A barrier to macroevolution & objections to it

I said I hadn't participated much, not that I hadn't read much. And judging by all the other replies, everyone else missed it, too. Because it wasn't there. You haven't identified a barrier. All you've done is argued that macro-evolution doesn't happen, and you've argued that beneficial mutations don't happen.The micro-walking/macro-walking analogy to micro-evolution/macro-evolution makes clear the problem in your argument. Just as each step you take changes your location, each mutation changes the genome. Just as there are no limits to the number of steps one can take, there is no limit to the number of mutations a genome can experience.The question for you becomes, if there is a limit to genomic change, a barrier of some kind, what is it? The coastline is the limit to walking on a small island. The speed of light, c, is the limit to velocity. That which provides the limit to genomic change is...?--Percy

I see this has already been pointed out, but it bears repeating. You're looking for the barrier that prevents macroevolution and the formation of things like novel organs. The formation of novel organs is not the barrier. The barrier is what prevents their formation. What is this barrier?An analogy: An accident blocks all traffic on a major highway. A few miles ahead at a rest area you're with a group of people who note the complete lack of traffic. Someone asks, "What's keeping all the cars off the highway?" You reply, "Traffic flow isn't happening." That's an observation, not an answer. The correct answer is that the accident is acting as a barrier to traffic flow.In other words, you need to identify the barrier to the evolutionary flow of novel organs.--PercyPS - I haven't addressed your claim that evolution does not produce novel organs, but you haven't offered any valid arguments for this claim. It is not a valid objection to combine incredulity with the fact that we can't directly observe a process that takes many, many generations.

Hi Mjfloresta,Let's see if we can salvage some mutual understanding here.The topic of this thread concerns a barrier to macroevolution. Creationists claims this barrier exists, evolutionists claim it doesn't.You seem to prefer the appearance of novel organs as an example of macroevolution, and you assume there are no examples of novel organs arising through evolutionary processes. If by example you mean observing it under laboratory conditions then you are correct, no examples exist. That's because processes which take thousands of years (at a minimum) cannot be directly observed. They can only be deduced and/or inferred from evidence. The evidence tells us that the diversity of forms found on earth today developed from the process of evolution.Now I realize you want to argue that novel organs never arise, but this is only a tiny subset of the actual topic of this thread, which is a barrier to macro-evolution. The evolution of, for example, the horse from eohippus (now renamed, but I don't recall the new name at present) to the modern horse did not involve any novel organs, but it did involve a lot of macro-evolution, meaning evolution beyond the species level. You can choose to believe that the evolution of novel organs is impossible, but it still leaves tons of examples of macro-evolution.The main issue of this thread is the supposed barrier to macroevolution. Creationists claim that evolution beyond a certain point isn't possible. Species (or kinds, if you prefer) can evolve only so far, and no further. What is this barrier preventing such change?The issue can really only be approached from a genetic level. Consider this genetic sequence of nucleotides, let's say it represents a gene: Now let's say that from one generation to the next this gene experiences a mutation where nucleotide 10 changes from G to T: A few generations later it experiences another mutation, this time nucleotide 23 changes from A to C: This process of changes to single nucleotides continues over the generations, but you believe that at some point further change is not possible. What prevents that change?--PercyPS - Keep in mind that the example is only explanatory and representative. There are actually millions of nucleotides in actual genomes, so the fact that there are only so many meaningful combinations possible in my short example sequence is not a valid counterargument.

