Evolution Essay ⋆ Environment Essay Examples ⋆ EssayEmpire

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Evolution is a theory of the origin and transformation of life forms over time. Plants and animals exist on earth in an enormous abundance of forms or species. Evolution seeks to explain scientifically the origin and the development of new species from old species, as well as the beginning of life itself.

The existence of enormous numbers of older species, most of which are now extinct, is supported by the evidence of fossils. The rise of newer species is supported by a variety of evidences, including their living existence. Evolution seeks to explain with only natural evidences that these enormous numbers of species (both extant and extinct) originated eons ago in the Pre-Cambrian Era as single-celled life forms. It also seeks to show that over the last 600 million years (when life first appeared on earth), those life forms have changed. The claim that life has evolved, that is, that species have changed from one kind of species into a new species, has been the subject of enormous scientific, religious, and political controversy.

The theory of evolution is closely associated with Charles Darwin, who published The Origin of the Species in 1859. Darwin’s publication was subsequently followed by many others. However, his earlier work, The Voyage of the Beagle, described the five years that he spent as a naturalist circumnavigating the world. It was a public version of the journal he kept during his journey.

Darwin’s journey aboard the H. M. S. Beagle had been his first job after college. In The Voyage of the Beagle, Darwin described how he began the voyage as a person who accepted the view, like many others, that the world was of a relatively young age: between 6,000 and 10,000 years old. The theory estimating the age of the earth at 6,000 or more years had been propounded by Bishop James Usher (1581-1656), who derived his calculation by counting the generations of people in the Bible.

As the Beagle sailed south, it took Darwin on a journey that enabled him to see vast regions of the world, including much of South America in what was still pristine condition. Eventually, he was forced to extend the timeline for the age of the earth to make it longer and longer.

Darwin described how he saw thick beds of sea shells along the coast of Argentina and was unable to believe that these were the product of a single global flood. He visited older mountain ranges in South America and saw newer ranges, thus forcing him to conclude that it took enormous numbers of centuries for the natural phenomena that he was observing to have occurred.

While the crew of the Beagle was making soundings to create naval charts of the coasts of South America, Darwin as the professional naturalist explored inland in Brazil, Argentina, and Uruguay. He collected great numbers of specimens of birds, plants, animals, reptiles, and minerals. These were catalogued and shipped to England for analysis. There are warehouses today with this great collection of specimens available for comparison with the fauna and flora of the regions that Darwin first explored.

As Darwin traveled, he saw enormous geological formation and evidence of change. He was also exposed to a massive earthquake while visiting Chile. Afterward, he was able to see geological forces at work building mountains. His visit to the Galapagos Islands was crucial to the development of his theory of evolution. It led him to develop the idea that the species of plants and animals that populate the world are not fixed but change.

While preparing to publish, Darwin read Thomas Malthus’s book, Essay on the Principles of Population, which postulates that populations grow geometrically while food supplies grow only arithmetically. The Malthusian principle is that life is a struggle for survival in the face of enormous competition for limited resources.

In 1859, Darwin published his views on the mutability of the species. His theory was met with numerous responses. One reaction was ready acceptance of the idea, because the developmental philosophy (German Idealism) of G.F.W. Hegel had helped to prepare the way. Darwin’s ideas influenced Karl Marx and his views on the development of world history and of human society. Using classes as his basic unit of analysis, he concluded that eventually the capitalist class would become extinct, and the proletarian class would take over the world.

In 1860, the theory of natural selection was applied to societies. The idea that people in societies struggle for survival was developed by Herbert Spencer. The natural selection in nature’s struggle to survive was transformed into Social Darwinism and interpreted as the survival of the fittest. The fittest, it turned out, were the rich and successful. In America and elsewhere, Social Darwinism was used to justify numerous laws that were harmful to the poor.

A famous Supreme Court decision, centered on the evolution debate, was known as the Scopes Monkey Trial. The case pitted Clarence Darrow, a leading trial lawyer of the day, against populist champion, unsuccessful presidential candidate, and former Secretary of State William Jennings Bryan. The outcome of the trial was mixed.

The verdict went against Scopes for teaching evolution at school. However, public opinion went against Bryan and the opponents of evolution. The case was broadcast on radio and was the first electronic media event. Eventually being for or against evolution became a political litmus test, and the issue is one that is alive and well today.

