Monday, August 15, 2005

Principle of Superposition

Geological Map of England and Wales and Part of Scotland From geology, the Principle of Superposition, briefly, that a stratum (a sedimentary rock layer in a tectonically undisturbed sequence) is younger than the one beneath it and older than the one above it. This allows the relative ordering by time of fossils found in the strata.

  • Lucy is a fossil specimen of Australopithecus afarensis.New biological forms appear at different times in the fossil record.
  • New forms are preceded by similar forms.
  • New features are modifications of features existing in a preceding form.
This creates a nested hierarchy, a diversification of forms from common ancestors.

From this, we can make predictions about intermediate forms. For instance, Darwin predicted that there would be found fossils of organisms that had shared features of both humans and other apes. Many species and examples of such intermediate forms have been found, and have been found in the appropriate strata, e.g. Australopithecus afarensis has been found in strata dated at about 3ΒΌ million years.

Geological strata containing an  evolutionary sequence of fossilsBut, even then, the fossil evidence is not the best evidence in support of the Theory of Evolution. The best evidence is in recently discovered genetic data.



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