The theory, much like the process, of evolution developed gradually over time. Charles Darwin was a scientist in the 1800s whose theories of evolution are still held today. Darwin originally believed the view of divine creation, the idea that every species was created by a divine being and is unchanging. It was while he was on a ship voyage around the world that he read the works of other scientists and observed animals in different continents, that he began to think that species must have changed gradually and were not made to exist only as they were created. He devoted his life to the study of plants and animals and after reading Thomas Malthus’s “Essay on the Principle of Population”, he concluded that species with superior physical and behavioral attributes are more likely to survive than their inferiors. These survivors would produce the most offspring, and the inherited attributes from the “superior species” would become the most common. Darwin called this process “natural selection”. He also decided that each species evolves to adapt to their environment, which is why similar species in different locations may have different traits.
Jean-Baptiste de Monet, Chevalier de Lamarck, was a French biologist at the end of the 18th century who suggested a theory as to how evolution occurs. Lamarck believed that evolution was the “acquired traits” of a species being inherited by its offspring. The acquired traits were acquired through continued use of a structure to perform a certain task, and the structure developing physically to make the task easier. An example is the growth of giraffes necks from straining reach higher for food, and then the new trait of a longer neck getting passed on to offspring. Darwin later read about Lamarck’s theory and used it when developing his own theory of evolution. Darwin’s ideas and the accepted theory of evolution, can be summarized as natural selection causes change within populations to allow them to survive, the isolation of a species leads to its formation, and the extinction of one species leads to their replacement by another.