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|  Juliano Martins
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| | | Sample translations submitted: 7| inglês para português: One side can be wrong | Texto de origem - inglês
It sounds so reasonable, doesn't it? Such a modest proposal. Why not teach "both sides" and let the children decide for themselves? As President Bush said, "You're asking me whether or not people ought to be exposed to different ideas, the answer is yes." At first hearing, everything about the phrase "both sides" warms the hearts of educators like ourselves.
One of us spent years as an Oxford tutor and it was his habit to choose controversial topics for the students' weekly essays. They were required to go to the library, read about both sides of an argument, give a fair account of both, and then come to a balanced judgment in their essay. The call for balance, by the way, was always tempered by the maxim, "When two opposite points of view are expressed with equal intensity, the truth does not necessarily lie exactly half way between. It is possible for one side simply to be wrong."
As teachers, both of us have found that asking our students to analyse controversies is of enormous value to their education. What is wrong, then, with teaching both sides of the alleged controversy between evolution and creationism or "intelligent design" (ID)? And, by the way, don't be fooled by the disingenuous euphemism. There is nothing new about ID. It is simply creationism camouflaged with a new name to slip (with some success, thanks to loads of tax-free money and slick public-relations professionals) under the radar of the US Constitution's mandate for separation between church and state.
Why, then, would two lifelong educators and passionate advocates of the "both sides" style of teaching join with essentially all biologists in making an exception of the alleged controversy between creation and evolution? What is wrong with the apparently sweet reasonableness of "it is only fair to teach both sides"? The answer is simple. This is not a scientific controversy at all. And it is a time-wasting distraction because evolutionary science, perhaps more than any other major science, is bountifully endowed with genuine controversy.
Among the controversies that students of evolution commonly face, these are genuinely challenging and of great educational value: neutralism versus selectionism in molecular evolution; adaptationism; group selection; punctuated equilibrium; cladism; "evo-devo"; the "Cambrian Explosion"; mass extinctions; interspecies competition; sympatric speciation; sexual selection; the evolution of sex itself; evolutionary psychology; Darwinian medicine and so on. The point is that all these controversies, and many more, provide fodder for fascinating and lively argument, not just in essays but for student discussions late at night.
Intelligent design is not an argument of the same character as these controversies. It is not a scientific argument at all, but a religious one. It might be worth discussing in a class on the history of ideas, in a philosophy class on popular logical fallacies, or in a comparative religion class on origin myths from around the world. But it no more belongs in a biology class than alchemy belongs in a chemistry class, phlogiston in a physics class or the stork theory in a sex education class. In those cases, the demand for equal time for "both theories" would be ludicrous. Similarly, in a class on 20th-century European history, who would demand equal time for the theory that the Holocaust never happened?
So, why are we so sure that intelligent design is not a real scientific theory, worthy of "both sides" treatment? Isn't that just our personal opinion? It is an opinion shared by the vast majority of professional biologists, but of course science does not proceed by majority vote among scientists. Why isn't creationism (or its incarnation as intelligent design) just another scientific controversy, as worthy of scientific debate as the dozen essay topics we listed above? Here's why.
If ID really were a scientific theory, positive evidence for it, gathered through research, would fill peer-reviewed scientific journals. This doesn't happen. It isn't that editors refuse to publish ID research. There simply isn't any ID research to publish. Its advocates bypass normal scientific due process by appealing directly to the non-scientific public and - with great shrewdness - to the government officials they elect.
The argument the ID advocates put, such as it is, is always of the same character. Never do they offer positive evidence in favour of intelligent design. All we ever get is a list of alleged deficiencies in evolution. We are told of "gaps" in the fossil record. Or organs are stated, by fiat and without supporting evidence, to be "irreducibly complex": too complex to have evolved by natural selection.
In all cases there is a hidden (actually they scarcely even bother to hide it) "default" assumption that if Theory A has some difficulty in explaining Phenomenon X, we must automatically prefer Theory B without even asking whether Theory B (creationism in this case) is any better at explaining it. Note how unbalanced this is, and how it gives the lie to the apparent reasonableness of "let's teach both sides". One side is required to produce evidence, every step of the way. The other side is never required to produce one iota of evidence, but is deemed to have won automatically, the moment the first side encounters a difficulty - the sort of difficulty that all sciences encounter every day, and go to work to solve, with relish.
What, after all, is a gap in the fossil record? It is simply the absence of a fossil which would otherwise have documented a particular evolutionary transition. The gap means that we lack a complete cinematic record of every step in the evolutionary process. But how incredibly presumptuous to demand a complete record, given that only a minuscule proportion of deaths result in a fossil anyway.
The equivalent evidential demand of creationism would be a complete cinematic record of God's behaviour on the day that he went to work on, say, the mammalian ear bones or the bacterial flagellum - the small, hair-like organ that propels mobile bacteria. Not even the most ardent advocate of intelligent design claims that any such divine videotape will ever become available.
Biologists, on the other hand, can confidently claim the equivalent "cinematic" sequence of fossils for a very large number of evolutionary transitions. Not all, but very many, including our own descent from the bipedal ape Australopithecus. And - far more telling - not a single authentic fossil has ever been found in the "wrong" place in the evolutionary sequence. Such an anachronistic fossil, if one were ever unearthed, would blow evolution out of the water.
As the great biologist J B S Haldane growled, when asked what might disprove evolution: "Fossil rabbits in the pre-Cambrian." Evolution, like all good theories, makes itself vulnerable to disproof. Needless to say, it has always come through with flying colours.
Similarly, the claim that something - say the bacterial flagellum - is too complex to have evolved by natural selection is alleged, by a lamentably common but false syllogism, to support the "rival" intelligent design theory by default. This kind of default reasoning leaves completely open the possibility that, if the bacterial flagellum is too complex to have evolved, it might also be too complex to have been created. And indeed, a moment's thought shows that any God capable of creating a bacterial flagellum (to say nothing of a universe) would have to be a far more complex, and therefore statistically improbable, entity than the bacterial flagellum (or universe) itself - even more in need of an explanation than the object he is alleged to have created.
If complex organisms demand an explanation, so does a complex designer. And it's no solution to raise the theologian's plea that God (or the Intelligent Designer) is simply immune to the normal demands of scientific explanation. To do so would be to shoot yourself in the foot. You cannot have it both ways. Either ID belongs in the science classroom, in which case it must submit to the discipline required of a scientific hypothesis. Or it does not, in which case get it out of the science classroom and send it back into the church, where it belongs.
In fact, the bacterial flagellum is certainly not too complex to have evolved, nor is any other living structure that has ever been carefully studied. Biologists have located plausible series of intermediates, using ingredients to be found elsewhere in living systems. But even if some particular case were found for which biologists could offer no ready explanation, the important point is that the "default" logic of the creationists remains thoroughly rotten.
There is no evidence in favour of intelligent design: only alleged gaps in the completeness of the evolutionary account, coupled with the "default" fallacy we have identified. And, while it is inevitably true that there are incompletenesses in evolutionary science, the positive evidence for the fact of evolution is truly massive, made up of hundreds of thousands of mutually corroborating observations. These come from areas such as geology, paleontology, comparative anatomy, physiology, biochemistry, ethology, biogeography, embryology and - increasingly nowadays - molecular genetics.
The weight of the evidence has become so heavy that opposition to the fact of evolution is laughable to all who are acquainted with even a fraction of the published data. Evolution is a fact: as much a fact as plate tectonics or the heliocentric solar system.
Why, finally, does it matter whether these issues are discussed in science classes? There is a case for saying that it doesn't - that biologists shouldn't get so hot under the collar. Perhaps we should just accept the popular demand that we teach ID as well as evolution in science classes. It would, after all, take only about 10 minutes to exhaust the case for ID, then we could get back to teaching real science and genuine controversy.
Tempting as this is, a serious worry remains. The seductive "let's teach the controversy" language still conveys the false, and highly pernicious, idea that there really are two sides. This would distract students from the genuinely important and interesting controversies that enliven evolutionary discourse. Worse, it would hand creationism the only victory it realistically aspires to. Without needing to make a single good point in any argument, it would have won the right for a form of supernaturalism to be recognised as an authentic part of science. And that would be the end of science education in America. | Tradução - português
Parece tão razoável, não? Uma proposta tão modesta. Por quê não ensinar “ambos os lados” e deixar que as crianças decidam por si mesmas? Como o Presidente Bush disse, “Você está me perguntando se pessoas deveriam ou não ser expostas a idéias diferentes, a resposta é sim.”. Ouvindo inicialmente, tudo sobre a frase “ambos os lados” aquece os corações dos educadores assim como nós.
Um de nós passou anos como um tutor em Oxford e era do seu costume escolher tópicos controversos para os ensaios semanais dos estudantes. Era requerido que eles fossem até a biblioteca, lessem sobre ambos os lados do argumento, fisessem um relato justo de ambos, e depois viessem para balancear um julgamento nos seus ensaios. A chamada para a balança, a propósito, era sempre temperada pela máxima, “Quando dois pontos de vista opostos são expressados com igual intensidade, a verdade não necessariamente fica exatamente no meio entre eles. É possível para um lado simplesmente estar errado.”
