Kuril Island Social Network Analysis Methodology Note (DRAFT) S. Colby Phillips and Erik Gjesfjeld

Social Networks Analysis

Social network analysis (SNA) is an approach that focuses on the relationships between social entities, the patterns that are present based on those relationships, and the implications of those relationships (Wasserman and Faust 1994). The networks utilized in SNA consist of nodes (such as actors, players, agents, or organizations) and ties between the nodes (such as links based on communication, economic transactions, or kinship) (Thompson 2003). While the conventional analysis of social science data compares actors based on their attributes, network analysis compares actors based on their relationships (Hanneman and Riddle 2005).

The conceptual and analytical use of network analysis provides a means for modeling prehistoric regional systems as networks formed by connections among sites. Analytically, the technique provides a tool for measuring the characteristics of regional systems quantitatively, and in turn, for objectively comparing systems with one another. Because networks are dynamic, and the types of interactions that produced network ties may shift over time, it is necessary to incorporate a diachronic element to the analysis and compare network structures as they changed through time (Nietzel 2000). Additionally, SNA provides a way to superimpose a measure of non-Cartesian social geography represented by human relationships on top of cartographic space to make comparisons between geographic and social space (Mackie 2001; Thomas 2001).

For this example, the relationships between archaeological sites in the Kuril Islands is explored via several methods, beginning with proximity similarity measures based on the distances between archaeological sites, and then through the analysis of ties between sites using specific sources of obsidian that are found in each site as a proxy for site ties. Thirteen archaeological sites present across the southern, central, and northern parts of the Kuril archipelago were chosen for analysis based on the presence of at least five obsidian flakes. A discussion of each of the methods used and an outline of the results follows below. Using Proximity Measures to Model Perceived Similarities

Several network analysis methods are used to model perceived or hypothesized similarities between network nodes based on geography. The technique of proximal point analysis (PPA) (also known as nearest neighbor analysis) is a way to explore what patterns of contact or relationships might exist if these relationships are influenced by geographic distance, and to hypothesize “neighborhoods” within a network. A 1st, 2nd, and 3rd order PPA for each site simply uses lines (edges) to connect each site of interest (nodes) to the 1st, 2nd, and 3rd closest nearest (proximal) sites (Terrell 1976, 1986, 2009 in press; Knappett et al. 2008). For the Kuril example, a distance matrix was created which lists the straight-line geographic distances in kilometers among the thirteen archaeological sites included in this study (Table 1). Based on these distances, for each site a line was drawn to the 1st, 2nd, and 3rd nearest sites; the lines were superimposed on a map of the Kuril Islands to show these linkages (Figure 1).

Another way to display the proximity of network nodes on a network map is to use multidimensional scaling (MDS). MDS represents proximities in two-dimensional space to show that nodes that are more proximate to each other based on the input data are closer together in network space. This may allow for further study of subgroups that are shown to be more proximal to each other (Wasserman and Faust 1994). The goodness of fit measure for MDS representations are based on stress measures, normalizations of the sum of squared differences between the MDS representations and the input data. High stress indicates a poor fit caused by MDS distortion of the input data, low stress indicates a good fit and little MDS distortion (DeJordy et al. 2007). Using the same one-mode symmetric matrix of site distances shown in Table 1, the matrix was transformed into a network map using the Ucinet 6 software program (Figure 2). The MDS network map shows a very close approximation to the location and proximity of sites shown in Figure 1 with little map distortion as measured by the low stress value of 0.005.

Graphic layout algorithms (GLAs) can also be used to model proximity data as networks, and are commonly used by social network analysis tools. Most GLAs are designed to work with binary data, and proximity data must be dichotomized in order to visualize relationships of interest (DeJordy et al. 2007). Figure 3 displays the site distance matrix data from Table 1 in an un-dichotomized network. Figure 4 on

the other hand shows the connections between sites when the distance between sites is 300 km. This network representation (which was rotated around and re-sized to better approximate the geographic layout of the Kuril archipelago) provides a way to examine relationships at specific distances of interest.

