| [ freeeXpression ] in KIDS 글 쓴 이(By): typhoon (♥한윤수♥) 날 짜 (Date): 1996년04월21일(일) 17시06분27초 KST 제 목(Title): 진화는 사실이며 이론이다 The talk.origins Interactive FAQ Korean Server 진화는 사실이며 이론이다 (Evolution is a Fact and a Theory) Larry Moran 번역 김진숙 jskim@bioinfo.kordic.re.kr (Last updated: 1/22/93) 비과학자들이 생물학적 진화를 이야기할 때는 진화의 정의가 가지는 두가지 다른 측면을 종종 혼돈한다. 한면에서는 현대의 생물이 더 오래된 조상으로부터 진화해 왔는 지, 또는 지금도 종들이 변화를 계속하고 있는 지의 여부에 관한 의문이다. 다른 면에서는 관찰된 변화들의 기작 ... 진화가 어떻게 일어났는가? 하는 의문들이 있다. 생물학자들은 생물학적 진화의 존재를 사실로 받아들인다. 이것은 지금 보여줄 수도 있고, 과거에 진화가 일어났다는 역사적인 증거는 저항할 수도 없는 것이다. 그러나 과학자들은 진화의 정확한 기작에 대해서는 불분명하다는 것을 즉시 받아들인다; 진화의 기작에 대해서는 몇가지 이론들이 있다. 스티븐 J. 굴드 (Stephen J. Gould) 는 다른 사람들과 마찬가지로 이런 점을 말하고 있다. "미국말로 "이론"이란 말은 종종 "불완전한 사실"이란 의미를 가진다 - 확신의 단계는 부분적으로 사실에서 이론에서 가설에서 추측으로 내려간다. 따라서 창조란들의 다음 주장의 힘을 느껴보라: 진화는 "단지" 하나의 이론일 뿐이며 현재는 이 이론의 많은 면에 있어서도 격렬한 논쟁이 일고 있다. 만약 진화가 사실보다는 단계가 낮고, 과학자들이 그 이론에 대해서조차 제대로 자신들의 믿음을 가질 수 없다면, 거기에서 우리는 무슨 확신을 가질 수 있을까? 실제로 미국의 전대통렬 레이건은 댈러스의 한 복음단체앞에서 이런 주장을 했다 (나는 진심으로 이 말이 선거용이었길 바란다) : '음, 그것은 이론입니다. 그것은 단지 과학적 이론일 뿐이며 최근 몇년동안 과학계의 도전을 받아왔습니다 - 즉 그것은 과학계에서 전처럼 틀림없는 것으로 받아들여지고 있지는 않습니다.' 물론 진화는 하나의 이론이다. 그것은 사실이기도 하다. 그리고 사실과 이론은 다른 것이다. 이들은 명확함이 증가하는 순서대로 계단을 이루는 사다리가 아니다. 사실은 이 셰계의 자료들이다. 이론들은 사실을 설명하고 해석하려는 사상들의 구조체이다. 과학자들이 사실을 설명하는 다른 이론을 반박할 때도 사실은 없어지는 것이 아니다. 20세기들어 아인쉬타인의 중력이론이 뉴톤의 중력이론을 대체했지만 사과가 결과를 미뤄둔 체 공중에 머룰려고는 하지않을 것이다. 그리고 사람은 원숭이와 비슷한 그들의 조상으로 보터 진화해왔다. 진화해온 방법이 다아윈이 제시했던 기작이던 아니면 아직 찾지못한 다른 기작이던 간에. 그러나 '사실'이 '절대적 확실성 (absolute certainty)'을 의미하는 것은 아니다; 흥미롭고 복잡한 세상에서 '절대적 확실성'이란 것이 없을 지도 모른다. 수학과 논리의 마지막 증명은 이미 언급된 전제에 의해 연역적으로 전개되어 얻어진다. 왜냐하면 이들은 실제 세계에 관한 것이 아니기 때문이다. 진화론자들은 영원한 진리을 주장하지 않는다 - 창조론자들이 때로 그러하긴 하지만 (그리고 그들이 좋아하는 식으로 진화론자들을 공격한다). 과학에서 '사실'이란 단지 '잠정적인 승인을 보류하는 것이 안되는 정도로까지 확실한' 것을 의미할 뿐이다. 나는 내일 사과가 크기 시작할 것이라고 제시한다. 하지만 그 확률이 물리학 강의실에서도 똑같은 시간을 받을 가치는 없다. 진화론자들은 처음부터 사실과 이론의 구분에 대해 명확히 하고 있었다. 왜냐하면 진화론자들은 진화 (사실) 를 일으키는 기작들 (이론) 을 완전히 이해하기는 아직 멀었다는 것을 항상 알고 있었기 때문이다. 다아윈은 그의 두 독립적인 커다란 업적의 차이를 계속 강조했다: 진화의 사실을 발견한 것과 이를 설명하기 위한 기작으로서 한 이론 (자연선택) 을 제시한 것의 두 업적의 차이를." - Stephen J. Gould, "Evolution as Fact and Theory"; Discover, May 1981 굴드는 과학계에 널리 퍼져있는 관점을 이야기하고 있다. 즉, 전문가들은 진화를 사실로 받아들인다. 이 생각은 다음 인용문에서 알 수 있듯이 굴드가 처음 생각한 것은 아니다; "자, 진화에 관해서 이성적인 탐구심으로 무엇을 이루었고 또 앞으로 연구해야 할 것들이 무엇인지에 대해 명확한 파악을 한번 해봅시다. 지구가 태동한 이래 항상 진행되어온 과정으로서의 진화를 의심하는 사람들은, 감정적 장애물이나 단순한 편협성때문에 증거를 무시해버리거나 거부하는 사람들 뿐입니다. 반면, 진화를 일으키는 기작들에 대해서는 확실히, 연구해서 좀 더 분명하게 할 필요가 있습니다. 진화를 대체하여 날카로운 검증을 보류할 수 있는 역사는 없습니다. 그러나 진화의 기작들에 대해서는 우리는 항상 새롭고 중요한 사실들을 배우고 있습니다. - 테오도시우스 도브잔스키 (Theodosius Dobzhansky), "생물학의 모든 것은 진화의 관점하에서만 의미를 가진다 (Nothing in Biology Makes Sense Except in the Light of Evolution)", American Biology Teacher vol.35 (March 1973) reprinted in Evolution versus Creationism, J. Peter Zetterberg ed., ORYX Press, Phoenix AZ 1983 "It is time for students of the evolutionary process, especially those who have been misquoted and used by the creationists, to state clearly that evolution is a FACT, not theory, and that what is at issue within bology are questions of details of the process and the relative importance of different mechanisms of evolution. It is a FACT that the earth with liquid water, is more than 3.6 billion years old. It is a FACT that cellular life has been around for at least half of that period and that organized multicellular life is at least 800 million years old. It is a FACT that major life forms now on earth were not at all represented in the past. There were no birds or mammals 250 million years ago. It is a FACT that major life forms of the past are no longer living. There used to be dinosaurs and Pithecanthropus, and there are none now. It is a FACT that all living forms come from previous living forms. Therefore, all present forms of life arose from ancestral forms that were different. Birds arose from nonbirds and humans from