Como professores, ambos concluímos que pedir para nossos estudantes analisarem controversias é algo de enorme valor para sua educação. O que está errado, então, em ensinar ambos os lados da alegada controversia entre evolução e criacionismo ou “Design Inteligente” (DI)? E, a proposito, não seja enganado pelo eufemismo não ingênuo. Não há nada novo sobre DI. Isso é simplesmente uma camuflagem criacionista com um novo nome para passar (com algum sucesso, graças a cargas de dinheiro livre de impostos e relações públicas profissionais) por debaixo do radar do mandato da Constituição dos EUA pela separação entre igreja e estado. Por quê, então, iriam dois educadores de longa data e advogados apaixonados do estilo de ensino “ambos os lados” juntar-se com essencialmente todos os biólogos e fazer uma exceção da alegada controversia entre criação e evolução? O que está errado com a aparente docê razoabilidade de “é somente justo ensinar ambos os lados”? A resposta é simples. Isso não é uma controversia científica, de forma nenhuma. E isso é uma distração de perca de tempo porque a ciência evolucionária, talvez mais do que qualquer outra grande ciência, está abundantemente dotada de contravérsias genuínas.
Entre as contravérsias que estudantes de evolução comumente encaram, esses são genuinamente desafiadores e de grande valor educacional: neutralismo versus selecionismo na evolução molecular; adaptacionismo; seleção de grupo; equilibrio pontuado; cladismo; “evo-devo”; a “Explosão Cambriana”; extinções de massa; competição interespécies; especiação simpátrica; seleção sexual; a evolução do próprio sexo; evolução psicologica; medicina Darwinista e assim por diante. O ponto é que todas essas controversias, e muitas outras, proporcionam material para argumentações facinanantes e vívidas, não apenas em artigos, mas para discussões entre estudantes tarde da noite.
Design Inteligente não é um argumento do mesmo tipo dessas controversias. Não é um argumento científico de nenhum jeito, mas um argumento religioso. Pode ser valioso discuti-lo em uma aula de história das idéias, em uma aula de filosofia sobre falácias lógicas populares, ou em uma aula de religião comparativa sobre a mitos da origem de todo o mundo. Mas isso não pertence a uma aula de biologia mais do que alquimia pertence a uma aula de química, flogisto a uma aula de física ou a teoria da cegonha em uma aula de educação sexual. Nesses casos, a demanda de tempo igual para “ambas as teorias” seria ridículo. Similarmente, em uma aula sobre história européia do século XX, quem pediria tempo igual para a teoria de que o Holocausto nunca aconteceu?
Então, por quê estamos tão seguros de que o design inteligente não é uma teoria científica real, merecedora do tratamento “ambos os lados”? Isso não é apenas nossa opinião pessoal? Essa é uma opinião compartilhada pela vasta maioria dos biologos profissionais, mas claro que a ciência não procede pelo voto da maioria entre cientístas. Por quê o Criacionismo (ou sua encarnação como Design Inteligente) não é apenas outra controversia científica, merecedora de debate científico como dúzias de tópicos de artigos que listamos acima? Aqui está o motivo.
Se DI realmente fosse uma teoria científica, evidência a favor disso, coletada através de pesquisa, iria preencher publicações científicas peer-review. Isso não acontece. Não é porque os editores se recusem de publicar pesquisas de DI. Simplesmente não existe nenhuma pesquisa de DI para se publicar. Seus proponentes pulam o processo científico normal apelando diretamente para o público não-científico e – com grande astúcia – para os oficiais do governo que eles elegem.
O argumento que os proponentes de DI colocam, tal como é, sempre é do mesmo tipo. Eles nunca oferecem evidência positiva a favor do design inteligente. Tudo que conseguimos é uma lista de alegadas deficiências na evolução. Nos dizem sobre “lacunas” no registro fóssil. Ou orgãos são afirmados, por criação e sem evidência comprovatória, de serem “irredutivelmente complexos”: muito complexos para terem evoluido por seleção natural.
Em todos os casos existe uma suposição “padrão” escondida (na verdade, eles dificilmente se incomodam em esconder isso) de que se a Teoria A possui alguma dificuldade ao explicar o Fenômeno X, nós devemos automaticamente preferir a Teoria B, sem ao menos perguntar se a Teoria B (criacionismo, nesse caso) é melhor em explica-lo. Perceba o quão desequilibrado é isso, e como isso dá a chance ao aparentemente razoável “vamos ensinar os dois lados”. Um lado é requerido para dar evidência, em todos os passos do caminho. O outro lado nunca é requerido para produzir nenhuma quantidade mínima de evidência, mas é conveniente ter ganhado automaticamente, no momento em que o primeiro lado encontra uma dificuldade – o tipo de dificuldade que todas as ciências encontram todos os dias, e vão trabalhar para resolver, com prazer.
O quê, sobretudo, é uma lacuna no registro fóssil? É a simples ausência de um fóssil que iria de outra forma ter documentado uma transição evolucionária particular. A lacuna significa que nos falta um registro cinematográfico completo de todos os passos no processo evolucionário. Mas como é incrivelmente presunçoso pedir um registro completo, dado que somente uma minuscula proporção de mortes resultam em um fóssil de qualquer jeito.
A demanda evidencial equivalente do criacionismo seria um registro cinematográfico completo do comportamento de Deus no diz em que ele foi trabalhar, digamos, os ossos do ouvido dos mamíferos ou o flagelo bacteriano – o menor orgão parecido com um cabelo que propulsiona bactérias móveis. Nem mesmo o mais ardente advogado do design inteligente afirma que tal videotape divino algum dia será disponível.
Biologos, por outro lado, podem confiantemente afirmar a equivalente sequência “cinematográfica” de fósseis para um grande número de transições evolucionárias. Nem todas, mas muitas mesmo, incluindo nossa própria descendencia do bípede Australopitecus. E – ainda mais importante – nem um único fóssil autêntico foi encontrado no lugar “errado” na sequência evolucionária. Tal fóssil acronológico, se algum fosse encontrado, iria destruir totalmente a evolução.
Como o grande biologo J. B. S. Haldane disse, quando perguntado o que poderia desprovar a evolução: “Fósseis de coelhos no pré-Cambriano.”. Evolução, como todas as boas teorias, se faz vulnerável para refutação. Nem é preciso dizer, ela tem se saído muito bem. Similarmente, a afirmação de que algo – digamos, o flagelo bacteriano – seja muito complexo para ter evoluído por seleção natural é alegado, por um lamentavelmente comum falso silogismo, para apoiar a “rival” teoria do design inteligente de forma padrão. Esse tipo de pensamento padrão deixa completamente aberta a possibilidade de que, se o flagelo bacteriano é muito complexo para ter evoluído, também deve ter sido muito complexo de ter sido criado. E na verdade, um pensamento momentâneo mostra que qualquer Deus capaz de criar um flagelo bacteriano (pra não dizer o universo) seria uma entidade muito mais complexo, e logo estatisticamente improvável, do que o próprio flagelo bacteriano (ou universo) – e precisaria muito mais de uma explicação do que o objeto que ele alegadamente criou.
Se orgânismos complexos pedem uma explicação, assim também um desenhista complexo. E não é solução levantar o apelo teologico de que Deus (ou o Desenhista Inteligente) é simplesmente imune às demandas normais de explicação científica. Fazer isso seria como dar um tiro no pé. Você não pode ter isso das duas maneiras. Ou DI pertence a sala de aula de ciências, que no caso deve se submeter à disciplina requerida de uma hipotese científica. Ou não pertence, que no caso sai da sala de aula de ciências e volta para a igreja, aonde pertence.
De fato, o flagelo bacteriano não é certamente tão complexo para ter evoluido, e nem qualquer outra estrutura viva que tenha cuidadosamente sido estudada. Biologos localizaram séries plausíveis de intermediários, usando ingredientes encontrados em sistemas vivos. Mas mesmo que algum caso particular fosse encontrado para o qual os biologos não pudesse oferecer uma explicação pronta, o importante é que a lógica “padrão” do criacionismo permanece inteiramente podre.
Não existe evidência a favor do design inteligente: somente lacunas alegadas na completude do registro evolucionário, acompanhada da falácia “padrão” que nós identificamos. E, enquanto é inevitávelmente verdade que existe uma incompletude na ciência evolucionária, a evidência positiva para o fato da evolução é verdadeiramente esmagadora, construída de centenas de milhares de observações que se corroboram. Essas vem de áreas como geologia, paleontologia, anatomia comparativa, fisiologia, bioquímica, etologia, biogeografia, enbriologia e – aumentando nos dias de hoje – genética molecular. O peso das evidências tem se tornado tão grande que a oposição ao fato da evolução é tola para todos que estão familiarizados com pelo menos uma fração dos dados publicados. Evolução é um fato: um fato tanto quanto as placas tectônicas ou o sistema solar heliocentrico.
Por quê, finalmente, importa se esses problemas forem discutidos na aula de ciência? Existe a possibilidade de dizer que não é problema – que os biologos não deveriam pegar tão firme no colarinho. Talvez nós devessemos simplesmente aceitar a demanda popular de que ensinemos DI assim como evolução na aula de ciências. Isso iria, depois de tudo, tomar apenas 10 minutos para exaurir o caso de DI, depois nós poderiamos voltar a ensinar ciência de verdade e controversias genuínas.
Tão tentador quanto isso seja, uma preocupação séria continua. A linguagem sedutiva “vamos ensinar os dois lados” ainda possui a idéia falsa, e altamente perniciosa, de que realmente existem dois lados. Isso iria distrair os estudantes da genuinamente importante e interessante controversia que vivificam o discurso evolucionário. Pior, isso iria dar ao criacionismo a única vitória que isso realmente aspira. Sem nem mesmo precisar fazer um único bom ponto em qualquer argumento, isso teria ganho o direito para uma forma de sobrenaturalismo ser reconhecido como uma autêntica parte da ciência. E seria o fim da educação científica na América. | | inglês para português: God and Evolution | Texto de origem - inglês
This is a collection of frequently asked questions and answers about the compatibility of belief in evolution and God from talk origins. This text presupposes the reader's belief in the Judeo-Christian God, but many answers are general enough to include most religions. There is no attempt to prove or disprove the existence of God, or the validity of any religion, as that is not the intent. Please contact me at kv07@iastate.edu with any questions or suggestions.
