Lovin my enlightened friends! Thanks Brian Stuhr Our understanding of the shape and pattern of the history of life depends on the accuracy of fossils and dating methods. Some critics, particularly religious fundamentalists, argue that neither fossils nor dating can be trusted, and that their interpretations are better. Other critics, perhaps more familiar with the data, question certain aspects of the quality of the fossil record and of its dating.These skeptics do not provide scientific evidence for their views. Current understanding of the history of life is probably close to the truth because it is based on repeated and careful testing and consideration of data. The rejection of the validity of fossils and of dating by religious fundamentalists creates a problem for them: They cannot deny that hundreds of millions of fossils reside in display cases and drawers around the world. Perhaps some would argue that these specimens- huge skeletons of dinosaurs, blocks from ancient shell beds containing hundreds of specimens, delicately preserved fern fronds —have been manufactured by scientists to confuse the public. This is clearly ludicrous. Otherwise, religious fundamentalists are forced to claim that all the fossils are of the same age, somehow buried in the rocks by some extraordinary catastrophe, perhaps Noah’s flood. How exactly they believe that all the dinosaurs, mammoths, early humans,heavily-armored fishes, trilobites,ammonites,and the rest could all live together has never been explained. Nor indeed why the marine creatures were somehow ‘drowned’ by the flood. The rejection of dating by religious fundamentalistsis easier for them to make, but harder for them to demonstrate. The fossils occur in regular sequences time after time; radioactive decay happens, and repeated cross testing of radiometricdates confirms their validity. Fossils occur in sequences Fossil sequences were recognized and established in their broad outlines long before Charles Darwin had even thought of evolution. Early geologists, in the 1700s and 1800s, noticed how fossils seemed to occur in sequences: certain assemblages of fossils were always found below other assemblages. The firstwork was done in England and France. Around 1800, William Smith in England, who was a canal surveyor,noticed that he could map out great tracts of rocks on the basis of their contained fossils.The sequences he saw in one part of the country could be correlated (matched) precisely with the sequences in another. He, and others at the time, had discovered the first principles of stratigraphy — that older rocks lie below younger rocks and that fossils occur in a particular,predictable order. Then, geologists began to build up the stratigraphic column,the familiar listing of divisions of geological time — Jurassic, Cretaceous, Tertiary, and so on. Each time unit was characterized by particular fossils.The scheme worked all round the world, without fail. From the 1830s onwards, geologists noted how fossils became more complex through time. The oldest rocks contained no fossils,then came simple sea creatures, then more complex ones like fishes,then came life on land,then reptiles, then mammals, and finally humans.Clearly,there was some kind of ‘progress’ going on. All became clear, of course, in 1859 when Charles Darwin published his “On the origin of species”. The ‘progress’ shown by the fossils was a documentation of the grand pattern of evolution through long spans of time.
Posted on: Sun, 18 Jan 2015 19:44:14 +0000
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