Overkill Hypothesis Essay ⋆ Environment Essay Examples ⋆ EssayEmpire

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The overkill hypothesis concerns the extinction of megafauna, particularly in the Americas and Australia. Archaeological excavations reveal that a number of species, perhaps more than 100, disappeared within a comparatively short period of time, less than 1,000 years.

Excavations also demonstrate that at least some of those animals were hunted and eaten by newly arriving humans. The hypothesis follows that the migrating humans were responsible for the extinctions because the animals were not frightened of them and so were easily hunted. A contrast is drawn with the megafauna of Africa and Eurasia, where a long period of cohabitation with humans taught the animals to be wary of humans. This hypothesis is controversial because the evidence does not convince all observers, and alternative explanations have been suggested, including the impact of climate change or the introduction of unfamiliar diseases.

The arrival of humans in North America and Australia is closely correlated with the disappearance of many large animal species. However, such correlation does not imply causation; further, reliance upon fossilization for evidence is suboptimal, principally because it is such a random method of preservation that it cannot be certain that those that have been preserved are representative of the population. Extinctions happened so rapidly that they have been conceptualized as a form of blitzkrieg, or lightning war resulting in mass extinctions. Some researchers object to this hypothesis for philosophical reasons, because it suggests that humanity cannot live in harmony with the natural environment.

Others maintain that it is impossible to rule out additional factors that would accompany such extinctions, as for example other creatures that would migrate alongside humans, or some other interaction between people and the environment. This has been observed in more recent examples of mammal extinctions, such as when old-world rats and other aggressive creatures have been introduced into island environments and native life has had insufficient time to adapt. Other problems with the hypothesis result from dating two possibly separate incidents with precision, when that precision is notoriously difficult to obtain.

Nevertheless, the evidence that has been gathered does lend support to the overkill hypothesis. One important finding is that it was not necessary for humans to have hunted down every single representative of a species, merely to kill more than were born, and this is quite possible in a 1,000-year period. In addition, the related Keystone Herbivore Hypothesis suggests that the large species, such as elephants and rhinoceroses, are significant environmental engineers and that their rapid disappearance would have a negative effect on the environment inhabited by large numbers of other creatures, some of whom would follow them into extinction.

New forms of scientific research are helping scientists to distinguish between overkill, disease, and climate change theories. Extraction of DNA and other organic material from frozen mammoths, for example, provides the opportunity to identify the presence of viruses or other disease-bearing organisms. Ice core analysis is able to provide more accurate information concerning climate change.

Bibliography:

E. Kaye, “Aboriginal Overkill: The Role of Native Americans in Structuring Western Ecosystems,” Human Nature (v.5/4, 1994);
Paul S. Martin, Twilight of the Mammoths: Ice Age Extinctions and the Rewilding of America (University of California Press, 2005);
Paul S. Martin and Richard G. Klein, , Quaternary Extinctions: A Prehistoric Revolution (University of Arizona Press, 1989);
Stephen Wroe et , “Megafaunal Exinction in the Late Quaternary and the Global Overkill Hypothesis,” Alcheringa (v.28, 2004).