1. Definitions
Science
A method of determine how the universe works by use of the scientific method.
Scientific method
The process of proposing a hypothesis, and then testing its accuracy by collecting data on events the hypothesis predicts. If the predictions match the new data the hypothesis is supported. Generally the best supported hypothesis is considered correct.
Evolution
The fact the frequency of the apperance of alleles in a population of organisms changes over time.
Allele
The pieces of DNA that cause a particular trait, ie. "blue eyes".
The theory of evolution
A number of theories that explain, to the best of current knowledge, by what mechanisms evolution occurs.
The theory of common descent
The theory that all living creatures on earth share a common, remote ancestor. More specifically, given any two living creatures there was a creature that is ancestor to both.
Creationism
One of several beliefs that incorporate a literal interpretation of Genesis. There are variations that allow some figurative interpretation.
Young Earth Creationism
An interpretation of Genesis 1 in which days are taken to be 24 hour events, and that by saying animals reproduce "after their kind" evolution is precluded.
Old Earth Creationism
An interpretation of Genesis 1 in which days are taken to be figurative lengths of time, and the time scales given by geologists are generally correct. However, the special creation of man precludes common descent.
Theistic Evolution
An interpretation of Genesis 1 in which the story line is considered as an explanation for the why and who of creation, but not the exact method. The purpose of this FAQ is to show that this position is not contradictory.
2. Evolution and Religion
Q1. Doesn't evolution contradict religion?
Not always. Certainly it contradicts a literal interpretation of the first chapter of Genesis, but evolution is a scientific principle, like gravity or electricity. To scientifically test a religious belief one first must find some empirical test that gives different results depending on whether the belief is true or false. These results must be predicted before hand, not pointed to after the fact.
Most religious beliefs don't work this way. Religion usually presupposes a driving intelligence behind it, and an intelligent being is not always predictable. Since experiments judging religious beliefs cannot have predictable results, and may give different results under the same circumstances it is not open to scientific inquiry. St. Augustine commented on this in _The Literal Meaning of Genesis_.
Some religious beliefs do make predictions. These predictions can be tested. If a religious belief fails a test, it is the test that contradicts that religious belief. The theory which makes the correct prediction should have nothing to say on the matter. This does not mean that scientists don't sometimes make the mistake of saying a theory contradicts something.
Q2. Isn't evolution a religion?
Evolution is based on the scientific method. There are tests that can determine whether or not the theory is correct as it stands, and these tests can be made. Thousands of such tests have been made, and the current theories have passed them all. Also, scientists are willing to alter the theories as soon as new evidence is discovered. This allows the theories to become more and more accurate as research progresses.
Most religions, on the other hand, are based on revelations, that usually cannot be objectively verified. They talk about the why, not the how. Also, religious beliefs are not subject to change as easily as scientific beliefs. Finally, a religion normally claims an exact accuracy, something which scientists know they may never achieve.
Some people build up religious beliefs around scientific principles, but then it is their beliefs which are the religion. This no more makes scientific knowledge a religion than painting a brick makes it a bar of gold.
So the answer is no, evolution is no more a religion than any other scientific theory.
Q3. Does evolution contradict creationism?
There are two parts to creationism. Evolution, specifically common descent, tells us how life came to where it is, but it does not say why. If the question is whether evolution disproves the basic underlying theme of Genesis, that God created the world and the life in it, the answer is no. Evolution cannot say exactly why common descent chose the paths that it did.
If the question is whether evolution contradicts a literal interpretation of the first chapter of Genesis as an exact historical account, then it does. This is the main, and for the most part only, point of conflict between those who believe in evolution and creationists.
Q4. If evolution is true, then isn't the whole Bible wrong?
First let me repeat that the underlying theme of the first book of Genesis can't be scientifically proven or disproven. No test has ever been found that can tell the difference between a universe created by God, and one that appeared without Him. Only certain interpretations of Genesis can be disproven.
Second, let us turn the question around. What if I asked you "If the story of the prodigal son didn't really happen, then is the whole Bible wrong?" Remember that the Bible is a collection of both stories and historical accounts. Because one part is a figurative story does not make the entire Bible so. Even if it did, the underlying message of the Bible would remain.
3. Evolution and God
Q5. Does evolution deny the existence of God?
No. See question 1. There is no reason to believe that God was not a guiding force behind evolution. While it does contradict some specific interpretations of God, especially ones requiring a literal interpretation of Genesis 1, few people have this narrow of a view of God.
There are many people who believe in the existence of God and in evolution. Common descent then describes the process used by God. Until the discovery of a test to separate chance and God this interpretation is a valid one within evolution.
Q6. But isn't this Deism, the belief that God set the universe in motion and walked away?
While it could be Deism, the Bible speaks more of an active God, one who is frequently intervening in His creation. If the Bible represents such a God in historical times there is no reason to assume that He was not active in the universe before then. A guiding hand in evolution could exist, even in the time before humans came around. Just because people were not there to observe does not mean that there was nothing to observe.
Q7. So if God directed evolution, why not just say he created everything at once?
Mainly because all the evidence suggests otherwise. If God created the universe suddenly, he created it in a state that is indistinguishable from true age. If he did create it that way there must be a reason, otherwise God is a liar. Whatever that reason may be, a universe that is exactly like one that is old should be treated as if it were old.
Q8. By denying creation, aren't you denying God's power to create?
No. Because God did not create the world in seven days does not mean that he couldn't. What did, or did not, happen is not an indication of what could, or could not, have happened. All evidence suggests that evolution is the way things happened. Regardless of what could have happened, the evidence would still point to evolution.
4. Evolution and Proof
Q9. Nobody can really prove anything anyway.
Except, of course, in mathematics. However, science does not require absolute proof, otherwise science textbooks would be empty. Science works by use of the scientific method: explanations are found, and tests made to tell which ones are correct. Evolution has passed thousands of tests, many of which separated it from theories indistinguishable to non-biologists.
Few people are aware, for instance, that Darwin's original hypothesis predicted the existence of genetic information. As said before, even if the theory is not correct in every detail, it is very close to the truth. Chris Colby's FAQ gives a clear picture of this.
Q10. Theories have been proven wrong in the past, why not evolution?
When Einstein proposed general relativity, he revolutionized physics. The theory replaced most of Newton's laws of physics. General relativity, though, still incorporates Newton's laws. This is due to the enormous number of observations and tests that Newton's laws had passed, so any new theory would have to account for them also.
Similarly, if another theory replaces evolution, the new theory must somehow explain why the current theory passed all the tests. So any new theory that replaces evolution would have to explain why it works so well. Creationism, then, is not a possible replacement.
Q11. Doesn't evolution promote evil?
Even if evolution did do this, it would not be a reason to assume it is wrong. Chemistry is responsible for millions of deaths every year, but we do not reject its findings because of this. How people use a theory is not a judgment of its accuracy.
Fortunately we do not face this dilemma. Evolution does not say what is right and what is wrong, but merely what has happened. A historical account of the sacking of Rome does not say that the act of sacking Rome is good or bad, just that it happened. Similarly evolution does not say that any conclusions people might draw from it are good or bad.
While many people have claimed the theory of evolution supports their injustice, never forget that many people have done the same with the Bible. One person's opinion should not be considered the whole truth.
Q12. So what would I need to have creationism accepted scientifically?
Read Chris Colby's FAQ for some evidence that must be explained. Also you need to propose a test that would give different results depending on whether creation or evolution is true. Most important, however, is the willingness to abide by the results, even if they disprove creationism. | Tradução - português
Essa é uma coleção de questões frequentemente perguntadas e respondidas sobre a compatibilidade da crença na evolução e Deus do talk origins. Esse texto pressupõe que os leitores acreditam no Deus Judáico-Cristão, mas muitas respostas são geralmente suficientes para incluir a maioria das religiões. Não existe tentativa de provar ou desaprovar a existência de Deus, ou a validade de qualquer religião, pois esse não é o objetivo. Por favor contate-me em kv07@iastate.edu com qualquer questão ou sugestão.
1. Definições
Ciência
Um método de determinar como o universo funciona pelo uso do método científico.
Método Científico
O processo de propor uma hipótese e depois testar sua precisão através da coleta de dados de eventos que a hipotese prediz. Se as predições combinarem com os novos dados, a hipotese é apoiada. Geralmente a hipotese melhor apoiada é considerada correta.
Evolução
O fato em que a frequência da aparição de alelos em uma população de orgânismos mudar ao longo do tempo.
Alelo
As peças de DNA que causam uma caracteristica particulas, ex.: “olhos azuis”.
A Teoria da Evolução
Um número de teorias que explicam, com o melhor do conhecimento atual, por quais mecânismos a evolução ocorre.
A Teoria do descendente comum
A teoria de que todos as criaturas vivas na Terra compartilham um comum e remoto ancestral. Mais especificamente, dadas quaisquer duas criaturas vivas, existiu uma criatura que é ancestral de ambas.
Criacionismo
Uma das várias crenças que incorpora uma interpretação literal do Gênesis. Existem variações que permitem uma interpretação figurativa.
