07-10-2005, 02:03 PM #1
Speciation, creationisnt read this site
found the link in a post by tock. Havent had time to read it through but it seems like he gives alot of examples of one species turning into another. A thing max2 has been requesting for a long time.
07-10-2005, 07:31 PM #2
sounds to me like hes trying to redifine the term species to make it fit what he believes. we have many different species. correct? each species has different DNA. correct? where did all these different DNA species come from? evolution will have you believe that one DNA living creature, evolved into another DNA living creature, into a different DNA living creature and so on until we have the many different species of today. that is what evolution is talking about with the beginning of life theory, and that isnt explained in that article. seems hes talking about microevolution and not macroevolution, but trying to make it seem like its macroevolution. am i wrong there or did i miss something in the article?
07-11-2005, 12:19 AM #3Originally Posted by max2extreme
A discussion of speciation requires a definition of what constitutes a species. This is a topic of considerable debate within the biological community. Three recent reviews in the Journal of Phycology give some idea of the scope of the debate (Castenholz 1992, Manhart and McCourt 1992, Wood and Leatham 1992). There are a variety of different species concept currently in use by biologists. These include folk, biological, morphological, genetic, paleontological, evolutionary, phylogenetic and biosystematic definitions. In the interest of brevity, I'll only discuss four of these -- folk, biological, morphological and phylogenetic. A good review of species definitions is given in Stuessy 1990.
If you have contributions to make to these egghead's views, I'd like to know why what you have to add should be taken as anything more than an opinionated layman's opinion.
Originally Posted by max2extreme
07-11-2005, 01:06 AM #4
well tock, ill let you name it whatever you want. a living creature with a certain DNA, later to be named by tock, evolving into a living creature with a different DNA, later to be named by tock, has zero backing.
do you not see hes trying to get around the truth by saying "oh well, it depends on what YOU say a species is". come on. you go to a dog show, and someone brings a monkey... "well it depends on what YOU say a dog is." whatever.
07-11-2005, 03:42 AM #220.127.116.11 Evening Primrose (Oenothera gigas)
While studying the genetics of the evening primrose, Oenothera lamarckiana, de Vries (1905) found an unusual variant among his plants. O. lamarckiana has a chromosome number of 2N = 14. The variant had a chromosome number of 2N = 28. He found that he was unable to breed this variant with O. lamarckiana. He named this new species O. gigas.
18.104.22.168 Hemp Nettle (Galeopsis tetrahit)
A species of hemp nettle, Galeopsis tetrahit, was hypothesized to be the result of a natural hybridization of two other species, G. pubescens and G. speciosa (Muntzing 1932). The two species were crossed. The hybrids matched G. tetrahit in both visible features and chromosome morphology.
Frandsen (1943, 1947) was able to do this same sort of recreation of species in the genus Brassica (cabbage, etc.). His experiments showed that B. carinata (n = 17) may be recreated by hybridizing B. nigra (n = 8) and B. oleracea, B. juncea (n = 18) may be recreated by hybridizing B. nigra and B. campestris (n = 10), and B. napus (n = 19) may be recreated by hybridizing B. oleracea and B. campestris.
22.214.171.124 Woodsia Fern (Woodsia abbeae)
Woodsia abbeae was described as a hybrid of W. cathcariana and W. ilvensis (Butters 1941). Plants of this hybrid normally produce abortive sporangia containing inviable spores. In 1944 Butters found a W. abbeae plant near Grand Portage, Minn. that had one fertile frond (Butters and Tryon 1948). The apical portion of this frond had fertile sporangia. Spores from this frond germinated and grew into prothallia. About six months after germination sporophytes were produced. They survived for about one year. Based on cytological evidence, Butters and Tryon concluded that the frond that produced the viable spores had gone tetraploid. They made no statement as to whether the sporophytes grown produced viable spores.5.2.1 Stephanomeira malheurensis
Gottlieb (1973) documented the speciation of Stephanomeira malheurensis. He found a single small population (< 250 plants) among a much larger population (> 25,000 plants) of S. exigua in Harney Co., Oregon. Both species are diploid and have the same number of chromosomes (N = 8). S. exigua is an obligate outcrosser exhibiting sporophytic self-incompatibility. S. malheurensis exhibits no self-incompatibility and self-pollinates. Though the two species look very similar, Gottlieb was able to document morphological differences in five characters plus chromosomal differences. F1 hybrids between the species produces only 50% of the seeds and 24% of the pollen that conspecific crosses produced. F2 hybrids showed various developmental abnormalities.