On the whole, these proximity measure methods of modeling similarities between Kuril Islands archaeological sites provide basic network representations which might form the basis for developing hypotheses about distance-related ties between sites. Incorporating archaeological data provides the next step in examining site relationships at a different level. Obsidian Source Data as a Proxy for Network Ties

Similarities in archaeological assemblages can be used as a proxy measure to infer ties between sites that can be modeled using social network analysis tools (Terrell in press). For the Kuril Island example, data from the source provenance analysis of obsidian artifacts recovered from Kuril archaeological sites was used to explore potential connections between sites (Phillips in press; Phillips and Speakman 2009). Table 2 is a matrix that shows the number of obsidian flakes from each of 11 different obsidian sources present in each of the 13 archaeological sites that are part of this study. This matrix was then converted into a binary presence-absence correlation matrix that represents which sites share at least on obsidian source with any other site (Table 3). The Table 3 matrix was then represented as a network using the NetDraw GLA tool to graphically show the ties between archaeological sites (Figure 5). As might be expected from observing the presence-absence matrix, this network structure is not very informative in terms of exploring network relationships – many site assemblages share at least one of the same obsidian sources, and therefore there are many site ties represented in the network.

One more informative way to explore the network is to compare the sites in terms of all of the different obsidian sources that are present in their artifact assemblages as a way to discover patterned groupings with as few assumptions as possible (Shennan 1997). Table 4 is a matrix of the presence or absence of each source in each site (a binary conversion of Table 2). This presence-absence matrix was converted into a matrix of Jaccard similarity coefficients, a statistic used to compare the similarity and differences in a sample set (Table 5). The Jaccard similarity coefficient ignores negative matches (sites are not grouped together because of the absence of specific obsidian sources), and coefficient values close to 1 indicate a strong similarity while values close to 0 indicate a strong difference. This similarity matrix is represented graphically as a network in Figure 6 based on similarity values > 0.40, which now shows which sites are more similar based on the presence of obsidian sources in their assemblages and demonstrates that the specific sources that each of the sites shares influence the network ties that are created. From this graphic we might infer social relationships (trade, exchange, familial, ceremonial, etc.) under the assumption obsidian source assemblages are material traces of social similarities (and by definition ties) that existed among the inhabitants of Kuril Island sites. References DeJordy,R., S.P. Borgatti, C. Roussin, and D.S. Halgin (2007). Visualizing Proximity Data. Field Methods 19(3):239-268. Hanneman, R.A. and M. Riddle (2005). Introduction to social network methods. Riverside, CA: University of California, Riverside (published in digital form at http://faculty.ucr.edu/~hanneman/ ). Knappett, C., T. Evans, and R. Rivers (2008). Modelling maritime interaction in the Aegean Bronze Age. Antiquity 82:1009-1024. Mackie, Q. (2001). Settlement Archaeology in a Fjordland Archipelago. BAR International Series 926, Oxford: Hadrian Books. Neitzel, J.E. (2000). What is a regional system? Issues of scale and interaction in the prehistoric Southwest. In The Archaeology of Regional Interaction, M. Hegmon (ed): 25-40. Proceedings of the 1996 Southwest Symposium. Boulder, Colorado University Press of Colorado. Phillips, S.C. Bridging the Gap Between Two Obsidian Source Areas in Northeast Asia: LA-ICP-MS Analysis of Obsidian Artifacts from the Kurile Island of the Russian Far East. In Crossing the Straits:

Prehistoric Obsidian Source Exploitation in the Pacific Rim, edited by M. Glascock, Y.V. Kuzmin, and R.J. Speakman. Smithsonian Institution Press: Washington, D.C. In press. Phillips, S.C. and R.J. Speakman (2008). Initial source evaluation of archaeological obsidian from the Kuril Islands of the Russian Far East using portable XRF. Journal of Archaeological Science 36(6): 1256-1263. Shennan, S. (1997). Quantifying Archaeology, 2nd Edition. Iowa City: University of Iowa Press. Terrell, J. (1976). Island biogeography and man in Melanesia. Archaeology and Physical Anthropology in Oceania 11(1):1-17. Terrell, J. (1986). Prehistory in the Pacific Islands. Cambridge: Cambridge University Press. Terrell, J. Language and Material Culture on the Sepik Coast of Papua New Guinea: Using Social Network Analysis to Simulate, Graph, Identify, and Analyze Social and Cultural Boundaries Between Communities. Journal of Island and Coastal Archaeology, in press. Thomas, J. (2001). Archaeologies of Place and Landscape. In Archaeological Theory Today, I. Hodder (ed.): 165-186. Cambridge: Polity Press. Thompson, G.F. (2003). Between Hierarchies and Markets: The Logic and Limits of Network Forms of Organization. New York: Oxford University Press. Wasserman, S. and K. Faust (1994). Social Network Analysis. Cambridge: Cambridge University Press.

