Реферат: Impact of Evolution on Human Thought Evolution
Impactof Evolution on Human Thought
Evolution by definition of Webster dictionary is a gradualdevelopment of simple matters into more complex. When most of the people hear “evolution” itassociates with development or history of the earth. History of the earth compiles of gazillionsof steps. The very first step in ourhistory is a birth of the earth, which took place over 4 billion years ago.
“Powerful telescopes reveal newstars coalescing from galactic dust, just as our sun did more than 4.5 billionyears ago. The earth itself formedshortly thereafter, when rock, dust, and gas circling the sun condensed intothe planets of our solar system. Fossilsof primitive microorganisms show that life had emerged on earth by about 3.8billion years ago (Teaching about evolution and the Natural of Science, ch. 1).”
Many people throughout the centuries have been trying tofind explanations to the questions like: Why are surrounding us things the waythey are?; why some type of animals resemble another one? It was hard to answer these questions withoutproper tools, experience and background knowledge. Even nowadays, not all questions areanswered. Darwin was the first human whosucceeded in responding to these questions. He was the first one who put discovered facts and knowledge available byhis time in one big picture. In attemptsto explain the history Darwin created the most outstanding achievement of humanbeings 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 amodern person to project back to the early half of the nineteenth century andreconstruct the thinking of this pre-Darwinian period, so great has been theimpact of Darwinism on our views (E. Mayr, pp. 1)
For our furtherdiscussion, one should explicitly distinguish between evolution andevolutionary theory. Evolution (history)is a serious of facts that occurred since the birth of the earth, whileevolutionary theory is the best way available nowadays to explain why evolutionhappened the way it happened, but not otherwise. Both evolution andevolutionary theory make series of claims. Some of them are secondary and some are primary. Primary claims if proved wrong, would changeentire theory.Primary Claims of Evolution
The earth is over4 billion years old. In the past when technology was not very developed it washard to prove age of the earth. Scientistshad been aging by measuring the rate of sedimentation. Another method of defining age, which wasused in 1800s, is noticing what kinds of fossil rocks have. Currently it is done by chemical analysis ofcomposition of fossil.
“Some elements such as uranium,undergo radioactive decay to produce to produce other elements. By measuring the quantities of radioactiveelements and elements into which they decay in rocks, geologists can determinehow 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 appearright after appearance of the earth. Thefirst sings of life were dated about 550 million years ago according to theoldest fossils. This fact does notspecifically mean that where was not life forms before that time. Life forms were very simple and lacked hardparts 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 incolumns like stacked pancakes (Teaching About Evolution, ch.3, pp. 2)
Extinction is amajor feature of biological evolution. It is in a tight connection with natural selection. Natural selection works only by means ofsurviving of changes, in some sense useful, and therefore, striking root. In the consequence, fast increase of thenumbers of all organic matters in geometrical progression, every naturalhabitat already filed to the limits by its habitants. From this it follows those more adapted formswill increase in numbers and less adapted, will decrease in numbers and becomerare. Rarity of the form is apredecessor of the extinction. Everyform represented by small numbers of individuals has big chances for a completeextinction in consequence of significant climatic swings within a year or inconsequence of temporary increase of enemies. Species, most abundant of individuals, have the biggest chances forappearance at any particular time of favorable changes. Rare individuals will at any particular timechange and perfect at a slower pace and in consequence of that will be defeatedin a life struggle with changed and improved descendants of more commonindividuals. From this it follows thatsince with a passage of time natural selection “creates” new species, thanother 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 mostof the generation becomes easy pray of sea birds. Since just hatched turtles do not have a hardcover that could protect them, many of them dye in the ocean. By maturity time only about one out ofthousand turtles stay alive. Currentlythere are billions of living organisms that inhabit the earth, but theyrepresent only around one percent of all living organisms that have ever livedon the earth since its birth. Ninetynine percent dyed out.<span Times New Roman",«serif»;mso-fareast-font-family:«Times New Roman»; mso-ansi-language:EN-US;mso-fareast-language:EN-US;mso-bidi-language:AR-SA">
Another example that mechanisms ofevolutionary change are observable and verifiable is the one described by HenryWalter Bates.
