Wooly mammoths survived on Wrangel Island off northeast Siberia Z-VAD-FMK clinical trial until about 3700 years ago (Stuart et al., 2004 and Vartanyan et al., 2008) and on Alaska’s Pribilof Islands until ∼5000 years ago (Yesner et al., 2005). These animals survived the dramatic climate and vegetation changes of the Pleistocene–Holocene transition, in some cases on relatively small islands that saw dramatic environmental change. Climate change proponents suggest, however, that these cases represent refugia populations in favorable habitats in the far north. Ultimately, additional data on vegetation shifts (studies from pollen and macrofloral evidence) across the Pleistocene–Holocene boundary, including investigation of

seasonality patterns and climate fluctuations at decadal to century scales, will be important for continued evaluation of climate change models. The human overhunting www.selleckchem.com/products/byl719.html model implicates humans as the primary driver of megafaunal extinctions in the late Quaternary. Hunting, however,

does not have to be the principal cause of megafauna deaths and humans do not necessarily have to be specialized, big game hunters. Rather, human hunting and anthropogenic ecological changes add a critical number of megafauna deaths, where death rates begin to exceed birth rates. Extinction, then, can be rapid or slow depending on the forcing of human hunting (Koch and Barnosky, 2006:231). The human overhunting model was popularized by Martin, 1966, Martin, 1967, Martin, 1973 and Martin, 2005 with his blitzkrieg model for extinction in the Americas. Martin Atezolizumab argued that initial human colonization of the New World by Clovis peoples, big game hunting specialists who swept across the Bering Land Bridge and down the Ice Free Corridor 13,500 years ago, resulted in megafaunal extinctions

within 500–1000 years as humans spread like a deadly wave from north to south. Similarly, the initial human colonization of Australia instigated a wave of extinctions from human hunting some 50,000 years ago. According to Martin (1973), this blitzkrieg was rapid and effective in the Americas and Australia because these large terrestrial animals were ecologically naïve and lacked the behavioral and evolutionary adaptations to avoid intelligent and technologically sophisticated human predators (Martin, 1973). Extinctions in Africa and Eurasia were much less pronounced because megafauna and human hunting had co-evolved (Martin, 1966). Elsewhere, Martin (1973) reasoned that since the interaction between humans and megafauna was relatively brief, very few archeological kill sites recording these events were created or preserved. Much of the supporting evidence for the overkill model is predicated on computer simulation, mathematical, and foraging models (e.g., Alroy, 2001, Brook and Bowman, 2004 and Mosimann and Martin, 1975). These suggest a rapid, selective extinction of megafauna was possible in the Americas and Australia at first human colonization.