Andrew Ugan

Species-specific responses of Late Quaternary megafauna to climate and humans

Despite decades of research, the roles of climate and humans in driving the dramatic extinctions of large-bodied mammals during the Late Quaternary period remain contentious. Here we use ancient DNA, species distribution models and the human fossil record to elucidate how climate and humans shaped the demographic history of woolly rhinoceros, woolly mammoth, wild horse, reindeer, bison and musk ox. We show that climate has been a major driver of population change over the past 50,000 years. However, each species responds differently to the effects of climatic shifts, habitat redistribution and human encroachment. Although climate change alone can explain the extinction of some species, such as Eurasian musk ox and woolly rhinoceros, a combination of climatic and anthropogenic effects appears to be responsible for the extinction of others, including Eurasian steppe bison and wild horse. We find no genetic signature or any distinctive range dynamics distinguishing extinct from surviving species, emphasizing the challenges associated with predicting future responses of extant mammals to climate and human-mediated habitat change.

When is technology worth the trouble

Human beings are unique in the degree to which they rely on technology to interface with their environment. Applications of biologically derived foraging models have typically taken this technology as a given when analyzing ethnographic and prehistoric subsistence practices. This paper departs from the standard approach by treating investment in technology as a decision variable and looking at how investment decisions might be expected to vary with changes in both the time available to forage and the nature of the local resource base. The study draws attention to the importance of understanding both the costs and the benefits of technological investment and how they relate to one another. We use ethnographic and hypothetical data to demonstrate how one might represent these relationships mathematically, discuss the importance for understanding investment decisions, and explore their implications in circumstances where resources are randomly and non-randomly encountered.

Does size matter? Body size, mass collecting, and their implications for understanding prehistoric foraging behavior

Zooarchaeologists regularly assume a positive relationship between body size and energetic return rates among animal taxa. Some researchers question the validity of this assumption, suggesting that small animals collected in mass can provide high returns and pose interpretive problems for methods relying on a clear correlation. A review of empirical data shows that while large fish and invertebrates can provide high returns, those for most small animals remain very low. Differences appear to result from disparities in the relative energetic value of various taxa, costs associated with mass collection, and the efficiency with which resources are handled once acquired. Mass collection is unlikely to pose an interpretive problem under most circumstances, and the low returns for mass collecting many small animals have interesting implications for interpreting changes in their relative frequencies.

On Prey Mobility, Prey Rank, and Foraging Goals

Abstract In their recent paper “In Pursuit of Mobile Prey,” Bird, Bliege-Bird, and Codding (2009) identify a negative relationship between body size and post-encounter returns among Martu prey in western Australia, attributing the phenomena to the greater mobility of large animals and associated risk of hunting failure. While this phenomenon has implications for archaeological applications of foraging models that assume body size and on-encounter returns are positively correlated, the Martu data may be less exceptional than they appear. Here we outline the reasons for our skepticism, point out areas in which we are in agreement, and build upon their findings by exploring the trade-offs between foraging to maximize efficiency and immediate returns and foraging for purposes other than immediate provisioning.

Alternative Interpretations of Intermediate and Positive d13C Isotope Signals in Prehistoric Human Remains from Southern Mendoza, Argentina

During the last several years, information from stable isotopes has been used to discuss the role of maize agriculture in prehistoric economies of southern Mendoza. Because maize is one of several sources of 13C enriched carbon, a full evaluation of prehistoric diets requires data on a range of potential C3 and C4 plant resources. In this paper, we present stable isotope data (N = 89) for a suite of five previously unstudied edible cacti possessing a Crassulacean acid metabolism (CAM) photosynthetic pathway. Our results show that these plants have δ13C values overlapping C4 photosynthesizers such as maize. In order to understand their potential economic importance, we present additional procurement, processing, and nutritional data from actualistic experiments and the published literature. Using these data, we show why low levels of CAM plant consumption should be expected and how doing so may mimic a pattern of isotopically mixed diets often attributed to maize use.

Prehistory of Nevada's northern tier : archaeological investigations along the Ruby Pipeline. (Anthropological papers of the American Museum of Natural History, no. 101)

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