Impact of Evolution on Human Thought
Evolution by definition of Webster dictionary is a gradual development of simple matters into more complex. When most of the people hear "evolution" it associates with development or history of the earth. History of the earth compiles of gazillions of steps. The very first step in our history is a birth of the earth, which took place over 4 billion years ago.
"Powerful telescopes reveal new stars coalescing from galactic dust, just as our sun did more than 4.5 billion years ago. The earth itself formed shortly thereafter, when rock, dust, and gas circling the sun condensed into the planets of our solar system. Fossils of primitive microorganisms show that life had emerged on earth by about 3.8 billion years ago (Teaching about evolution and the Natural of Science, ch. 1)."
Many people throughout the centuries have been trying to find explanations to the questions like: Why are surrounding us things the way they are?; why some type of animals resemble another one? It was hard to answer these questions without proper tools, experience and background knowledge. Even nowadays, not all questions are answered. Darwin was the first human who succeeded in responding to these questions. He was the first one who put discovered facts and knowledge available by his time in one big picture. In attempts to explain the history Darwin created the most outstanding achievement of human beings that had enormous impact of our thinking—evolutionary thinking. Ernest Mayer, in his book "One Long Argument" says following about impact of Darwin's work on human thinking.
"It is almost impossible for a modern person to project back to the early half of the nineteenth century and reconstruct the thinking of this pre-Darwinian period, so great has been the impact of Darwinism on our views (E. Mayr, pp. 1)
For our further discussion, one should explicitly distinguish between evolution and evolutionary theory. Evolution (history) is a serious of facts that occurred since the birth of the earth, while evolutionary theory is the best way available nowadays to explain why evolution happened the way it happened, but not otherwise. Both evolution and evolutionary theory make series of claims. Some of them are secondary and some are primary. Primary claims if proved wrong, would change entire theory.
Primary Claims of Evolution
The earth is over 4 billion years old. In the past when technology was not very developed it was hard to prove age of the earth. Scientists had been aging by measuring the rate of sedimentation. Another method of defining age, which was used in 1800s, is noticing what kinds of fossil rocks have. Currently it is done by chemical analysis of composition of fossil.
"Some elements such as uranium, undergo radioactive decay to produce to produce other elements. By measuring the quantities of radioactive elements and elements into which they decay in rocks, geologists can determine how much time has elapsed since the rock cooled from initially molten state (Teaching About Evolution and the Nature of Science)."
Life on the earth did not appear right after appearance of the earth. The first sings of life were dated about 550 million years ago according to the oldest fossils. This fact does not specifically mean that where was not life forms before that time. Life forms were very simple and lacked hard parts like bones or shells and could rarely preserve in the fossils.
"However, a few pre-Cambrian organisms left traces of their existence. Some ancient rocks contain stromatolities—the remnants of bacteria that grew in columns like stacked pancakes (Teaching About Evolution, ch. 3, pp. 2)
Extinction is a major feature of biological evolution. It is in a tight connection with natural selection. Natural selection works only by means of surviving of changes, in some sense useful, and therefore, striking root. In the consequence, fast increase of the numbers of all organic matters in geometrical progression, every natural habitat already filed to the limits by its habitants. From this it follows those more adapted forms will increase in numbers and less adapted, will decrease in numbers and become rare. Rarity of the form is a predecessor of the extinction. Every form represented by small numbers of individuals has big chances for a complete extinction in consequence of significant climatic swings within a year or in consequence of temporary increase of enemies. Species, most abundant of individuals, have the biggest chances for appearance at any particular time of favorable changes. Rare individuals will at any particular time change and perfect at a slower pace and in consequence of that will be defeated in a life struggle with changed and improved descendants of more common individuals. From this it follows that since with a passage of time natural selection "creates" new species, than other species become more rare, and finally extinct.
For example, during laying eggs season, sea turtles hay hundreds of thousands eggs. While hatching and getting to the ocean most of the generation becomes easy pray of sea birds. Since just hatched turtles do not have a hard cover that could protect them, many of them dye in the ocean. By maturity time only about one out of thousand turtles stay alive. Currently there are billions of living organisms that inhabit the earth, but they represent only around one percent of all living organisms that have ever lived on the earth since its birth. Ninety nine percent dyed out.1
Another example that mechanisms of evolutionary change are observable and verifiable is the one described by Henry Walter Bates.
"In 1862, Henry Walter Bates made brilliant use of the Darwinian mechanism of natural selection asking why it is that some species of butterfly very closely mimic species of butterfly, essentially quite different, Bates proved beyond doubt that the answer lies in adaptive advantage brought about by natural selection. The mimicked insects are highly distasteful to birds who think that they belong to distasteful species. Bates showed experimentally that birds learn to avoid distasteful insects, and that the closer the mimic, the less change there is that the insect will be eaten."
Secondary Claims of Evolution
When the earth appeared for the first time it was very different from its current conditions. The surface of the earth was represented by bare bedrock. At the time of its birth, the earth represented cold matter, close by its composition to meteorites. Material it was mad of, contained radioactive elements. In consequence of the heat excretion while radioactive decomposition of the core and gravitational compression. However, because of continuous loss of heat through he surface and lack of radiation heat complete melting of the earth did not happen. In result of earth's melting, water and different gases were brought up to the surface. This water began formation of hydrosphere.
Location of continents and oceans were very different. According to Wegener's hypothesize, which he later supported by evidence, earth's continents used to be a single land, which was called Pangea. About two hundred million years ago Africa and South America slowly began their movement toward their current location. Wegener supported his hypothesize by geological and biological evidence. At the place where the continents were aligned, were found fossilized animals and plants dated more than two hundred million years old. Besides, if Africa and South America had always been separate continents as they are now, both of them would have had very different flora and fauna, which are not.
Starting at 1950 up to 1970 evidence begin exposing to the world that support hypothesis of continent's slow movement. Sonar mapping of the ocean floor showed winding, continuous ridges system around the planet. The ridges appeared where molten matter was coming up from the earth's inside.
Not only topography of the earth has changed, but composition atmosphere has changed as well. Current atmosphere contains a lot of oxygen, which is result of existence of life. During photosynthesis, green plants consume water and dioxide and release oxygen in atmosphere. This is considered to be a secondary claim because even if the earth would not developed as it considered, it would have no impact on evolutionary theory.
Origin of human being was an interest of human more than origin of plant and animals. Attempt to understand and explain origin of humans is expressed in religions, legends of all kind of trails and folks. For a long period of time science knowledge were abrupt and incomplete in order to solve a problem of human origin. Only in 1857 Darwin expressed hypothesis, and in 1871 in his book "The Origin of man and relation to sex," convincelly proved that humans originate from pre-existing humanlike, but were not created by intelligent designer. Role of social factors, which was pointed out by Darwin, was detailly described by Fredrik Engels in his book "Role of labor in the process of turning ape into humans." (1896)
Human and vertebrates commonness is strongly supported by similar arrangement of internal organs: skeleton, nerve system, blood system, respiration, and digestion.
Rudiments and atavisms are very important evidences of human relatedness to animals. There are about 90 rudiments in human body: coccyx bone (remaining of the reduced tail); folds in the corner of the eyes (remaining of the blinking tympanum; thin body hair (remaining of the hair). All these rudiments are inherited from an animal ancestor. An external tail, which sometimes people are born with, is related to atavisms. Another atavism is abandon hair on the face and body.