5.9.2 Morphological Changes in Bacteria
Shikano, et al. (1990) reported that an unidentified bacterium underwent a major morphological change when grown in the presence of a ciliate predator. This bacterium's normal morphology is a short (1.5 um) rod. After 8 - 10 weeks of growing with the predator it assumed the form of long (20 um) cells. These cells have no cross walls. Filaments of this type have also been produced under circumstances similar to Boraas' induction of multicellularity in Chlorella. Microscopic examination of these filaments is described in Gillott et al. (1993). Multicellularity has also been produced in unicellular bacterial by predation (Nakajima and Kurihara 1994). In this study, growth in the presence of protozoal grazers resulted in the production of chains of bacterial cells.
I have a friend who says since we have never seen a species actually split into two different species during recorded history that he has trouble believing in the theory of evolution. Is this bogus and have humans seen animals bred into different species? (The various highly bred english dogs come to mind but I suppose this would be easier to find in vegetation. Corn, wheat strains? Donkeys and mules? )
This is bogus. We've seen it happen naturally without our tampering with the process. From the FAQ:
"Three species of wildflowers called goatsbeards were introduced to the United States from Europe shortly after the turn of the century. Within a few decades their populations expanded and began to encounter one another in the American West. Whenever mixed populations occurred, the specied interbred (hybridizing) producing sterile hybrid offspring. Suddenly, in the late forties two new species of goatsbeard appeared near Pullman, Washington. Although the new species were similar in appearance to the hybrids, they produced fertile offspring. The evolutionary process had created a separate species that could reproduce but not mate with the goatsbeard plants from which it had evolved."
The article is on page 22 of the February, 1989 issue of Scientific American. It's called "A Breed Apart." It tells about studies conducted on a fruit fly, Rhagoletis pomonella, that is a parasite of the hawthorn tree and its fruit, which is commonly called the thorn apple. About 150 years ago, some of these flies began infesting apple trees, as well. The flies feed an breed on either apples or thorn apples, but not both. There's enough evidence to convince the scientific investigators that they're witnessing speciation in action. Note that some of the investigators set out to prove that speciation was not happening; the evidence convinced them otherwise.
if you are looking for a experiment that shows a population of dogs suddenly turns into elephants that wont happen. Would you accept one bacteria turning into another as a good example of a spieces change?
07-11-2005, 04:00 AM #6
why faith isnt needed to belive in evolution
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.
Evolution never clamining to know the origin of the first life form
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.
07-11-2005, 04:13 AM #7The strongest evidence for macroevolution comes from the fact that suites of traits in biological entities fall into a nested pattern. For example, plants can be divided into two broad categories, non- vascular (ex. mosses) and vascular. Vascular plants can be divided into seedless (ex. ferns) and seeded. Vascular seeded plants can be divided into gymnosperms (ex. pines) and flowering plants (angiosperms). Angiosperms can be divided into monocots and dicots. Each of these types of plants have several characters that distinguish them from other plants. Traits are not mixed and matched in groups of organisms. For example, flowers are only seen in plants that carry several other characters that distinguish them as angiosperms. This is the expected pattern of common descent. All the species in a group will share traits they inherited from their common ancestor. But, each subgroup will have evolved unique traits of its own. Similarities bind groups together. Differences show how they are subdivided.
07-11-2005, 04:16 AM #8
Transitional forms have been found
The theory of punctuated equilibrium is an inference about the process of macroevolution from the pattern of species documented in the fossil record. In the fossil record, transition from one species to another is usually abrupt in most geographic locales -- no transitional forms are found. In short, it appears that species remain unchanged for long stretches of time and then are quickly replaced by new species. However, if wide ranges are searched, transitional forms that bridge the gap between the two species are sometimes found in small, localized areas. For example, in Jurassic brachiopods of the genus Kutchithyris, K. acutiplicata appears below another species, K. euryptycha. Both species were common and covered a wide geographical area. They differ enough that some have argued they should be in a different genera. In just one small locality an approximately 1.25m sedimentary layer with these fossils is found. In the narrow (10 cm) layer that separates the two species, both species are found along with transitional forms. In other localities there is a sharp transition.
