Darwin’s Theory at a Glance
   • Darwin’s Theory of 
    Evolution actually contains 
    two major ideas:
    • organisms change over time, 
     life on Earth has changed as 
     descendants diverged from 
     common ancestors in the past
    • evolution occurs by natural 
     selection, the process in 
     which living things with 
     beneficial traits produce more 
     offspring than others do 
     resulting in changes in the 
     traits of living things over 
     time
    Where did Darwin’s Ideas 
    Come From????
     • Voyage of the HMS       • Galapagos Islands
      Beagle
        Scientists Who Influenced 
        Darwin’s Ideas
          •  James Hutton (1726-1797) Scottish                   • Thomas Malthus (1766–1834) English 
             geologist; proposed that the Earth is                 economist; essay titled On Population, 
             shaped by geological forces t over                    argued that human populations grow 
             extremely long periods of time;                       faster than the resources they depend 
             estimated that the Earth  was millions                on. 
             of years old–not thousands of years                 • Georges Curvier (1769-1832) French 
             old.                                                  naturalist.; developed support for the 
          •   Jean Baptiste Lamarck (1744–1829)                    idea that fossil remains of unknown 
             French naturalist.;  the first scientists             organisms were not just the remains of 
             to propose that species change over                   some type of ’freak of nature’ but were 
             time.                                                 actually the remains of organisms that 
          •  Charles Lyell (1797–1875) English                     had existed at one point in history and 
             geologist.; book, Principles of                       had since become extinct. 
             Geology, argued that gradual                        • Adam Sedgewick (1785-1873) English 
             geological processes have gradually                   geologist; proposed the Devonian 
             shaped Earth’s surface                                period and the Cambrian period of the 
                                                                   Earth’s geological timescale based on his 
                                                                    observations and the data he had 
                                                                   collected while studying Welsh rock 
                                                                   strata. 
   Wallace’s Theory
   • Wallace’s adventures took place 20 years after Darwin’s but 
    Darwin had not published his ideas….
   • Did you ever hear the saying that ‘‘great minds think alike???” 
    It certainly applies to Charles Darwin and another English 
    naturalist named Alfred Russel Wallace. Wallace lived at about 
    the same time as Darwin. He also traveled to distant places to 
    study nature. Wallace wasn’t as famous as Darwin. However, 
    he developed basically the same Theory of Evolution. While 
    working in distant lands, Wallace sent Darwin a paper he had 
    written. In the paper, Wallace explained his evolutionary 
    theory. This served to confirm what Darwin already thought.
   Darwin’s Theory of Evolution 
   by Natural Selection
   • Darwin spent many years thinking about the work of Lamarck, 
    Lyell, and Malthus, what he had seen on his voyage, and 
    artificial selection. What did all this mean? How did it all fit 
    together? It fits together in Darwin’s theory of evolution by 
    natural selection. It’s easy to see how all of these influences 
    helped shape Darwin’s ideas.