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The disappearance of mammoths and mastodons
Mastodons eating black ash trees.
[Image courtesy of Barry Roal Carlsen, University of Wisconsin-Madison]
For years, researchers have believed that large prehistoric creatures like mammoths and mastodons went extinct about 11,000 years ago due to human hunters and changes in their environment. Some researchers also proposed that a meteor, striking the Earth about 13,000 years ago, could have contributed to their extinction as well.
Now, it seems like their extinction may have been a cause of some environmental changes-involving plant growth and wildfire, for example-rather than a result of it.
How did scientists make this discovery? Jacquelyn Gill and a team of researchers used a particular fungus called Sporomiella that grows in the dung of large plant-eating creatures in order to create a timeline of when these massive creatures lived and died. Since the amounts of Sporomiella can tell the researchers how much waste these prehistoric animals were producing, they could get a good idea of about how many of the creatures were alive at different points throughout history.
The researchers then combined their fungus data with other records of prehistoric pollen and charcoal in order to find out how many plants were growing and how much fire was burning at the time as well.
Gill and her team found that populations of large creatures like mammoths and mastodons began disappearing from the planet more than a thousand years before the Clovis people—human hunters—arrived in that area of the world. They also found that the creatures were already becoming extinct before more plants and fire began flooding their environment.
This new timeline of when mammoths and mastodons lived and died also rules out the possibility of a meteor impact as the cause of their extinction.
This research appears in the 20 November 2009 issue of Science.