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Lecture 9

Lecture 9

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Michael Schillaci

Chapter 9: From Tree Shrew to Ape During Permian and early Triassic periods, much of worlds fauna was dominated by therapsids, a diverse group of reptiles that possessed traits, such as warm blooded, and covered with hair One therapsid lineage evolved and diversified to become first true mammals o Probably mouse sized, nocturnal creatures that fed mainly on seeds and insects o Had internal fertilization but still laid eggs By end of Mesozoic era, 65 mya, placental and marsupial mammals that bore live young evolved Modern humans have many complex adaptations- grasping hands, bipedal locomotion, tool making abilities, language, and large scale cooperation Continental drift and climate change To understand evolution of our species, important to understand geological, climatic, biological conditions under which these evolutionary changes occurred World become much colder and drier in last 20 million years Positions of continents have changed relative to each other and to the poles One factors that contributed to change of world is movement of continents continental drift Enormous and relatively light plates of rock that make up continents slowly wander around globe, floating on denser rock that forms floor of deep ocean 200 mya, all of land making up present-day continents joined together in single, huge landmass call Pangaea 125 mya, Pangaea began to break apart into separate pieces o Northern half, Laurasia, included North America and Eurasia minus India o Southern half, Gondwanaland consisted of others By time dinosaurs became extinct in 65 mya, Gondwanaland broken up into several pieces o Africa and India separated, India headed north, crashing into Eurasia, remainder of Gondwanaland stayed in south o Eventually Gondwanaland separated into South America, Antarctica, Australia o South America did not drift north to join N.A. until about 5mya Continental drift important to history of human lineage: o Oceans serve as barriers that isolate certain species from others, so position of continents play important role in evolution of species o Continental drift is one of engines of climate change, climate change has fundamentally influenced human evolution Climate changed substantially during last 65 million years, becoming warmer and less variable and then cooling, finally fluctuating widely in temperature Very large continents tend to have severe weather When continents restrict circulation of water from tropics to poles, world climates seem to become cooler The methods of paleontology Much of knowledge of history of life comes from study of fossils, the mineralized bones of dead organisms Palaeontologists scientists who recover, describe, and interpret fossil remains In order to assign fossil to particular position in phylogeny, must know how old it is Radiometric methods: provide one of most important ways to date fossils All atoms of particular element have same number of protons in nucleus For any particular isotope, radioactive decay occur at constant Several different radiometric methods: o Potassium-argon dating Used to date age of volcanic rocks found in association with fossil material
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