Evaluating network science in archaeology. A Roman Archaeology perspective

475 Pages·2015·12.76 MB·English

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FACULTY OF HUMANITIES
DEPARTMENT OF ARCHAEOLOGY
Evaluating network science in archaeology.
A Roman Archaeology perspective
by
Tom Brughmans
VOLUME I: THESIS
Thesis for the degree of Doctor of Philosophy
October 2014
Evaluating network science in archaeology
ABSTRACT
In the last decade, network science techniques have become more common in archaeology.
But is this just a short-lived trend caused by the popularity of these techniques in other
disciplines, the availability of big data, and the rise of the World-Wide Web and online social
networks? Or does network science hold the potential of making a unique contribution to our
discipline? This PhD project aims to evaluate this potential.
It starts with the claim that the unique contribution of network science to archaeology lies in
its ability to deal with network data. It evaluates this claim through a literature review and
three archaeological case studies. Two of the case studies concern research themes in Roman
archaeology, to focus the evaluation process on one archaeological subdiscipline rather than
tackling the full diversity of research themes and data types in archaeology. This thesis takes
a Roman archaeology perspective to evaluating network science, and further discusses the
implications of its results for the archaeological discipline at large. This project not only aims
to evaluate whether network science does indeed offer a unique contribution, but also
whether archaeologists have need for such techniques. Do archaeologists commonly ask
research questions that are best addressed through the analysis of network data? Does
network science allow archaeologists to ask new questions? Are archaeologists commonly
confronted with network data?
The literature review reveals that formal network techniques have been used in archaeology
since at least the 1960s, but have only recently become more commonly applied. Moreover, it
concludes that the methodological range of network techniques applied in archaeology is
limited and that its place in the archaeological research process is ill-defined. It suggests
these issues can be tackled by taking a broad multi-disciplinary scope, by letting the
archaeological research context dominate the adoption and development of network
techniques, and by working explicitly through a network science research process. These
three lessons subsequently influenced the selection of three archaeological case studies that
have the ability to address this project’s research questions, to evaluate possible
particularities in the use of network science for Roman archaeology, and that have the
potential to allow the application of network techniques that have never before been applied
in archaeology.
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Evaluating Network Science in Archaeology
The first case study presents a citation network analysis of the adoption, use and adaptation of
formal network techniques in archaeology. This case study can be seen as a network analysis
of the literature review, using exploratory network techniques and visualisations. It illustrates
how an exploratory network analysis allows one to gain insights that cannot be obtained from
a close reading in a literature review, and how some of the conclusions of the literature
review can be identified or reproduced through the use of exploratory network techniques.
The second case study is an analysis of inter-settlement visibility in Iron Age and Roman
Southern Spain. It introduces a statistical modelling approach (Exponential Random Graph
Modelling (ERGM)) for simulating dependence assumptions surrounding visibility networks:
theoretical assumptions formulated by archaeologists as hypotheses of why lines of sight
between settlements matter. Finally, the third case study presents an agent-based network
model of tableware distribution in the Roman Eastern Mediterranean. It focuses on the
potential of network science methods for performing confirmatory analyses by evaluating
two complex hypotheses surrounding the functioning of the Roman trade systems.
This thesis concludes that archaeologists commonly formulate (implicitly or explicitly)
dependence assumptions, that they are confronted with network data, and that in such cases
network science techniques can offer methodological advantages over other methodological
tools used by archaeologists. This conclusion firmly establishes network science in the
archaeologist’s methodological toolbox. The main contributions of this PhD project are,
therefore, i) to argue why network science offers archaeologists unique and necessary
methodological advantages, ii) to provide three critical practical examples of how it can be
applied, iii) to offer a number of suggestions which could guide the future archaeological use
of network science, iv) to introduce innovative methods of citation analysis and statistical
network modelling to our discipline, and v) to emphasise the importance and possibility of
falsifying and abstracting Roman archaeology hypotheses as transparent and comparable
conceptualisations.
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Tom Brughmans

Fig. 1. Word cloud of the full text of this PhD thesis. It’s about networks!

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Evaluating Network Science in Archaeology
TABLE OF CONTENTS

CHAPTER 1. Introduction: why evaluate network science in archaeology?.............................. 16
1.1. Aims .................................................................................................................................................... 16
1.2. What is network science? .................................................................................................................... 17
1.3. Why does archaeology need network science? ................................................................................... 24
1.4. Research questions .............................................................................................................................. 27
1.5. Why a Roman archaeology perspective? ............................................................................................ 28
1.6. The structure of this PhD .................................................................................................................... 29

