The droppings of prehistoric herbivores found at the bottom of a lake could open new scenarios for the disappearance of large mammals such as mammoths, mastodons and giant sloths.
Elisabetta Intini, 20 November 2009
Decades of historical speculations caused by a bit of poop. A pile of manure left perhaps by a mammoth in the forests of Indiana (North America), could help rewrite the history of the extinction of the great disappeared mammals.
The discovery recently published in the journal Science, provides valuable information on the ecological consequences of the disappearance of the prehistoric great-grandparents of elephants.
"Polluted" lake. The "fault" is all of a fungus: the Sporormiella, whose spores develop mainly in the faeces of large herbivores. A team of researchers from the University of Wisconsin in Madison (United States) collected samples of these droppings at the bottom of Lake Appleman, Indiana. The "bisognini" - belonged to a mammoth or some other large mammal - were mixed with different layers of mud and sediments of the basin.
Through the spore and pollen counts in the findings, the scientists attempted to reconstruct the history of the ancient environmental changes that occurred in the area. With surprising results: the decline of the megafauna to which the mammoths also belonged would have begun, in this area, between 14 thousand 800 and 13 thousand 700 years ago, a period in which the Sporormiella spores begin to disappear from the sediments.
Alleged innocents. This type of dating would exonerate from the list of possible "suspects" for the disappearance of mammoths, the prehistoric hunters of the Clovis population, which appeared in North America a thousand years later. After the discovery of tools suitable for hunting large animals, this people had been indicated in the past as a possible co-responsible for the extinction of large herbivores. Among the new "suspects", there may be some populations prior to the Clovis, whose presence in the area, however, is still discussed.
According to the researchers, the hypothesis of the disappearance due to the fall of a meteorite (or of another celestial object) on Earth 12 thousand 900 years ago is to be set aside. The mammoths, according to the analysis of the dung, would have begun to die out well before the impact.
The rescue of the forest. The study then focused on the consequences that the disappearance of mammoths would have on vegetation. In fact, the pollens found in the sediments would indicate, for the period following extinction, an increase in deciduous plants that were probably kept "under control" by the appetite of these beasts. The discovery could also have implications for the modern balance between fauna and vegetation: "We know that large herbivores are among the most threatened animals in the landscape, " said Jacquelyn Gill, head of the research. "Now we are starting to understand how important their role is to ecology".
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See also the photo of Ljuba, the perfectly preserved baby mammoth