LATERES COCTILES – The early use of fired bricks in Europe
The project LATERES COCTILES concerns the use of fired bricks, from its introduction in Europe around 350 BC until its final breakthrough in the Roman period. The aim is to investigate a previously disregarded archaeological material, in order to trace the distribution and spread of this technology. The study provides immediate insights into Hellenistic architecture, but more importantly it furthers our understanding of the diffusion of innovations in antiquity. The project was awarded funding by the Swedish Research Council in 2009 and was conducted as an interdisciplinary collaboration by an archaeologist and a physicist between 2010 and 2013. Additional funding was granted by the Faculty of Humanities at Lund University in 2014. The project has been successful and well received, not least through an innovative application of network theory on archaeology, placing it in the very front line of research. So far the project has generated six original peer reviewed articles, treating different aspects of the investigation. However, the archaeological material, which forms the basis of the study, a detailed and contextually framed synthesis, and a concluding historical interpretation still remain to be published. A monograph that combines these aspects is being prepared and large parts of the manuscript already exist as drafts. A sabbatical of six months would enable the applicant to bring the project to a conclusion and present a long awaited synthesis of the topic.
Final report
LATERES COCTILES - The early use of fired bricks in Europe
The research project has generated six peer-reviewed papers and two additional papers. One additional paper and one monopgraph is forthcoming. The results have been presented at five international conferences and six public lectures/seminars.
The present study has brought to light various aspects of the use of fired bricks in Hellenistic Europe and suggested a new approach to the diffusion of innovations in antiquity. Overall, it has confirmed the slightly paradoxical impression that emerged from the outset; that fired bricks were introduced surprisingly late in the Graeco-Roman world, considering for example the long tradition of using terracotta roof tiles, but at the same time much earlier and with more wide-ranging applications than is usually acknowledged. Based on current evidence, the use of fired bricks for masonry was permanently introduced in Europe in the mid-4th century BCE. The innovation was first adopted in the north Aegean and the Thracian inland, but was preceded by the use of terracotta tiles in pavements. During the following centuries fired bricks spread over large parts of south-east Europe, the Italian peninsula and Sicily. While the geographical reach of the innovation was far-ranging, the use was limited in extent as well as sporadic, both spatially and temporally. Fired bricks were only taken up in the city of Rome at a very late stage, perhaps not until the Augustan period. This coincided with a general take-off in the use of the innovation and was followed by the introduction of relatively thin standardised Roman bricks. However, the large Hellenistic bricks continued to be used in many parts of the Empire.
The analysis of similarity networks, generated from the archaeological data, has indicated, with a high statistical significance, that the innovation of using fired bricks spread as a result of a continuous diffusion process, or several interweaving diffusion processes. That is, fired bricks were generally not invented independently by different people at different sites.
The introduction of fired bricks in the north Aegean area and Thracian inland in the mid-4th century BCE may not have been the first appearance in the Greek world (the Greeks were aware of fired bricks before that date), but at this occasion the innovation took hold. This may be understood as the fortuitous involvement of innovative craftsmen/builders in building projects that reflected the interests and needs of a well-connected and equally innovative elite. Close ties with Anatolia, whence the idea may have originally derived, and a mixed cultural environment were probably also important. It is likely that those responsible for the earliest uses of fired bricks drew from experiences of other terracotta elements (roof tiles and floor tiles). The possibility for commissioners to steer the production of roof tiles in a new direction may also have been critical. The order in which roof tiles, floor tiles and bricks for masonry were introduced in the Graeco-Roman world probably reflects the inherent conditions of the terracotta industry, as the same sequence was repeated in the Middle Ages.
The production of fired bricks did not require any major technical advances; the necessary technology already existed in most places. Builders and commissioners (sponsors) of buildings were identified as key actors in the diffusion process; in other words, the people who decided on the use of fired bricks. However, only very rarely can we discern the individuals behind the buildings. Instead, the discussion centred on different actor groups. Besides the rather elusive group of “master builders”, “elite commissioners” have been given a prominent place, represented by the frequent occurrence of public or monumental buildings in the compiled material. Some finds point to the significance of royal benefaction, particularly in the early phase. There is also a trend of public manufacture and use of fired bricks, subsequently giving over to private entrepreneurs and domestic use.
The diffusion process was the result of social contacts between individual decision makers who exerted some kind of influence on each other. Mostly these contacts were short range, which resulted in a high degree of spatial clustering. Concomitant with the geographical spread, the attributes of the innovation changed in various respects, for example with regard to how it was used. In the similarity networks, the distribution of variations gave rise to the formation of clusters of relatively homogeneous use. These topological network clusters often correspond with spatial clusters and can thus be identified as regional “brick cultures”. However, some contacts encompassed very large distances. Although relatively few in number, these long-distance contacts had a profound impact on the diffusion process, significantly enhancing the geographical reach of the innovation. The social network of potential adopters may thus be labelled a “small world”, and the spread of fired bricks definitely did not proceed as a wave front.
