Darwin's Theory of Evolution

Charles Darwin - wrote On the Origin of Species  

• contemporaries believed that species were unchangeable, structures made due to will of the Divine Creator
• proposed that natural laws produced change/evolution over time
• never challenged the existence of a Divine Creator
• based his ideas on studies in S America and Galápagos Islands
• didn't publish his results for 16 years until Alfred Russel Wallace submitted similar theory independently
• The Descent of Man - argues that humans and apes have similar ancestors

Darwin's evidence - from expeditions to the Americas  

• fossils of extinct armadillos found in the same area where similar armadillos lived
• 14 species of finches on the Galápagos Islands all had different beaks from eating different food, but otherwise very similar
• resemblances in plants in close areas, not similar climates

Thomas Malthus - wrote Essay on the Principle of Population  

• pointed out that human population grew geometrically, but food supply grew arithmetically
• only death prevents populations from growing out of control
• his ideas made Darwin realize that only organisms w/ superior attributes survive

natural selection - survival of the fittest; environment only allows the best fit to survive  

• artificial selection - breeders selecting specific organisms to pass along desired characteristics
• organisms ill-suited for the environment die out; their attributes don't get passed on

evidence of evolution after Darwin - more support for evolution has come up since his time  

• fossil record - goes back 2.5 billion years; shows how organisms changed from simple to complex
• age of the earth - estimated to be 4.5 billion years; people of Darwin's time thought the earth was only a few thousand years old
• genetics - explains how new variations occur in organisms
• comparative anatomy - limbs and appendages of different organisms containing the same type of bones
• homologous bones - have same evolutionary origin, but have different uses
• analogous bones - have similar structure but different evolutionary origins
• molecular evidence - more closely related organisms have less differences in DNA
• molecular clock - constant change that occurs to proteins over time
• phylogenetic tree - pattern of descent that maps out the history of an organism