Stimulated Variation and Cascades: Two Processes in the Evolution of Complex Technological Systems

Michael Schiffer’s theoretical and methodological contributions to archaeology are substantial. For the last two decades, Schiffer has become increasingly interested in the history of electrical technology, including portable radios, electric automobiles, eighteenth-century electrostatic technology, and, most recently, nineteenth-century electric light and power systems. Schiffer has long held a behavioral view, which focuses analytical attention on interactions between humans and material things, including complex technological systems (CTSs). For Schiffer, two key aspects of the evolution of CTSs are stimulated variation, defined as an increase in invention resulting from changing selective conditions, and cascading, defined as sequential spurts of invention that occur through the recognition of emergent performance problems in a CTS. To attain maximum usefulness, these concepts should be placed in a modern evolutionary framework that correctly identifies, and does not oversell, the role played by cultural selection. Research on individual and social learning provides the critical link between Schiffer’s stimulated variation and cascade models and the diffusion of CTSs.     

Land Snail Shell Beads in the Sub-Saharan Archaeological Record: When,Where, and Why?

Shell beads are well established in the archaeological record of sub-Saharan Africa and appear as early as 75,000 BP; however, most research has focused on ostrich eggshell (OES) and various marine mollusc species. Beads made from various land snails shells (LSS), frequently described as Achatina, also appear to be widespread. Yet tracking their appearance and distribution is difficult because LSS beads are often intentionally or unintentionally lumped with OES beads, there are no directly dated examples, and bead reporting in general is highly variable in the archaeological literature. Nevertheless, Achatina and other potential cases of LSS beads are present at over 80 archaeological sites in at least eight countries, spanning the early Holocene to recent past. Here, we collate published cases and report on several more. We also present a new case from Magubike Rockshelter in southern Tanzania with the first directly dated LSS beads, which we use to illustrate methods for identifying LSS as a raw material. Despite the long history of OES bead production on the continent and the abundance of land snails available throughout the Pleistocene, LSS beads appear only in the late Holocene and are almost exclusively found in Iron Age contexts. We consider possible explanations for the late adoption of land snails as a raw material for beadmaking within the larger context of environmental, economic, and social processes in Holocene Africa. By highlighting the existence of these artifacts, we hope to facilitate more in-depth research on the timing, production, and distribution of LSS beads in African prehistory.     

An Interview with James Kwesi Anquandah

Professor James Kwesi Anquandah was Ghana’s first archaeologist. He was also the first Ghanaian to become head of the Archaeology Department at the University of Ghana, which was the first archaeology department in sub-Saharan Africa, established in 1951. Dedicating his life to Ghanaian archaeology, particularly during the difficult years in Ghana in the 1980s and early 1990s, Anquandah had a significant impact on the development of archaeology in Ghana. In addition to his research, advisory and curatorial work, Professor Anquandah was instrumental in the training of three generations of Ghanaian archaeologists. During the course of a professional career that spanned nearly six decades, Professor Anquandah made archaeology relevant and accessible to all Ghanaians.     

NEARCHOS. Networked Archaeological Open Science: Advances in Archaeology Through Field Analytics and Scientific Community Sharing

The full release and circulation of excavation results often takes decades, thus slowing down progress in archaeology to a degree not in keeping with other scientific fields. The nonconformity of released data for digital processing also requires vast and costly data input and adaptation. Archaeology should face the cognitive challenges posed by digital environments, changing in scope and rhythm. We advocate the adoption of a synergy between recording techniques, field analytics, and a collaborative approach to create a new epistemological perspective, one in which research questions are constantly redefined through real-time, collaborative analysis of data as they are collected and/or searched for in an excavation. Since new questions are defined in science discourse after previous results have been disseminated and discussed within the scientific community, sharing evidence in remote with colleagues, both in the process of field collection and subsequent study, will be a key innovative feature, allowing a complex and real-time distant interaction with the scholarly community and leading to more rapid improvements in research agendas and queries.     

The Structural and Functional Complexity of Hunter-Gatherer Technology

The complexity of hunter-gatherer technology has been measured by counting artifact parts or production steps. There are a variety of alternative approaches to the measurement of artifact or system complexity. If technological complexity is assumed to reflect the complexity of the problem (or amount of entropy reduction) that the artifact is designed to address, the most appropriate measure of technological complexity is functional design complexity, which entails application of the entropy formula from information theory to the making and using of an artifact and the results obtained by its use. Functional complexity is related to structural or hierarchical complexity, because the entropy formula can be represented as a hierarchy (or step-by-step reduction of entropy) and the functional differentiation is related to the structural differentiation of an artifact. Another approach to hunter-gatherer technological complexity entails definition of a class of “complex artifacts” on the basis of general design characteristics (e.g., incorporation of moving parts). The most structurally and functionally complex artifacts are those that possess multiple states, either through changes in the physical relationship between parts (or sub-parts) during use or through structural differentiation. Although functional complexity is difficult to measure, structural or hierarchical complexity may be measured—and multiple-state artifacts may be counted—with adequate ethnographic and archaeological data on hunter-gatherer technology.     

A Cost-Based Ripley’s <Emphasis Type="Italic">K</Emphasis> Function to Assess Social Strategies in Settlement Patterning

Most quantitative approaches to distributional analysis in archaeology assume a homogeneous study surface that is amenable to easy generalisations. This framework has been widely used to describe settlement processes, disregarding the spatial heterogeneity inherent to geographic reality. In other words, researchers have often assumed that the correlation between the elements of a spatial distribution is a function of the Euclidean distance (i.e. straight line distance) between them. Other archaeological studies have tested alternative measures to Euclidean distances, such as cost-based ones, both to describe optimal routes and to assess spatial autocorrelation in a point pattern. Nevertheless, until now there has been no suitable model to introduce these measures into spatial statistical equations. In order to overcome this obstacle, we approach the implementation problem inversely by embedding the spatial pattern under study into a Euclidean frame of reference based on its cost-distance pairwise matrix. This paper describes the application of this methodology on one of the main tools used by archaeologists to assess settlement patterns: Ripley’s K function. We present two case studies, covering both macroscale and mesoscale, with significant variations in the results depending on the use of the Euclidean or cost-based approach. Data, functions and results have been R-packaged for the sake of reproducibility and reusability, allowing other researchers to build upon our methods.     

Time-Averaging Slows Down Rates of Change in the Archaeological Record

Measuring the pace of cultural change, and understanding its determinants is a fundamental goal of anthropological research. The archaeological record is the main source of information about the pace of cultural change, but it is an imperfect one, as taphonomic loss and mixing distort rate measurements. Here, I focus on the impact of time-averaging on rate measurements. Time-averaging arises when archaeological materials associated with activities and events that took place at different points in time are mixed into the same unit, whether because of depositional processes, disturbance factors, or because archaeologists lump together archaeological contexts when creating analytical units. I use analytical models to show how time-averaging can slow down the observed rates of change under two general modes of cultural change: random drift and directional change. I test this prediction using empirical rates of change from the archaeological record of North America. I show that empirical rates of change are indeed inversely correlated with the duration of time-averaging and provide a range estimate for this correlation.