Table 1: Matrix of distances (in kilometers) between Kuril Island archaeological sites.

   Rikorda  Sernovodsk Peschanaya 2  Berezovka  Kubyushevskaya 

Ainu Creek 

Peschanaya Bay  Vodopodnaya 

Broutona Bay  Drobnyye  Savushkina  Baikova  Bolshoi 

Rikorda   0  29  36  148  219  378  525  640  651  878  1113  1119  1123 

Sernovodsk   29  0  8  119  193  355  503  620  626  847  1091  1092  1096 

Peschanaya 2  36  8  0  122  191  351  501  614  624  845  1089  1091  1093 

Berezovka  148  119  122  0  70  228  379  491  503  727  971  972  977 

Kubyushevskaya  219  193  191  70  0  164  312  425  434  655  901  903  905 

Ainu Creek  378  355  351  228  164  0  154  265  276  504  755  756  759 

Peschanaya Bay  525  503  501  379  312  154  0  112  122  351  604  604  607 

Vodopodnaya  640  620  614  491  425  265  112  0  10  243  498  498  502 

Broutona Bay  651  626  624  503  434  276  122  10  0  234  489  490  492 

Drobnyye  878  847  845  727  655  504  351  243  234  0  255  255  258 

Savushkina  1113  1091  1089  971  901  755  604  498  489  255  0  7  7 

Baikova  1119  1092  1091  972  903  756  604  498  490  255  7  0  3 

Bolshoi  1123  1096  1093  977  905  759  607  502  492  258  7  3  0 

Figure 1: Map showing PPA with lines drawn between each Kuril Island archaeological site and its 1st, 2nd, and 3rd nearest neighbor.

Rikorda Sernovodsk Peschanaya 2

BerezovkaKubyushevskaya

Ainu CreekPeschanaya BayVodopodnayaBroutona Bay

Drobnyye

SavushkinaBaikovaBolshoi

Figure 2: MDS network map representation of Kuril Island site distances from Table 1.

Figure 3: GLA network representation of Kuril Island site distances from Table 1.

Figure 4: GLA network representation of Kuril Island site distances from Table 1 when network ties are based on distances < 300 km.

Table 2: Frequency matrix of the presence of obsidian flakes from 11 obsidian sources in 13 Kuril Island archaeological sites.

   Rikorda Sernovodsk Peschanaya 

2  Berezovka  Kubyushevskaya Ainu Creek 

Peschanaya Bay  Vodopodnaya 

Broutona Bay  Drobnyye  Savushkina  Baikova  Bolshoi 

Shirataki‐A 

12  0  6  4  4  145  0  3  0  0  0  0  0 

Shirataki‐B 

30  2  11  8  9  71  0  0  0  2  0  0  0 

Oketo‐1  69  20  16  15  7  353  0  3  0  2  0  1  0 

Oketo‐2  3  4  3  0  0  13  0  0  0  0  1  1  0 

Kam‐01  1  0  0  0  0  1  7  10  1  39  35  59  0 

Kam‐02  0  0  0  0  0  2  1  34  2  84  6  16  5 

Kam‐04  0  0  0  0  0  0  0  20  0  4  55  2  1 

Kam‐05  16  0  1  0  0  1  0  10  0  6  0  0  0 

Kam‐07  0  0  0  0  0  0  2  25  7  1  0  0  0 

Group‐A  0  0  0  4  0  0  0  0  0  0  0  6  0 

Group‐B  4  1  0  0  0  1  6  4  0  0  1  2  0 

Total 135  27  37  31  20  587  16  109  10  138  98  87  6 

Table 3: Correlation matrix of sites that share at least one obsidian source.

