Gaines Unravels Cambrian Explosion Mystery
The oceans teemed with life 600 million years ago, filled with simple, soft-bodied creatures that would hardly be recognizable as the ancestors of nearly all the animals on Earth. Then something incredible happened. Over a few million years - a relative blink in geologic terms - a burst of evolution led to a flurry of diversification and increasing complexity, including the expansion of multicellular organisms and the appearance of the first shells and skeletons. This burst, the “Cambrian Explosion” of animal life, is a singular event in the history of life. Nothing remotely similar has happened before or since.
Why and how this happened when it did has remained a mystery. New research by department chair Robert Gaines and Shanan Peters (University of Wisconsin, Madison), published in the April 19 issue of the journal Nature, shows that the answer may lie in a second geological curiosity: the Great Unconformity, a dramatic boundary in the geologic record between ancient igneous and metamorphic basement rocks, and much younger sediments. Whereas Darwin and other naturalists have interpreted this gap as a failure of the rock record, Peters and Gaines find evidence that the formation of the Great Unconformity may have in fact triggered the Cambrian Explosion by means of uplift, exposure and chemical weathering of basement rocks on an unprecedented scale, which flooded the oceans with chemical byproducts that animals use to build skeletons.
More Information: http://pomona.edu/news/2012/04/18-gaines-nature-journal.aspx