Researchers have long debated what caused the mass extinction of woolly mammoths and other large animals in several parts of the world toward the end of the Pleistocene epoch. One popular theory posits that climate shifts during the last Ice Age extinguished the megafauna. But studies described today in the journal Science side with the other leading hypothesis, which holds that early humans brought about the end of these beasts.

In the first study, Australian researcher Richard G. Roberts of the University of Melbourne and his colleagues determined that Australia's megafaunal mass extinction event¿which claimed some early kangaroos and other giant marsupials, to name a few¿occurred not 20,000 years ago, as previously thought, but around 46,000 years ago. The team arrived at the new date using both radiometric and "optical" dating methods on sediments from 27 sites across the country that had contained megafauna fossils. This revised timing for the die-off, the researchers note, means that the climate factors that had supposedly done these animals in can no longer be invoked to explain their disappearance. Moreover, the team's finding places the extinction much closer to the arrival of humans to Australia, suggesting that the two events were linked. The new date alone, however, cannot reveal whether human hunting, habitat destruction or some other human factor caused the die-off.

In the second report, John Alroy of the University of California at Santa Barbara describes a computer simulation of the end-Pleistocene megafaunal extinction in North America showing that even low levels of human hunting would have driven the Ice Age behemoths out of existence. Importantly, the simulation, which assumes a slow human population growth rate and low maximum hunting efforts, correctly predicts the fate of 32 out of 41 megafaunal species. These findings, Alroy argues, show that in fact anthropogenic extinction was unavoidable. "The overkill model thus serves as a parable of resource exploitation," he concludes, "providing a clear mechanism for a geologically instantaneous ecological catastrophe that was too gradual to be perceived by the people who unleashed it."

4 Comments

1. 1. peanutbutter 08:26 AM 1/3/09

   I believe the hunt to extinction theory myself, since we have done and still do that very thing everyday. It's not kill or be killed, nor is it survival of the fittest. It's all about ego. Prove what a big macho jerkoff you are by wiping out every other living thing. Sport hunting should be illegal the world over. Sport hunting is the blackest evil ever thought up by humans.

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2. 2. physicsfan in reply to peanutbutter 09:33 PM 4/12/10

   Your ignorance of sport hunting and its effect in the U.S. is appalling. The only reason we have the diversity and numbers of animals today is because of the financial and planning contributions of sportsmen. Shouldn't you at least know your hat from a hole in the ground before you form such a rigid opinion? I assume you are too young to realize how immature this kind of statement sounds
   

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3. 3. Extremophile in reply to physicsfan 04:35 AM 6/2/10

   There is no evidence at all that humans drove megafaunas to extinction at the end of the pleistocene.
   
   You can build any simulation you like to make your point, just twist some variables and some dependencies and you will get the wanted result.
   
   Temporal correlation of non-recurring events also proves nothing. If you have a big number of events and can apply regression analysis or a scatter diagram to show the correlation, this could be a starting point for further analysis.
   
   But try to build a scatter diagram or a regression analysis from a single one-time event...
   
   We have
   
   I prefer American Scientific to focus on science and not on wild speculations and modern mythology that are not substantiated.
   
   @physicsfan,
   
   Hunters do not preserve diversity. They preserve what has a value for them and will destroy everything that has in their eyes no value. Hunters are not moral people, they are just people. Selfish people, generally spoken, i.e. there may be exceptions.
   
   As I said above, I do not believe that SciAm should be the place to spread myths.

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4. 4. morgana11 08:12 PM 12/15/10

   "The overkill model thus serves as a parable of resource exploitation," he concludes, "providing a clear mechanism for a geologically instantaneous ecological catastrophe that was too gradual to be perceived by the people who unleashed it."
   
   This stament couldn't be any more relevant to the times we are living in.
   

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