1/17 Steve Wolverton explores the debate of #rewilding North America with extant mammals in his 2010 paper ‘The North American Pleistocene overkill hypothesis and the re-wilding debate’. 
2/17 The proposal to #rewild North America with extant species is in part backed by the overkill hypothesis and the ethical obligation that humans have in response to our role in the extinction of certain megafauna species…
3/17 Wolverton argues that conservationists need to be sure of the underlying assumptions of the hypothesis to inform rewilding. Ignoring these assumptions, he writes, is costly to science and archaeology as it oversimplifies the argument.
4/17 The overkill hypothesis, that humans are the driving force of Pleistocene extinctions, has gained credence within ecology, geology, and archaeology. The debate is still ongoing, however, with some scientists viewing evidence as inconclusive.
5/17 The importance of this is the validity behind the ethical argument of humans returning modern proxies of extinct species to the US.
6/17 The counter arguments to human-driven extinction include environmental disturbances. E.g. rather than Asian megafauna escaping extinction through avoidance of humans, they survived due to seasonality shifts at temperate latitudes not occurring in the same parts of Asia.
7/17 Additionally, rather than humans hunting megafauna, there are arguments that humans were not big-game specialists during this time.
8/17 These points, along with others, the author writes, is evidence of an ongoing debate of a human role in these extinctions, meaning it may not act as a good basis for rewilding without further concrete evidence.
9/17 What are the archaeological implications of the overkill hypothesis? Firstly, multiple kill sites must show frequent hunting of Pleistocene mammals. However North American sites show limited evidence of hunting and for only two taxa.
10/17 An equally important factor is evidence of environmental change at the end of the Pleistocene that may have caused extinctions. Further information on timing and extent of human migration into N.America means that arguments tend to change as new evidence arises.
11/17 This means that the assumption of human arrival correlating exactly with megafauna loss, whilst not being outright rejected can at least be challenged.
12/17 Studies into human demography, agency and spatial patterning adds to archaeological records and bolsters the debate. Other approaches include viewing extinctions as multi-continental, focusing on the correlations between human arrival and species loss.
13/17 An issue with the latter approach of focusing on extinctions at that scale is the risk of ignoring environmental/cultural variability, which likely works at a finer geographic basis.
14/17 What then is the importance of this debate in understanding our role in megafauna extinctions? Wolverton argues that the ethical charge of ‘because humans cause extinctions we have an obligation to reintroduce living proxy species’ constitutes a huge change in practice…
15/17 While this may be of interest, it is important that the role of the overkill debate is not overlooked, otherwise, instead of #rewilding, what could result is a form of biological invasion of novel species in North America.
16/17 It is necessary then to thoroughly test this hypothesis, not just for palaeozoological research, but for real-world consequences in conservation. The overkill hypothesis, he concludes, should not be treated as factual, but rather hypothetical to avoid deception.
17/17 You can access Steve Wolverton’s full paper here: onlinelibrary.wiley.com/doi/pdf/10.111…
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