Theory of Evolution
In 1859, Charles Darwin published convincing evidence that species evolve. He further explained how this process occurs. From that evidence and explanation, we have what scientists and others call today, the Theory of Evolution.
Like all scientific theories, the theory of evolution has developed through decades of scientific observations and experimentation. Today almost all scientists accept that evolution is the basis for the diversity of life on earth.
After years of research and study, Darwin suggested that by surviving long enough to reproduce, populations have the opportunity to pass on favorable characteristics to offspring. Over time, these characteristics will increase in a population and the nature of that population will gradually change. Darwin called this process by which populations change in response to their environment natural selection.
Darwin suggested that organisms differ from place to place because their habitats present different challenges to survival and reproduction. As a result, each species has evolved in response to their specific environment. This changing process in response to a particular environment is called adaption. Darwin concluded that the species in a particular place evolved from a species that previously lived there or that migrated from a nearby area.
Darwin's evidence was based on the idea that in any population, individuals that are best suited to survive and do well in their environment will produce the most offspring. By doing so, the traits of that offspring will be passed on and become more common as each new generation arrives. Traits are the genetic characteristics that may be physical, such as hair color; or behavioral, such as birds building nests.
Scientist now know that genes are responsible for inherited traits. Therefore, certain forms of a trait become more common because more of the species carry the gene that is passed on. In other words, natural selection causes the frequency of genes in a population to increase or decrease over time.
Fossils offer the most direct evidence that evolution takes place. A fossil is the preserved or mineralized remains or imprint of an organism that lived past life-forms. Change over time, or evolution can be seen in the fossils. For example, fossil links have been found between fish and amphibians, between retiles and birds, and between reptiles and mammals. All of which add valuable evidence to the history of vertebrates.
Today, Darwin's theory of evolution is almost universally accepted by scientists as the best available explanation for the biological diversity on earth. Based on this supporting evidence, most scientist agree on the following three major points: 1) Earth is about 4.5 billion years old, 2) Organisms have inhabited earth for most of its history, and 3) All organisms living today evolved from earlier, simpler life-forms.
In summary, at age 22, Charles Darwin set off on a journey by the urging of his college professor on the naval voyage of the HMS Beagle that forever changed his life and the way people think of themselves. It was on this journey that evidence was collected to support what is universally accepted today as Darwin's Theory of Evolution.