A requiem for North American overkill

Abstract

The argument that human hunters were responsible for the extinction of a wide variety of large Pleistocene mammals emerged in western Europe during the 1860s, alongside the recognition that people had coexisted with those mammals. Today, the overkill position is rejected for western Europe but lives on in Australia and North America. The survival of this hypothesis is due almost entirely to Paul Martin, the architect of the first detailed version of it. In North America, archaeologists and paleontologists whose work focuses on the late Pleistocene routinely reject Martin's position for two prime reasons: there is virtually no evidence that supports it, and there is a remarkably broad set of evidence that strongly suggests that it is wrong. In response, Martin asserts that the overkill model predicts a lack of supporting evidence, thus turning the absence of empirical support into support for his beliefs. We suggest that this feature of the overkill position removes the hypothesis from the realm of science and places it squarely in the realm of faith. One may or may not believe in the overkill position, but one should not confuse it with a scientific hypothesis about the nature of the North American past.

Synchronous extinction of North America's Pleistocene mammals

“…Although we are unable to point to any one causal mechanism, we note that a major criticism of Martin's (6,(8)(9)(10) overkill hypothesis is that humans could not possibly have contributed to the extinction of any animal that disappeared before human arrival on the continent (18)(19)(20)(21). By extension, the same critique could be leveled at the extraterrestrial impact hypothesis.…”

“…Paleontologists and archaeologists have long provided conflicting interpretations of the chronology of North American late Pleistocene extinctions, with some arguing for a temporally staggered extinction (18,20,21) and others envisioning the extinction as an abrupt and catastrophic event (6-8, 10, 22, 23). This discrepancy has fueled the debate surrounding the mechanisms responsible for the extinction.…”

“…For decades archaeologists and paleontologists have debated the causes of their extinction (1)(2)(3)(4)(5), with explanations including overkill (6)(7)(8)(9)(10)(11), environmental change (12,13), hyperdisease (14), and an extraterrestrial impact (15)(16)(17). Crucial to the development of explanatory models is the chronology of the extinctions, which some envision as a longterm process occurring throughout the late Pleistocene (18)(19)(20)(21) and others characterize as a synchronous event that wiped out all taxa between 12,000 and 10,000 radiocarbon years B.P. (6-8, 13, 22, 23) (Ϸ13,800-11,400 calendar years B.P.).…”

Younger Dryas “black mats” and the Rancholabrean termination in North America

“…If all remaining elements of Rancholabrean megafauna, other than bison, terminated at the end of the Allerød chronozone, as indicated stratigraphically by the Z2 contact, the exact time of the catastrophic event is not resolvable within Ͻ100 years by radiocarbon dating, although this will improve significantly with tree-ring calibration (4). Grayson and Meltzer (43,44) argue that Pleistocene extinction was gradual with some elements dying out long before others. This may indeed be true for a number of taxa but for many forms there are still inadequate geochronological data to accurately determine the exact age of their extinction.…”

Megafauna biomass tradeoff as a driver of Quaternary and future extinctions

“…Causes of the QME have been explored primarily through analyzing the chronology of extinction, geographic differences in extinction intensity, timing of human arrival vs. timing of climate change, and simulations that explore effects of humans hunting megafauna (1)(2)(3)(4)(5)(6)(7)(8)(9)(10)(11). Results of past studies indicate that human impacts such as hunting and habitat alteration contributed to the QME in many places, and that climate change exacerbated it.…”