Dating the fossil record


One of the great success stories in the examination of the fossil record was the finding of a near-perfect fossilized transition between a vertebrate adapted for water and one adapted for land.Evolutionary biologist Neal Shubin set out to find a more complete transitional specimen than the 1998 fin.This tetrapod had a hand-like fin, confirming a prediction of evolutionary biology.Though the fossil record does not include every plant and animal that ever lived, it provides substantial evidence for the common descent of life via evolution.I provide a few recent examples of this, and then show that stratigraphic-range extension is not the exception but the rule.

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They’re all lined up nice and neat from beginning to end.These fossils date from a time when the dentary and squamosal bones were beginning to take over the role of jaw hinge (hinge #2). However, a common objection is that few transitional fossils have been discovered; thus many lineages cannot be traced smoothly.This allowed the articular and quadrate bones to evolve into the second and third bones of the mammalian ear, as shown on the right. There are several reason for these gaps in the fossil record. Plus, transitional species tend to appear in small populations, where rapid changes in the environment can provide a stronger evolutionary drive.The fossil record is a remarkable gift for the study of nature. In rocks more than 1 billion years old, only fossils of single-celled organisms are found.

Moving to rocks that are about 550 million years old, fossils of simple, multicellular animals can be found.

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