The Theory of Evolution

Running Head: EVOLUTION

The Theory of Evolution

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Charles Darwin’s theory of evolution has been a topic of controversy since it was promulgated in the late 1800s. Nonetheless, its tenets remain strong, with many modern day scientists making discoveries that support Darwin’s theories of evolution, natural selection, and survival of the fittest.

In The Origin of Species, Darwin calls the process of natural selection or survival of the fittest, the preservation of favorable individual differences and variations, and the destruction of those, which are injurious (Darwin, 1901). Darwin’s theory of evolutionary change and process of natural selection surmises that variations exist in every population of species. Organisms compete for the limited resources available to them, and may produce more offspring that can naturally survive, therefore, only a few organisms are successful in leaving progeny. Each organism passes on genetic traits and characteristics to their offspring, and the organisms that inherit the most beneficial traits are more likely to survive and reproduce (Darwin, 1901). Homologous traits are those found in different species that are structurally and functionally similar in nature and that arose through genetic ancestry. Those animals that have the greatest number of homologous traits are more closely related than those with fewer homologues (Water, Rethlingshafer, & Caldwell, 1960). Alternatively, analogous traits are structurally and functionally similar to one another, but did not come about through genetics, and have arisen independently on more than one occasion (Griffiths, 1997).

Behavioral traits evolve during various adaptations through mating, hunting, means of cooperation, and methods of escaping predators. This evolution takes place through changes in neural or brain mechanisms, hormonal changes, and patterns of learning, thereby revealing physiological and behavioral systems evolving in concert with one another (Beecher-Monas & Garcia-Rill, 2006). An example of this behavioral evolutionary process is the “fight or flight” response that humans have been genetically disposed to in order for early man to be able to escape dangerous predators. This stress response filled the human body with strength, stamina, and speed to escape a hazardous situation, and those who fought and won, or fled and lived, were the fittest and survived. In Western civilization today, this response is no longer needed for survival, however, the body still responds to stressors with this “fight or flight” response (Beecher-Monas & Garcia-Rill, 2006). Therefore, the behavior this response is meant to coincide with has evolved into one in which modern day stress is the “predator”, rather than a wild animal or a competing tribe.

The fossil record has been used by scientists to support Darwin’s theory, which provides evidence of change over time “of descent and modification” (“Science”, 2007). Common animal structures have also support evolution by using comparative anatomy to show common ancestral traits through stages of transition. The science of biogeography has examined living species and compared them to local fossils to determine whether they are similar in structure,