Did humans cause the Quarternary megafaunal mass-extinction?
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Was a 'hyperdisease' responsible for the late Pleistocene megafaunal extinction?

All contributing authors (S. Kathleen Lyons, Felisa A. Smith, Peter J. Wagner, Ethan P. White, James H. Brown) are associated with the Dept. of Biology University of New Mexico, except for Peter J. Wagner, who is associated with the Dept. of Geology at the Field Museum of Natural history in Chicago, IL.

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In this study, a different hypothesis is put to the test. The typical debate is "climate change vs. human overkill," but this study scientifically analyzes the theory that humans brought a disease with them that killed of the megafauna. The idea is that the megafauna were vulnerable due to lack of exposure to this disease. They apparently lacked the reproductive capacity to fight the disease's mortality rate. The researchers conducting the study discovered that there are too many specifics involved in the extinctions for them to be caused by disease, such as the extinction of one species but not another, closely related species.  Additionally, the timeframes of the extinctions are too scattered for them to be attributed to human disease being spread to animals. On top of all that, there was no known disease that met the criteria of a "hyperdisease" until the US met the West Nile Virus, which the researchers used as a model for the proposed disease.

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Examining the Extinction of the Megafauna

Article written by Robin Gibbons when she was a senior majoring in Human Biology at Stanford University; published in Stanford Undergraduate Research Journal, 2004

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This article offers a unique perspective on the "human overkill vs. climate change" debate. The author hypothesizes that neither one nor the other was solely responsible for megafaunal extinctions; instead, both played major roles in making the giant animals extinct. She argues that climate change reduced the habitable zones for many species, which not only introduced interspecific competition (humans included), but also subsequently made hunting these animals a much easier task for humans. As she concisely summarizes her research, "Both hypotheses seem to have holes that are most logically filled with data from the opposing argument."

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Quantitative global analysis of the role of climate and people in explaining late Quaternary megafaunal extinctions

Quantitative global analysis of the role of climate and people in explaining late Quaternary megafaunal extinctions | Did humans cause the Quarternary megafaunal mass-extinction? | Scoop.it

All contributing authors (Graham W. Prescott, David R. Williams, Andrew Bamford, Rhys E. Green, Andrea Manica) are associated with the Department of Zoology at the University of Cambridge.

Ryan Adams's insight:

This study was also conducted to prove that both sides of the debate are responsible for the mass-extinction of megafauna. The researchers analyze the relationships between megafaunal extinctions, climatic variables, and human arrival on five different landmasses. Their calculations led them to these findings regarding models of extinction scenarios:
"Climate and human arrival together account for 55.9–78.8% of the deviance [depending on the extinction scenario, with 24.2–47.1% attributable solely to anthropogenic effects and 1.7–19.7% attributable solely to climate effects.]"
So, while humans are *more* responsible for the extinctions, they are not the sole culprits, according to the study at hand. 

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Global late Quaternary megafauna extinctions linked to humans, not climate change

Global late Quaternary megafauna extinctions linked to humans, not climate change | Did humans cause the Quarternary megafaunal mass-extinction? | Scoop.it

All contributing authors (Chistopher Sandom, Søren Faurby, Brody Sandel, Jens-Christian Svenning) associated with the Dept. of Bioscience at Aarhus University.

Ryan Adams's insight:

This study provides scientific research conducted in order to prove that humans are to blame for the extinctions of megafaunal species in the late Quarternary period. Records of climate change and human migration are cross-examined with records of megafaunal extinctions to discover if there is an existing relationship between any of the factors (or all three). What they found was a significant correlation between the arrival of humans in certain areas and the estimated time of extinction for species previously living in those areas, along with a weak correlation between climatic events and the extinction of species specifically in Eurasia (not globally). In addition, it is noted that some of the species included in the studied had already survived similar climates in the past, so why would it be any different this time? Finally, the researchers add that the animals' food sources did not go extinct, so it is assumed that their extinction was not due to starvation, either.

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