Because of perceived shortcomings of the Overkill or Climate Change hypotheses alone, some scientists support a combination of Climate Change and Overkill.
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Research shows that species interactions play a pivotal role in conservation efforts. Communities where species evolved in response to Pleistocene megafauna (but now lack large mammals) may be in danger of collapse. Most living megafauna are threatened or endangered; extant megafauna have a significant impact on the communities they occupy, which supports the idea that communities evolved in response to large mammals. Pleistocene rewilding could "serve as additional refugia to help preserve that evolutionary potential" of megafauna. Reintroducing megafauna to North America could preserve current megafauna, while filling ecological niches that have been vacant since the Pleistocene.
Humans and the Extinction of Megafauna in the Americas
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The survivors are in some ways as significant as the losses: , (a latest Pleistocene immigrant through ), , , , , , , and . All save the pronghorns descended from Asian ancestors that had evolved with human predators. Pronghorns are the second fastest land mammal (after the ), which may have helped them elude hunters. More difficult to explain in the context of overkill is the survival of bison, since these animals first appeared in North America less than 240,000 years ago and so were geographically removed from human predators for a sizeable period of time. Because evolved into living bison, there was no continent-wide extinction of bison at the end of the Pleistocene (although the genus was regionally extirpated in many areas). The survival of Bison into the Holocene and recent times is therefore difficult to explain via overkill, since these animals -- separated from human hunters by more than 200,000 years -- would almost certainly have been very nearly as naive as native North American large mammals.
in the late Quaternary and the global overkill hypothesis.
Meltzer largely argues that the presence of humans in the Americas prior to the invention of Clovis spear point technology refutes the blitzkrieg hypothesis (1). At the time, pre-Clovis archaeological sites, including Monte Verde in Chile, were still suspect (1), but Monte Verde is now generally accepted as pre-Clovis (7). Meltzer argues that the “apparent chronological correlation” between extinction of megafauna and the appearance of Clovis may not exist. He further further argues that, as defined by Martin, the hypothesis requires Clovis to be the first human culture in North America, and that mtDNA molecular clock, linguistic, and archaeological evidence make this unlikely (1). The confirmation of pre-Clovis cultures in the Americas would therefore appear to refute the overkill hypothesis. I would argue that while this may refute the hypothesis as presented at the time, this does not actually refute that humans or even human hunting using Clovis technology were responsible for megafauna extinctions.
Franzen believes that Martin’s overkill hypothesis arose ..
The most obvious change associated with the termination of an ice age is the increase in temperature. Between 15,000 and 10,000 BP, a 6 increase in global mean annual temperatures occurred. This was generally thought to be the cause of the extinctions.