“In 1862, Henry Walter Bates made brilliant use of the Darwinian mechanism ofnatural selection asking why it is that some species of butterfly very closelymimic species of butterfly, essentially quite different, Bates proved beyonddoubt that the answer lies in adaptive advantage brought about by naturalselection. The mimicked insects arehighly distasteful to birds who think that they belong to distastefulspecies. Bates showed experimentallythat birds learn to avoid distasteful insects, and that the closer the mimic,the less change there is that the insect will be eaten.”
When the earth appeared for the first time it was very differentfrom its current conditions. The surfaceof the earth was represented by bare bedrock. At the time of its birth, the earth represented cold matter, close byits composition to meteorites. Materialit was mad of, contained radioactive elements. In consequence of the heat excretion while radioactive decomposition ofthe core and gravitational compression. However, because of continuous loss of heat through he surface and lackof radiation heat complete melting of the earth did not happen. In result of earth’s melting, water anddifferent gases were brought up to the surface. This water began formation of hydrosphere.
Location of continents and oceans were very different. According to Wegener’shypothesize, which he later supported by evidence, earth’s continents used tobe a single land, which was called Pangea. About two hundred million years ago Africaand South America slowly began their movement toward their currentlocation. Wegenersupported his hypothesize by geological and biological evidence. At the place where the continents werealigned, were found fossilized animals and plants dated more than two hundredmillion years old. Besides, if Africaand South America had always been separate continents as they are now, both ofthem would have had very different flora and fauna, which are not.
Starting at 1950 up to 1970 evidence begin exposing tothe world that support hypothesis of continent’s slow movement. Sonar mapping of the ocean floor showedwinding, continuous ridges system around the planet. The ridges appeared where molten matter wascoming up from the earth’s inside.
Not onlytopography of the earth has changed, but composition atmosphere has changed aswell. Current atmosphere contains a lotof oxygen, which is result of existence of life. During photosynthesis, green plants consumewater and dioxide and release oxygen in atmosphere. This is considered to be a secondary claimbecause even if the earth would not developed as it considered, it would haveno impact on evolutionary theory.
Origin of humanbeing was an interest of human more than origin of plant and animals. Attempt to understand and explain origin ofhumans is expressed in religions, legends of all kind of trails and folks. For a long period of time science knowledgewere abrupt and incomplete in order to solve a problem of human origin. Only in 1857 Darwin expressed hypothesis, andin 1871 in his book “The Origin of man and relation to sex,” convincelly proved that humans originate from pre-existinghumanlike, but were not created by intelligent designer. Role of social factors, which was pointed outby Darwin, was detailly described by Fredrik Engels in his book “Role of labor in the process of turningape into humans.” (1896)
Human andvertebrates commonness is strongly supported by similar arrangement of internalorgans: skeleton, nerve system, blood system, respiration, and digestion.
Rudiments andatavisms 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 ananimal ancestor. An external tail, whichsometimes people are born with, is related to atavisms. Another atavism is abandon hair on the faceand body.
Common details ofthe body arrangement are evidence of close relativenessof human and anthropoids: wrist with flat nails, shape of eyes and years, thesame number of canine and molar teeth, complete change of baby teeth, and soforth. Physiological commonness is veryimportant: the same blood groups,diseases (tuberculosis, fly, smallpox, cholera, AIDS, pneumonia) and parasites(louse). Besides numerous commonfeatures, there is a number of explicit differences evidencing that its currentstage, human is considered to be different species. Only human has ability of upright walking andrelated to that peculiarity of structure of the S-shaped backbone with explicitneck and lumber bend, low extended pelvis, and etc. Human skull is higher and more roundedwithout superciliary arch; brain part of skull is inmost part dominated by facial; high forehead, weak jaws with small canine. Human brain is about two and half timesbigger than one of humanlike apes, and 3-4 times heavier.
