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Study Provides Insight into Extinction Of Large Animals
At the University of Wisconsin-Madison, Scientists have advanced towards solving the mystery of extinction of mammoths, mastodons, and other large animal species that roamed North America during the last ice age.
by Priyanka - November 20, 2009 - comments
Roughly between 10,000 and 20,000 years ago, the end of many large species started in the North America.
By studying the traces of dung left by these giant animals in ancient lake beds, scientists have got insightful information into the matter; that the climatic change might not be the reason behind the extinction of megafauna--animals like saber-tooth tigers, mastodons, giant sloths etc.
In an online study published by scientists on Thursday in the journal Science, scientists have not reached a concrete conclusion but criticized the theory of powerful comet collision resulting in extinction.
“Mega-faunal populations collapsed from 14,800 to 13,700 years ago, well before the final extinctions,” the authors wrote.
Events associated with the disappearance of giants
More than a few major events occurred at around the same time the animals vanished from the face of earth. These events, like an asteroid explosion over North America, major environmental changes linked with the end of ice age and the arrival of the man, are associated with big animals’ extinction.
The team of scientists researching the idea, led by UW geography professor John W. Williams and graduate student Jacquelyn L. Gill, took samples from bottom of muddy Appleman Lake in northeastern Indiana.
They then separated pollen, charcoal, and spores of fungus from animal dung.
The youngest fossils of megafauna are found to be around 13,300 to 12,900 years old, and the asteroid that is thought to have caused the impact on Earth’s atmosphere around 12,900 years ago seems like a likely reason for the cause of extinction. But the short-lived Clovis culture inhabiting the North America at that time clears the asteroid blamed for the impact.
Still these results do not clear humans of the North American mammoths’ extinction, because there are butchered bones some 14,500 years old that have been found in Wisconsin.
It’s not even clear whether these people were equipped with weapons capable of taking down such mammoth creatures.
According to the commentary written in Science by Christopher Johnson, who was studying the extinction of the Australian megafauna at James Cook University in Queensland, “If people were responsible for the decline, they must have been pre-Clovis settlers.”
Conclusions drawn from analysis of dung
To make some concrete observations, researchers decided to take help of a fungus called Sporomiella—known to leave spores on bird or mammal dung.
According to the analysis of the dung, more the spores on the dung, the larger the animal in question. By studying the evidence collected from these spores, pollen and charcoal collected from a lake in Indiana, ecological changes of that period can be constructed to know the answers.
The number of spores declined starting from 14,800 to 13,700 years ago, indicating the decline of large mammals during that time period. Around 13,700 years ago, new communities of plants stated to form.
"We are in a world today that is changing very rapidly," Williams said. "Species are being moved around the world by accident and on purpose. Species are becoming extinct."