Those who adhered to a strict creationist viewpoint won the battle, but lost the campaign. Other supporters have opposed evolution with the theory that the universe exhibits evidence of intelligent design, a scientific version of a teleological argument for the existence of God.

Darwin, along with his supporter Julian Huxley, engaged in a long debate over the nature of evolution. The idea was not completely new, as Darwin acknowledged in The Origin. At least the germ of the idea can be found in the metaphysical philosophy of the Greek philosopher-scientists, as early as five centuries before the birth of Christ. The Thales (624-548 B.c.) and Anaximande (588-24 B.c.), physical monists and members of the Miletian Schools, included developmental elements in their philosophies. The pluralist philosopher Empedocles (495-35 B.c.) saw fossils in the mountains of Sicily and suggested that life began in the sea along with others after them had espoused the idea.

The works of Aristotle were to give fodder to later opponents and supporters of the idea. From Aristotle, opponents took the idea of the fixity of the species and applied it to the Genesis account of creation. They interpreted the meaning of created “after their own kind” as an Aristotelian fixity of the species. However, during the Age of Discovery, so many new plants and animals brought new questions to help with understanding the enormous diversity of the species along with the idea of extinction.

In the 1700s, lawyer James Hutton applied the idea of uniformity to the development of species. In 1802, John Playfair published Illustrations of Huttonian Theory of the Earth. The idea of uniformitarianism was given further explication. Then Sir Charles Leyll published in 1832 Principles of Geology, which espoused inorganic evolution.

Inorganic evolution is the view that the inorganic world also has a biography that can be discovered and read. This view has been extended to the whole universe. The dominant theory today is the Big Bang Theory, which has a part of modern cosmology.

Organic evolution was espoused prior to Darwin by Jean Baptiste de Lamarck in Philosophie Zoologique (1809). He claimed that species adapted to life and then passed these adaptations on to their offspring. The Lamarckian theory seemed to apply nicely to the development of species. While this theory was also to heavily influence Social Darwinism, it was eventually to be refuted by the work in genetics of Gregor Mendel, a monk and a physicist. In order to help his fellow monks with their crops, he undertook crop experiments. With a mathematical eye to simple laws, he stated the conclusions of his experiments with breeding peas in a paper in 1865. Unfortunately, the paper was published in an obscure journal and was not widely read until 1900. By 1909, the term gene was invented to describe the hereditary particles that were described by Mendel in his paper.

Explaining Evolution

Darwin’s theory explained that species show variation, which is a characteristic of all plants and animals. Darwin did not know that species undergo mutations, so he stressed slow incremental changes. He also observed that more individual organisms are born than there is food to support them, implying their struggle to survive in competition with each other and also against the vicissitudes of nature. In addition, the numerous variations presented by the members of different groups make it easier for some to survive and for others to fall by the wayside in the struggle for existence. The idea of the survival of the fittest therefore lies at the center of the process of natural selection. And as individuals survive, they are more easily able to pass these successful variations to their own offspring through succeeding generations.

The slight changes in the generations makes offspring better adapted to the changes in the environment that facilitate survival and propagation. Given enough generations, the changes can be significant enough that new species develop through the ongoing process of natural selection. The process of natural selection then can cause divides, so that one line develops characteristics that mark it as a different species from another line from the same parents that becomes a different species.

The intuitive appeal of Darwin’s theory soon promoted its wide acceptance. It also continued to be rejected by others. One of the concerns addressed by some was that variations appear in many species that may be interesting but that have nothing significant about them. These variations neither help nor hinder the survival of the individuals with the characteristics nor enhance their survival. At the time of Darwin, this was a puzzle. Today, it is an accepted fact that these variations are simply nonadaptive differences controlled by genes.

Darwin’s theory faced a different challenge after 1900, when the work of Mendel was discovered. Two corrections were made necessary by Mendel’s theory of genes. The first was that to be useful for natural selection, genetic material must be inherited as a variation. Secondly, the fact of geographic or genetic isolation is necessary to prevent interbreeding.

The theory of evolution as espoused by Darwin did not include genetics; modifications were seen as evolutionary changes. However, the variations between living organisms that are caused by environmental actions are modifications, not permanent genetic changes that mutations in genes cause. For example, physical or chemical actions on an embryo may cause it to develop a congenital herniated diaphragm, a modification of the normal diaphragm. However, if the infant lived to reproduce that birth defect, it would not be transmitted to offspring. It is merely a modification of a physical feature that was probably caused by a chemical interference in the fetus’ development. For each step in evolution to occur, an infant with a birth defect would have to have a line of descendants with the same defect.

