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Evolution of Modern Humans
•! Savannah theory: early humans lived on the dry plains of the African savannah
•! Aquatic Ape theory: early humans Modern Humans first lived in an aquatic environment
By Land or by Sea? •! Mosaic model: early humans Exploring the hypothesis of the evolution of Homo Sapiens evolved from other land mammals http://blogs.sundaymercury.net/ weirdscience/assets_c/2010/10/ cavemen-food-nutrition- thumb-450x301.jpg Megan Carlton, Alysia Brengman, An Le, Helen Wiltsey
Aquatic Ape Theory (AAT) Aquatic Ape Theory (AAT)
•! Sir Alister Hardy suggested this •! early ancestors of apes and humans were theory in 1960 aquatic to some capacity ! in response to the Pliocene drought •! varying degrees of the theory are ! circulated in scientific community !!resided in the Afar Triangle shown in the figure •! most accepted theories involve the prehominid ape in a semi-aquatic existence
•! the most drastic theories attempt to use parts of the theory to prove existence of mermaids, not accepted in the scientific community http://longandluxe.com/2013/10/11/ of-mermaids-secrets/ Evans, P. 1992. “The paranasal sinuses and other enigmas: an aquatic evolutionary theory”. The journal of larynology and otology 106: 214-225.
Traits in Support of AAT Traits in Support of AAT
•! bipedalism •! bipedalism
•! loss of body hair, •! loss of body hair, subcutaneous fat subcutaneous fat
•! excess of sweat and •! excess of sweat and sebaceous gland sebaceous gland
•! large brains •! large brains
Evans, P. 1992. “The paranasal sinuses and other enigmas: an Verhaegen, M., Puech, P., Munro, S. 2002. aquatic evolutionary theory”. The “Aquaboreal Ancestors?”. TRENDS in Ecology journal of larynology and otology and Evolution 17(5): 212-217. 106: 214-225.
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AAT Conventional Inadequacies The Savannah Theory
•! Evolution due to climatic and behavioral •! bipedalism: climbing/suspensory complex bridges gap changes toward human bipedalism •! Loss of forest habitat and extension of •! loss of body hair, subcutaneous fat: situational savannahs application of thermoregulation strategies (just-so stories) •! Changes in behavior due to changes in diet •! excess sweating not necessary in an aquatic environment •! Transition to bipedal hominids http://askwhy.co.uk/dinosauroids/wp- content/uploads/2012/07/ • large brains: balance of fatty acids can be obtained from ! !!Scan for prey bipedal_skeleton0.jpg other sources besides a marine diet !!Gathering and foraging
The Savannah Theory cont… Mosaic Model & others
•! Criticisms: •! Mosaic Model: a few large changes at a time, evident in !!Advantages temporary many other species ! No other primates or savannah ! •! Variability selection hypothesis: High amounts of historical mammals have developed constraint, lots of environmental change bipedalism for similar reasons Why not all models? !!Ill-suitedness of man to life on •! the savannah !! Phenotypic expression of advantageous traits !! Use of tools, not genes, to supplement adaptations http://historyplanet.files.wordpress.com/ !! Habitat-specific explanations 2010/03/aa5.jpg don’t account for all changes http://unmaskingevolution.com/images/ evolution.gif
In Conclusion Discussion Questions
•! 1. What process of creating phylogenies to determine evolutionary trends does this model directly conflict with? •! These three models attempt to explain evolution of modern humans •! 2. Since species evolve by adapting to changing •! Both savannah and aquatic ape models have been environments, why is it that humans have supposedly criticized due to … evolved in this way from aquatic ancestors while other aquatic species living in the same time period and •! While certain human traits can be explained by the environment did not adapt and evolve in the same way? aquatic ape theory and Savannah theory, possible alternative explanations include convergent evolution •! 3. How can we avoid “just-so stories” and subsequent theories when talking about the evolution of the modern •! Mosaic model is most commonly accepted among human? scientists
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References
•! Evans, P. 1992. “The paranasal sinuses and other enigmas: an aquatic evolutionary theory”. The journal of larynology and otology 106: 214-225.
•! Langdon, J. 1997. “Umbrella hypotheses and parsimony in human evolution: a critique of the Aquatic Ape Hypothesis”. Journal of Human Evolution 33: 479-494.
•! Potts, R. 1998. “Environmental hypotheses of hominin evolution”. Am J Phys Anthropol 27:93-136.
•! Verhaegen, M. 1991. “Aquatic Ape Theory and Fossil Hominids”. Medical Hypotheses 35: 108-114.
•! Verhaegen, M., Puech, P., Munro, S. 2002. “Aquaboreal Ancestors?”. TRENDS in Ecology and Evolution 17(5): 212-217.
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