07-11-2005, 04:22 AM #9
I like these quotes
Let me try to make crystal clear what is established beyond reasonable doubt, and what needs further study, about evolution. Evolution as a process that has always gone on in the history of the earth can be doubted only by those who are ignorant of the evidence or are resistant to evidence, owing to emotional blocks or to plain bigotry. By contrast, the mechanisms that bring evolution about certainly need study and clarification. There are no alternatives to evolution as history that can withstand critical examination. Yet we are constantly learning new and important facts about evolutionary mechanisms.
- Theodosius Dobzhansky "Nothing in Biology Makes Sense Except in the Light of Evolution", American Biology Teacher vol. 35 (March 1973) reprinted in Evolution versus Creationism, J. Peter Zetterberg ed., ORYX Press, Phoenix AZ 1983
It is time for students of the evolutionary process, especially those who have been misquoted and used by the creationists, to state clearly that evolution is a fact, not theory, and that what is at issue within biology are questions of details of the process and the relative importance of different mechanisms of evolution. It is a fact that the earth with liquid water, is more than 3.6 billion years old. It is a fact that cellular life has been around for at least half of that period and that organized multicellular life is at least 800 million years old. It is a fact that major life forms now on earth were not at all represented in the past. There were no birds or mammals 250 million years ago. It is a fact that major life forms of the past are no longer living. There used to be dinosaurs and Pithecanthropus, and there are none now. It is a fact that all living forms come from previous living forms. Therefore, all present forms of life arose from ancestral forms that were different. Birds arose from nonbirds and humans from nonhumans. No person who pretends to any understanding of the natural world can deny these facts any more than she or he can deny that the earth is round, rotates on its axis, and revolves around the sun.
The controversies about evolution lie in the realm of the relative importance of various forces in molding evolution.
- R. C. Lewontin "Evolution/Creation Debate: A Time for Truth" Bioscience 31, 559 (1981) reprinted in Evolution versus Creationism, op cit.
This concept is also explained in introductory biology books that are used in colleges and universities (and in some of the better high schools). For example, in some of the best such textbooks we find:
Today, nearly all biologists acknowledge that evolution is a fact. The term theory is no longer appropriate except when referring to the various models that attempt to explain how life evolves... it is important to understand that the current questions about how life evolves in no way implies any disagreement over the fact of evolution.
- Neil A. Campbell, Biology 2nd ed., 1990, Benjamin/Cummings, p. 434
Since Darwin's time, massive additional evidence has accumulated supporting the fact of evolution--that all living organisms present on earth today have arisen from earlier forms in the course of earth's long history. Indeed, all of modern biology is an affirmation of this relatedness of the many species of living things and of their gradual divergence from one another over the course of time. Since the publication of The Origin of Species, the important question, scientifically speaking, about evolution has not been whether it has taken place. That is no longer an issue among the vast majority of modern biologists. Today, the central and still fascinating questions for biologists concern the mechanisms by which evolution occurs.
- Helena Curtis and N. Sue Barnes, Biology 5th ed. 1989, Worth Publishers, p. 972
One of the best introductory books on evolution (as opposed to introductory biology) is that by Douglas J. Futuyma, and he makes the following comment:
A few words need to be said about the "theory of evolution," which most people take to mean the proposition that organisms have evolved from common ancestors. In everyday speech, "theory" often means a hypothesis or even a mere speculation. But in science, "theory" means "a statement of what are held to be the general laws, principles, or causes of something known or observed." as the Oxford English Dictionary defines it. The theory of evolution is a body of interconnected statements about natural selection and the other processes that are thought to cause evolution, just as the atomic theory of chemistry and the Newtonian theory of mechanics are bodies of statements that describe causes of chemical and physical phenomena. In contrast, the statement that organisms have descended with modifications from common ancestors--the historical reality of evolution--is not a theory. It is a fact, as fully as the fact of the earth's revolution about the sun. Like the heliocentric solar system, evolution began as a hypothesis, and achieved "facthood" as the evidence in its favor became so strong that no knowledgeable and unbiased person could deny its reality. No biologist today would think of submitting a paper entitled "New evidence for evolution;" it simply has not been an issue for a century.
