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Anthro 1Z03- Fossils and Their Place in Time and Nature.docx

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Department
Anthropology
Course
ANTHROP 2FF3
Professor
Hendrik Poinar
Semester
Winter

Description
Fossils and Their Place in Time and Nature (Ch.7) Anthropology 1Z03- February 3, 2010 What are Fossils?  Physical remains of once living organisms  Organisms chemically changed into minerals (Fe and Silica)  Organics have been replaced (i.e. became inorganic) through ground water  Microfossils: o Corals and marine creatures/shells o Ancient tool makers noticed these indentations o Date back to 500-345 mya (well before dinosaurs)  Paleontology: study of fossils  Pale anthropology: study of extinct humans and their ancestors How are Fossils formed?  Taphonmy: the laws of burial (study of what happens to decaying organisms)  Requires an anoxic (no O2) environment where decomposition is limited  Organisms must be buried quick- so that there is no exposure to microorganisms  Primarily found in sedimentary rock- esp. those deposited in oceans  BUT… also found in ancient cave sites (e.g. South Africa) What are the limitations to the fossil record?  There is always some sort of “bias”  Representation bias: not all kinds of animals will be represented everywhere  Some areas will not permit fossilization  Fossil record only provides a snapshot of life in the past  Fossil findings must be “pieced” together to create a story (i.e. things are interpreted) Reconstruction of Fossil Skeletons  Record mostly comes from looking at dentition (number, arrangement, size)  Dental formula (2.1.2.3)  Note: Retention of P3 (third premolar) in more recent ape mandible, but loss of P2 and P4 in earlier ape forms  Changes could either be a result of mutations or changes in environment  Also can look at Cusp morphology AND Enamel thickness How to read the fossil record  Comparison of fossilized skeletons to living primates  Looking for a “post-orbital bar” – the eye socket surrounding the eye Geological Time Divisions  Eon, Era, Period, Epoch (smallest geological time categories)  K-T Boundary Cretaceous- Tertiary- asteroid impact (destruction of dinosaurs)  Age of mammal – tertiary period (Cenozoic)  Continental Drift (plate tectonics) o Early Mesozoic era (c.225 mya)- Pangaea o Late Mesozoic era (135 mya) o Cenozoic (65 mya)- continents drift apart Fossils and Their Place in Time and Nature (Ch.7) (cont’d) History of Thought Backgrounder  Hooke- looked at fossil wood (i.e. cells under primitive microscope)  Hutton- long time to make geological data (what is happening now, happened long ago) o Uniformitarianism  Cuvier- fossils, catastrophism (no gradual changes), floods + earthquakes o Looked at extinction events  Lyell- father of geology, suggested aging other organisms surrounding fossils  Steno’s law of superposition: o Rock layers that are deeper are older than the strata near the surface o Looked at the relative order of rock layers (to age the fossils)  William Smith: o Surveyor- mapped geological strata of southern Great Britain o Noted that different fossils in different rocks were “markers of time” o Called this the “Principal of Faunal Succession” o First geological map of region (1815) Methods of Aging a Fossil  Relative dating: relies on stratigraphy and association o Note: Law of superposition- looking at position of fossils in strata o Four types of relative dating: 1. Stratigraphic Correlation (William Smith- match chemical and physical properties/signatures)
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