CHAPTER 2. Literature review: the roots and shoots of archaeological network science......... 35
2.1. Introduction ......................................................................................................................................... 35
2.2. Origins in graph theory? ...................................................................................................................... 36
2.3. Social network analysis ....................................................................................................................... 43
2.3.1. An introduction to SNA.............................................................................................................. 43
2.3.2. An early archaeological model ................................................................................................... 44
2.3.3. Diffusion of material and immaterial resources ......................................................................... 46
2.3.4. Network centrality ...................................................................................................................... 48
2.3.5. Affiliation networks ................................................................................................................... 51
2.3.6. Ego-networks ............................................................................................................................. 52
2.4. Discussion: beyond SNA .................................................................................................................... 54
2.5. Complex networks and physics ........................................................................................................... 56
2.5.1. Small-world networks ................................................................................................................ 57
2.5.2. Scale-free networks and power-laws .......................................................................................... 58
2.5.3. Small-world and scale-free networks in archaeology ................................................................. 60
2.5.4. Discussion: complex networks beyond popular models ............................................................. 62
2.5.5. Dynamic network models in archaeology .................................................................................. 64
2.6. Network science in Roman Archaeology ............................................................................................ 68
2.7. Conclusion: the need to evaluate network science in archaeology...................................................... 71
2.8. Implications for developing case studies............................................................................................. 74

CHAPTER 3. ... Case study 1: a citation network analysis of the adoption, use, and adaptation of
formal network techniques in archaeology .............................................................................. 79
3.1. Introduction ......................................................................................................................................... 79
3.2. Citation network analysis and archaeology ......................................................................................... 80
3.3. Data collection, citation network creation and sample size issues ...................................................... 82
3.4. Methods ............................................................................................................................................... 85
3.5. Results ................................................................................................................................................. 88
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3.5.1. Local scale: network of archaeological applications .................................................................. 89
3.5.2. Meso scale: ego-network of archaeological applications ........................................................... 94
3.5.3. Global scale: combined dataset ................................................................................................ 102
3.6. Discussion ......................................................................................................................................... 104

CHAPTER 4. ..... Case Study 2: understanding inter-settlement visibility in Iron Age and Roman
Southern Spain with exponential random graph models for visibility networks ................... 113
4.1. Introduction ....................................................................................................................................... 113
4.2. Visibility networks ............................................................................................................................ 114
4.2.1. The study area .......................................................................................................................... 114
4.2.2. Why study visibility networks in Iron Age II and Roman Southern Spain? ............................. 120
4.2.3. Why processes of emerging inter-visibility? ............................................................................ 124
4.2.4. Hypotheses of visibility network creation processes ................................................................ 125
4.2.5. Previous archaeological applications of visibility networks ..................................................... 129
4.2.6. What does inter-visibility mean? .............................................................................................. 130
4.3. Data: topography, sites, chronology, and attributes .......................................................................... 132
4.3.1. Digital Elevation Model ........................................................................................................... 132
4.3.2. Settlement data ......................................................................................................................... 132
4.3.3. Chronology ............................................................................................................................... 134
4.3.4. Site attributes ............................................................................................................................ 135
4.4. Method: an approach for exploring changing visibility networks ..................................................... 136
4.4.1. Probable viewsheds .................................................................................................................. 136
4.4.2. Observation point locations ...................................................................................................... 138
4.4.3. Visibility network creation ....................................................................................................... 139
4.4.4. Exploratory Network Analysis ................................................................................................. 140
4.4.5. Exponential Random Graph Models ........................................................................................ 140
4.4.6. Software ................................................................................................................................... 150
4.5. Results of the combined approach .................................................................................................... 150
4.5.1. Exploratory network analysis ................................................................................................... 152
4.5.2. Exponential Random Graph Models ........................................................................................ 159
4.6. Discussion: towards a better understanding of urban connectivity in Iberian and Roman Southern
Spain 166

CHAPTER 5. ........... Case study 3: Bang’s Roman Bazaar and/or Temin’s Market Economy? An
agent-based network model of tableware distribution in the Roman East............................. 175
5.1. Introduction ....................................................................................................................................... 175
5.2. Tableware studies, distribution patterns, and processes .................................................................... 180
5.2.1. Introduction .............................................................................................................................. 180
5.2.2. Studying Roman pottery distributions ...................................................................................... 181
5.2.3. Distribution processes .............................................................................................................. 182
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5.2.4. Being wrong can be useful: questions, methods, and issues for a new approach ..................... 199
5.3. Tableware distribution patterns: data and the state of the art ............................................................ 202
5.3.1. Tableware fabric-groups in the Roman East ............................................................................ 202
5.3.2. The ICRATES database ........................................................................................................... 204
5.3.3. Issues with the data ................................................................................................................... 205
5.3.4. Chronological overview tableware distribution in the Roman East ......................................... 207
5.4. Exploratory data analysis .................................................................................................................. 212
5.4.1. Introduction .............................................................................................................................. 212
5.4.2. Typologies and functional categories ....................................................................................... 212
5.4.3. Gaussian distribution ................................................................................................................ 213
5.4.4. Number of sherds per ware ....................................................................................................... 214
5.4.5. Number of forms per ware ....................................................................................................... 215
5.4.6. Number of sites per ware .......................................................................................................... 216
5.4.7. Frequency distributions ............................................................................................................ 217
5.4.8. Exploratory network analysis results ........................................................................................ 221
5.4.9. Conclusion ................................................................................................................................ 223
5.5. Agent-based model............................................................................................................................ 225
5.5.1. Model description ..................................................................................................................... 226
5.5.2. Results ...................................................................................................................................... 241
5.5.3. Conclusions .............................................................................................................................. 255
5.6. Discussion ......................................................................................................................................... 256

