Evolution: Pick One

Con has defined myth as "any invented story, idea or concept." In the context of this debate, invented means something that is false. (That is not a complete definition, but a necessary condition.)Preliminary ArgumentFirst, but not foremost, I will present a very basic argument for macroevolution (hereafter MaE) itself.Con, I take it, does not dispute that microevolution (hereafter MiE) has occurred, and does occur, all the time. However, the changes that occur in MiE are cumulative; they don't go away when further changes come along. We have observed these changes become so great over a number of generations that speciation has occurred in the wild, where members of what had been the same species became incapable of interbreeding.[1][2][3]Therefore, there is a contradiction between the following four propositions:(1) Stabilizing selection[4] has not occurred in all populations, in all physical respects, since the beginning of life.(2) There is no genetic barrier which prevents the accumulation of so many MiE changes that MaE is achieved.(3) The Earth is too young for MiE changes to have accumulated to macro scale.(4) MaE has not occurred.All four of the above propositions cannot be true; at least one must be false.We know that (1) is true by witnessing the many instances of disruptive[5] and directional[6] selection in populations around the earth. We have every reason to believe that (2) is true, since no such mechanism has ever been identified. And we know from several methods, most directly the measuring of lead isotope ratios, that the age of the Earth is about 4.55 billion years.[7] This is more than enough time for MiE changes to accumulate to macro scale. So (3) is true.Thus, proposition (4) must be false. MaE has occurred on Earth.This is perhaps the most direct argument for MaE, but there is an even more compelling, and even more grand in scale, argument:Common DescentCommon descent (hereafter CD) is the idea that all organisms on Earth are genealogically related. Cats are distant cousins of dogs, horses are distant cousins of dolphins, and we humans are very distant cousins of the bacteria inside our own bodies. If CD is true, then MaE as Con has defined it has obviously happened on a massive scale.A Digression on ScienceCD (and MaE itself) is a scientific theory. (The word "theory" in this context does not mean "guess;" it means a body of propositions related to a particular field, such as relativity theory or music theory.) As such, it is not required to be established to an absolute certainty to be regarded as true. Stephen Jay Gould correctly defined a scientific fact as a theory that has been "confirmed to such a degree that it would be perverse to withhold provisional consent."[8]What's the catch? A scientific theory must be testable. This means that, based on a given theory, we must be able to make predictions about what is likely or unlikely to be true if the theory is correct. The scientific method works roughly like this:1) Make observations.2) Formulate hypotheses -- not from the imagination, but from induction from the observations.3) Make predictions based on those hypotheses.4) Confirm or deny the predictions. If the predictions are denied, return to step 2. If they are confirmed, then the hypothesis is given a correspondingly higher degree of certainty.For instance, we observed the planets moving in just such a manner around the sun. Based on those observations, Newton formulated the theory that bodies attract each other according to a certain formula relating to their masses. Based on this hypothesis, we predicted that an object falling on the Moon should take six times as long as on Earth -- and sure enough, that's what the Apollo astronauts discovered. If they had taken exactly as long, or twenty times as long, or if they had flown away from the Moon, Newton would be disconfirmed and we would be looking for a new theory to explain the observations of the planets.This raises an important point. Con will no doubt try to present defeaters to MaE. However, aside from being true and logically valid, such defeaters must be contrary to predictions actually made by MaE. For instance, saying "we never see dogs giving birth to cats!" is not a defeater, since MaE does not predict that such a silly thing will occur.Back to my own case: many predictions have been made based on CD, and these predictions have been confirmed. Here are just a few.Evidence(1) If CD is true, all living organisms should inherit the same basic structures which perform the functions necessary for life, namely replication, heritability, catalysis and metabolism. Sure enough, we see that out of hundreds of naturally occurring amino acids, all protein molecules are built from the same set of 22. Out of hundreds of naturally occurring polymers, all life uses only three. No life fails to use polynucleotides, polypeptides or polysaccharides, or fails to use DNA, or uses DNA without nucleic acids.[9]There is no reason to expect this if all modern organisms, or their immediate ancestors, were created separately at the same time -- this is the notion of special creation (hereafter SC).2) If CD is true, all species should fall into nested hierarchies. That is, we should be able to develop an objective classification scheme for all organisms. This is the case with languages; every linguist agrees, for example, that English descends from Proto-Germanic, and not from the Italic or Celtic languages.[10] Anyone who learned the phrase "kings play chess on funny green squares" in school will know that this is the case in biology as well. Here is a basic phylogenetic tree: (Note that "hypothetical" doesn't mean "we guess that it exists," but rather "we infer its existence.")We see no life today that could not be classified into this tree, such as an organism that plants seeds and has a placenta, as we might expect under SC.[11]3) If CD is true, vestiges should exist. Since a given feature of a species doesn't necessarily disappear when another species descends from it, there should be vestiges: anatomical or molecular structures that serve little or no purpose, but would serve a great purpose in another, perhaps closely related species. And sure enough, we see anatomical features such as ostrich wings, python pelvises, and the human coccyx, which is a skeletal structure that serves as the base of a tail we no longer have. We would not expect this given SC.[12]4) If CD is true, the geographical distribution of species should be consistent with their genealogical relationships, since the Earth is dynamic and change occurs in space as well as time. What do we observe? All marsupials on the Earth are native to Australia, or to regions that were once connected to Australia. All alligators on Earth are native to eastern North America and eastern Asia, which again were once connected. We do not see cacti growing natively in Australia, for instance, or lions roaming the North American plains.[13]5) If CD is true, transitional forms should appear in the fossil record. Given the rare circumstances under which it is possible for an organism to fossilize, we would not expect fossils of all or even most species which ever lived; but those that we do find should be consistent with the phylogenetic tree.[14] And sure enough, we have many transitional fossils. One of the most famous examples is Archaeopteryx, a species that lived millions of years ago and fits on the phylogenetic tree at the point where reptiles and birds would share a common ancestor.[15] There is no reason for this to be true under SC.I could go on at great length, but hopefully this suffices to show that the evidence for CD is plentiful and compelling; so much so that, given awareness of the evidence, perversity is needed to deny CD, and thus to deny macroevolution.Sources: http://www.debate.org...