Source: NOVA: "In Search of Human Origins"
The remains of the vast majority of organisms that die are eaten by scavengers or decompose beyond recognition before they can be preserved. The conditions under which fossils can successfully form are unusual, and the odds that a fossil will then be exposed at the surface again, and discovered, are smaller still. Footage courtesy of NOVA: "In Search of Human Origins."
NARRATOR: It takes a rare set of circumstances to turn a living creature into fossilized bone. In the case of Lucy, the famous hominid fossil discovered in Ethiopia's Great Rift Valley in 1974, there is no evidence that she met a violent death. No predator or scavenger found her body before it began rotting in the lake's soft sediments. Her bones, which settled in the mud, may have been cracked or shattered by animals roaming around the shore.
Heavy rains gradually washed in enough sand and gravel to bury her bones. These deposits built up over thousands of years, burying her remains hundreds of feet deep. The calcium in her bones, molecule by molecule, was replaced by minerals from these deposits, the bones to stone.
She remained buried over millions of years, while the earth's crust moved constantly, forcing the remains of her body closer to the surface. Heavy storms beating down on the earth eroded the sediment and most likely brought her once again to the earth's surface. Her exposure made it possible for anthropologists to later discover her remains some three million years after her death. (thunder rumbling)
Academic standards correlations on Teachers' Domain use the Achievement Standards Network (ASN) database of state and national standards, provided to NSDL projects courtesy of JES & Co.
We assign reference terms to each statement within a standards document and to each media resource, and correlations are based upon matches of these terms for a given grade band. If a particular standards document of interest to you is not displayed yet, it most likely has not yet been processed by ASN or by Teachers' Domain. We will be adding social studies and arts correlations over the coming year, and also will be increasing the specificity of alignment.