ANT%20151%2002

ANT%20151%2002 - 1 Lecture 2 The Fossil and Molecular...

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Unformatted text preview: 1 Lecture 2 The Fossil and Molecular Records of Primates How to become a fossil and impress your friends! • The chances of an animal's bones becoming fossilized after death are very small… • The chances of such a fossil being discovered by a paleontologist are even smaller… How to become a fossil and impress your friends! • Because of this, it has become clear that our interpretation of the fossil record is biased. • We are likely to find only a small percentage of the species that once roamed the earth. • So, we undoubtedly underestimate the number and diversity of extinct species. • Fossilization: – Possible only when animal's carcass is made inaccessible to predators and scavengers immediately after death – Can take place in very dry conditions but may take much longer since moisture is necessary to the process • In the absence of excessive microbial activity, hard parts of the body, such as the bones and teeth, are preserved by gradual replacement by minerals present in the surrounding medium. How to become a fossil and impress your friends! • The length of time it takes for complete mineral replacement of organic material will depend on the conditions of burial. • However, once a skeleton is entombed in this way it is preserved for as long as the surrounding rock remains undisturbed. • Over time the surrounding rock layers are eventually eroded away, exposing the fossil. How to become a fossil and impress your friends! The body of a dinosaur is washed into a small lake, where it sinks to the bottom and decomposes. After some time has passed, only the hard bones and teeth remain. Here’s an example… 2 Fine mud and clay settling on the bottom of the lake cover the decomposing body. Chemical substances from the mud penetrate the bones, preserving them from decay. Over time, the mud hardens into rock, and the fossilized skeleton may remain unchanged for many millions of years. Next… Erosion exposes the rock strata that formed in the bottom of the ancient lake, and parts of the fossilized skeleton can now be seen. Careful excavation will be required to remove the whole skeleton from the surrounding rock. Then… How to become a fossil and impress your friends! • Due to the biased nature of the fossil record, we are unlikely to sample the “first” anything. 3 Studying Fossils • Paleontology depends on the science of geology for understanding how old fossils are and their environmental context. • Geology has established the geological time scale… Geologic time scale of the Cenozoic Era See also FTS , p. 20 Geological time is difficult to comprehend without practice We live in a world composed of short time periods, but evolutionary time is extraordinarily vast....
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This note was uploaded on 12/13/2009 for the course ANT 151 taught by Professor Lynn during the Winter '09 term at UC Davis.

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ANT%20151%2002 - 1 Lecture 2 The Fossil and Molecular...

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