- Douglas J. Futuyma, Evolutionary Biology, 2nd ed., 1986, Sinauer Associates, p. 15
There are readers of these newsgroups who reject evolution for religious reasons. In general these readers oppose both the fact of evolution and theories of mechanisms, although some anti-evolutionists have come to realize that there is a difference between the two concepts. That is why we see some leading anti-evolutionists admitting to the fact of "microevolution"--they know that evolution can be demonstrated. These readers will not be convinced of the "facthood" of (macro)evolution by any logical argument and it is a waste of time to make the attempt. The best that we can hope for is that they understand the argument that they oppose. Even this simple hope is rarely fulfilled.
There are some readers who are not anti-evolutionist but still claim that evolution is "only" a theory which can't be proven. This group needs to distinguish between the fact that evolution occurs and the theory of the mechanism of evolution.
We also need to distinguish between facts that are easy to demonstrate and those that are more circumstantial. Examples of evolution that are readily apparent include the fact that modern populations are evolving and the fact that two closely related species share a common ancestor. The evidence that Homo sapiens and chimpanzees share a recent common ancestor falls into this category. There is so much evidence in support of this aspect of primate evolution that it qualifies as a fact by any common definition of the word "fact."
In other cases the available evidence is less strong. For example, the relationships of some of the major phyla are still being worked out. Also, the statement that all organisms have descended from a single common ancestor is strongly supported by the available evidence, and there is no opposing evidence. However, it is not yet appropriate to call this a "fact" since there are reasonable alternatives.
Finally, there is an epistemological argument against evolution as fact. Some readers of these newsgroups point out that nothing in science can ever be "proven" and this includes evolution. According to this argument, the probability that evolution is the correct explanation of life as we know it may approach 99.9999...9% but it will never be 100%. Thus evolution cannot be a fact. This kind of argument might be appropriate in a philosophy class (it is essentially correct) but it won't do in the real world. A "fact," as Stephen J. Gould pointed out (see above), means something that is so highly probable that it would be silly not to accept it. This point has also been made by others who contest the nit-picking epistemologists.
The honest scientist, like the philosopher, will tell you that nothing whatever can be or has been proved with fully 100% certainty, not even that you or I exist, nor anyone except himself, since he might be dreaming the whole thing. Thus there is no sharp line between speculation, hypothesis, theory, principle, and fact, but only a difference along a sliding scale, in the degree of probability of the idea. When we say a thing is a fact, then, we only mean that its probability is an extremely high one: so high that we are not bothered by doubt about it and are ready to act accordingly. Now in this use of the term fact, the only proper one, evolution is a fact. For the evidence in favor of it is as voluminous, diverse, and convincing as in the case of any other well established fact of science concerning the existence of things that cannot be directly seen, such as atoms, neutrons, or solar gravitation ....
So enormous, ramifying, and consistent has the evidence for evolution become that if anyone could now disprove it, I should have my conception of the orderliness of the universe so shaken as to lead me to doubt even my own existence. If you like, then, I will grant you that in an absolute sense evolution is not a fact, or rather, that it is no more a fact than that you are hearing or reading these words.
- H. J. Muller, "One Hundred Years Without Darwin Are Enough" School Science and Mathematics 59, 304-305. (1959) reprinted in Evolution versus Creationism op cit.
07-11-2005, 04:31 AM #10
07-11-2005, 05:20 AM #11
i think this is getting above our heads, or at least the ones that are contributing, if not, at least it is above mine... if this was what the arguement is trying to be, i think it would be big news and scientists would be on tv, in news, saying "weve proven evolution" but we dont see that happening. theres got to be a reason why, and its above me to rebute it. thanks for the posts though johan and tock.
heres unbiased info.
