distribution networks seems to reflect the absorption of the region into a small-­‐world system, with a few nodes, the harbours, being exceptionally well-­‐connected, and allowing a widespread occurrence of new pottery wares across the region. 2) Material networks This brings us to the material networks represented by distribution artefact patterns. An interesting case study of such networks was published recently by Brughmans (2010), who performed a range of exploratory analyses on fine ware pottery in the Eastern Mediterranean. Studying the distribution of eastern sigillata C from Pergamon, he could point out trade routes and even different trade volumes passing through them. Studying the distribution and co-­‐presence of specific pottery shapes, he argues that is also possible to study in more detail the trade mechanisms behind the observed distribution patterns. Within our project, we intend to apply this approach to study mechanisms of re-­‐distribution within the Pontine region. Presuming that at trading sites the number of available pottery shapes is larger than at consumption sites, these trading sites should stand out in terms of co-­‐presence or concurrence of different shapes. In the course of our project we will therefore build up a regional pottery database that allows us to plot for the entire region the occurrence of such imports, and also the variability in shapes between sites. Fig. 6. Production sites of amphorae and dolia in relation to roads, waterways, harbours and minor centers Besides using imported wares, we will also look at the distribution of locally produced pottery. With archaeometric studies, we aim to identify local products, and trace the scale and geographical extent of their distribution. The relation with geographic networks will be a main concern, particularly of waterways as potential ‘shortcuts’ that extended the distributional range (fig. 6). An example is the Rio Martino, a canal that connects the Pontine plain with the coast: its construction, presumably in the late Republican period, probably caused a shift in trade routes between the coast and the plain. Amphorae produced on the coast reached the interior plain, while a workshop producing large storage vessels is situated close to the canal. By mapping the distribution of the products of these workshops in more detail, we will hopefully be able to investigate the role of this canal and the two minor centres of Astura and Ad Turres Albas that may have functioned as transhipment places. 3) Social networks The economic activities discussed above, pottery production, trade, but also the investments in road building and port construction, are of course strongly tied to the state, elites and their power relations. To understand the changes in geographic and material networks it is therefore important to also consider the social networks of elite individuals, gentes and the Imperial court as these can be traced through historical and epigraphic sources. The potential of such a study was shown by Graham (2006), who analysed the involvement of various gentes in the brick trade using evidence from brick stamps and known production sites in the Tiber valley north of Rome. Not only was he able to show that there was a complex organization that targeted the rural market in Rome’s hinterland, but he also identified key figures in the networks of brick producers that could control access to the lucrative urban market at Rome. Although with the evidence available for our study area a similarly detailed analysis of a single industry will probably not be feasible, it will be interesting to map such patterns of economic involvement. While an inventory of available evidence is yet to be made, there is evidence for the presence of members of the Roman elite in the Pontine region from the later 4th century BC onwards. The via Appia and Forum Appi being named after Appius Claudius and one of his descendents being mentioned on a mid-­‐3rd century milestone, it is clear that the gens Claudia had major interests in the region. In addition, a praetor by the name of L. Vargunteius Rufus and Postumius Albus, consul in 110 BC, undertook the construction of a temple near Sezze in the 2nd century BC.9 It seems highly likely that these individuals owned estates and had economic interests in the pontine plain. Similarly, historical sources refer to the villae maritimae of many high-­‐ranking Romans on the Pontine coast in the first century BC. It is no coincidence that such grand villae cluster around the harbours of Antium, Astura, Circeii and Tarracina.10 Archaeological evidence suggests that on some of these estates brick and tile production took place; the gens Aemilia was surely involved in such industrial activities, as is clear from a die used to stamp tiles produced at a coastal villae between Antium and Astura.11 Where it concerns the infrastructure of the region, important improvements were made by Nero and Trajan, commissioning the construction of the harbours at Antium and Tarracina respectively. Secondary harbours north of Monte Circeo and at Torre Astura are connected to villae maritimae that may have been Imperial property as well. It therefore seems likely that the Emperors had private economic interests in the Pontine region as well. 9
Bruckner, E., 2003, Considerazioni sui culti e luoghi di culto a Setia e nel suo territorio in età repubblicana ed imperiale, in Quilici, L. & S. Quilici-­‐Gigli eds, Santuari e luoghi di culto nell'Italia antica, Roma, pp. 75-­‐98; Cassieri, N., 2004, Il deposito votivo di Tratturo Caniò a Sezze, in Papi, G. ed., Religio Santuari ed ex voto nel lazio meridionale, Terracina, pp. 162-­‐181. 10
Lafon, X., 2001, Villa Marittima. Recherches sur les villas littorales de l'Italie Romaine (IIIe siècle av. J.-­‐C. / IIIe siècle ap. J.-­‐C.), Roma; Piccarreta, F., 1977, Astura, Firenze; Lugli, G., 1926, Ager Pomptinus pars prima Anxur-­‐
Tarracina, Roma; Lugli, G., 1928, Ager Pomptinus pars secunda Circeii, Roma. 11
De Haas, T., G. Tol, & P. Attema, 2011, Investing in the colonia and ager of Antium, Facta, 5. Concluding remark In this paper we have tried to show the potential of network analysis for an archaeological study of settlement and economy by discussing three types of networks. As Graham has put it, ‘[…] the movement of information, people [and goods] along networks, and the intensification of relationships when networks intersect, can transform a region.’ (Graham 2006: 26) This quote summarizes very well the role we see for network analysis in studying the economy of the Pontine region. It provides a range of tools that can be applied in different ways and to a range of data, including infrastructure, artefactual and textual sources. Thank you for your attention.