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Unformatted text preview: Chapter 10: F rom T ree Shrew to Ape- The first t rue mammals probably evolved from a therapsid that originally lived during the Permian and early Triassic periods o Therapsid: a diverse group of reptiles that possessed mammalian traits, such as being warm-blooded and covered with hair They probably resembled something like a contemporary shrew- According to Darwins theory, complex adaptations are assembled gradually, in many small steps each step favored by natural selection o Humans have grasping hands, bipedal locomotion, toolmaking abilities, language, and large-scale cooperation Continental Drift and Climate Change- To understand the evolution of our species, it is important to understand the geological, climatic, and biological conditions under which these evolutionary changes occurred o If the environment varied through time, them evolution would have to track a moving target and new characteristics seen in fossils would not have to represent progress in a single direction- The positions of the continents have changed relative to each other and to the poles o Continental drift About 200 million years ago, all of the continents were joined in one huge landmass called Pangaea 125 mya, it split into two o The northern half was called Laurasia I t consisted of North America, Europe, and Asia (not including India) o The southern half was Gondwanaland I t consisted of Africa, India, South America, Antarctica, and Australia South America and North America did not come together until about 5 mya o Continental drift is important in human lineage because oceans serve as a barrier to isolate certain species from others, and it is the cause for climate change, which has fundamentally influenced human evolution- The climate has changed substantially during the last 65 million years first becoming warmer and less variable, then cooling, and finally fluctuating widely in temperature o Very large continents tend to have severe weather Because Pangaea was so large, winters must have been very extreme o Scientists think that when continents restrict the circulation of water from the tropics to the poles, world climates seem to become cooler The Methods of Paleontology- Much of our knowledge of the history of life comes from the study of fossils, the mineralized bones of dead organisms o Mineralized bones are bones of dead organisms that have been preserved long enough for the organic material in the bones to be replaced by minerals o Paleontologists interpret fossils- There are several radiometric methods for estimating the age of fossils o Radiometric methods are based on the fact that the isotopes of certain elements are unstalb., so they will change spontaneously from one isotope to another of the same element, or maybe even a different elements These changes occur at a regular rate, allowing us to date fossils o Potassium-Argon dating Used to date the age of volcanic rocks found in association with fossil material...
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This note was uploaded on 04/21/2009 for the course ANTH 200Lg taught by Professor Yamashita during the Fall '07 term at USC.
- Fall '07