   Rikorda  Sernovodsk Peschanaya 

2  Berezovka  Kubyushevskaya Ainu Creek 

Peschanaya Bay  Vodopodnaya 

Broutona Bay  Drobnyye  Savushkina  Baikova  Bolshoi 

Rikorda    1  1  1  1  1  1  1  1  1  1  1  0 

Sernovodsk  1    1  1  1  1  1  1  0  1  1  1  0 

Peschanaya 2  1  1    1  1  1  0  1  0  1  1  1  0 

Berezovka  1  1  1    1  1  0  1  0  1  0  1  0 

Kubyushevskaya  1  1  1  1    1  0  1  0  1  0  1  0 

Ainu Creek  1  1  1  1  1    1  1  1  1  1  1  1 

Peschanaya Bay  1  1  0  0  0  1    1  1  1  1  1  1 

Vodopodnaya  1  1  1  1  1  1  1    1  1  1  1  1 

Broutona Bay  1  1  0  0  0  1  1  1    1  1  1  1 

Drobnyye  1  1  1  1  1  1  1  1  1    1  1  1 

Savushkina  1  1  1  0  0  1  1  1  1  1    1  1 

Baikova  1  1  1  1  1  1  1  1  1  1  1    1 

Bolshoi  0  0  0  0  0  1  1  1  1  1  1  1    

Figure 5: GLA network representation of Table 3 correlation matrix of Kuril Island archaeological sites sharing at least one obsidian source.

Table 4: Presence-absence matrix of obsidian sources present in Kuril Island archaeological sites.

   Rikorda  Sernovodsk Peschanaya 

2  Berezovka  Kubyushevskaya  Ainu Creek Peschanaya 

Bay  Vodopodnaya Broutona 

Bay  Drobnyye  Savushkina  Baikova  Bolshoi 

Shirataki‐A  1  0  1  1  1  1  0  1  0  0  0  0  0 

Shirataki‐B  1  1  1  1  1  1  0  0  0  1  0  0  0 

Oketo‐1  1  1  1  1  1  1  0  1  0  1  0  1  0 

Oketo‐2  1  1  1  0  0  1  0  0  0  0  1  1  0 

Kam‐01  1  0  0  0  0  1  1  1  1  1  1  1  0 

Kam‐02  0  0  0  0  0  1  1  1  2  1  1  1  1 

Kam‐04  0  0  0  0  0  0  0  1  0  1  1  1  1 

Kam‐05  1  0  1  0  0  1  0  1  0  1  0  0  0 

Kam‐07  0  0  0  0  0  0  1  1  1  1  0  0  0 

Group‐A  0  0  0  1  0  0  0  0  0  0  0  1  0 

Group‐B  1  1  0  0  0  1  1  1  0  0  1  1  0 

Table 5: Jaccard similarity matrix for Kuril Island archaeological sites.

Rikorda Sernovodsk

Peschanaya 2 Berezovka Kubyushevskaya

Ainu Creek

Peschanaya Bay Vodopodnaya

Broutona Bay Drobnyye Savushkina Baikova Bolshoi

Rikorda 1.000 .571 .714 .375 .429 .875 .222 .500 .111 .400 .333 .400 .000

Sernovodsk .571 1.000 .500 .333 .400 .500 .143 .200 .000 .222 .286 .375 .000

Peschanaya 2 .714 .500 1.000 .500 .600 .625 .000 .300 .000 .333 .111 .200 .000

Berezovka .375 .333 .500 1.000 .750 .333 .000 .200 .000 .222 .000 .222 .000

Kubyushevskaya .429 .400 .600 .750 1.000 .375 .000 .222 .000 .250 .000 .111 .000

Ainu Creek .875 .500 .625 .333 .375 1.000 .333 .600 .222 .500 .444 .500 .111

Peschanaya Bay .222 .143 .000 .000 .000 .333 1.000 .500 .750 .375 .500 .375 .200

Vodopodnaya .500 .200 .300 .200 .222 .600 .500 1.000 .375 .667 .444 .500 .250

Broutona Bay .111 .000 .000 .000 .000 .222 .750 .375 1.000 .429 .333 .250 .250

Drobnyye .400 .222 .333 .222 .250 .500 .375 .667 .429 1.000 .333 .400 .286

Savushkina .333 .286 .111 .000 .000 .444 .500 .444 .333 .333 1.000 .714 .400

Baikova .400 .375 .200 .222 .111 .500 .375 .500 .250 .400 .714 1.000 .286

Bolshoi .000 .000 .000 .000 .000 .111 .200 .250 .250 .286 .400 .286 1.000

Figure 6: GLA network representation of Jaccard similarity matrix of Kuril Island archaeological sites.