Thursday, January 10, 2013

"When Alligators Roamed the Arctic" --Big Global Change 34-Million Years Ago Shows Shift from Greenhouse Age to Ice Age

The image above shows how North America appeared in the Eocene Epoch,33.9 - 55.8 million years ago. Earth's climate was warm relative to today. Polar ice sheets were smaller and sea level was higher. The climate in Nebraska was warm and humid, but began to cool and become more arid toward the end of the epoch Eocene. To the west, the Rocky Mountains continued to form. Sediment shed from the uplifting mountains was carried eastward by river systems and deposited in Nebraska.

The dominant factors in the rise and fall of the diversity of life on Earth has been a point of debate for scientists nearly as long as they have studied the processes of evolution. In the 1970s, evolutionary biologist Leigh Van Valen began calling the case for biological factors (such as competition with other organisms for food, space and mates) the "Red Queen" hypothesis, after Lewis Carroll's "Through the Looking-Glass" character who tells Alice she must run hard in Wonderland just to stay in the same place. The alternative argument, backing the nonbiological forces of the environment (physical characteristics like chemistry and temperature or relative catastrophes like asteroid impacts), came to be known as the "Court Jester" hypothesis.
"This question—which one is pulling the strings?—is a big one for people who study the history of life on Earth," says Shanan Peters, a University of Wisconsin–Madison geoscience professor. "And what we've found is that it's actually both. They just play very different roles."
Peters and Clay Kelly, a fellow UW–Madison geoscience professor, chose to pit the Red Queen and Court Jester against each other on the high seas, over planktonic foraminifera: tiny, shelled, ocean-dwelling creatures with an outsized impact on the planet and science. Read More