The available data also indicate that the network was not “scale free”, i.e. there were no dominating hubs with a disproportionate number of edges. Instead, the diffusion process may be described as “democratic”, in the sense that all users exerted more or less the same influence. This is a somewhat surprising and perhaps even counterintuitive result, considering that the large metropolises of the Hellenistic world have been described as “super hubs”. Not only is there an absence of significant topological hubs, many sites that might be called “centres” on historical and archaeological grounds (i.e. politically, culturally and economically important cities) seem to have adopted the innovation only at a relatively advanced stage in the diffusion process, as it was reaching a point of take-off. Most striking is the late involvement of Athens and Rome in the diffusion process. This phenomenon can at least partly be explained by an inherent feature of the diffusion process, here called the “conservatism factor”, which impedes the diffusion of new innovations in a highly interconnected subset of a social network. Together with a general predisposition towards conformity, such interconnectedness may contribute to the preservation of existing practices and work to the disadvantage of new ideas. A main perquisite for this phenomenon is that the innovation in question is of a “competing” rather than a “supplementary” kind. The use of previously established alternatives may then have the advantage of being the norm.
Even if the “conservatism factor” is reasonable per se, it goes against the intuition that there was a stronger incentive to adopt new technologies in densely urbanised areas, due to a higher level of competition. However, the apparent absence (or delay) of this mechanism may be due to the fact that the perceived relative advantages of fired bricks (countered by high costs and lack of associated status) for a long time were seen as marginal by many decision makers. It is possible that the final take-off in the late 1st century BCE and the subsequent breakthrough of the use of fired bricks are related to the eventual adoption of the innovation in the city of Rome. It is then likely that the continuing diffusion process, from the Augustan period onwards, would have generated a scale-free network.
The development of adoption rates, suggested by the compiled material, can be described as slow and hesitant until the very end of the Hellenistic period. The time elapsing from the introduction of the innovation until it reached a point of take-off (c. 325 years) is longer than for other comparable innovations, but not excessively so, and it is important that we question our perception of what a “normal” period of diffusion would be. Also on a local level, the use of fired bricks was often limited and sporadic. Two possible explanations for this present themselves. One reason may be the one suggested above, that the perceived relative advantages of using fired bricks were marginal, or at least unclear to most decision makers, contributing to a relatively high threshold for adoption. This is seemingly contradicted by the fact that fired bricks were often chosen, and apparently appreciated, because of their specific material properties: plasticity (before firing), durability, water resistance etc. The other explanation is that general conditions for diffusion among primary decision makers (i.e. commissioners of buildings and master builders) were unfavourable, as indicated by the simulation model. This would have been partly due to the nature of the innovation, which restricted the number of potential adopters; relevant decision makers were few and far apart. In spite of the apparent geographical reach of their social networks, the diffusion process was therefore constantly on the verge of extinction.
The vulnerable nature of the diffusion process, indicated by a very long initial phase before take-off, also seems to be characteristic of many other innovations in antiquity. This might lead us to ask: how many Hellenistic innovations failed to diffuse and were ultimately lost due to the limitations of interpersonal networks? The remarkable and unique Antikythera mechanism is a pertinent reminder in this regard.
The research project has generated six peer-reviewed papers and two additional papers. One additional paper and one monopgraph is forthcoming. The results have been presented at five international conferences and six public lectures/seminars.
The present study has brought to light various aspects of the use of fired bricks in Hellenistic Europe and suggested a new approach to the diffusion of innovations in antiquity. Overall, it has confirmed the slightly paradoxical impression that emerged from the outset; that fired bricks were introduced surprisingly late in the Graeco-Roman world, considering for example the long tradition of using terracotta roof tiles, but at the same time much earlier and with more wide-ranging applications than is usually acknowledged. Based on current evidence, the use of fired bricks for masonry was permanently introduced in Europe in the mid-4th century BCE. The innovation was first adopted in the north Aegean and the Thracian inland, but was preceded by the use of terracotta tiles in pavements. During the following centuries fired bricks spread over large parts of south-east Europe, the Italian peninsula and Sicily. While the geographical reach of the innovation was far-ranging, the use was limited in extent as well as sporadic, both spatially and temporally. Fired bricks were only taken up in the city of Rome at a very late stage, perhaps not until the Augustan period. This coincided with a general take-off in the use of the innovation and was followed by the introduction of relatively thin standardised Roman bricks. However, the large Hellenistic bricks continued to be used in many parts of the Empire.
The analysis of similarity networks, generated from the archaeological data, has indicated, with a high statistical significance, that the innovation of using fired bricks spread as a result of a continuous diffusion process, or several interweaving diffusion processes. That is, fired bricks were generally not invented independently by different people at different sites.
