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Lecture 6 Ch 8 - Lecture 6 Primate Origins and Evolution...

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Lecture 6 Primate Origins and Evolution: The First 50,000,000 Years. Chapter 8
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In-Class Learning Assessment A shorter test - A mix of question styles – One hour VOTE: All here in this room (cramped) OR Some of you will need to relocate to another room after the lecture
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end of the Mesozoic era’s Cretaceous period and beginning of the Cenozoic Era’s Tertiary period – c. 65 mya Paleocene epoch (65-55 mya) Eocene epoch (55-34 mya) Oligocene epoch (34-24/23 mya) Miocene epoch (24/23-5 mya) Pliocene epoch (5 mya-1.8)
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‘Age of Mammals’ age of apes cooling cycles begin age of humanity intense cold c. 2.5mya Geological Time Scale warm period c. 55mya
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Overview: - Oligocene epoch (35 - 23.5 mya) - 26 mya - earliest African apes (e.g. Aegyptopithecus ) –first hominoids semi-terrestrial - Miocene epoch (c. 23.5 - 5.2 mya) – many ape forms (e.g. Proconsul, Sivapithecus , Dryopithecus ) - After c. 17 mya – cooling and drying period – forests become patchy and seasonal tall grass savannah/grassland (fewer trees, open expanses)
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- 11 – 5 mya – ‘gap’ in fossil record (note recent research suggests Sahelanthropus c. 7/6 mya and Orrorin c. 6 mya and Ardipithecus ramidus c. 5.8 mya) - 8 – 5 mya – cold/dry period - inference: first bipeds = first hominids - (5.8?) 4.5 mya – widely accepted fossil evidence for first bipeds (e.g. Ardipithecus ramidus ) - Pliocene epoch (5.2 - 1.6 mya) – various bipedal species and migrations ‘out of Africa’
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new ecological niches, perhaps due to K-T Boundary - meteor/bolide impact (transition between Mesozoic and Cenozoic eras) - cooling Many species died out. Those that could survive became the leaders of new lineages. First major adaptive radiation of placental mammals - expansion into new environments (poss. associated with speciation - i.e. a generalised species becomes many more specialised species in the new habitats, some of whom later go extinct)
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Cenozoic Era : The Age of Mammals Adaptive Radiation : rapid expansion & diversification of life forms into new ecological niches
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plesiadapiforms : Plesiadapis (65- 55mya) - early primate-like mammals ( not actual primates ) from Palaeocene – various places around the world - lack postorbital bar and convergent orbits, claws, gap between front and rear teeth, lack opposable thumb - aka Proprimates
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One plesiadapiform, Carpolestes , from
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