Ancient Microbial DNA in Dental Calculus: A New method for Studying Rapid Human Migration Events

Ancient human migrations provide the critical genetic background to historical and contemporary human demographic patterns. However, our ability to infer past human migration events, especially those that occurred over rapid timescales, is often limited. A key example is the peopling of Polynesia, where the timing is relatively well defined, but the exact routes taken during the final stages and the source populations are not. Here, we discuss the technical limitations of current methods for inferring rapid human migration events, using the final stages of Polynesian migration as an example. We also introduce a promising new proxy method to infer human migrations—patterns of bacterial evolution within ancient dental calculus (calcified plaque). While we focus on Polynesia, this method should be applicable to other past migrations, enhancing our understanding of human prehistory and revealing the crucial events that shaped it.     

Enterprise Zones and Individual Welfare: A Case Study of California*

Abstract. This research examines the benefits to individual workers hired under California's enterprise zone (EZ) program. The analysis reveals that EZ program participation has a positive impact on both wages and adjusted gross income of EZ participants, and the benefits appear to be greater for taxpayers with very low initial income. It is unclear whether the income boost from EZ participation is permanent or transitory. We also find that participation in the EZ program increases the likelihood that an individual will file a tax return. Because this is a case study, we caution that additional analysis is needed to fully determine the extent to which these results can be generalized.     

Spatial Analysis of the Factors Contributing to the Relationship between the Transient,Meridional Eddy Sensible,and Latent Heat Flux in the Southern Hemisphere

In this paper principal component analysis (PCA) and singular value decomposition (SVD) are used to define the importance of the variables contributing to the relationship between the transient latent and sensible heat fluxes and to show their temporal and spatial variation. SVD is offered as an alternative means of isolating spatial and temporal structures in data with the advantage that it can depict simultaneous space‐time variations that are aggregates of the results produced by PCA. Both methods of analysis produced two very important uncorrelated modes of variability in January and July, indicating that the transient heat fluxes are influenced by few controlling factors. We suggest that these modes of variability represent the influences of the meridional temperature gradient, atmospheric moisture, and activity within the source and sink regions of the transient heat fluxes. The physical relationships between the heat fluxes that appear to represented by the statistical modes of variability are discussed.