The introduction of fired bricks in the north Aegean area and Thracian inland in the mid-4th century BCE may not have been the first appearance in the Greek world (the Greeks were aware of fired bricks before that date), but at this occasion the innovation took hold. This may be understood as the fortuitous involvement of innovative craftsmen/builders in building projects that reflected the interests and needs of a well-connected and equally innovative elite. Close ties with Anatolia, whence the idea may have originally derived, and a mixed cultural environment were probably also important. It is likely that those responsible for the earliest uses of fired bricks drew from experiences of other terracotta elements (roof tiles and floor tiles). The possibility for commissioners to steer the production of roof tiles in a new direction may also have been critical. The order in which roof tiles, floor tiles and bricks for masonry were introduced in the Graeco-Roman world probably reflects the inherent conditions of the terracotta industry, as the same sequence was repeated in the Middle Ages.
The production of fired bricks did not require any major technical advances; the necessary technology already existed in most places. Builders and commissioners (sponsors) of buildings were identified as key actors in the diffusion process; in other words, the people who decided on the use of fired bricks. However, only very rarely can we discern the individuals behind the buildings. Instead, the discussion centred on different actor groups. Besides the rather elusive group of “master builders”, “elite commissioners” have been given a prominent place, represented by the frequent occurrence of public or monumental buildings in the compiled material. Some finds point to the significance of royal benefaction, particularly in the early phase. There is also a trend of public manufacture and use of fired bricks, subsequently giving over to private entrepreneurs and domestic use.
The diffusion process was the result of social contacts between individual decision makers who exerted some kind of influence on each other. Mostly these contacts were short range, which resulted in a high degree of spatial clustering. Concomitant with the geographical spread, the attributes of the innovation changed in various respects, for example with regard to how it was used. In the similarity networks, the distribution of variations gave rise to the formation of clusters of relatively homogeneous use. These topological network clusters often correspond with spatial clusters and can thus be identified as regional “brick cultures”. However, some contacts encompassed very large distances. Although relatively few in number, these long-distance contacts had a profound impact on the diffusion process, significantly enhancing the geographical reach of the innovation. The social network of potential adopters may thus be labelled a “small world”, and the spread of fired bricks definitely did not proceed as a wave front.
The available data also indicate that the network was not “scale free”, i.e. there were no dominating hubs with a disproportionate number of edges. Instead, the diffusion process may be described as “democratic”, in the sense that all users exerted more or less the same influence. This is a somewhat surprising and perhaps even counterintuitive result, considering that the large metropolises of the Hellenistic world have been described as “super hubs”. Not only is there an absence of significant topological hubs, many sites that might be called “centres” on historical and archaeological grounds (i.e. politically, culturally and economically important cities) seem to have adopted the innovation only at a relatively advanced stage in the diffusion process, as it was reaching a point of take-off. Most striking is the late involvement of Athens and Rome in the diffusion process. This phenomenon can at least partly be explained by an inherent feature of the diffusion process, here called the “conservatism factor”, which impedes the diffusion of new innovations in a highly interconnected subset of a social network. Together with a general predisposition towards conformity, such interconnectedness may contribute to the preservation of existing practices and work to the disadvantage of new ideas. A main perquisite for this phenomenon is that the innovation in question is of a “competing” rather than a “supplementary” kind. The use of previously established alternatives may then have the advantage of being the norm.
Even if the “conservatism factor” is reasonable per se, it goes against the intuition that there was a stronger incentive to adopt new technologies in densely urbanised areas, due to a higher level of competition. However, the apparent absence (or delay) of this mechanism may be due to the fact that the perceived relative advantages of fired bricks (countered by high costs and lack of associated status) for a long time were seen as marginal by many decision makers. It is possible that the final take-off in the late 1st century BCE and the subsequent breakthrough of the use of fired bricks are related to the eventual adoption of the innovation in the city of Rome. It is then likely that the continuing diffusion process, from the Augustan period onwards, would have generated a scale-free network.
The development of adoption rates, suggested by the compiled material, can be described as slow and hesitant until the very end of the Hellenistic period. The time elapsing from the introduction of the innovation until it reached a point of take-off (c. 325 years) is longer than for other comparable innovations, but not excessively so, and it is important that we question our perception of what a “normal” period of diffusion would be. Also on a local level, the use of fired bricks was often limited and sporadic. Two possible explanations for this present themselves. One reason may be the one suggested above, that the perceived relative advantages of using fired bricks were marginal, or at least unclear to most decision makers, contributing to a relatively high threshold for adoption. This is seemingly contradicted by the fact that fired bricks were often chosen, and apparently appreciated, because of their specific material properties: plasticity (before firing), durability, water resistance etc. The other explanation is that general conditions for diffusion among primary decision makers (i.e. commissioners of buildings and master builders) were unfavourable, as indicated by the simulation model. This would have been partly due to the nature of the innovation, which restricted the number of potential adopters; relevant decision makers were few and far apart. In spite of the apparent geographical reach of their social networks, the diffusion process was therefore constantly on the verge of extinction.
The vulnerable nature of the diffusion process, indicated by a very long initial phase before take-off, also seems to be characteristic of many other innovations in antiquity. This might lead us to ask: how many Hellenistic innovations failed to diffuse and were ultimately lost due to the limitations of interpersonal networks? The remarkable and unique Antikythera mechanism is a pertinent reminder in this regard.