Evolution

Charles Darwin had two great themes in "On the Origin of Species" which accounted for the similarities and adaptations

characteristic of living organisms. To account for the adaptations of organisms and those innumerable features that equip

them for survival and reproduction, Darwin (and Wallace) independently came up with the central theory of evolutionary

process: natural selection. Natural selection gives insight in to why organisms are the way that they are. Adaptations are

phenotypic variants that result in the highest fitness among a specified set of variants in a given environment. In reference

to humans, there are many traits that have been selected and adapted for throughout their evolutionary history giving them

the characteristics that they have today. In this paper I will discuss some parts of the human body, which have been found

to be selected for by the evolutionary mechanisms of natural selection, adaptation and mutation.

Natural selection, adaptation, and mutations are three components of the evolutionary process, each one having either

positive or negative effects on the other. What exactly is natural selection? There are many variations of the definition but

most agree that it must include the following concepts: some attribute or trait must vary among biological entities, and there

must be a consistent relationship, within a defined context, between the trait and one or more components of reproductive

success, where "reproductive success" includes both survival and the reproductive processes themselves (Futuyma, 1998).

Charles Darwin's theory of natural selection states "if variations useful to any organic being ever occur, assuredly

individuals thus characterized will have the best chance of being preserved in the struggle for life; and from the strong

principle of inheritance, these will tend to produce offspring similarly characterized." Regardless of how it is defined,

natural selection and its action can have tremendous effects on the members of a population. It is natural selection that

causes adaptation, and these adaptations evolve to ensure the survival of a species.

Evolution, in a very broad sense, is defined as descent with modification and often with diversification (Futuyma, 1998).

Darwin's idea of evolution was that it occurred by descent with modification, from common ancestors. Some mechanisms

involved in evolution are mutation, recombination, gene flow, isolation, random genetic drift, and natural selection. These

ideas together constitute our idea of the evolutionary theory. When you factor in all of these elements of evolution you can

view evolution as a "progressive development through time from simple to gradually more complex and more diverse

organisms" (Ayala, 1997).

Darwin devoted one single sentence in "The Origin of Species" to the controversial topic of human evolution: "Light

will be thrown on the origin of man and his history"(Futuyma, 1998). Although his evasion did not work, human evolution

is still a controversial topic today. Since this area is so controversial there have been many studies conducted in the area

of human evolution. These evolutionary studies have provided us with abundant, well-documented evidence on the

relationship of humans to other species, on the steps by which some human characteristics evolved, and on genetic

variation within and among human populations.

Some theorists believe that natural