Criacionismo da Terra Jovem
Uma interpretação de Gênesis 1 na qual dias são tomados como eventos de 24 horas, e que por dizer que animais se reproduzem “de acordo com seus tipos” a evolução é excluida.
Criacionistas da Terra Velha
Uma interpretação de Gênesis 1 na qual dias são tomados com comprimentos figurativos de tempo, e as escalas de tempo dadas pelos geologos são geralmente corretas. Contudo, a criação especial do homem exclui a descendencia comum.
Evolução Teísta
Uma interpretação do Gênesis 1 na qual a linha da história é considerada como uma explicação do motivo e quem da criação, mas não o método exato. O propósito desse FAQ é mostrar que essa posição não é contraditória.
2. Evolução e Religião
Q1. A evolução não contradiz a religião?
Nem sempre. Certamente ela contradiz uma interpretação literal do primeiro capítulo do Gênesis, mas a evolução é um princípio científico, como a gravidae ou eletricidade. Para se testar cientificamente uma crença religiosa, a pessoa primeiro deve encontrar algum teste empírico que dê resultados diferentes dependendo se a crença é verdadeira ou falsa. Esses resultados devem ser preditos anteriormente, e não apontados depois dos fatos.
A maioria das crenças religiosas não funciona desse jeito. A religião normalmente presupõe um direcionamento inteligente atrás disso, e um ser inteligente nem sempre é preditível. Desde que os experimentos que julgam crenças religiosas não podem ter resultados preditíveis, e podem dar diferentes resultados sob a mesma circunstância, eles não estão abertos para inquisição científica. Santo Agostinho condenou isso em _O Significado Literal do Gênesis_.
Algumas crenças religiosas fazem predições. Essas predições podem ser testadas. Se uma crença religiosa falhar no teste, é o teste que contradiz a crença religiosa. A teoria que faz a predição correta não deveria ter nada a dizer sobre o problema. Isso não significa que cientístas algumas vezes não cometem erros dizendo que uma teoria contradiga algo.
Q2. A evolução não é uma religião?
A evolução é baseada no método científico. Existem testes que podem determinar se uma teoria está correta ou não da forma como ela é descrita, e esses testes podem ser feitos. Milhares de tais testes têm sido feitos, e a teoria atual tem passado em todos eles. Também, cientístas estão desejosos para alterar a teoria tão rápido quanto nova evidência for encontrada. Isso permite que as teorias tornem-se mais e mais precisas ao longo do progresso científico.
A maioria das religiões, por outro lado, estão baseadas nas revelações, que normalmente não podem ser objetivamente verificadas. Eles falam do motivo, mas não sobre a maneira. Também, crenças religiosas não estão sujeitas a mudanças tão facilmente quanto as crenças científicas. Finalmente, uma religião normalmente afirma com uma precisão exata, algo que cientístas sabem que podem nunca conseguir.
Algumas pessoas constroem crenças religiosas ao redor de princípios científicos, mas então são suas crenças que são a religião. Isso não torna o conhecimento científico uma religião assim como pintar um tijolo não o transforma em ouro.
Então a resposta é não, a evolução não é uma religião mais do que qualquer outra teoria científica.
Q3. A evolução contradiz o criacionismo?
Existem duas partes para o criacionismo. A evolução, especificamente a descendência comum, nos conta como a vida veio a ser o que é, mas isso não diz o motivo. Se a questão é se a evolução desaprova o tema principal do Gênesis, que Deus criou o mundo e a vida nele, a resposta é não. A evolução não pode dizer exatamente o motivo da descendencia comum ter escolhido o caminho que escolheu.
Se a questão é se a evolução contradiz a interpretação literal do primeiro capítulo do Gênesis como um acontecimento histórico exato, então ela faz isso. Isso é o principal, e na maior parte o único, ponto de conflito entre aqueles que acreditam em evolução e criacionistas.
Q4. Se a evolução for verdadeira, então toda a Bíblia está errada?
Primeiro, deixe-me repetir que tema principal do primeiro livro do Gênesis não pode ser cientificamente provado ou desaprovado. Nenhum teste foi encontrado que possa dizer a diferença entre um universo criado por Deus, e um que apareceu sem Ele. Somente certas interpretações do Gênesis podem ser desaprovadas.
Segundo, vamos virar a pergunta. E se eu te perguntasse “Se a história do filho pródigo realmente não aconteceu, então toda a Bíblia está errada?”. Lembre-se que a Bíblia é uma coleção de tanto contos como acontecimentos históricos. Por que uma parte é figurativa não torna toda a Bíblia assim. E mesmo se torna-se, a mensagem principal da Bíblia seria mantida.
3. Evolução e Deus
Q5. A evolução nega a existência de Deus?
Não. Veja a questão 1. Não existe razão para acreditar que Deus não tenha sido uma força direcionadora por trás da evolução. Enquanto isso não contradisser algumas interpretações específicas de Deus, especialmente aquelas que requerem uma interpretação literal de Gênesis 1, poucas pessoas têm essa visão estreita de Deus.
Existem muitas pessoas que acreditam na existência de Deus e na evolução. A descendência comum então descreve o processo usado por Deus. Até a descoberta de um teste para separar a sorte e Deus, essa interpretação é uma válida dentro da evolução.
Q6. Mas isso não é Deísmo, a crença que Deus organizou o universo em movimento e foi embora?
Enquanto isso pode ser Deísmo, a Bíblia fala mais de um Deus ativo, aquele que está frequentemente intervindo na Sua criação. Se a Bíblia representa tal Deus nos tempos históricos, não existe razão para assumir que Ele não estivesse ativo no universo antes. Uma mão direcionadora na evolução poderia existir, mesmo nos tempos antes dos humanos chegarem. Só porque as pessoas não estavam lá para observar isso não significa que não havia nada para ser observado.
Q7. Então se Deus direcionou a evolução, por quê não somente criar tudo de uma vez?
Principalmente porque toda a evidência sugere o contrário. Se Deus criou o universo repentinamente, ele criou-o em um estado que é indistinguivelmente da idade verdadeira. Se ele criou-o desta forma, deve haver uma razão, ao contrário, Deus é um mentiroso. Qualquer que seja a razão, um universo que é exatamente como é um universo velho deveria ser tratado como se fosse velho.
Q8. Negando o criacionismo, você não está negando o poder de Deus para criar?
Não. Porque Deus não criou o mundo em sete dias não significa que não poderia. O que aconteceu ou não aconteceu, não é uma indicação do que poderia ou não poderia ter acontecido. Todas as evidências sugerem que a evolução é a forma de como as coisa aconteceram. Independente do que poderia ter acontecido, a evidência ainda aponta para a evolução.
4. Evolução e Prova
Q9. De qualquer jeito, ninguém pode provar nada.
Exceto, é claro, na matemática. Contudo, a ciência não requer a prova absoluta, senão os livros texto de ciências estariam vazios. A ciência funciona pelo uso do método científico: explicações são encontradas e testes são feitos para dizer quais estão corretos. A evolução passou por milhares de testes, muitos dos quais separaram isso de teorias indistinguivelmente para não-biologos.
Poucas pessoas estão cientes, por exemplo, de que a hipotese original de Darwin predizia a existência de informação genética. Como dito antes, mesmo que a teoria não esteja correta em todos os detalhes, ela está muito próxima da verdade. As FAQs de Chris Colby dão uma imagem clara disso.
Q10. Teorias foram provadas erradas no passado, por quê não a evolução?
Quando Einstein porpôs a relatividade geral, ele revolucionou a física. A teoria substituiu a maioria das leis da física de Newton. A relatividade geral, contudo, ainda incorpora as leis de Newton. Isso é devido ao enorme número de observações e testes pelos quais as leis de Newton passaram, então qualquer teoria nova teria que passar por eles também.
Similarmente, se outra teoria substituir a evolução, a nova teoria deve, de alguma forma, explicar por que a teoria corrente passou em todos os testes. Então, qualquer teoria nova que substitua a evolução teria que explicar por que ela funciona tão bem. O criacionismo, então, não é uma substituição possível.
Q11. A evolução não promove o mal?
Mesmo que a evolução fizesse isso, isso não seria uma razão para ser assumida errada. A química é responsável por milhões de mortes todo ano, mas nós não rejeitamos suas descobertas por causa disso. Como as pessoas usam uma teoria não é julgamento da sua precisão.
Felizmente, não enfrentamos esse dilema. A evolução não diz o que é certo ou errado, mas meramente o que tem acontecido. Um relato histórico do saque de Roma não diz que o ato de saquear Roma é bom ou ruim, diz somente que isso aconteceu. Similarmente, a evolução não diz que as conclusões que as pessoas devem tomar dela sejam boas os ruins.
Enquanto muitas pessoas tem afirmado que a teoria da evolução apoia suas injustiças, nunca esqueça que muitas pessoas têm feito o mesmo com a Bíblia. A opinião de uma pessoa não deveria ser considerada como toda a verdade.
Q12. Então o que seria preciso para o criacionismo ser aceito cientificamente?
