December 12, 2017

13.04.10- Mammoth Extinction vs. Impact Theory.

An Ice Age extinction mystery has just got more complicated. North America used to be home to some amazing mega-animal life, including wooly mammoths, saber-toothed cats the size of grizzly bears, and armadillos the size of Volkswagens. Then, around the time period known as the Younger Dryas about 12,900 years ago, a mass continent-wide extinction event occurred. Key theories include massive climate change, a large cometary impact, and that greatest of all predators, man. Now, research by Jacuelyn Gill of the University of Wisconsin has dealt a blow (pun intended) to the cometary impact hypothesis. Key evidence for a large airburst over the Laurentide ice sheet comes in the form of an iridium layer seen in the sedimentary deposits laid down at the time, as well as the discovery of minuscule nano-diamonds generated by the heat and blast of the explosion. The problem is, Gill’s studies of fungus spores found in fossilized dung finds the extinction event was already underway well before the impact, around 14,000 years ago. In addition, a mastodon skeleton in the Cincinnati museum has been found to have been dated from circa 10,055 years ago, well after the impact! This seems to put the appearance of Clovis man and overhunting as the key to large mammal extinction in the Ice Age North American scene. Perhaps even a combination of the factors was the cause. The concept of the Early Dryas extinction is unique because it is the most recent extinction event (other than the one we’re currently undergoing!) along a timeline of multiple events throughout the history of life on Earth. Being the most recent, perhaps more evidence for complicating factors is simply lying around for us to find. This debate is thus the hottest topic of all large extinction events. And one has to wonder; what would life in modern U.S. suburbia and camping trips be like if there were still saber-toothed cats around?

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