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European Bronze Age Cultures and technical evolution: a Phylogenetic Approach

Final Report Summary - BRONZE AGE (European Bronze Age cultures and technical evolution: a phylogenetic approach)

The European Middle Bronze Age (from 1650 to 1350 BC) was a multipolar world, composed of many cultures marked by strong expansion of metal production through the control of copper alloying with tin and the technique of casting. This specialised craft plays a crucial role in social distinctions and intercultural relations. Control of resources and their distribution implements social power and the complex interplay of large trade networks of ore and objects. If cross-cultural interactions have always been a dominant theme of research within the scientific community, paradoxically they are based on a minority of individuals composed of the elite, intermediate and skilled crafts. Domestic and popular crafts such as pottery are studied, but cross-cultural comparisons are based on the features most sensitive to change and easier to imitate: the form and decoration of objects. In contrast, we know almost nothing of the technical traditions of each culture, such as those involved in the shaping of ceramics. However, the 'ways of doing' cannot be copied. They require a long learning process that takes place with a master or parent. Each past or present culture has its own technical traditions passed down from generation to generation. In fact, the study of technical behaviour provides a relevant perspective on the nature of the evolution of cultures and the depth of cross-cultural interactions.

This Marie Curie project is centred on a fundamental question: Did the European Bronze Age cultures evolve through a process of phylogenesis or ethnogenesis? In other words, from generation to generation, do the technical ceramic traditions evolve only inside each culture or instead are we in the presence of process technology transfers between cultures? This question is difficult to resolve in the absence of methods and modelling tools. Biological evolution is based on a simple but fundamental principle, descent with modification. In other words, it is the passage of a primitive character state to a derived character state. Applied to the concept of technical system, a phylogenetic tree would model both the diversity of chaînes opératoires, their evolution and their family relationship within a cultural group (phylogeny) and any inter-cultural transfer (ethnogenesis).

The traditional ceramic techniques known in two regions (Centre West of France with the Duffaits Culture; English and Norman communities of the English Channel-North Sea Complex) were used to support the Marie Curie project. A total of 60 chaînes opératoires of shaping and finishing identified from 1 400 ceramics from 14 archaeological sites of the Bronze Age were used. Ongoing training in the theoretical and practical approaches of phylogenetic and evolutionary archaeology - performed in the Institute of Archaeology, University College London - has helped to build a multidisciplinary methodology involving the use of phylogenetics software such as Mesquite or TNT.

The first stage was marked by the development of characters capable of coding in a relevant manner of chaîne opératoire in a matrix that could be used for phylogenetic analysis. This fundamental step is the heart of this work, requiring the construction and testing of more than 60 matrices, involving up to 15 780 data elements. As in biology, the choice of characters and character states (primitive and derived) is the key step of the scientific analysis. This matrix must satisfy two constraints: be usable in cladistics and respect the basis of the concept of chaîne opératoire, which reflect a series of operations that transform raw material into a finished product, based on the techniques and methods of the craftspeople, according to the physical manner in which the clay is shaped and following sequences or organised set of operations. In other words, developed characters must integrate the notion of series of operations and the theoretical independence of the evolution of each gesture, each tool, each method and each technique used by the potter.

60 chaînes opératoires of shaping have been completely redesigned and adapted to phylogenetic analysis: while the original description was based on 19 observable criteria, 263 characters were developed during this Marie Curie project to model their evolution with a high resolution of analysis. The constitution of this matrix is the support of three stages of analysis. The first verifies that the matrix contains a phylogenetic signal. The second develops a phylogenetic tree in order to represent and analyse the relationships of descent and kinship between the technical traditions of each cultural group; each clade of the tree represents the evolution of an apprenticeship network. The third stage is devoted to the interpretation of the origin, the nature of the differences and similarities obtained in the parsimony analysis.

The results are relevant at three different levels. First, the methodology developed shows that it is possible, on both theoretical and practical terms, to create a bridge between the anthropology of techniques and phylogenetics. The technical traditions of the Duffaits Culture, Norman and English groups have a common origin rooted in the Early Atlantic Bronze Age. However, their evolution through the Middle Bronze Age operates on the basis of apprenticeship lineages that do not relate the communities installed around the Channel. The English technical traditions do not have an insular origin and it is probable that the deep interactions between the Early Bronze Age cultures located in Wessex and Brittany are the source of dissemination of the technical traditions.

These evolutionary mechanisms are complex and operate on 13 levels of evolution during this period of 300 years. They are divided into two phases: a first phase of evolution involves both the operations of shaping and finishing, while a second phase reveals a stability of shaping behaviours even though finishing operations continued to evolve until the end of the Middle Bronze Age. Some apprenticeships generate many traditions while others evolve very little.

The final result shows that 82 % of the similarities between technical traditions are related to a process of descent with modification from a common ancestor. This means that these cultural groups are largely based on a process of phylogenesis. The horizontal transfers (18 %) operate between contemporary apprenticeship networks within the same culture. This horizontal transfer is a process of transmission by ricochet between different apprenticeship networks that have no direct historical link between them. This phenomenon of ricochet may have its source within the Duffaits culture or come from an extra-cultural origin and then spread inside Duffaits Culture by ricochet between apprenticeship networks, such as the technique of beating. However, the rarity of horizontal transfers between apprenticeship lineages implies a society organised in communities where few exchanges take place, even though the various social groups are cyclically linked to one another, because they share the same ritual caves.

In the absence of relevant comparison for the Bronze Age and the anthropology of techniques, these results can be compared with the work of biologists and specialists in evolutionary archaeology through the Retention Index (RI) and the comparative catalogue of Collard, Shennan and Tehrani (2006, Evolution and Human Behavior, 27.3) involving databases on material culture (21 cultures) and biological data on several species (21 contexts: morphological, ethological and DNA data). Cultures catalogued show a range of RI between 0.42 and 0.78 and RI between 0.35 and 0.94 for biological data. The RI of the Marie Curie project is RI = 0.952. It is significantly above cultural norms and it is similar to the best biological data. This result indicates that the high level of vertical transmission by apprenticeship and acquisition of motor habits, a phenomenon not included in the catalogue of Collard et al., proves to be as conservative as genetic transmission and is part of the process of gene-culture co-evolution. In this context, the possibility of transmission of biological type (parent-child) seems the most plausible explanation for such conservatism in these Bronze Age cultures.

These results therefore show the opposite of current beliefs that European Bronze Age societies are rich in extra-cultural interactions and exchange networks. In other words, if such cross-cultural interactions take place among the elites - results largely highlighted by numerous studies on specialised crafts such as amber or metallurgy - at the domestic level, in the heart of family units, the Marie Curie results indicate a completely opposite situation, where cultures evolve mainly endogenously.

These results contribute to the international debate on the dominant nature of the evolution of cultures around the world, opposing upholders of a process of phylogenesis to the upholders of ethnogenesis as the dominant force. The Marie Curie results provide another example in support of the hypothesis of phylogenesis, based on a new domain, transmission apprenticeship and the acquisition of motor habits. The methodology developed is applicable to any archaeological and ethno-archaeological context. In the European context, it is therefore appropriate to continue the analysis and model the whole of the European Bronze Age to confirm or qualify this result.

Contact details: s.manem@ucl.ac.uk; s.shennan@ucl.ac.uk