Leia as FAQs de Chris Colby para algumas evidências que precisam ser explicadas. Você também tem que propor um teste que daria diferentes resultados dependendo em se a criação ou evolução seja verdadeira. Mais importante, contudo, é a vontade de estar preparado para o resultado, mesmo que este desaprove o criacionismo. | | inglês para português: Irreducible Complexity Demystified | Texto de origem - inglês
Introduction
A new term, irreducibly complex, (IC) has been introduced into public discussions of evolution. The term was defined by Michael Behe in 1996 in his book Darwin's Black Box: The Biochemical Challenge to Evolution (1). Irreducible complexity (also denoted IC) has gained prominence as the evidence for the intelligent design (ID) movement, which argues that life is so complicated that it must be the work of an intelligent designer (aka God) rather than the result of evolution. As you may have heard, the ID movement wants this taught in public schools as a new scientific theory. This essay will, I hope, prove helpful to any school teachers, boards of education, legislators and members of the press who may be wondering about it.
The argument from IC to ID is simply:
IC things cannot evolve
If it can't have evolved it must have been designed
This article just looks at the first part, the argument that irreducibly complex systems cannot be produced by evolution, either because they just can't evolve, or because their evolution is so improbable that the possibility can be ignored.
Let's take a look at the definition of IC, and then see if we can figure out its relation to evolution, and why scientists are so unimpressed. Here is the definition, from page 39 (page numbers refer to Darwin's Black Box unless otherwise noted):
"By irreducibly complex I mean a single system composed of several well-matched, interacting parts that contribute to the basic function, wherein the removal of any one of the parts causes the system to effectively cease functioning." [emphasis in original]
IC is now a single defined term. The new definition, not the ordinary meaning of the words, is now our guide. IC refers to an organism doing something (the function) in such a way that the system (that portion of the organism that directly performs the function) has no more parts than are strictly necessary.
How do we decide when the term IC applies? Organisms don't come with parts, functions and systems labeled, nor are 'part', 'system' and 'function' technical terms in biology. They are terms of convenience. We might say, for instance, that the function of a leg is to walk, and call legs walking systems. But what are the parts? If we divide a leg into three major parts, removal of any part results in loss of the function. Thus legs are IC. On the other hand, if we count each bone as a part then several parts, even a whole toe, may be removed and we still have a walking system. We will see later that Behe's treatment of cilia and flagella follows this pattern.
What about the boundary of the system? This too is up to us. Take the digestive system for example. We may be interested only in the action of acids and enzymes in the stomach, or we may include saliva and chewing, or the lower intestine where some extraction of water and nutrients continues.
As a mental exercise, try before reading on to formulate an argument to prove that IC systems cannot evolve. IC is supposed to be the biochemical challenge to evolution, and thus the case when the parts are molecules, usually proteins, is the important case. So of course there may be multiple copies of a part. Losing a part means losing all copies of it, or at least so many that the function is effectively lost.
The Argument That Irreducible Complexity Cannot Evolve
Behe's argument that IC cannot evolve is central to ID, so it deserves our attention. His method is to divide evolution into what he calls 'direct', which he defines in a special way, and 'indirect' (everything else). He finds that direct evolution of IC is logically impossible, and indirect evolution of IC is too improbable. The argument against 'direct' evolution of IC is contained in this long sentence right after the definition:
"An irreducibly complex system cannot be produced directly
(that is, by continuously improving the initial function, which continues to work by the same mechanism)
by slight, successive modifications of a precursor system
because any precursor to an irreducibly complex system that is missing a part is by definition nonfunctional."
The last part of the sentence, "...because any precursor to an irreducibly complex system that is missing a part is by definition nonfunctional." is why we should agree to the rest of the sentence. There are some problems:
The first part of the sentence refers to slight changes. Removing a whole part is a major change;
this is a major 'disconnect' between the parts of Behe's argument.
It is not true that a precursor missing a part must be nonfunctional. It need only lack the function we specified. Even a single protein does something.
The actual precursor may have had more parts, not fewer.
If the individual parts evolve, the precursor may have had the same number of parts, not yet codependent. We will learn more about this possibility shortly.
How can one construct a valid argument that IC cannot be produced directly? ID proponents have not found a way. Yet it's easy (and left as an exercise for the reader) once you realize that a valid argument from definitions requires carefully defining the terms so that the argument becomes a tautology. This may be accomplished by redefining 'direct' or 'IC', or (best, I think) by defining Behe's expression 'be produced' which he uses in place of 'evolve'.
A precursor to IC lacking a part can have any functions except the specified one, which brings us to 'indirect' evolution. Consider a cow's tail. So far as I know, the main thing a cow uses its tail for is to swat flies. Did tails originally evolve for this function? Hardly. There were tails before there were flies. Long ago, tails helped early chordates to swim. Going back still farther, some very early animals started to have two distinct ends; one end for food intake (with sense organs for locating food) and the other end for excretions. As a consequence, this back end, and muscular extensions of it, could also be used to help the animal move. This illustrates yet another important facet of evolution: not only single mutations, but even large organs may begin more or less accidentally. It also illustrates that biological functions evolve. Indeed organisms and ecosystems evolve. It may not even make sense to expect a precursor to have had the same function.
The long term evolution of most features of life has not been what Behe, or indeed most people, would call direct. And even short term evolution can be indirect in Behe's terms. So it is surprising to read, on page 40, Behe's argument against indirect evolution of IC systems. Here is the crux of it:
"Even if a system is irreducibly complex (and thus cannot have been produced directly), however, one can not definitely rule out the possibility of an indirect, circuitous route. As the complexity of an interacting system increases, though, the likelihood of such an indirect route drops precipitously." (page 40)
He simply asserts that evolution of irreducible complexity by an indirect route is so improbable as to be virtually out of the question, except in simple cases. He makes no special connection between indirect evolution and IC. He offers no evidence. He just asserts that it is too improbable.
Actually, a more complex system probably has a long evolutionary history. Since evolution does not aim at anything in advance, the longer the history, the more circuitous it may be. And his very limited meaning of 'direct' renders much indirect that is not circuitous at all. Yet he insists:
"An irreducibly complex biological system, if there is such a thing, would be a powerful challenge to Darwinian evolution." (page 39)
Here's another exercise: before reading on, try to think of ways that IC systems, including biochemical ones, might evolve after all.
How Might Irreducible Complexity Evolve?
How might an IC system evolve? One possibility is that in the past, the function may have been done with more parts than are strictly necessary. Then an 'extra' part may be lost, leaving an IC system. Or the parts may become co-adapted to perform even better, but become unable to perform the specified function at all without each other. This brings up another point: the parts themselves evolve. Behe's parts are usually whole proteins or even larger. A protein is made up of hundreds of smaller parts called amino acids, of which twenty different kinds may be used. Evolution usually changes these one by one. Another important fact is that DNA evolves. What difference does this make, compared to saying that proteins evolve? If you think about it, each protein that your body makes is made at just the right time, in just the right place and in just the right amount. These details are also coded in your DNA (with timing and quantity susceptible to outside influences) and so are subject to mutation and evolution. For our purposes we can refer to this as deployment of parts. When a protein is deployed out of its usual context, it may be co-opted for a different function. A fourth noteworthy possibility is that brand new parts are created. This typically comes from gene duplication, which is well known in biology. At first the duplicate genes make the same protein, but these genes may evolve to make slightly different proteins that depend on each other.
We can summarize these four possibilities this way:
Previously using more parts than necessary for the function.
The parts themselves evolve.
Deployment of parts (gene regulation) evolves.
New parts are created (gene duplication) and may then evolve.
The first of these only comes up if we are looking for IC. The others are the major forms of molecular evolution observed by biologists, phrased in terms of parts. They can lead to new protein functions, sometimes slowly and sometimes, especially when parts are redeployed, abruptly. Gene duplication and changes in protein deployment may introduce a new protein 'part' into a system. Then the parts may coevolve to do something better, but in a codependent manner so that all are required, without further change in the number of parts. But what happens in nature?
Irreducible Complexity in Nature
Can evolution lead to IC or not? It is time to look at living examples and let nature decide. Behe's most famous example is a mousetrap. But since a mousetrap is not alive, it doesn't tell us much about whether or how living IC systems might evolve. How about a flytrap instead?
Venus' Flytrap
The Venus' flytrap, Dionaea muscipula, is a small flowering plant which grows naturally in acidic wetlands in North and South Carolina. It has a ferocious looking tooth-edged trap for unwary creatures. It traps and digests insects to make up for the lack of nitrogen in the soils of its habitat.
Here's how the trap works. When an insect brushes against the trigger hairs in the center, the lobes snap most of the way shut with surprising speed. If a small insect is caught, it may escape between the teeth, and then the trap reopens without fully closing. If a good sized bug is caught it is digested over the next few days as the trap closes the rest of the way. Then the trap reopens. A trap can only be fully closed about 4 times, so it must be used sparingly.
Do we have an IC system here? We must specify a function and all the parts needed to carry it out (and no extra parts). The function of interest is trapping insects for food in a manner that brings the plant more benefit than the cost of the trap. The parts are the two lobes, the hinge between the lobes (the midrib of the leaf, which anchors the lobes), the trigger hairs, and spines projecting from the edges of the lobes that make a set of bars as the trap closes. The system is just all these parts, and the trap needs all its parts in order to work. Hence it is an IC system.
