New food products, new technologies or even new religions – they all can be viewed as cultural innovations. We can ask why some of these innovations become popular in a society while others vanish immediately or why some innovations spread very quickly while others need centuries to be accepted. Of course, this has a lot to do with nature of the innovation itself: what do we expect from it, how much does it cost, or how attractive is it? Someone can easily start buying organic food after seeing it once in a supermarket, while it may take a lot of time to decide to buy a new solar powered house. Thus, an innovation can be very simple and its adoption very cheap (like in the case of buying new food product) or extremely complex (like buying untypical house).
Picture 1: Jonah Thrown to the Whale (Catacombs of St. Peter and Macellinus, 3rd c. CE): one of the most widespread pictorial representation in pre-Constantinian Christianity; source: EIKON.
Religious innovations, which I will discuss below in more detail, are somewhere on this scale. The interesting question concerns the factors that lead someone to choose one religious innovation instead of another, even though its actual prospects, functions or rewards are difficult to understand. Contemporary research on religion provides a broad variety of hypotheses how to approach this complex interplay: Does a religious innovation help someone to feel more comfortable? Or should innovation be seen primarily as tool that enables a group of people to maintain their identity? Or is it that religious innovations rise and die just as they attract people in a way similar to fashion? Below I will suggest how the study of ancient societies can contribute when solving these types of questions.
Spread of Innovations in Modern vs. Premodern Environment
We should first realize that the adoption and spread of an innovation is a process involving complex social causation. To see something new in the supermarket is typically not enough. More often, we discover an innovation from newspapers, television, billboards, flyers or internet, or discussions with other people. This may lead us to search additional information on the internet. In the past, people could not rely on all of these options. Just a few decades ago, the situation was similar regarding the fact that people also realized existence of an innovation via newspapers, radio or television. However, to get more knowledge about it, they did not have the option to open the internet browser. In that respect, they rested more directly on the opinions of their peers. A few centuries ago, there was no radio or television, but still, there were newspapers, flyers and something similar to the billboards of today. The possibilities to become aware of an innovation were very broad, but the role of actual social relationships was probably even more important. Since there was no phone, to get opinion of your peers immediately, you had to meet them.
One of the most important changes in human history affecting the adoption of new ideas was printing technology. Print radically lowered the price of information. It is print what enables supermarkets to advertise their goods by overfilling our mailboxes and, again, it is print what is responsible for the fact that there are so many bad books in modern bookstores. Before print, there was much higher correspondence between a number of copies of a text in circulation and the real demand for it or interest in it by the society. In other words, the real quality of an innovation mattered much more. Of course, even before print institutions like a state, or the church, or even influential individuals had an important role in getting particular thing into circulation, but their impact was typically limited to a only few domains .
Before the invention of print, telegraph, phone and internet, the flow of information was completely dependent on the structure of the social network. There was much higher correspondence between real connectivity of social network, physical distance, costs and time. Being a new food product, new technology, or new religion, people had to be able to carry it with them, either in material form(like a text), or stored as a memory somewhere in their head. To be able to transmit the beliefs to someone else, they had to be able to communicate them, more or less directly.
Relevance of a Premodern Setting
Why is this historical environment important for the study of cultural transmission? What can we learn about diffusion of innovations in general? Because everything relies on actual contacts of individuals in physical space, the spatio-temporal distribution of an innovation documented in historical sources offers crucial insights. For example, if a scholar discusses a broad range of factors being responsible for the documented spread of particular crop among a number of prehistoric settlement sites, he knows with certainty that the influence of mass media was not among them. If a historian realizes that there are hundreds of manuscripts of particular premodern text, he can guess that this text was considered as important by a number of people over time. He is probably dealing with something much more reflecting interests of actual people than if he would examine copies of a modern supermarket advertisement. When an archeologist investigates a building complex with a number of features shared with another building complex distanced thousands of kilometers far away, he can assume there was a direct physical contact between the two sites, definitely not a virtual one. Under such conditions, we can get much better understanding of the interplay between actual motivational factors revealing perceived quality of an innovation and real prospects of it for its adopters. On this basis, we can then attempt to evaluate their relative value for our process of interest.
Imagine, for instance, that we find that there were two crops used by a prehistoric society. If we know how much energy it takes to grow the crops (the motivational factor) and if we know their real nutritional value (the real prospect), we can examine their relative importance in cultural transmission. Let’s imagine that in a premodern society there circulated two central myths, which basically differed in two respects: The one involved a number of supernatural characters what made it highly memorable, while the other was not so much attention grabbing, but included a moral lesson and promoted cooperative behavior among those who took it seriously. Which of them is more widely distributed in historical records? Did the people really care about moral concerns of their myths or are we justified to conclude that memorability is the most decisive factor? Again, it is much easier to get a hint what is going on in such a society than in a modern setting. Like in a laboratory, we have here almost something like a controlled environment, without the disturbing effect of mass-media or modern communication.