Another feature of Darwin’s version of the theory of evolution was that isolation was necessary for the members of a group to change so that a new species would eventually develop that could not longer breed successfully with other descendant of the original stock. Geographic isolation is the most common kind, and was what Darwin found in the Galapagos Islands as well as what primate researchers think is the source of the differences between chimpanzees and bonobos. Separated by the Congo River, they have followed different developmental tracks.

Another form of isolation is genetic isolation. If two isolated groups that were originally the same species are reunited and after breeding produce only sterile offspring, then genetic isolation has occurred. Ecological isolation can occur if the same species develops in close proximity, but in different local habits they may cease to interbreed. It may be due to such things as breeding at different times of the year as well. Darwin also assumed, erroneously, that variations were permanent.

Preadaptation, a theory of natural selection, recognizes that mutations occur randomly and does not have to be beneficial. It can be insignificant, or so harmful that it leads to a failure to survive. There are several types of mutations. Chromosomal mutations change the structure of the chromosome. Changes by addition or subtraction can produce polyploids that are larger and more robust than their parents. This feature of change has been used to produce bigger cultivated varieties of crops.

The theory of evolution is not without its difficulties, one of which has to do with prediction. It is virtually impossible to predict when genetic mutations or isolation events that will occur as the first step in the evolution of a new species. Another problem is that early evolutionists held to the idea that evolution was an almost deterministic straightline path of progress, or orthogenesis. Investigators, especially paleontologists, have reported that the fossil record does not support this viewpoint. Rather, fossils show that orthogenesis is not normal and has probably never occurred. Species seem to flourish and then experience a massive extinction. The survivors of the few remaining species then repopulate and evolve a new set of species.

The late Stephen Jay Gould argued that the early understanding of evolution was deeply influenced by the idea of progress. This led to ideas that were rigidly deterministic and value-laden even when they appeared not to be. In fact, in the early 1900s, the idea of progress and racism were closely associated, and was assumed that progress was always from primitive to superior, which acquired a moral status: It was good, while the primitive was bad.

Another theory of evolution is hybridization. African bees bred with South American bees produce killer bees, a hybrid that is more aggressive and a better producer of honey than the gentler European honey bee. Whether this is a hybrid that will lead to future changes and new species of bees remains to be seen. If so, then it will support the idea that cross fertilization is what led to the development of the numerous species, at least in some cases.

At stake in the theory of evolution is the truth about the origin and development of life. Also at stake is the worth of people and of the world. If life is a mere cosmic accident, does that mean that there are only the values that the strongest impose? Or was life brought forth by divine fiat speaking the Word? If so, then humans created in the image of their creator are valuable and are worthy of respect. If not, perhaps anything goes in the survival of the fittest.

Bibliography:

Michael J. Behe, Darwin’s Black Box: The Biochemical Challenge to Evolution (Free Press, 2006);
Charles Darwin, The Origin of the Species: By Means of Natural Selection or the Preservation of Favoured Races in the Struggle for Life (New American Library, 1958);
Douglas Futuyma, Evolution (Sinauer Associates, Incorporated, 2005);
Stephen Gould, Wonderful Life: The Burgess Shale and the Nature of History (W. W. 1989);
Stephen Jay Gould, Ever Since Darwin: Reflections in Natural History (W. W. Norton, 1992): Stephen Jay Gould, Rocks of Ages: Science and Religion in the Fullness of Life (Ballantine Books, 1999);
Stephen Jay Gould, The Panda’s Thumb: More Reflections in Natural History (W. W. Norton, 1992);
Phillip Johnson, Darwin on Trial (Intervarsity Press, 1993);
Eli C. Minkoff, Evolutionary Biology (Addison-Wesley Publishing Co., 1984);
Ralph O. Muncaster, Dismantlling Evolution: Building the Case of Intelligent Design (Harvest House Publishers, 2003);
James Lawrence Powell, Night Comes to the Cretaceous: Comets, Craters, Controversy, and the Last Days of the Dinosaurs (Harcourt Brace & , 1998);
Mark Ridley, Evolution (Blackwell Publishers, 2003);
William Schopf, Cradle of Life: The Discovery of Earth’s Earliest Fossils (Princeton University Press, 1999);
Bernard Wood, Human Evolution: A Very Short Introduction (Oxford, 2005).