How might this trap have evolved? I say 'might' have because Venus' flytraps haven't left any fossils that I know of, except a few grains of pollen. Are there any related plants that might provide a clue? Let's look at the well known sundews (Drosera). Sundews trap insects using flypaper traps, slowly closing around insects that get stuck. Darwin, whose book Insectivorous Plants (2) is now available online, made careful observations of these remarkable plants, especially the round leaf sundew D. rotundifolia. As Darwin notes,
If a small organic or inorganic object be placed on the glands in the centre of a leaf, these transmit a motor impulse to the marginal tentacles. The nearer ones are first affected and slowly bend towards the centre, and then those farther off, until at last all become closely inflected over the object. This takes place in from one hour to four or five or more hours. [...] Not only the tentacles, but the blade of the leaf often, but by no means always, becomes much incurved, when any strongly exciting substance or fluid is placed on the disc. Drops of milk and of a solution of nitrate of ammonia or soda are particularly apt to produce this effect. The blade is thus converted into a little cup. The manner in which it bends varies greatly. (2, pp 9, 12)
Here is D. rotundifolia with a fly; Makoto Honda (3) shows the action with a faster species, D. intermedia. Recent genetic research confirms that Venus's flytrap and the waterwheel plant Aldrovanda are related and are in the sundew family Droseraceae, and that snap-traps very likely evolved from flypaper traps (4) as Darwin thought:
CONCLUDING REMARKS ON THE DROSERACEAE.
The six known genera composing this family have now been described in relation to our present subject, as far as my means have permitted. They all capture insects. This is effected by Drosophyllum, Roridula, and Byblis, solely by the viscid fluid secreted from their glands; by Drosera, through the same means, together with the movements of the tentacles; by Dionaea and Aldrovanda, through the closing of the blades of the leaf. In these two last genera rapid movement makes up for the loss of viscid secretion. [...] The parent form of Dionaea and Aldrovanda seems to have been closely allied to Drosera, and to have had rounded leaves, supported on distinct footstalks, and furnished with tentacles all round the circumference, with other tentacles and sessile glands on the upper surface. (2, pp 355-6, 360).
How did the Venus' flytrap avoid the argument that IC can't evolve? In two ways. First, rather than gaining a part, it lost a part - the glue that the sundews use. Even more interestingly, the trap was able to evolve because the parts evolved. The trap started out as a Drosera-like leaf, and the parts of the leaf were progressively changed. This makes a striking contrast with the mousetrap which Behe has repeatedly presented to illustrate why IC cannot evolve. As a manufactured item the mousetrap neatly illustrates his definition, but with its static parts it cannot model evolution. With evolving parts, nature can create a snap-trap after all. The mechanical and manufacturing analogies so influential in Behe's thinking miss the flexibility of living things.
How to Eat Pentachlorophenol
Pentachlorophenol (PCP) is a highly toxic chemical, not known to occur naturally, that has been used as a wood preservative since the 1930's. It is now recognized as a dangerous pollutant that we need to dispose of. But how?
Evolution to the rescue! A few soil bacteria have already worked out a way to break it down and even eat it. And conveniently for us, they do it in an irreducibly complex way. The best known of these bacteria is called Sphingomonas chlorophenolica (also called Sphingobium chlorophenolicum).
The PCP molecule is a six carbon ring with five chlorine atoms and one hydroxyl (OH) group attached. The chlorines and the ring structure are both problems for bacteria. S. chlorophenolica uses three enzymes in succession to break it down, as follows: the first one replaces one chlorine with OH. The resulting compound is toxic, but not quite as bad as PCP itself. The second enzyme is able to act on this compound to replace two chlorines, one after the other, with hydrogen atoms. The resulting compound, while still bad, is much easier to deal with, and the third enzyme is able to break the ring open. At this point, what is left of PCP is well on its way to being food for the bacterium.
All three enzymes are required, so we have IC. How could this IC system have evolved? First of all, bacteria of this type could already metabolize some milder chlorophenols which occur naturally in small amounts. In fact the first and third enzymes were used for this. As a result the cell is triggered to produce them in the presence of chlorophenols. The second enzyme (called PcpC) is the most interesting one; the cell produces it in sufficient quantity to be effective all the time instead of just when it is needed in its normal metabolic role. Thanks to this unusual situation PcpC is available when it is needed to help eat PCP.
The inefficient regulation of PcpC is evidently the key to the whole process. So far as biologists can tell, a recent mutation that changed the deployment of this enzyme is what made PCP degradation possible for this bacterium. It also happens that both PcpC and the first enzyme in the process are now slightly optimized for dealing with PCP; they handle it better than the corresponding enzymes in strains of S. chlorophenolica that use PcpC only in its normal role, but not nearly as well as would be expected for an old, well adapted system. These factors, combined with the fact that PCP is not known to occur naturally, make a strong circumstantial case that this system has evolved very recently.
The chemistry and probable evolution of this system are explained in much greater detail in Shelly Copley's article "Evolution of a metabolic pathway for degradation of a toxic xenobiotic: the patchwork approach" in Trends in Biochemical Sciences (5).
Hemoglobin for the Active Life
Hemoglobin is a wonderful protein that picks up oxygen in our lungs and delivers it to the rest of our cells. Oxygen binds to hemoglobin very quickly in our lungs and stays bound. Then in our tissues oxygen is released very quickly. How does this happen? What we call a hemoglobin molecule is a complex of four hemoglobin chains, or subunits. There are two each of two different chains called alpha and beta hemoglobin. The complex binds reversibly to oxygen, one O2 molecule per each subunit. It tends not to bind to the first oxygen until the oxygen concentration is fairly high, which is the usual situation in our lungs. Then the complex changes shape so that the next O2 binds more readily, the third still faster, and the fourth faster yet. Then it holds the oxygen until the surrounding oxygen concentration is quite low, which happens in our tissues. When finally one oxygen is released, the next is released faster and so on. This mechanism for oxygen transport is much more efficient than can be achieved with alpha or beta hemoglobin alone, and allows for our active life style. It takes all four parts to do this; take away part of the complex and it doesn't work (6). So we have another IC system. Behe discusses hemoglobin briefly (pp 206-207), mainly commenting that it makes a poor case for Design. He doesn't mention that it is IC. This talk.origins post (7) has some sharp commentary on the subject.
The hemoglobins (globular proteins incorporating a heme group, which in turn cradles an atom of iron) turn out to be a widespread protein family with a long history. They occur in plants and bacteria as well as in animals, and have diverse functions including oxygen transport, oxygen storage, scavenging oxygen to protect some metabolic processes from it, and electron transfer. Interestingly, these diverse functions depend critically on when and where the protein is deployed. Commenting on this in his article "The Evolution of Hemoglobin", Ross Hardison says "This suggests that the creation of new protein functions arises as much from changes in regulation as from changes in structure." (8, p 126). Fetal hemoglobin, which must extract oxygen from the mother's hemoglobin, is a good example of this. We always have the genes for it, but only make it at the right time. Gene duplication has also played a key role. Lampreys and hagfish, which don't have jaws, also don't have the alpha and beta varieties of hemoglobin. Instead they have just one variety of hemoglobin in their blood, and not so efficient oxygen transport. The gene duplication which led, after further changes, to our distinct alpha and beta chains evidently happened in the ancestor of all living vertebrates with jaws.
Let's take stock of what we have learned before moving on to more complicated examples. Venus' flytrap makes an instructive comparison with Behe's mousetrap. In one, the parts evolve. In the other, they don't. What a difference this detail makes. The protein parts of biochemical systems also evolve, so the flytrap is a good model for them and the mousetrap isn't. The flytrap and hemoglobin show in different ways that removing a part is often not the same as evolution in reverse. The flytrap has already lost a part (the glue that Drosera use to trap insects). With hemoglobin, taking away either the alpha or the beta chain would be a disaster unless the whole animal could be 'evolved back' to a much earlier stage.
Both hemoglobin and the recent evolution of a way to metabolize PCP show that what we have called 'deployment of parts' is important in evolution. Biologists usually call this regulation of gene expression, or just gene regulation. From another point of view, it is called co-option or recruitment of a protein to a new function. If a protein takes on two roles, any subsequent duplication of the corresponding gene will be subject to selection for both its regulation and the separate functions. Hence this duplication will be more likely to persist and spread in the population.
Here's another interesting thing about the PCP example: it amounts to 'adding a part to a previously non-functional system', which is exactly what Behe thinks cannot happen, because he thinks the organism couldn't have lived without that part. It turns out that a single mutation can create a new function and mechanism, allowing the organism to live better or in a new environment. This is indirect evolution in Behe's terms, but to DNA it is just another mutation.
So far IC seems to be no problem for evolution. Is there anything to the biochemical challenge? Let's look at the impressively complicated examples on which IC's reputation rests.
The Blood Clotting System: is it IC?
Blood clotting is an example of what biochemists call a cascade: one protein does something, which starts another protein doing something, which starts another.... Cascades, and the clotting cascade in particular, are among the favorite examples of ID proponents. Yet giving a precise specification of system, parts, and function so that the specified system is IC turns out to be difficult. Hard to specify or not, it is still one of Behe's favorite examples. He devotes his entire fourth chapter to it. After explaining how it works, he indicates that scientists know almost nothing about how it evolved. His main evidence for this is a nontechnical lecture given by Russell Doolittle. But of course that talk, using analogies to Yin and Yang, was not meant to convey a technical understanding. After several people commented on this, Behe responded with an online essay "In Defense of the Irreducibility of the Clotting Cascade" (9). The defense comes down to saying that evolution of this system would require too many 'unselected steps'. But this is not true, as pointed out by Ken Miller in Finding Darwin's God (10) and in his online article (11) where he gives more details than the publisher wanted in the book.