Laboratory of the Roman Empire
Because its political unity and stability over long period of time, high economic connectivity, relative freedom in domains like religion, the Roman world represents a perfect environment in an attempt to establish such a laboratory. Here one can study cultural transmission of things like new religions on a macro-scale, i.e. processes taking several decades at least and concerning millions of people. Despite of the fact that the historical material is often quite scarce, we can cover here much bigger space and time extent than it is possible when studying any contemporary society.
In recent years, a number of crucial historical sources from this period have been made available on internet. Several projects now offer high quality digital maps showing spatial distribution of particular historical material [1-6], while another enables full-text searching in digitalized versions of ancient Greek and Latin texts  or the examination of meta-data about ancient manuscripts .One platform even enables us to model travelling through the Roman world, counting distance, duration or cost of travel . Although these tools are designed primarily to serve historians of this period, they can be used as a basis for our virtual laboratory of cultural transmission as well.
Let’s take early Christianity as an example of a religious innovation which emerged in this environment. We know where it started, we know that it reached some destinations earlier than others and we know that it blossomed in some places better than somewhere else [see Map 1 based on 10]. We also know something about social networks on which early Christian beliefs spread . We can further take this historical knowledge and compare it with our data about economic structure of the Empire, Roman transportation networks and ancient social networks in general. In such a way, we can try to evaluate what was responsible for the reported spatio-temporal patterns. To formulate this in computational terms, we can use our virtual laboratory of the Roman world to “re-grow“ our process of interest in an artificial environment .
Map 1: The Spread of Christianity: red, green and blue – sites with Christian congregations before the year 100, 200 and 304 respectively. Based on ; coded by Vojtěch Kaše; the map created by Adam Mertel.
Without doubt, results of this kind of research have a potential to catch the attention of historians. But what can they teach us about cultural transmission on a more general level? First of all, we should realize that religious traditions like Christianity cannot be taken as stable packages of beliefs and practices being transmitted from one person to another. Christian beliefs and practices were evolving over time, spreading from one place to another and competing each other. Only a limited number of variations survived over time. This moves us beyond a group-centric view of religious history, which risks overlooking the internal dynamics of religious beliefs and practices.
Examining Cultural Transmission of Religions
Scholars of religion have formulated a number of hypotheses concerning what can contribute to success of a religious innovation: Can belief in an afterlife attract new adherents to join a religious group and to feel more comfortable? Can belief in one God with moral interests help a group of people to cooperate more effectively and therefore be more successful than groups that do not ? Or should we take seriously that religious beliefs and practices evolved as an evolutionary by-product and that there are hidden mechanisms in our mind, which can substantially influence the kind of religious ideas that people remember and the kind of practices they intuitively perceive as being effective ? All of these factors have been explored in recent empirical research. However, to evaluate their impact at large-scale level, scholars now have to turn to historical processes. In that respect, I argue that the world of ancient Mediterranean is an ideal target for this kind of research.
Approaching the history of religions in the Roman world, we can put all these hypotheses under scrutiny. To use our previous example, analyzing early Christian texts, early Christian manuscripts and other material artefacts and their spatio-temporal distribution, we can ask, for instance, how important was belief in one moralizing God and what impact it had on behavior. According to a preliminary observation, the earliest Christian material culture reveals that its producers were interested in a number of symbols, but those referring to the one high God were far from being central [15; see Picture 1]. Instead of this, number of texts and material artefacts from this period reflects high popularity of miracle stories (healing etc.), and in that way indicates importance of such elements for the early Christians . This is more in agreement with expectations of those who advocate the by-product account of religion. Further, we evidence increasing popularity of magical beliefs accompanying collective rituals like early Christian Eucharist, somehow weakening the social integrative function of this ritual . Again, this observation challenges some trends in recent research on religion and offers support to an alternative view. However, only adoption of quantitative methods in analyzing such material can bring satisfying conclusions.
I hope that the virtual laboratory built by the GEHIR project moves us on a solid ground when addressing these issues and offers enough empirical material to evaluate the hypotheses listed above. Drawing on available information about the historical environment and spatio-temporal distribution of particular sources on a macro-scale, we can examine, for instance, what is the relative importance of attraction of an innovation (e.g. memorability of a miraculous religious narrative) in comparison to the social function fulfilled by it (e.g. a religious narrative promoting charity behavior among the peers). In that respect, our virtual ancient Mediterranean world represents an ideal environment to ask why some innovations become popular quite quickly while others either die out immediately or need centuries to be accepted by the masses.
by Vojtěch Kaše (vojtech.kaseATgmail.com), PhD. candidate, GEHIR - Masaryk University & REECR - University of Helsinki (the author thanks to Justin Lane for helpful suggestions)
 Digital Atlas of Roman and Medieval Civilization (http://darmc.harvard.edu/icb/icb.do?keyword=k40248&pageid=icb.page188868)
 Ancient World Mapping Center: À-la-carte Map (http://awmc.unc.edu/awmc/applications/alacarte/)
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