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Published on Jul 10, 2007
http://www.myspace.com/acorvettes The study of how life evolved would be impossible if not for the history that is told in the fossilized remains going back billions of years. Scientists have described about 250,000 different fossil species, yet that is a small fraction of those that lived in the past.
The oldest fossils are remains of marine organisms that populated the planet's oceans. When they died, the plants and animals were buried by mud, sand, or silt on the sea floor. Land animals and plants usually decomposed or were eaten, and mainly the hard parts -- teeth, bones, shells, or wood -- were preserved.