Human being evolved from other pre-existingspecies. Even in ancient times it hasbeen noticed that humans have a lot of in common with a other animals just likeother animals human had the same internal organs (heart, lungs, liveretc.). Ancient Greeks had a scale ofliving organisms known by their time. Human being was placed at the end of the scale. Below were higheranimals like houses, sheep and so forth, but it is hard to believe that humanswere next step in the biological evolution of living organisms right afterhigher animals. Only by the eighteenthcentury ape-like being became known to Europe. This discover shed light on ahuge gap between higher animal and humans (Darwinism defended, Ruse, pp.230). After that some scientists (forexample Huxley) assumed that humans descended from apes. Later, having examined all differencesbetween apes and humans, Huxley came to conclusion that humans and apesdescended from a common ancestor. Onewould probably ask why our common ancestor did split into two branches, apesand Australopithecus afarensis (which is consideredto be an ancestor of all hominids). There is a scientific explanation, which relates to climatic changes inAfrica. Our ancestor was used to live inthe area of heavy precipitation. With a passage of time climate started turninginto dry one and forestlands began retreating, leaving behind Savannah’s. Some species stayed in dwindlingforests. Others (our ancestors) startedadvancing toward opened spaces.
With a changeof place of inhabitation, there were some changes in diet of our ancestor. Anthropologists suggested that toothreduction took place because our ancestor started to use grass seeds and thelike as a food source (Darwinism Defended).
H. sapiens<img src="/cache/referats/9853/image001.gif" v:shapes="_x0000_s1026 _x0000_s1027 _x0000_s1028 _x0000_s1029 _x0000_s1030 _x0000_s1031 _x0000_s1032 _x0000_s1033 _x0000_s1034 _x0000_s1035 _x0000_s1036">
Major Claims of Evolutionary Theory
Natural selectionis the major moving factor of the evolution of the living organisms. Almost at the same time, several Englishnaturalists arrived at the idea of existence of natural selection (P. Mathew(1831), A. Blight (1935), A. Wallace (1858), C. Darwin (1858)), but only Darwinsucceeded in exposing of the meaning of this phenomenon as the major factor ofevolution and created the theory of natural selection. On the contrary, to artificial selection heldby humans, natural selection is conditioned by influence of surroundingenvironment upon the organisms. According to Darwin natural selection is survival of the mostaccommodated organisms, in consequence of which, on the basis of undefinedinherited changeableness in the series of generations evolution occurs.
In process ofnatural selection species more accommodated to surrounding environment survive,those who do are not, go extinct. Explicit example of that is our ancestors that had advantage of standingupright to look out and look for possible object of prey. Natural selection does not specifically haveto lead to perfection. It leads only tosurviving of species that can survive. If entire kind of particular animals can not survive in changedenvironment, entire kind will dye out.
“Organisms in nature topicallyproduce more offspring that can survive and reproduce given the constraints offood, space, and other resources in the environment. These offspring often differ from one anotherin ways that are heritable—that is, they can pass on the differencesgenetically to their own offspring. Ifcompeting offspring have traits that are advantageous in a given environment,they will survive and pass on those traits. As differences continue to accumulate over generations, populations oforganisms diverge from their ancestors.”
Process ofnatural selection consists of two steps: the first one is reproduction of genetically different species; thesecond step is surviving of the most adopted individuals in surroundingenvironment. An example can be nest of birds in which some nestlings have alittle bit different coloring than others. If this coloring better matches the tree these birds in habit, this willgive them advantage of better hiding from predators, which leads to increase inchanges of reproduction. Below areexample that Wallace, Alfred Russle uses in his book“Contributions to the theory of Natural Selection” to demonstrate naturalselection.
