Anth121-2008PrimateOrigins

Anth121-2008PrimateOrigins - Early Primate Adaptations The...

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Early Primate Adaptations • The earliest primates were similar to modern tree shrews in their adaptations and body form. • Like the tree shrew they were small animals with claws instead of nails, laterally-placed orbits, and long snouts. • They undoubtedly used their well-developed sense of smell to forage for insects and fruit on the forest floor.
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Primate Origins
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What is the adaptive significance of the primate trends? The Arboreal Theory: Explains the trends in terms of adaptation to life in the trees The manual predatory theory: Explains the trends in terms of a arboreal feeding adaptation
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The arboreal theory of primate origins • Smell lost its usefulness since the trees form a discontinuous substrate in which scent trails are difficult to follow. • Vision and tactile exploration and eye-hand coordination became more important because of the problems of getting around in the trees Increase in brain size relative to body size would allow better eye- hand coordination and facilitate feeding in a complex environment
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Arguments against the arboreal theory Some rodents and marsupials do fine in the trees without showing a convergence with the primates These forms are not overly specialized and thus appear to have the potential to evolve grasping hands and feet if natural selection had favored them If the primate traits are so advantagous for life in the trees, why are there so many mammals who do fine in the arboreal environment without them?
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The Manual Predator (“sneaky bug snatcher”) theory
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Predation as an explanation of the primate traits • Predation is associated with ¾ Binocular vision ¾ Big brains ¾ Grasping capabilities
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The manual predator theory of primate origins • The “sneaky bug snatcher” theory • Proposed by Mat Cartmill • Posits that: ¾ Binocular vision gave better depth perception for locating and capturing prey in the trees ¾ Prehensile hand were better for grasping prey ¾ Cerebral cortex expansion for eye-hand coordination ¾ Closed orbit increases visual acuity
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Why reduce the olfactory apparatus? • Smell would loose its usefulness in the discontinuous substrate of the arboreal environment • The “use it or lose it” principal would result in reduced because the energetic cost of a large nose would be greater than the reproductive benefits
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Primate Origins • When did our order originate? • What were the adaptations of the earliest primates? • What selective pressures were responsible?
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Early Primate Adaptations • The earliest primates were similar to modern tree shrews in their adaptations and body form. • Like the tree shrew they were small animals with claws instead of nails, laterally-placed orbits, and long snouts.
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This note was uploaded on 08/06/2008 for the course ANTH 121 taught by Professor Walker during the Spring '08 term at UCSB.

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Anth121-2008PrimateOrigins - Early Primate Adaptations The...

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