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a201-11f-03-WhyEvolutionHappens - Introduction to...

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Introduction to Biological Anthropology: Notes 3 Why evolution happens Copyright Bruce Owen 2011 - Announcements - Class user ID and password - Please send in photographs - Recall that Darwin's observations on the Beagle convinced him of the fact of evolution - that is, that populations of organisms change over time - The problem was to explain how evolution could occur. - There was already a theory for this, originally proposed by Jean Baptiste Lamarck in several volumes from 1815-1822, when Darwin was still a child - called Lamarck’s theory of inheritance of acquired characteristics - Like Darwin and some others, Lamarck also believed that evolution occurred - he explained it by proposing that organisms changed over their lifetimes - body parts that they used a lot developed more, and ones that they used less developed less - for example, a giraffe that spent its life straining to reach high leaves would develop a longer neck than it would have it if had grazed on grass - a longer neck due to use during life would be an “ acquired characteristic - since the individual was not born with the characteristic - but acquired it due to events during its life - Lamarck then suggested that these acquired characteristics would be inherited by the animal's offspring - so that the next generation of giraffes would start with a slightly longer neck to begin with, and would develop it even further if they kept reaching for high leaves - this sounds reasonable, but there was no evidence of acquired characteristics actually being inherited - you can observe that tanned parents have kids who are born just as pale as the kids of their un-tanned relatives - children of people who work out and become strong or fast are not born with any greater strength or speed than children of parents who never exercised - animal breeders did not succeed in creating - faster horses by vigorously training them, generation after generation, - or fatter cows by overfeeding them over several generations - it just didn't work - Darwin (like many people at the time) was aware of how animal breeders actually did develop new variants - by controlling mating - breeders would select the individual animals that had the desired characteristics - and allow them to mate, and not the others - then pick the offspring with the features they wanted - and allow those to mate, and not the others
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Intro to Biological Anthro F 2011 / Owen: Why evolution happens p. 2 - and so on, generation after generation - this method was well known to actually produce new variants - pigeons with larger tails, flatter faces, odd flying patterns, etc. - dogs that were larger or smaller, more or less aggressive, different kinds of hair, etc. -
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