Essay, Research Paper: Theories Of Evolution

What is a theory? What are some different theories of evolution? These questions and many more will be answered in this paper. This paper includes some amazing facts. People once believed that maggots (a fly-like insect) came from rotten meat, not from their parents like all animals do. Charles Darwin and Alfred Wallace came up similar theories on Natural Selection (a theory that is explained later in this paper) at around the same time, but Darwin?s theory is more commonly heard of. Also, Pierre Louis Moreau de Maupertuis was the first known theorist to come up with a theory of evolution. The purpose of this paper is to show that there are many theories of animal evolution that are still being talked about today, and to discuss some of those theories.
A scientific theory is like the last step to the scientific method. It?s different from an everyday theory (Berra, 1990, pg.4). An example of a scientific theory is Alfred Wegener?s theory of continental drift which states that the continents were once connected and formed one continent called Pangaea. Theories are tested. If they?re good, they have known facts and might also make predictions about new theories that haven?t yet been observed or tested (Stein, 1986, pg. 17).
Charles Darwin was a theorist who developed the theory of Natural Selection. Darwin went on a trip to the Galapagos Islands. On the islands, he observed and studied the different species of birds and tortoises on each island. He noticed the similarities and differences between the finches. From his observations her stated, ?:To my astonishment, I discovered that all the finches from Charles Island belonged to one species (and had the same shaped beak); all from Albermarle Island belonged to another species (and had the same shaped beak); and all from James and Chatham Islands to still other species.? (Gallant, 1989). This quote means that Darwin noticed

how the different species of the same type of animal vary. In this theory, there are three important ideas. The first idea is, not every being in a species is identical. They can vary in color or size, for example. The second idea is, an offspring can inherit some of the variations from their parents. For example, if one bird is dark blue and its sibling is light blue, the light blue bird would have a light blue offspring, and the dark blue bird would have a dark blue offspring. The third idea is, an environment can put pressure on a species to survive because they might have to fight for food and shelter (Time Life, 1992, pgs. 12-13). Another element of Natural Selection is, breeders breed animals that people want, so Darwin thinks that the same thing must happen in nature. The strong and fast animals survive, and the slow and weak animals die out. The earth is already overpopulated, so there just aren?t enough of life?s necessities such as food and shelter to go around. All organisms have their own special traits, but some might lose that same trait and not pass it on to their young. This way, different species evolve (Pond, 1991, pgs. 38-39).
Between the years of 1900 and 1925, many of Darwin?s theories were proven to be incorrect. Alfred Wallace was another theorist who, around the same time as Darwin, came up with a similar theory on Natural Selection, but Darwin?s theory is much more commonly discussed (Grolier Multimedia, 1993).
Francesco Redi was a theorist who proved that organisms did not evolve from nonliving organisms like people thought, but from other living organisms. For instance, maggots didn?t evolve from rotting meat, but from other maggots. He also saw that organisms changed their form. The maggots were inactive and turned into hard balls. Redi had a hypothesis that the balls were eggs. Redi then started the foundation of biology called Biogenesis. Biogenesis is that like only comes from other living things (Gallant, 1989, pgs. 27-30).
Jean Baptiste Lamarck was a theorist who created Lamarckism. Lamarckism is

the theory that in every generation, things change a little. One example of this theory is that a giraffes neck used to be short, but in every generation, they stretched their necks further to reach the leaves of tall trees and eventually, their necks were long. Many other people believed the same thing, but genetics proved the theory to be incorrect. Traits can?t change genetic makeup (Grolier Multimedia, 1993).
There are many other theories of evolution. Elaine Morgan is a theorist who developed the sea-ape theory for human evolution. The sea-ape theory is that humans (and apes) evolved from the sea. Evidence of this theory is that the human heart slows down when the head goes underwater to help a person hold their breath. Also, an extra layer of fat is located under the skin to keep a person warm while in cold water (Dickinson, 1992). Gregor Mendel is a theorist who discovered the basics of inheritance, such as inheriting a certain trait from a parent, in 1865. Strangely, Darwin didn?t know of his work because it was lost, and scientists found it again around 1900. Carolus Linnaeus saw the close similarity between some species of animals, like between a house cat and a lion. Thomas Robert Malthus thought that because of all the famine and disease in the world, animal growth was limited to a certain amount. Pierre Louis Moreau de Maupertuis was the first theorist to come up with a theory of evolution. His theory was that hereditary material went from parent to offspring (Grolier Multimedia, 1993).
In conclusion, there are many theories of evolution. These theories are based on research and observation of the earth and of animals. None of these theories would be complete if Francesco Redi hadn?t proved that life only comes from other life. Because there are so many theories, it is hard for me to choose which one I believe. If I had to pick what I think is the most logical theory, I would pick Elaine Morgan?s sea-ape theory because I partially agree that we evolved from the sea, but maybe it is easier for you to choose which theory you believe. Darwin?s theory is currently the

most popular and most commonly heard of theory of evolution because it has the most amount of information. Although Lamarckism was very common too, until it was proven to be incorrect. Since there are so many theories of evolution, it is very likely that you have heard of another one.