Huh? Being literal and being simple are two different things. I have no requirements regarding complexity, but it would be nice not to see the English language too badly mangled.I'm all in favor of not being overly literal, but even by Humpty Dumpty standards you're not employing the word "barrier" correctly. Arguments that evolution does not produce significant change in no way identifies a barrier. All it does is argue that evolution doesn't do what evolutionists think it does. Your argument fails the "Can I make this argument myself" test. If I were to adopt your position in debate and attempt a response to the question, "How does what you're describing represent a barrier," I couldn't do it. Nobody could, including you, as the rest of your post makes clear. With the exception of extinction, the process never ends because of mutation. Dog breeding is just a demonstration of how extreme artificial selection, caused by breeders who often focus too exclusively on including or excluding very specific traits, can limit genetic diversity. It can happen in the wild, too, when a population's size is significantly reduced to a small number of individuals. The cheetah is a good example of low genetic diversity in the wild, thought to be caused by a population bottleneck some thousands of years ago. Well, first let the record show that I just acknowledged that artificial selection in the form of animal breeding can reduce genetic diversity. There's nothing to fight in that regard. All evolutionists acknowledge that reduction in genetic diversity happens. There's no way evolutionists could fail to acknowledge this, because literally millions of species have gone extinct, and every single extinction event is an extreme example of reduction of genetic diversity.Picking and choosing your evidence isn't going to lead you to any valid conclusions. Evolutionary processes interacting with the environment produce both increases and decreases in genetic diversity. Discarding all evidence of increases in genetic diversity just gives you a distorted view.Going by what you say about dogs, it appears that dog breeders have bred their charges into severe genetic blind alleys that require forms of genetic rescue. The counterexample is the wolf from which dogs are descended. The wolf appears to be doing just fine and is in no need of such genetic assistance, efforts at control by humans notwithstanding. Either RAZD made a mistake or you misunderstood him. I suspect he was trying to describe how a severe population reduction that causes a genetic bottleneck does not permanently reduce diversity, as the accumulation of mutations continues unhindered after the bottleneck event, unless the species actually goes extinct. It is not "merely assumed." The population geneticists mathematically demonstrated the role of mutations in creating diversity back in the 1920's and 1930's. The ability of favorable mutations to spread rapidly through bacteria populations has been demonstrated time and again. Genetic analysis of species related to varying degrees clearly shows where unique mutations have appeared in the genome.You are correct that mutations cannot be counted on to rescue a species in trouble, such as the dog. They are too unpredictable. Mutations build up in the genome over time like interest gathering in the bank, and during periods of stress they can be drawn upon to produce the variation necessary for a species to evolve through an ecological crisis.Repeating what I said earlier about the term "barrier", independent of whether you're right or wrong, it really isn't the correct term for the point you're arguing.--Percy

Sounds right on the money to me.--Percy

During the 1920's and 1930's the population geneticists demonstrated the sufficiency of mutation to provide variation, leading to the Modern Synthesis of Darwinian evolution and genetics, what we today formally call the Synthetic Theory of Evolution, and usually just refer to as the theory of evolution.Meaningful experiments can be conducted in reasonable time periods on organisms with very short reproductive cycles, such as bacteria, and such experiments have demonstrated time and again that favorable mutations quickly spread through populations and act as a source of variation.Your specific example of novel organs fits neatly within an evolutionary context. Duplication produces an extra organ, and then individuation (further mutations causing change in one of the duplicate organs but not the other) causes it to become unique. One example would be multi-legged insects like centipedes, where different yet still very similar species developed from common ancestors by duplication to produce more legs (in some cases) and removal to produce less legs (in other cases).All this evidence means that the role of mutation in evolution is *not* weakly inferred but rather is strongly supported. This is a good summary, and perhaps the best response is, "Yes, of course," but one minor correction is worth mentioning. While there may be scenarios where an essential organ evolves a new and different function, none come to mind right now, and this isn't a scenario anyone from the evolution side is promoting. We've been talking about duplication followed by evolutionary individuation over time through successive generations.What you're probably neglecting to consider is that the low odds of a successful mutation are easily overcome because each reproductive event is a genetic experiment, and there are literally billions of reproductive events every day. Reproduction is imperfect. If the "imperfections" (i.e., genetic differences from parents) produce unfavorable changes in the organism, it competes less successfully with its peers and the "imperfections" tend to become less well represented in the population or even disappear entirely. If the "imperfections" produce favorable changes in the organism, it competes more successfully with its peers and the "imperfections" tend to become increasingly well represented in the population, perhaps even eventually become ubiquitous. I think you meant 4 raised to the power of the number of nucleotides. And it's not as simple as that, either, since the nucleotides are collected into groups of 3 to code for the (I think) 20 amino acids. But the math isn't important to this particular argument, and you go on to say: To the contrary, laboratory studies precisely confirm this, and even genetic algorithms from the field of computer science reinforce the ability of this process to do precisely what you deny is possible. You continue, also incorrectly: Gene duplication during reproduction is a common mutation. So is chromosome duplication (Down's syndrome is a duplication of all or part of the 21st chromosome). Chromosome duplication is extremely common in some plants, and there are some well-known speciation events deriving from this process. Duplicate organs occur all the time as a result of genetic mutations. Since organ duplication is your favored example, let me cite the first study that came up in a Google search: Wnt-5/pipetail functions in vertebrate axis formation as a negative regulator of Wnt/-catenin activity: "Organ duplication was verified in several maternal-zygotic ppt^-/- (mzppt) embryos...".--Percy