Despite decades of research, the roles of climate and humans in driving the dramatic extinctions ... more 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.
Questions of mobility, settlement pattern, and their relation to economic organization and resour... more Questions of mobility, settlement pattern, and their relation to economic organization and resource use are central to ongoing work in central-western Argentina. Here we analyze geographic patterns in the distribution of 178 human bone carbonate <delta>18O samples, 46 human tooth enamel carbonate <delta>18O samples, and 48 water <delta>18O samples from throughout the Andean Cordillera and Monte Desert andevaluate their implications for prehistoric mobility and economy. We confirm and refine previous generalizations regarding a highland/lowland dichotomy in water <delta>18O values and show that the range of human carbonate <delta>18O values generally reflect available water sources. While there is little withinlifetime change in patterns of water use, we show that most individuals have stable isotope signatures consistent with water use from multiple areas or areas other than where they were ultimately interred. These data indicate high levels of residential mobility, and we conclude by discussing their implications for our understanding of regional prehistory.
Zooarchaeologists regularly assume a positive relationship between body size and energetic return... more 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.
Models in evolutionary ecology have been applied to non-human decision making for decades. Archae... more Models in evolutionary ecology have been applied to non-human decision making for decades. Archaeologists have been especially attracted to foraging models, because the evidence of past subsistence activities is a common component of the archaeological record world-wide. No foraging model, though, accounts for the effects of subsistence technology. The ‘Tech Investment Model’ we describe here does just this. Assuming that most technologies serve to reduce handling time, a critical component of a resource’s protability, the model generates predictions about how much time an individual should invest in any particular technology. Although preliminary, data from an initial test case in the Great Basin conform to the general expectations of the model. Most importantly, the exercise forces attention to the relationships between tools and the resources handled with them, and has implications for subsistence transitions world-wide.
Despite decades of research, the roles of climate and humans in driving the dramatic extinctions ... more 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.
Questions of mobility, settlement pattern, and their relation to economic organization and resour... more Questions of mobility, settlement pattern, and their relation to economic organization and resource use are central to ongoing work in central-western Argentina. Here we analyze geographic patterns in the distribution of 178 human bone carbonate <delta>18O samples, 46 human tooth enamel carbonate <delta>18O samples, and 48 water <delta>18O samples from throughout the Andean Cordillera and Monte Desert andevaluate their implications for prehistoric mobility and economy. We confirm and refine previous generalizations regarding a highland/lowland dichotomy in water <delta>18O values and show that the range of human carbonate <delta>18O values generally reflect available water sources. While there is little withinlifetime change in patterns of water use, we show that most individuals have stable isotope signatures consistent with water use from multiple areas or areas other than where they were ultimately interred. These data indicate high levels of residential mobility, and we conclude by discussing their implications for our understanding of regional prehistory.
Zooarchaeologists regularly assume a positive relationship between body size and energetic return... more 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.
Models in evolutionary ecology have been applied to non-human decision making for decades. Archae... more Models in evolutionary ecology have been applied to non-human decision making for decades. Archaeologists have been especially attracted to foraging models, because the evidence of past subsistence activities is a common component of the archaeological record world-wide. No foraging model, though, accounts for the effects of subsistence technology. The ‘Tech Investment Model’ we describe here does just this. Assuming that most technologies serve to reduce handling time, a critical component of a resource’s protability, the model generates predictions about how much time an individual should invest in any particular technology. Although preliminary, data from an initial test case in the Great Basin conform to the general expectations of the model. Most importantly, the exercise forces attention to the relationships between tools and the resources handled with them, and has implications for subsistence transitions world-wide.
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