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We construct a reliable estimation method for evolutionary parameters within the Wright–Fisher model, which describes changes in allele frequencies due to selection and genetic drift, from time-series data. Such data exist for biological populations, for example via artificial evolution experiments, and for the cultural evolution of behavior, such as linguistic corpora that document historical usage of different words with similar meanings. Our method of analysis builds on a Beta-with-Spikes approximation to the distribution of allele frequencies predicted by the Wright–Fisher model. We introduce a self-contained scheme for estimating parameters in the approximation, and demonstrate its robustness with synthetic data, especially in the strong-selection and near-extinction regimes where previous approaches fail. We further apply the method to allele frequency data for baker’s yeast (Saccharomyces cerevisiae), finding a significant signal of selection in cases where independent evidence supports such a conclusion. We further demonstrate the possibility of detecting time points at which evolutionary parameters change in the context of a historical spelling reform in the Spanish language.Guerrero Montero and Blythe introduce a method for estimating effective population size and selection coefficients from time-series of allele frequency data; the method is based on the Beta-with-Spikes approximation to the Wright-Fisher process. The authors demonstrate its robustness with synthetic data and apply it to detecting selection in previously published allele frequency data for Saccharomyces cerevisiae. They extend the method to account for abrupt changes in model parameters, applying this extension to detecting language reforms in word-frequency data in Spanish.

Images of a number of natural subjects have for some time been made using wavelengths longer than those to which film is sensitive. This has been done by use of instruments employing mechanical scanning and cooled semiconductor detectors. Some of this imagery is now becoming available for general use. In this paper, we describe some of the physical effects causing observable changes in the imagery, comment upon some of those factors observed in a selected set of images of both natural and man-made features recorded by the Bendix thermal mapper, and suggest some uses and potential uses for such data for some scientific and general purposes.

A transmission-type optical interference filter has been constructed which controls the color of the light passing through it in accordance with the magnitude of a dc electrical signal. This is accomplished by magnetostrictively varying the separation of a pair of plane parallel quartz optical flats having thin film coatings. The results indicate that such devices are feasible. Some theory for the filter action is given, and data for this particular laboratory model are shown.

In a combinatorial communication system, some signals consist of the combinations of other signals. Such systems are more efficient than equivalent, non-combinatorial systems, yet despite this they are rare in nature. Why? Previous explanations have focused on the adaptive limits of combinatorial communication, or on its purported cognitive difficulties, but neither of these explains the full distribution of combinatorial communication in the natural world. Here, we present a nonlinear dynamical model of the emergence of combinatorial communication that, unlike previous models, considers how initially non-communicative behaviour evolves to take on a communicative function. We derive three basic principles about the emergence of combinatorial communication. We hence show that the interdependence of signals and responses places significant constraints on the historical pathways by which combinatorial signals might emerge, to the extent that anything other than the most simple form of combinatorial communication is extremely unlikely. We also argue that these constraints can be bypassed if individuals have the socio-cognitive capacity to engage in ostensive communication. Humans, but probably no other species, have this ability. This may explain why language, which is massively combinatorial, is such an extreme exception to nature's general trend for non-combinatorial communication.