Mark E. Madsen

Physical space and long-tail markets

The Internet is known to have had a powerful impact on on-line retailer strategies in markets characterised by long-tail distribution of sales [1]. Such retailers can exploit the long tail of the market, since they are effectively without physical limit on the number of choices on offer. Here we examine two extensions of this phenomenon. First, we introduce turnover into the long-tail distribution of sales. Although over any given period such as a week or a month, the distribution is right-skewed and often power law distributed, over time there is considerable turnover in the rankings of sales of individual products. Second, we establish some initial results on the implications for shelf-space strategy of physical retailers in such markets.

Behavioral Modernity and the Cultural Transmission of Structured Information: The Semantic Axelrod Model

Cultural transmission models are coming to the fore in explaining increases in the Paleolithic toolkit richness and diversity. During the later Paleolithic, technologies increase not only in terms of diversity but also in their complexity and interdependence. As Mesoudi and O’Brien (Biolog Theory 3:63–72, 2008) have shown, selection broadly favors social learning of information that is hierarchical and structured. We believe that teaching provides the necessary scaffolding for transmission of more complex cultural traits. Here, we introduce an extension of the Axelrod (J Confl Resolut 41:203–226, 1997) model of cultural differentiation in which traits have prerequisite relationships, and where social learning is dependent upon the ordering of those prerequisites. We examine the resulting structure of cultural repertoires as learning environments range from largely unstructured imitation, to structured teaching of necessary prerequisites, and we find that in combination with individual learning and innovation, high probabilities of teaching prerequisites leads to richer cultural repertoires. Our results point to ways in which we can build more comprehensive explanations of the archaeological record of the Paleolithic as well as other cases of technological change.

A Theoretically-Sufficient and Computationally-Practical Technique for Deterministic Frequency Seriation

Frequency seriation played a key role in the formation of archaeology as a discipline due to its ability to generate chronologies. Interest in its utility for exploring issues of contemporary interest beyond chronology, however, has been limited. This limitation is partly due to a lack of quantitative algorithms that can be used to build deterministic seriation solutions. When the number of assemblages becomes greater than just a handful, the resources required for evaluation of possible permutations easily outstrips available computing capacity. On the other hand, probabilistic approaches to creating seriations offer a computationally manageable alternative but rely upon a compressed description of the data to order assemblages. This compression removes the ability to use all of the features of our data to fit to the seriation model, obscuring violations of the model, and thus lessens our ability to understand the degree to which the resulting order is chronological, spatial, or a mixture. Recently, frequency seriation has been reconceived as a general method for studying the structure of cultural transmission through time and across space. The use of an evolution-based framework renews the potential for seriation but also calls for a computationally feasible algorithm that is capable of producing solutions under varying configurations, without manual trial and error fitting. Here, we introduce the Iterative Deterministic Seriation Solution (IDSS) for constructing frequency seriations, an algorithm that dramatically constrains the search for potential valid orders of assemblages. Our initial implementation of IDSS does not solve all the problems of seriation, but begins to moves towards a resolution of a long-standing problem in archaeology while opening up new avenues of research into the study of cultural relatedness. We demonstrate the utility of IDSS using late prehistoric decorated ceramics from the Mississippi River Valley. The results compare favorably to previous analyses but add new details into the structure of cultural transmission of these late prehistoric populations.

Saving culture from selection Comment on "An evolutionary framework for cultural change: Selectionism versus communal exchange" by L. Gabora

Most researchers working on evolutionary approaches to culture do so within the Darwinian paradigm, and accept the role of selection in shaping variation. Liane Gabora is an exception, and has been steadfast in articulating the need for an evolutionary but “non-Darwinian” theory of cultural change. In [1] she argues that culture does not meet the definitional requirements to evolve by natural selection, and introduces an alternative process called “communal exchange.” We find her argument that culture cannot be subject to selection deeply flawed. Indeed, it seems to us that Gabora’s primary mission is to “save culture” from being subject to natural selection, by analyzing selection in three ways that allow culture to be excluded from its domain. First, Gabora’s argument is based upon a non-standard account of selection. Few if any geneticists or biologists would recognize genetic inheritance as powered by “self-replicating automata” of the von Neumann type. A “gene” (an incredibly complex concept in its own right [2]) certainly does not code both for the machinery to interpret itself, and for the protein its sequence represents. SRA’s or replicators are not needed for selection [3]. Indeed, while the “replicator” concept was useful in illuminating the “units of selection” problem, employing it as an empirical unit is problematic [3–7]. Second, Gabora adds unnecessary conditions to the requirements for selection [8]. For example, the sequestration of inherited information, as in the isolation of germ-line cells in many animal lineages, is a derived characteristic which evolved quite late in the history of life [9]. Natural selection proceeds handily in many taxa which do not sequester heritable information. Nor is it required that new variation be approximated by a random process [10]. Third, Gabora criticizes the transfer of biological concepts to culture, by confusing theoretical concepts and empirical instances. For example, she claims that “generations” are not applicable to culture. In reality, organismal