Previous research suggests that the complex symbolic, technological, and socioeconomic behaviors that typify had roots in the middle Pleistocene<200,000 years ago, but data bearing on human behavioral origins are limited. We present a series of excavated Middle Stone Age sites from the Olorgesailie basin, southern Kenya, dating from ≥295,000 to ~320,000 years ago by argon-40/argon-39 and uranium-series methods. Hominins at these sites made prepared cores and points, exploited iron-rich rocks to obtain red pigment, and procured stone tool materials from ≥25- to 50-kilometer distances. Associated fauna suggests a broad resource strategy that included large and small prey. These practices imply notable changes in how individuals and groups related to the landscape and to one another and provide documentation relevant to human social and cognitive evolution.

Archaeologists frequently underestimate the importance of children as well as craft skill acquisition in the formation of archaeological assemblages. Perhaps even more often they conflate the terms "novice" and "child" in ways that oversimplify the factors that are involved in incorporating new producers into craft production. In particular, the skill acquisition involved in stone tool production is influenced by a variety of factors, including danger, raw material value, raw material availability, and raw material recyclability, as well as a variety of social factors. This paper examines the influence of each of these factors and also suggests patterns useful in recognizing and distinguishing between novices and children in the archaeological record.

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Based on a simple model of lithic procurement, reduction, and use, we generate predictions for patterns in source diversity and average distance-to-source measurements for flaked stone assemblages left behind by small-scale and residentially mobile populations. We apply this model to geochemical data from obsidian artifacts from three regions in western North America. As predicted, results show markedly different patterns in the geochemical composition of small flakes, large flakes, and formal tools. While small flakes and tools tend to have greater source diversity and are on average farther from their original source, the large flake assemblage is composed of fewer and closer sources. These results suggest that a failure to include very late stage reduction (e.g., pressure flakes) and microdebitage in characterization studies may bias interpretations about the extent of residential mobility and/or trade patterns because more distant sources will be underrepresented.

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