nonhumans. No person who pretends to any understanding of the natural world can deny these facts any more than she or he can deny that the earth is round, rotates on its axis, and revolves around the sun. The controversies about evolution lie in the realm of the relative importance of various forces in molding evolution." - R. C. Lewontin "Evolution/Creation Debate: A Time for Truth" Bioscience 31, 559 (1981) reprinted in Evolution versus Creationism, op cit. This concept is also explained in introductory biology books that are used in colleges and universities (and in some of the better high schools). For example, in some of the best such textbooks we find, "Today, nearly all biologists acknowledge that evolution is a fact. The term THEORY is no longer appropriate except when referring to the various models that attempt to explain HOW life evolves... it is important to understand that the current questions about how life evolves in no way implies any disagreement over the fact of evolution." - Neil A. Campbell, Biology 2nd ed., 1990, Benjamin/Cummings, p.434 "Since Darwin's time, massive additional evidence has accumulated supporting the fact of evolution - that all living organisms present on earth today have arisen from earlier forms in the course of earth's long history. Indeed, all of modern biology is an affirmation of this relatedness of the many species of living things and of their gradual divergence from one another over the course of time. Since the publication of The Origin of Species, the important question, scientifically speaking, about evolution has not been whether it has taken place. That is no longer an issue among the vast majority of modern biologists. Today, the central and still fascinating questions for biologists concern the mechanisms by which evolution occurs." - Helena Curtis and N. Sue Barnes, Biology 5th ed. 1989, Worth Publishers, p.972 One of the best introductory books on evolution (as opposed to introductory biology) is that by Douglas J. Futuyma, and he makes the following comment, "A few words need to be said about the 'theory of evolution', which most people take to mean the proposition that organisms have evolved from common ancestors. In everyday speech, 'theory' often means a hypothesis or even a mere speculation. But in science, 'theory' means 'a statement of what are held to be the general laws, principles, or causes of something known or observed", as the Oxford English Dictionary defines it. The theory of evolution is a body of interconnected statements about natural selection and the other processes that are thought to cause evolution, just as the atomic theory of chemistry and the Newtonian theory of mechanics are bodies of statements that describe causes of chemical and physical phenomena. In constrast, the statement that organisms have descended with modifications from common ancestors - the historical reality of evolution - is not a theory. It is a fact, as fully as the fact of the earth's revolution about the sun. Like the heliocentric solar system, evolution began as a hypothesis, and achieved "facthood" as the evidence in its favor became so strong that no knowledgeable and unbiased person could deny its reality. No biologist today would think of submitting a paper entitled "New evidence for evolution"; it simply has not been an issue for a century." - Douglas J. Futuyma, op. cit., p.15 There are readers of these newsgroups who reject evolution for religious reasons. In general these readers oppose both the FACT of evolution and THEORIES of mechanisms although some anti-evolutionists have come to realize that there is a difference between the two concepts. That is why we see some leading anti-evolutionists admitting to the fact of "microevolution" - they know that evolution can be demonstrated. These readers will not be convinced