Comparing the DNA of different organisms can show how closely related they are. Since for each species the DNA information is organized in a characteristic number of chromosomes, the number of chromosomes is a reasonable indicator of the relatedness of two simliar species.
Sometimes the DNA information on a chromosome is reorganized. Chromosomes can sometimes fuse with each other or can exchange chromosome "arms". When this happens, DNA information is not always lost, but it can become mixed up. This sort of rearrangement may not cause problems for the individual who carries the change --- as long as all the DNA is still present.
A mule is the product of two different species (a horse and a donkey) mating with each other. The fact that these two different types of animals can mate and produce viable offspring tells scientists that horses and donkeys are closely related. However, mules are always sterile. Why is this? Horses and donkeys have different chromosome numbers (see below). The fact that horses and donkeys have different chromosome numbers tells scientists that these two are different species.
For the mule, having parents with different chromosome numbers isn't a problem. During mitotic cell division, each of the chromosomes copies itself and then distributes these two copies to the two daughter cells. In contrast, when the mule is producing sperm or egg cells during meiosis, each pair of chromosomes (one from Mom and one from Dad) need to pair up with each other. Since the mule doesn't have an even number of homologous pairs (his parents had different chromosome numbers), meiosis is disrupted and viable sperm and eggs are not formed.
Using chromosomes to classify plant species
One Utah species originally assigned to Notholaena has 27 chromosomes.
Variations in chromosome number are even more common in the plant kingdom. In plants, chromosome number is an important indicator for determining relationships between plant species.
Scientists at the Utah Museum of Natural History recently used studies of chromosome number to show that a Utah fern was not the same species as a very similar fern found in other states. Studies of the Utah Jones Cloak Fern (originally thought to be a Notholaena species) showed that the cells of this plant have 27 chromosomes. Other species of Notholaena found in other states have 30 chromosomes. When combined with the results of other studies, the difference in chromosome number helped to prove that the Utah species actually belonged in the genus Argyrochosma, a very distant relative of Notholaena .
This sort of information is important because it helps conservation biologists understand the distribution of each different species of plant. With this sort of information, scientists are better able to decide which plants are rare and require protection by means such as the endangered species list.
07-11-2005, 05:29 AM #12
one thing i do know though, in order for evolution to happen from the first lifeform, additions have to be made to the DNA....nowhere in this post (that i saw) says that this happened. leads me to believe that it was a mixup of the dna, but not an addition.
07-11-2005, 05:30 AM #13
yes its above my head to.
But to be honest the ending qoutes(wich seems to be shared by the ENTIRE scientific comunity, from science mags to egghead proffesors) shows that evolution doesnt need to be proven. It IS considered a solid fact in the scientific world. Just as theory of relativity or any other grand theory is. A small small amount of creationists is trying to stir the pot and make it seem like it isnt like that. But if looking at talkorigins for instance a good rebuttle to every creationist claim can be found. The creationists that got all this started recently hasnt even answered or recognised the rebuttles to his claims like irreversible complexity. He knows he is defeated and try to play it off. A joke.
So enormous, ramifying, and consistent has the evidence for evolution become that if anyone could now disprove it, I should have my conception of the orderliness of the universe so shaken as to lead me to doubt even my own existence. If you like, then, I will grant you that in an absolute sense evolution is not a fact, or rather, that it is no more a fact than that you are hearing or reading these words.We also need to distinguish between facts that are easy to demonstrate and those that are more circumstantial. Examples of evolution that are readily apparent include the fact that modern populations are evolving and the fact that two closely related species share a common ancestor. The evidence that Homo sapiens and chimpanzees share a recent common ancestor falls into this category. There is so much evidence in support of this aspect of primate evolution that it qualifies as a fact by any common definition of the word "fact."
Let me try to make crystal clear what is established beyond reasonable doubt, and what needs further study, about evolution. Evolution as a process that has always gone on in the history of the earth can be doubted only by those who are ignorant of the evidence or are resistant to evidence, owing to emotional blocks or to plain bigotry
07-11-2005, 05:32 AM #14Originally Posted by max2extreme
07-11-2005, 05:33 AM #15
anyway Im working evening and night today yuck and need to get to work. This is a good thread I love threads like this forces me to read alot of interesting stuff
have a nice day guys.