CHAPTER 6. Discussion: addressing challenges in archaeological network science .............. 266
6.1. Lessons learned from the case studies ............................................................................................... 266
6.1.1. Case study 1: methodological implications .............................................................................. 266
6.1.2. Case study 2: methodological implications .............................................................................. 267
6.1.3. Case study 3: methodological implications .............................................................................. 269
6.1.4. Implications for Roman archaeology ....................................................................................... 270
6.2. ‘We shall overcome’: challenges and suggested solutions ................................................................ 272
6.2.1. Method ..................................................................................................................................... 273
6.2.2. Data .......................................................................................................................................... 277
6.2.3. Space ........................................................................................................................................ 279
6.2.4. Process ...................................................................................................................................... 280
6.2.5. Past social networks ................................................................................................................. 283
6.3. A ‘guide to good practice’: specifications for future archaeological network science ...................... 284

CHAPTER 7. Conclusion: the potential of network science in archaeology ............................ 290
7.1. The contribution of this PhD ............................................................................................................. 290
7.2. Where to go from here? Archaeological network science beyond the “hype” .................................. 292

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8. Bibliography .................................................................................................................. 297
9. Appendix I: literature review ......................................................................................... 324
9.1. Publications used to compile figure 5 ............................................................................................... 324
10. Appendix II: case study 1 ........................................................................................... 332
10.1. Bibliography local scale .................................................................................................................... 332
10.2. Bibliography tables 4-6 ..................................................................................................................... 336
11. Appendix III: case study 2 .......................................................................................... 340
11.1. Sites index: dates, urban status, location, road and river networks ................................................... 340
11.1.1. All 190 sites included in this case study in alphabetical order ................................................. 340
11.1.2. All 190 sites included in this case study sorted according to their project ID .......................... 345
11.1.3. All sites with an urban status .................................................................................................... 355
11.1.4. Sites on the Via Augusta .......................................................................................................... 356
11.1.5. Sites on the river network ......................................................................................................... 356
11.2. Cumulative viewsheds ...................................................................................................................... 358
11.3. Results of the node-based network measures .................................................................................... 363
11.3.1. Iberian period network up to 20km .......................................................................................... 363
11.3.2. Republican period network up to 20km.................................................................................... 365
11.3.3. Early Imperial period network up to 20km............................................................................... 367
11.3.4. Middle Imperial period network up to 20km ............................................................................ 369
11.3.5. Late Imperial period network up to 20km ................................................................................ 370
11.4. ERGM results .................................................................................................................................... 372
11.4.1. Goodness of fit of Bernoulli random graph models ................................................................. 372
11.4.2. ERGMs without attributes ........................................................................................................ 384
11.4.3. ERGMs of Early Imperial attributed networks ......................................................................... 399
12. Appendix IV: case study 3 .......................................................................................... 417
12.1. Lists of sites and forms used ............................................................................................................. 417
12.2. Exploratory network analysis case study 2 ....................................................................................... 426
12.2.1. Introduction .............................................................................................................................. 426
12.2.2. Similarity of forms’ distributions: the Brainerd-Robinson coefficient ..................................... 427
12.2.3. Creating and exploring similarity networks ............................................................................. 430
12.2.4. Network structure and sensitivity analysis ............................................................................... 431
12.3. Agent-based model code ................................................................................................................... 449
13. Glossary ...................................................................................................................... 470
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BOX SUMMARIES
Box 1. Summary: what is network science? ............................................................................ 24
Box 2. Summary Chapter 1 ...................................................................................................... 32
Box 3. Summary chapter 2....................................................................................................... 76
Box 4. Network science research process case study 1 ........................................................... 88
Box 5. Summary chapter 3..................................................................................................... 110
Box 6. Network science research process case study 2 ......................................................... 151
Box 7. Summary of chapter 4 ................................................................................................ 172
Box 8. Research outline of case study 3 ................................................................................ 180
Box 9. Network science research process ABM case study 3 ............................................... 242
Box 10. Summary of chapter 5 .............................................................................................. 264
DEFINITIONS AND ABBREVIATIONS USED
This thesis uses concepts, techniques, and abbreviations uncommon in archaeology and
adopted from other disciplines. It was therefore decided to include an elaborate glossary that
explains these, see section 13 at the end of this thesis.
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