The clotting cascade is a member of a family of cascades with a long pedigree. Our immune system includes a related cascade which Behe considers to be IC, but see Matt Inlay's article "Evolving Immunity" (12). A recent paper by Krem and Di Cera (13) pursues the evolution of cascades farther down the evolutionary tree. They discuss biochemically similar cascades in horseshoe crabs, fruit flies, and ourselves. They find that "Extensive similarities suggest that these cascades were built by adding enzymes from the bottom of the cascade up and from similar macromolecular building blocks." Behe argues that this type of evolution would not happen because there would be unselected steps. But he thinks in terms of precursor systems with missing parts, not in terms of ancestor organisms in different environments with different problems to solve. This may reflect a difference between thinking like a chemist and thinking like a biologist. Early forms of the cascade occurred in animals without a high pressure circulatory system like ours. In horseshoe crabs, for instance, a simpler form of the clotting cascade serves to entangle invading bacteria. There is no reason to presume unselected steps (other than gene duplication, which may be neutral at first) if the organism and its way of living and its environment are changing.
But have you noticed something missing from our discussion of the clotting cascade? We haven't proven that it is IC. The way to do this, as Behe tells us on page 42, would be to take the parts one by one and show that each is required for clotting. Or point to published research that does this. Surely Behe took care of this detail in the fourth chapter of his book? No. He 'proved' it rhetorically, but not systematically. Well then, when he published a web page several years later entitled "In Defense of the Irreducibility of the Blood Clotting Cascade" (9) he must have filled in the details? No again. He advanced his argument against the evolvability of the clotting cascade, but that has been answered (10, 11, 13, 14). Meanwhile, the little matter of proving that it is IC has been overlooked. And there is evidence to the contrary: whales, mammals like us, lack a key part called Hageman factor but their blood clots anyway (15). Under questioning at a recent meeting (16) Behe finally agreed that the cascade is not IC after all. Indeed, Acton gives reasons why he never should have thought so (14). (As far as I know, Behe has not 'done his homework' on any of his examples except the mousetrap).
Swimming Systems
We come now to what have become the very most important purported examples of IC in nature: swimming systems. These are flexible projections that microbes use to move themselves through fluids. The three main types of microbes, bacteria, archaea, and single celled eukaryotes, use different swimming structures, and there are major differences between species of each type. Some bacteria even manage to swim without flagella, including little understood Synechococcus (17) and much better understood Spiroplasma melliferum (18). Of course microbial motion is not limited to swimming. They also have ways to move along surfaces and maneuver in sand and ooze. Bardy et al. review almost all of the known ways bacteria and archaea move (19).
Swimming systems depend on what are called molecular motors, a favorite topic of molecular biologists. Those who are curious about molecular motors may start here (20). Brownian ratchets, fascinating in their own right (21), are one of the energy sources for these tiny motors.
From a biological perspective, the function of an organism is to live and grow enough to reproduce. The function of any part of the organism is to contribute to this in any ways whatsoever. Appendages can help a cell in various ways such as sensing the environment, finding food or mates or communicating with other cells. It helps if the appendage can move about. This in turn will move the cell a little. (Think of waving your arm under water). In an environment where swimming is advantageous, it is not surprising that the ability to swim would evolve. Never the less, as the evolution of vertebrate systems like the clotting cascade and the immune system has become better understood, ID proponents have come to rely more and more on swimming systems, especially the bacterial flagellum, as the real evidence for Design in nature.
The Eukaryote Cilium
Eukaryotes are any organisms like trees, people, protozoa and amoebae which, unlike bacteria, have their DNA in a separate nucleus within the cell. Many eukaryote microbes propel themselves through water by waving projections called cilia, which they also use to collect food such as bacteria. A bit of terminology: cilia are also called flagella, especially when a cell only has one or two. The microbes are then called flagellates. But eukaryote flagella and bacterial flagella are entirely different structures.
How do we define an IC system in the case of the eukaryotic cilium? Behe first specifies the system as the entire cilium. The function of the system is to move the cell through liquid by a sort of waving action. What about parts? At the level of biochemical machines, one usually thinks of individual proteins as parts. But Behe simply divides a cilium into three large parts, which he calls 'motor, connector, and paddle' (page 65). It is clear that a cilium wouldn't work without each of these big parts, so we have IC. Cilia are many and diverse (for examples see Finding Darwin's God (10, page 142)) and may contain two hundred or so different proteins and various numbers of microtubules. Some proteins are always present; others vary from microbe to microbe. If we take proteins as our parts (the biochemical challenge), then cilia aren't IC; no one has been able to find a real cilium with an 'irreducible' set of proteins. If we take microtubules as our parts as Miller does, the cilium is not IC. But with Behe's parts it is IC. Remember, it's up to us to choose function, system and parts to satisfy the definition. Or not. So it turns out that being IC or not is not a property of the cilium itself. It depends on choices we make.
With the parts (motor, connector and paddle) so removed from the mutation-by-mutation level of change, how does Behe relate the ICness of the system to its evolution? First, with his choice of function, parts and system, it is IC. This rules out 'direct' evolution to his satisfaction. What about 'indirect', i.e. normal evolution, taking into account that everything changes including functions? This is ridiculed on pages 65-67. Although the cilium is an extension of the cell's cytoskeleton, he suggests that a proto-cilium would be disadvantageous. He winds up:
"... but even if [a proto-cilium] were at the cell surface, the number of motor proteins would probably not be enough to move the cilium. And even if the cilium moved, an awkward stroke would not necessarily move the cell. And if the cell did move, it would be an unregulated motion using energy and not corresponding to any need of the cell."
So a proto-cilium would be useless and probably even a harmful waste of resources until it was perfected, in Behe's opinion.
Microbes do not agree, and make use of a variety of projections that have the 'defects' that Behe mentions. The amoeba Raphidiophrys pallida, shown here (22) has projections called axopodia which it uses to capture prey and to move itself along a surface such as a bit of pond weed. The protozoan Actinophrys in this Pond Scum Action Video (23) explores with gently waving axopodia. Foraminifera are very common protists in the oceans and in the ooze beneath. They use projections called reticulopodia to find and capture food, and to maneuver among sand grains (24). These projections, although dependent on many of the same proteins for motion, are not cilia. But they resemble the clumsy cilia that Behe objects to, and show that his objections do not hold up in nature.
Now, what about cilia in the strict sense? The cilium in its early form would have been too short to function as a rowing device. What could it have done? The first flagellates are long gone, but we can still learn from the ones at the base of the family tree as it now exists. The soil dwelling flagellate Phalansterium is about as basal as any. It is hard to watch in action, but it probably uses its cilium to sense the environment and to collect bacteria to eat. The eukaryote family tree has two main branches, leading to plants and animals. At the base of these branches we find water dwelling flagellates that push water in opposite directions (25, 26). Mastigamoeba creep along surfaces and move their cilium to create a slight current toward themselves, drawing in food particles. Choanoflagellates, on the line leading to animals, use their cilium to push water away (27). This draws in more water, and food along with it.
Any projection that could stir the water at all would help to bring more food to the microbe. Gradually improving it naturally leads to a swimming system. Behe's objections overlook evolutionary change of function, which would naturally occur to a biologist but perhaps not to a chemist like him.
The Archaeal Flagellum
Archaebacteria, or Archaea for short, have recently been recognized as an important group of microbes distinct from bacteria and from eukaryotes. Their flagellum is analogous to a bacterial flagellum, but simpler and quite different in detail. As the diagram shows, it resembles another kind of projection called a type IV pilus, to which it is probably related (19). Type IV pili themselves are not used for swimming, but bacteria use them for simpler ways of moving called twitching and social gliding (19, 28, 29). Behe has not discussed archaeal flagella, and I am not sure how he would divide them into parts. They don't appear to fit his preferred three part division (a motor, then a rotor or connector, then a third part which pushes against the medium) on which he bases his statement that "the complexity is inherent in the task itself" (page 65).
The Bacterial Flagellum
Here it is -- the number one argument for design in nature. ID advocates have even made a movie called Bacterial Flagella: A Paradigm for Design. It is on sale at the ARN web site (30) and briefly discussed in talk.origins (31). Behe said recently:
"If [biologist Jerry] Coyne demonstrated that the [bacterial] flagellum, (which requires approximately forty gene products) could be produced by selection, I would be rather foolish to then assert that the blood clotting system (which consists of about twenty proteins) required intelligent design". (32)
Bacterial flagella are many, diverse, and complicated. Behe concludes that any bacterial flagellum is composed of at least three parts: a paddle, a rotor, and a motor, and so with swimming as the specified function must be IC (page 72). Even at this crude level, the ICness of a flagellum is not so clear. The problem is that there are additional parts to a complete flagellum. For instance, there are proteins at the base that react to external stimuli and turn the motor on and off, and in some flagella cause it to change directions. And there are other proteins that are arranged in rings where the flagellum passes through the cell membrane.
But the more interesting question is: could a flagellum be IC with proteins, not paddles etc. as parts? Remember, IC is supposed to be the biochemical challenge to evolution. We've already seen that it isn't such a challenge after all, but so much has been made of the purported ICness of the flagellum that one should be well informed on the subject just to be more interesting at parties :). In order to decide, one must first choose a flagellum. Even within a single bacteria species, different strains may have different proteins and different numbers of proteins in their flagella. Even a single rod-shaped bacterium may have quite different flagella at its ends and around its sides. Next, discover and list all the proteins in that particular flagellum. This requires deciding just where it begins, and one's decision about this may depend on the exact function one has in mind for 'the' flagellum. Then comes the hard part: proving that every last protein is required for the function. Oddly, ID proponents show no interest in doing any of this work, not even picking a particular flagellum of a particular bacterium to start on. It is as if just asserting the ICness of 'the' flagellum gives them full satisfaction.
