From 2014 to 2020, we compiled radiocarbon ages from the lower 48 states, creating a database of more than 100,000 archaeological, geological, and paleontological ages that will be freely available to researchers through the Canadian Archaeological Radiocarbon Database. Here, we discuss the process used to compile ages, general characteristics of the database, and lessons learned from this exercise in “big data” compilation.

Autism spectrum disorder (ASD) and attention-deficit/hyperactivity disorder (ADHD) are believed to share partially overlapping causal mechanisms suggesting that early risk markers may also overlap. Using latent profile analysis (LPA) in a sample of infants enriched for ASD and ADHD, we first examined the number of distinct groups of 3-year-old children, based on ADHD and ASD symptomatology. To investigate early predictors of ASD and ADHD symptom profiles, we next examined differences in trajectories of infant behaviors among the LPA classes spanning general development, negative affect, attention, activity level, impulsivity, and social behavior. Participants included 166 infants at familial risk for ASD (n = 89), ADHD (n = 38), or low-risk for both (n = 39) evaluated at 12, 18, 24, and 36 months of age. A three-class solution was selected reflecting a Typically Developing (TD) class (low symptoms; n = 108), an ADHD class (high ADHD/low ASD symptoms; n = 39), and an ASD class (high ASD/ADHD symptoms; n = 19). Trajectories of infant behaviors were generally suggestive of a gradient pattern of differences, with the greatest impairment within the ASD class followed by the ADHD class. These findings indicate a mixture of overlapping and distinct early markers of preschool ASD- and ADHD-like profiles that can be difficult to disentangle early in life.

In this paper we use radiocarbon dates to evaluate the signature of the Younger Dryas Chronozone (YDC) in eastern North America. Using an approach that examines radiocarbon dates by region, we argue that the northeastern United States shows a better overall representation of radiocarbon dates when compared to the Mid-Atlantic and Southeast. These data result in a peak in summed probability distributions during the YDC, which is often interpreted as evidence of population growth. Further examination of these distributions, however, illustrates that differential standard deviations, varying sample size, and the effect of taphonomic and research biases likely overwhelm any demographic signatures in our study sample. Consequently, the frequency of radiocarbon dates by itself is insufficient for understanding the relationship between climate, culture and demography in eastern North America.

In eastern North America, there are few stratified sites dating to the Late Pleistocene epoch (> 11,700 cal B.P.). Instead, researchers have relied on the distribution of surface sites and isolated finds to make inferences about how the early inhabitants of the region used the landscape. While proxies for modern recovery bias have been found to affect artifact recovery at a national scale, in the southeastern United States, I argue, they are poor predictors for the frequency of Clovis type bifaces (ca. 13,250–12,850 cal B.P.) from counties in the southeastern United States as reported in the Paleoindian Database of the Americas (PIDBA). Instead, counties with the highest density of Clovis bifaces are near sources of lithic raw material, and in particular the intersection of major rivers, physiographic boundaries, and lithic raw material sources. I contend that these locations could represent seasonal aggregation loci. Alternatively, they could reflect areas where lithic raw material is more readily available, which may have resulted in higher rates of artifact discard. Determining which of these hypotheses is a more accurate reflection of past human behavior requires that we untangle the degree to which the amount of time people spent at these locations was successive versus coeval.