07-11-2005, 08:07 AM #16Originally Posted by JOHAN
Originally Posted by JOHAN
Originally Posted by JOHAN
about the ape to man thing, id be interrested in starting a thread about that. i dont remember if we had one or not before.
Last edited by max2extreme; 07-12-2005 at 09:14 PM.
07-11-2005, 12:45 PM #17Originally Posted by max2extreme
Originally Posted by max2extreme
If the experts don't agree on a naming protocol (and who knows just how much of a disagreement there is, anyway?) I don't really care, and I'm pretty sure I'm not gonna be much help in settling any dispute.
** yawn **
07-11-2005, 12:47 PM #18Originally Posted by max2extreme
07-11-2005, 07:11 PM #19
im not saying naming species, im saying the term "species". whatever term you want to use for anything living with a DNA make-up.
07-11-2005, 09:27 PM #20Originally Posted by max2extreme
I'd really rather not get into debating a subject I don't know much about. All I know about evolution is that most scientists say it makes sense, most Christian Fundamentalists say it's blasphemy. Most scientists make contributions to the well-being of the planet, most Christian Fundamentalist preachers are ignorant bigots wedded to a 3000 year old ideology that wasn't any good even back then.
So go ahead, make your points, slander science, slander the scientific method, slander evolution. They will all be standing proud and tall long after Christian Fundamentalism is ground into the dust and long forgotten.
07-12-2005, 04:46 AM #21Originally Posted by max2extreme
I think the debate about evolution is caused simply because of religion. If there was no religious interest to se the theory wrong there would be no major debate. Or well there is no major debate even now. Just a tiny fraction of creationists trying to make it seem like there is alot of doubt.
Originally Posted by max2extreme
There is also found alot of transitional forms(the creationist major claim against evolution was that there are no trasitional form found but they where wrong. Same with ireversible complexity that was also a flawed argument) isnt that enough proof of macro evolution? What would you need to be proven wrong? Would you ever admit that macro evolution is a existing process? No matter the evidence presented?
Every claim the creationist makes have more or less been proven wrong. The guy that started the creationist controversy lately(cant remember his name, he wrote some books and got semi famous because of it) REFUSES TO RESPOND TO THE REBUTTLES. Shouldnt that say ALOT about the validity of the creationist claims?
Originally Posted by max2extreme
BTW I think there is less evidence and more controversy concering global warming then there is about evolution, but that is not a debated the media is putting any attention to. If religion wasnt involved this whole debated would never have anyones attention.
07-12-2005, 09:48 PM #22Originally Posted by johan
Originally Posted by JOHAN
Originally Posted by JOHAN
Originally Posted by JOHAN
Last edited by max2extreme; 07-12-2005 at 09:55 PM.
07-13-2005, 04:46 AM #23Originally Posted by max2extreme
I never understood the big clash betwen evolution and religion. To me they can coexist. Ok it would mean that some parts of the bible isnt meant to be taken literaly, but if the ammount of time it take to create everything is under debate by christians, why cant theý debate wheter god created all life as it is now or if he just set evolution into motion.
Originally Posted by max2extreme
Would a hereditary mutation that gives a survival advantage be seen as a addition to dna from your point of view?
Originally Posted by max2extreme
Originally Posted by max2extreme
One example of ireducible complexity developing(very recently also, I wonder how big the dna change is in that bacteria and if it would be considered a new spieces).
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 de****g 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.
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).
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 comes down to the same things: Given a population with inherited variation and also new variations from mutation or immigration, evolution occurs. Natural selection (instead of only random drift) occurs if some heritable variations are related to reproductive success. This process takes no notice of whether the changes that occur are direct or not, or whether something is becoming IC. Likewise, evolution just doesn't notice the other barriers proposed by creationists.
There is one difference that may be of interest to school boards. In the past, creationists have, naturally enough, formed creationist organizations such as the venerable Institute for Creation Research and the net-based Answers in Genesis. The leaders of the ID movement on the other hand are all high ranking members of a political organization calling itself the Discovery Institute (46).
Irreducible complexity, intelligent design's closest brush with biology, is marked by three ironies.
