Hominids - Fossil is the preserved remains of once living...

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Fossilization entails the replacement of organic material with minerals. It usually requires submersion, which must occur before the organism decomposes. Ordinarily, only bone lasts long enough to fossilize. The scientific study of the primate and hominid fossil record is paleontology. Conditions conducive to the formation of fossils prevent weathering and to exclude oxygen and bacteria, thereby preventing decay. Otzi comes out of the deep freeze. Sampling errors in the fossil record: Few things become fossilized in the first place Even fewer are found Older fossils are more difficult to find than more recent ones Certain environments preserve better than others Bones and teeth preserve better than other organic material Large bones preserve better than small bones Paleontologist Michael Anderson with fossilized Ediacara fauna – pre-Cambrian (575 mya) organisms that are soft-bodied and therefore rarely fossilize. Once dated, a fossil must be interpreted. Based largely on comparison (with existing fossil record) and analogy (to living species). 2 types of dating methods are to date sites and fossils: Relative: dating determines only whether an object is older or younger than other objects Chronometric: dating provides an estimate of age in years based on radioactive decay Some relative dating techniques: Stratigraphy: based on the law of superposition, that a lower stratum (layer) is older than a higher stratum. The earliest dating method, first proposed in the late 18 th century. Primarily used with sedimentary and layered volcanic rocks. Based on the law of superposition, the idea that in an un-deformed stratigraphic sequence, the oldest strata occur at the base of the sequence. Fluorine analysis: applies to buried bones and groundwater seepage. Bones incorporate fluorine during fossilization. Biostratigraphy: related to changes in the skeletons and dentition of animals occurring elsewhere. It is strata from widespread locations containing the same fossil fauna and flora can be correlated in time. Palemagnetism: based on the shifting of the geomagnetic pole. Some absolute (chronometric) techniques: The age of an object can be determined by measuring the rate of disintegration: Potassium / argon (K/Ar) dating involves the decay of potassium into argon gas. K/Ar has a half-life of 1.25 billion years. Based on measuring the products of the radioactive decay of potassium (K). The radioactive isotope K-40 decays to Ar-40 and Ca-40 with a half-life of 1.25 billion years. Material reheated and escaping argon gas is measured. Best samples come from material heated to extremely high temperatures (driving off accumulated argon gas). Used extensively for materials from 5-1 mya.
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This note was uploaded on 05/26/2011 for the course ANTH 1 taught by Professor Jenny during the Fall '10 term at East Los Angeles College.

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Hominids - Fossil is the preserved remains of once living...

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