Monday, November 23, 2009

How Did the Mammoths Die Off?

The Los Angeles Times has an article by John Johnson Jr. about why the woolly mammoths died out. He writes:
To track the population of large herbivores, scientists analyzed the pollen, charcoal and fungus in ancient sediments beneath Appleman Lake, a 35-foot-deep body of water left behind when the last ice age ended 20,000 years ago. The research focused on the amounts of the fungus Sporormiella present in the sediments, according to Jacquelyn Gill, a graduate student at the University of Wisconsin, Madison and a co-author of the paper appearing in today's issue of the journal Science.

Because the fungus is commonly found in the dung of large plant-eaters, its prevalence in the fossil record should be a direct measure of population density, Gill said. The research team found that the decline of the large mammals started about 14,800 years ago -- and was virtually complete a thousand years later.

"About 13.8 thousand years ago, the number of [fungus] spores drops dramatically," Gill said.

In the end, a total of 34 types of large animal disappeared.
This, it is said, refutes the current hypothesis that a bolide of some kind was responsible, leaving humans the likely culprit.

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