IC is supposed to be important because it cannot evolve. But it can evolve, in the same ways that anything else does.
Not one of the impressively complex biochemical systems said to be IC by IC/ID proponents has been shown to be in fact IC and several are known not to be. The known cases of IC are simpler and their evolution is understood.
Although the subject is religiously motivated, proponents have focused on bacterial flagella as the last hope for a highly complex IC system. This has the unintended consequence of making The Designer (aka God) responsible for serious diseases.
It is easy to see why scientists are not impressed by the claim that IC cannot evolve. IC is a matter of an observer specifying a combination of function, parts and system so that the specified function requires all the parts. There is no way for evolution to be sensitive to this, no way for it to matter at all. Nor does nature care about 'direct' vs 'indirect' evolution as perceived by us. Indirect evolution is as normal as tails on cows. Evolution merely requires populations with heritable variation. The processes of mutation, natural selection and random drift are not sensitive to whether a change will be deemed direct or not, nor whether a function, system and parts as specified by some observer are changing to meet the 'all parts required' condition.
There was supposed to be a special reason why it was impossible or at least very difficult for evolution to arrive at an 'all parts required' situation, but there is no such reason. The proposed reason was based on overlooking standard evolutionary processes and making analogies to manufactured items. Comparing Behe's mousetrap to Venus' flytrap confirms the reasonable suspicion that analogies and arguments based on manufactured items lead to underestimating nature. Since IC can occur in the ordinary course of events we have a known process, evolution, which is acting in the present and which given time is sufficient to produce the adaptations that Behe finds perplexing. This is like the raising of the Rocky Mountains; a known process acting in the present is sufficient, given time, to produce the result. Of course there is no way to predict all the details in either case, nor is it necessary.
Finally, this version of 'gap theology', basing the Designer on gaps or purported gaps in our knowledge (which is not mainstream religion), ends up implicating the Designer in human disease. This makes ID rather questionable as a public school lesson. Gap theology is bad enough at best, and always has the problem that the gaps keep getting smaller. This new version of it is especially bad. Darwin did theologians a favor by freeing them from this sort of thing.
Despite all this, there is a strong political drive to force public schools to misrepresent neocreationism as science. But misrepresentation is not acceptable. And it would be awkward to tell teachers to teach ID science when there isn't any. If it becomes politically necessary to teach something about the subject, the present essay contains material for several lessons. And if the plan is to teach 'the controversy', it would be proper to tell the students that there is no scientific controversy, although there is a public one. Books like Darwin's Black Box: The Biochemical Challenge to Evolution are surely part of the reason. Yet the widespread public acceptance of Behe's thesis is stark evidence that we need stronger science education, especially about evolution.
Originally Posted by max2extreme
07-13-2005, 04:54 AM #24
didnt read this one but it might be good.
It seems to deal(in the end) with the odds calculations creationists are so fond of.
Classically, one of the most widely-repeated charges made by anti-evolutionists is that the fossil record contains wide "gaps" for which transitional fossils have never been found. Therefore, the intervention of a creative agency, an intelligent designer, must be invoked to account for each gap. Such gaps, of course, have been filled with increasing frequency by paleontologists – the increasingly rich fossil sequences demonstrating the origins of whales are a useful examples (Thewissen, Hussain, and Arif 1994; Thewissen, Williams, Roe, and Hussain 2001). Ironically, the response of anti-evolutionists to such discoveries is frequently to claim that things have only gotten worse for evolution. Where previously there had been just one gap, as a result of the transitional fossil, now there are two (one on either side of the newly-discovered specimen).
07-13-2005, 06:49 AM #25
im not going to let this thread go permanently, but for the time being i must.. my brain hurts! from this and all rl moving getting everything hooked up, etc stuff. ill get back into it, but i need to talk about something a little less involved...my apologies.
fyi, my camera is recharging overnight, so this weekend ill post some pics of china.
07-13-2005, 06:51 AM #26
my brain hurts to so Il glady give it a rest. This entire summer has been spent reading about scientific stuff so I feel like a utter egghead
Users Browsing this Thread
There are currently 1 users browsing this thread. (0 members and 1 guests)