THE THEORY OF EVOLUTION

Theory of Evolution

Evolution implies a change in one or more characteristics in a population of organisms over a period of time. The concept of evolution is as ancient as Greek writings, where philosophers speculated that all living things are related to one another, although remotely. The Greek philosopher Aristotle perceived a “ladder of life,” where simple organisms gradually change to more elaborate forms. Opponents of this concept were led by several theologians who pointed to the biblical account of creation as set forth in the Book of Genesis. One prelate, James Ussher, calculated that creation had taken place on October 26, 4004 B.C., at 9 a.m.

Opponents of the creationist argument were encouraged by geologists who postulated that Earth is far older than 4,004 years. In 1785, James Hutton postulated that Earth was formed by an ancient progression of natural events, including erosion, disruption, and uplift. In the early 1800s, Georges Cuvier suggested that Earth was 6,000 years old, based on his calculations. In 1830, Charles Lyell published evidence pushing the age of Earth back several million years.

Amid the controversy over geology and Earth’s age, French zoologist Jean-Baptiste Lamarck suggested a theory for evolution based on the development of new traits in response to a changing environment. For example, the neck of the giraffe stretched as it reached for food. Lamarck’s theory of “use and disuse” gained favor, and his concept of “acquired characteristics” was accepted until the time of Charles Darwin, many years later.

Charles Darwin was the son of an English physician. As a naturalist on the ship H.M.S. Beagle, Darwin traveled to remote regions of South America and other destinations. His observations on this trip led him to develop his own theory of evolution. Darwin was particularly interested in the finches and tortoises of the Galapagos Islands. He pondered how different species of animals could have developed on this remote set of islands 200 miles west of Ecuador.

Darwin returned to England from South America in 1838 and continued to ponder the theory of evolution. He was influenced by Thomas Malthus’s Essay on the Principle of Population. In his book, Malthus pointed out the human population’s continual struggle for survival and that a population’s natural tendency is to produce more offspring than can possibly survive. Darwin applied this principle to animals and plants, and his theory of evolution began to develop.

In 1858, another English naturalist, Alfred Russel Wallace, developed a concept of evolution similar to Darwin’s. Wallace wrote a paper on the subject and corresponded with Darwin. The two men decided to simultaneously present papers on evolution to London’s scientific community in 1858. The next year, 1859, Darwin published his famous book, On the Origin of Species by Means of Natural Selection, or the Preservation of Favoured Races in the Struggle for Life. The book has become known simply as The Origin of Species.