What's the answer? Is any flagellum IC with proteins as parts or not? As this would depend on arbitrary criteria, scientists have not pursued this question as such. But quite a bit has been learned about various flagella. It is clear that all of them absolutely require a good many of their proteins in order to function as swimming systems. But not one is yet known to require every last protein, and some are known not to (19, 33, 34). Could a flagellum be IC with proteins as parts? Sure. As we have seen in the much simpler case of hemoglobin, proteins can evolve to become codependent. There may be a perfectly IC flagellum out there just waiting to be discovered.
Even so, it wouldn't be the simplest swimming system. As the diagram shows, a bacterial flagellum is much more complex than an archaeal one. This is in part because it is built from, in fact secreted by what is called a type three secretion system (TTSS). This is a complicated thing in itself. It is a tiny tube which starts below the cell wall and sticks out through it, and serves as a conduit for protein export. The flagellar TTSS (there are other kinds) specializes in secreting the rest of a flagellum. The TTSS base counts as part of the flagellum, and is itself about as complex as an archaeal flagellum.
Since it is more complicated than is required for swimming alone, you might suspect that a bacterial flagellum has other functions. You would be right. These other functions vary from bacterium to bacterium and from situation to situation, and scientists have only recently been able to observe them. First, some flagella also export proteins, including ones that cause sickness (35). This is not too surprising since that's what the other TTSS's are known for.
But spirochetes, the spiral shaped bacteria, use flagella in a way one wouldn't expect. Their flagella don't stick out, yet are used for swimming, burrowing, and maintaining the cell's shape. Flagella are grown at both ends and extend toward the middle under the outer membrane. The flagella maintain the cell's spiral shape, and by rotating can create a moving wave along the cell, causing the cell to move in the opposite direction (19).
It is not easy to observe the behavior of individual bacteria in the wild. Just recently though, Danish researchers noticed some unusual behavior by bacteria living on low oxygen marine sediments. To see exactly what the bacteria were doing, they recreated the ecosystem in the laboratory. Who would have thought that some bacteria, shaped like slightly bowed rods, would tether themselves to the sediment with a mucus stalk secreted from the center and then use flagella at both ends to move like a propeller? But that's what these bacteria do. They create a tiny current, refreshing the water around them much faster than diffusion alone could do it (36).
Bacteria can move across surfaces in organized swarms, and quickly colonize a new food source such as your own much larger cells. When swarming, they often grow more flagella than usual and make cell-to-cell contacts with these flagella (37). Some bacteria also use their flagella to hang on to our cells as they try to break in and eat the cell contents (38).
This brings us to the dark side of design. Flagella participate in the cause of quite a few bacterial diseases, including diarrhea (38), ulcers and urinary tract infections (39). If the Designer is directly responsible for flagella then he is implicated as a cause of human diseases. Diarrhea is no joke; it is a leading cause of infant death in some parts of the world. To make matters worse, one can hardly give the Designer credit for flagella without also crediting him with TTSS's in general (40). This puts the Designer solidly behind Bubonic plague (41, 42) and many other diseases (43). Happily, science makes such beliefs unnecessary.
Swimming systems provide a good illustration of how (not) to think about evolution. Behe argues that evolution can't produce them because they are IC (a dubious claim and not an obstacle to evolution as we have seen). He buttresses this by arguing that is quite improbable that a swimming system good enough to be useful would appear all at once. And it wouldn't evolve slowly, he supposes, because until it became an effective swimming system, there would be nothing for natural selection to select. However, he envisions a part that sticks out, but that has no use at all other than swimming - and at first it can't even do that. But parts that stick out can have a number of functions, and bacterial flagella clearly have several. If there is another reason for it to be there, the sticking out part can gradually evolve more abilities. This involves change of function, or indirect evolution as Behe calls it. He dismisses this possibility, calling it improbable. A closer look shows the opposite.
IC Cores
Have you noticed that none of our complex examples is IC at the molecular level? The argument that IC can't evolve is made in general terms, but it is at the molecular level that the 'biochemical challenge to evolution' is supposed to really count. Granted, we have seen that IC can evolve, but proponents of 'IC implies ID' are able to overlook this. They have not entirely overlooked the fact that not even one impressively complicated molecular system has been shown to be IC. The proposed solution to this problem is that these systems have 'IC cores': if you remove proteins one by one, at some point what is left will be IC. And if you remove parts in a different order, you may find other IC cores. But arbitrarily removing parts that have become coadapted is not "evolution in reverse", so IC cores don't tell us about evolution. And how are they relevant to IC if nature uses more than the core? All I know is that IC cores seem to matter to ID proponents.
Now let's take a more biological look at it. The whole irreducible complexity argument is based on fixed functions, parts, systems, organisms and environments. In nature all these things vary. Evolution, appropriately enough, is all about change. The search for what might be called an evolutionarily irreducible core to any of the complex examples will take you back, back, back to who knows what? The immediate precursor may have had more parts. Or if it had fewer parts, it is probably not appropriate to remove a part before modifying the parts so that they are not coadapted and codependent. Perhaps the whole organism should be modified and placed in a different environment before removing a part. Where do you stop (14)?
Since we found that simple IC systems readily evolve, why are complicated ones hard to find? Some of the same modes of change that can produce IC can just as well add complications that don't fit the definition. Most genes are members of gene families that have grown through gene duplication over time. The time since a particular duplication happened can be estimated by the amount of difference between members of the family. This is a dead giveaway that the organism's ancestors got along with fewer "parts". And given a large number of parts, these parts are likely to have additional functions, which is a good reason for there to be more parts than the minimum needed for what we decide is 'the' function of those parts. For example, we noted earlier that whales lack one of our blood clotting proteins, called Hageman factor. People are sometimes born with a mutation that leaves them with only 40 to 60 percent of the normal amount of Hageman factor. Their blood still clots. But women with reduced Hageman factor tend to have more miscarriages.
How Does Irreducible Complexity Get Its Charm?
Evolution doesn't even notice whether a combination of parts, system and function chosen by an observer happens to satisfy a definition in a book. It just doesn't matter. This is in a nutshell what scientists have been saying since Darwin's Black Box was published (44). Yet the book has been very influential with the public (see for instance the 370 or so reviews at amazon.com (45)). And it provides the one seemingly scientific reason to teach ID in public school science classes.
How can the book's success with laymen be explained? First, it appears that evolution is hardly taught in the US. Basic knowledge such as the four modes of evolutionary change given at the beginning of this essay would show a reader that evolution is much too flexible for IC to be an issue. Biological basics and careful reading would enable one to see that Behe's theoretical argument that IC can't evolve is unsound.
Without a good basic understanding of biology, a tricky ambiguity sets in. First, there is the definition of IC. Then comes the apparent proof that it cannot evolve. After that, 'unevolvable' is casually used as the meaning of IC. To complete the picture, the subtext all along is that IC is impressively complicated. Thus one's attention is directed away from simple cases which directly show how basic modes of evolutionary change may lead to IC. The definition is used to argue that IC exists, and the other two meanings seal the conviction that IC systems are very unnatural indeed. It is a case of using words which seem to mean what some people want them to mean, but on closer examination don't. This results in the reader losing sight of the fact that none of Behe's examples are in fact IC in biochemical terms, and of the fact that IC doesn't matter for evolution in any case, so that there actually is no 'biochemical challenge to evolution' at all.
IC, ID, and Creationism
Is IC/ID a form of creationism? It looks like it to many people, but proponents reject that label. Let's see if we can sort it out.
You may have heard that ID differs from creationism in not insisting that the earth is only a few thousand years old. It's not quite that simple. Creationists come in both 'young earth' and 'old earth' varieties. So do ID proponents. The difference is that old and young earth creationists are at odds. ID, on the other hand, takes a 'big tent' approach. You are free to accept geological evidence or wave it aside. The Designer could have made the earth look older than it is.
ID mirrors creationist thinking in a fundamental way that you might not notice if you are not familiar with the genre. All creationists agree that there are some inherited genetic changes. The different breeds of dogs, for instance, are not held to be special creations. But creationists always divide evolutionary changes into two kinds: there is a simple kind of change, which they agree evolution can do. But evolution is always somehow blocked from causing the really significant changes, either because evolution just can't do it, or it is so improbable that you can forget about it in practice. Is this beginning to sound familiar? IC biochemical systems are what biochemist Behe has decided evolution cannot produce. According to him, they literally can't evolve directly and their indirect evolution is too improbable.
Creationists often assert that intermediate forms along the way to things they say could not evolve just would not work, and make fun of intermediates (as described by themselves). As we have seen, Behe also does this. In support of this view, he proposes what he calls minimal function as "... another difficulty for Darwin" (page 45). This is explained by imagining being stranded in the middle of a lake in a small boat powered by a propeller that only turns at one revolution per hour. The implication is that a flagellum must have been a quite capable swimming system the first time out, or it couldn't evolve. This idea is another consequence of dismissing change of function, or indirect evolution as he calls it, out of hand. As we already know, parts that stick out, including flagella as the finely adapted swimming organs that they now are, can have other functions. The projection that became the flagellum as we know it may not have have started as a swimming system at all, and is very unlikely to have had that function alone.
Precisely pinpointing a barrier that evolution can't cross is the Holy Grail of creationism. Behe claims to have done it. Naturally creationists are enthusiastic, nor is it surprising that many observers see IC and ID as simply a new version of creationism. Still, leading proponents try to distance themselves from the term. The term 'neocreationism' is a good compromise. It acknowledges new developments and important continuities alike.
Why are biologists never convinced that the barriers claimed by creationists are real? It always come |
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