of the "facthood" of (macro)evolution by any logical argument and it is a waste of time to make the attempt. The best that we can hope for is that they understand the argument that they oppose. Even this simple hope is rarely fulfilled. There are some readers who are not anti-evolutionist but still claim that evolution is "only" a theory which can't be proven. This group needs to distinguish between the fact that evolution occurs and the theory of the mechanism of evolution. We also need to distinguish between facts that are easy to demonstrate and those that are more circumstantial. Examples of evolution that are readily apparent include the fact that modern populations are evolving and the fact that two closely related species share a common ancestor. The evidence that Homo sapiens and chimpanzees share a recent common ancestor falls into this catagory. There is so much evidence in support of this aspect of primate evolution that it qualifies as a fact by any common definition of the word "fact". In other cases the available evidence is less strong. For example, the relationships of some of the major phyla are still being worked out. Also, the statement that all organisms have descended from a single common ancestor is strongly supported by the available evidence, and there is no opposing evidence. However, it is not yet appropriate to call this a "fact" since there are reasonable alternatives. Finally, there is an epistemological argument against evolution as fact. Some readers of these newsgroups point out that nothing in science can ever be "proven" and this includes evolution. According to this argument, the probability that evolution is the correct explanation of life as we know it may approach 99.9999...9% but it will never be 100%. Thus evolution cannot be a fact. This kind of argument might be appropriate in a philosophy class (it is essentially correct) but it won't do in the real world. A "fact", as Stephen J. Gould pointed out (see above), means something that is so highly probable that it would be silly not to accept it. This point has also been made by others who contest the nit-picking epistemologists. "The honest scientist, like the philosopher, will tell you that nothing whatever can be or has been proved with fully 100% certainty, not even that you or I exist, nor anyone except himself, since he might be dreaming the whole thing. Thus there is no sharp line between speculation, hypothesis, theory, principle, and fact, but only a difference along a sliding scale, in the degree of probability of the idea. When we say a thing is a fact, then, we only mean that its probability is an extremely high one: so high that we are not bothered by doubt about it and are ready to act accordingly. Now in this use of the term fact, the only proper one, evolution is a fact. For the evidence in favor of it is as voluminous, diverse, and convincing as in the case of any other well established fact of science concerning the existence of things that cannot be directly seen, such as atoms, neutrons, or solar gravitation .... So enormous, ramifying, and consistant has the evidence for evolution become that if anyone could now disprove it, I should have my conception of the orderliness of the universe so shaken as to lead me to doubt even my own existence. If you like, then, I will grant you that in an absolute sense evolution is not a fact, or rather, that it is no more a fact than that you are hearing or reading these words." - H. J. Muller, "One Hundred Years Without Darwin Are Enough" School Science and Mathematics 59, 304-305. (1959) reprinted in Evolution versus Creationism op cit. In any meaningful sense evolution is a fact but there are various theories concerning the mechanism of evolution. ---------------------------------------------------------------------------- |