Essay 3 - Joe Pucci Hist 2870 December 4, 2008 TA: Mari...

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Joe Pucci Hist 2870 December 4, 2008 TA: Mari Crabtree Essay #3 The Tree of Life Argument Introduction The theory of evolution is one that has been itself evolving for hundreds of years . At the core of this theory is the “tree of life.” This is the basic premise that all living organisms can be traced back, generation through generation, to eventually reach one original progenitor . This school of thought has come under much scrutiny, especially with the developments in genetics and microbiology, which have changed some of the ways we classify organisms . This essay will present and argument against the tree of life, and then provide some evidence for a tree of life . Ultimately, this essay will show that it is more reasonable to assume a tree of life versus a web of life for life forms in the present . It is however also reasonable to assume a non-linear progression in the early forms of microbial life . Darwin-A Review To be able to comprehend the arguments against the Tree of Life Hypothesis, one must first be able to understand what Darwin’s argument for a tree of life hypothesis is . Darwin, after his expeditions to the Galapagos Islands, wrote his book entitled The
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Origin of Species . In this book, he describes his theories on natural selection and descent based on modification . To understand some how these intertwine is to get to the core of his tree of life hypothesis . Darwin was a revolutionary in that he concluded that beings descended from lower forms of life . He mentions this throughout the book, including here: “From the first dawn of life, all organic beings are found to resemble each other in descending degrees, so that they can be classed in groups under groups . This classification is evidently not arbitrary like the grouping of the stars in constellations .” (Darwin, 711) He is also in this quotation alluding to his theory of the tree of life . He expands on his tree of life hypothesis in his fourth chapter, where he actually uses the analogy of a tree to illustrate the classification of his theory .”The affinities of all of the beings of the same class have sometimes been represented by a great tree . I believe this simile largely speaks the truth . The green and budding twigs may represent existing species; and those produced during former years may represent the long succession of extinct species…The limbs, divided into great branches, and these into lesser and lesser branches, were themselves once, when the tree was young, budding twigs, and this connection of the former and present buds by ramifying branches may well represent the classification of all extinct and living species in groups subordinate to groups .” (Darwin, from D+P article) This description accurately depicts Darwin’s Darwin’s tree of life hypothesis . Basically, like a tree, species branch out from older species until you
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eventually get to the root, which would be equivalent to the progenitor . It is a form of classical hierarchy . Darwin’s theory also discusses the similarities between species and what they
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This note was uploaded on 01/17/2009 for the course HIST 2870 taught by Professor Macneill during the Fall '07 term at Cornell University (Engineering School).

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Essay 3 - Joe Pucci Hist 2870 December 4, 2008 TA: Mari...

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