“The Duke of Argyll, in his “Reigh of Law,” has pointed out the admirable adaptation ofthe colors of the woodcock to its protection. The various browns and yellows and pale ash-color that occur in fallenleaves are all reproduced in its plumage, so that when according to its habitit rests upon the ground under trees, it is almost impossible to detectit. In snipes the colors are modified soas to be equally in harmony with the prevalent forms and colors of marshyvegetation. Mr. J.M.Lester, in a paperread before the Rugby School Natural History Society, observes: --“Thewood-dove, when perched amongst the branches of its favorite fir, is scarcelydiscernible; whereas, were it among some lighter foliage, the blue and purpletints in its plumage would far sooner betray it. The robin redbreast too, although it might bethought that on its breast made it much easier to be seen, is in reality not atall endangered by it, since it generally contributes to get among some russetor yellow fading leaves, where the red matches very well with the autumn tints,and the brown of the rest of the body with the bare branches.”
Core of naturalselection is variation within the kind. If variation does not exist either entire kind will survive and stayunchanged or it will go extinct. Butwhat it a source of variation? The ultimate source of variation is mutations ingenes. If new traits gained throughmutation leads to successful survival and reproduction than new traits will beinherited and spread within the population. Mutation is random, but natural selection is not.
All living organisms that currently inhabit the earthshare common ancestry. Through thehistory by means of natural selection and variation first, simple forms of lifewere evolving into different, more complex forms. How to prove it?
“The discovery of the structure ofDNA by Francis Crick and James Watson in 1953 extended the study of evolutionto most fundamental level the sequence of the chemical basis in DNA bothspecifies the order of amino acids in proteins and determines which proteinsare source of both change and continuity in evolution. The modification of DNA through occasionalchanges or rearrangements in the base sequences underlies the emergence of newtraits, and thus of new species, in evolution. At the same time, all organisms use the same molecular codes totranslate DNA base sequences into Protein amino acid sequences. This uniformity in genetic code is powerevidence for the interrelatedness of living things.” (Teaching About Evolutionand the Nature of Science, ch. 2, pp. 4)
Another powerful argument that supports common ancestryis a fact that man is developed from an ovule, about the 125th of aninch in diameter, which does not differ from the ovules of other animals. At a very early period, the embryo can hardlybe distinguished from another member of vertebrate kind.
In order toconvince one that evolution happened the way evolutionary theory describes itevidences must be presented. Majorevidence and argument of evolutionary theory is that all of the mechanisms ofevolutionary theory change are currently observable. Let us take for example main mechanism ofevolutionary change—natural selection. Nowadays our society is facing serious public health problem. Bacteria that medicine used to successfullyfight with antibiotics is becoming more resistant to one. This means that week bacteria go extinct andonly strong (more resistant to antibiotics) bacteria survived. (Teaching aboutevolution, ch. 2, pp. 5) “continued use and overuse of antibiotics hashad the effect of selecting for resistant population because the antibioticsgive these strains and advantage over non-resistant strains”Bibliography
1)<span Times New Roman"">“Long Argument,” Ernest Mayr,Harvard University Press, 1991.
2)<span Times New Roman"">“Darwinism defended,” Michael Ruse, Addison-WesleyPublishing Company, 1982.
3)<span Times New Roman"">“The Descent of Man and Selection in Relation toSex,” Charles Darwin, 1974.
4)<span Times New Roman"">“Wonderful Life,” Stephen Jay Gould, W.W.Norton & Company, 1989.
5)<span Times New Roman"">“Contributions to the theory of natural selection,”Wallace, Alfred Russel, AMS Press, 1973.
<span Times New Roman",«serif»;mso-fareast-font-family:«Times New Roman»;mso-ansi-language: EN-US;mso-fareast-language:EN-US;mso-bidi-language:AR-SA">Teaching about Evolution