Calilasseia wrote:The assertion of magic barriers preventing speciation is, of course, rendered wholly untenable by those 48 scientific papers on speciation I cited elsewhere. Which includes documentation of gene families known to be implicated in speciation. But then real world evidence has never been a hindrance to the peddling of creationist lies.

Shrunk wrote:Now, let's apply this claim to a real life situation. The most contentious evolutionary claim for creationists to deal with, of course, is common ancestry between humans and chimpanzees. As luck would have it, the genomes of both of these organisms have been sequenced, and the differences between them well-characterized. It is well-known that the similarity between the two genomes is on the order of about 96%. Given that the human genome consists of approx. 6 billion base pairs, these means the difference between the two genomes is roughly on the order of 240 million base pairs.

Shrunk wrote:

Oeditor wrote:

Shrunk wrote:Now, let's apply this claim to a real life situation. The most contentious evolutionary claim for creationists to deal with, of course, is common ancestry between humans and chimpanzees. As luck would have it, the genomes of both of these organisms have been sequenced, and the differences between them well-characterized. It is well-known that the similarity between the two genomes is on the order of about 96%. Given that the human genome consists of approx. 6 billion base pairs, these means the difference between the two genomes is roughly on the order of 240 million base pairs.

The creationists are working on that correspondence, and a former member of the scientific panel of the creationist organisation "Truth in Science", Richard Buggs, claims (http://www.refdag.nl/chimpanzee_1_282611) that the figure is actually much lower because the genomes do not align exactly. Richard Buggs says that the real figure is nearer 70% or even less, which makes the creationists much happier. This argument is now cited by IDCreationist sites such as Uncommon Descent and the misleadingly self styled Evolution News. Richard Buggs, by the way, is a signatory of the Discovery Institute's "A Scientific Dissent from Darwinism" list http://www.discovery.org/scripts/viewDB/filesDB-download.php?id=660.

Yes, creatonists are endlessly creative in coming up with meaningless numbers to support their doctrine. I can't find the reference at the moment, but I recall one creationist who came up with a figure in the neighbourhood of 60%. What he did was divide the genomes up into sequences of some randomly determined length, then determined how many of those were exactly identical. So if you had two sequences of 1000 nucleotides each (for the sake of argument; I don't recall what that actual length used was) and they differed by only one base pair, they would be scored as 0% similar, even though in terms over the overall sequence they were 99.9% similar.

Shrunk wrote:There seem to be a number of arguments that are repeatedly offered in support of creationism...

Shrunk wrote: It's really not possible to say what the creationist position is, since creationism does not aspire to any of the standards of evidential support and peer review that allows consensus positions to be arrived at in legitimate science. However, at least some creationist sources accept that novel mutations can occur. From Answers in Genesis:

Calilasseia wrote:Actually, all evolution requires 'new information'. Even if a gene only acquires a neutral mutation, it's still coding for a new protein that wasn't coded for before.

Shrunk wrote:There seem to be a number of arguments that are repeatedly offered in support of creationism. While it is often effective to simply answer them by providing examples of the evidence from evolutionary biology that refutes them, these arguments can also be effectively addressed on their own terms, by demonstrating how they rely on claims that are refuted simply on logical and/or empirical grounds, without even necessarily having to provide a counter argument in favour of evolution.

As an example, I will here address the "species barrier" that creationists frequently claim demonstrates that evolutionary change cannot occur. This claim depends on creationism's idiosyncratic distinction between "microevolution" and "macroevolution". They accept that the former occurs, and often refer to it as "change within kinds". By this, they mean that certain changes can occur in the appearance, behaviour or other characteristics of a species, and that these could even follow the principles of random mutation and natural selection as desribed by Darwinian theory. However, they deny that "macroevolution" can occur. By this, they mean larger scale change that results in the emergence of completely new species. This claim requires the existence of some sort of limit or barrier to the degree of genetic change that can occur, such that an organism will always remain of the same "kind" (to use the preferred creationist term).

To illustrate why this idea is problematic, let's use the hypothetical two very simple organisms, and represent their genomes as the following:

ACGGCG CCGGTA

Obviously, such simple genomes are not likely to produce viable organisms, but this is just to illustrate a point. Now, evolutionary theory will require that these two organisms will have shared a common ancestor. Another way of stating this is that it should be possible to gradually change these genomes until they become identical. For instance:

ACGGCG CCGGTA

CCGGCG CCGGCA

CCGGCT CCGGCT

So, in thise case, it only takes two mutations each to arrive at a common ancestor. But that is not the only pathway. For instance, it could also go like this:

ACGGCG CCGGTA

ACGGTG CCGGTG

GCGGTG GCGGTG

Or this:

ACGGCG CCGGTA

ACTGCG CCGGTA

ACTGTG ACGGTA

ACTGTA ACTGTA

And so forth. In fact, even in these unrealistically simple "organisms," the number of possible pathways to common ancestry is quite large.

However, the existence of the "creationist species barrier" depends on every single one of these pathways being impossible. Although I am not aware of any creationists explicitly stating why these pathways are impossible, presumably it is because they all require mutations that will, at some point, result in non-viable organisms. (Although, to be honest, I'm not sure most creationists who use this argument have even thought it thru to that extent. For the most part, they simply make claims along the lines of "We never see a fish give birth to a cat, so macroevolution is impossible.")

Now, let's apply this claim to a real life situation. The most contentious evolutionary claim for creationists to deal with, of course, is common ancestry between humans and chimpanzees. As luck would have it, the genomes of both of these organisms have been sequenced, and the differences between them well-characterized. It is well-known that the similarity between the two genomes is on the order of about 96%. Given that the human genome consists of approx. 6 billion base pairs, these means the difference between the two genomes is roughly on the order of 240 million base pairs.

What this means is the hypothetical number of possible mutational pathways to common ancestry, in the manner demonstrated by our two simple hypothetical genomes above, is, well, a lot. I have no idea how many, but the number is undoubtedly huge, if it can even be calculated at all.

So what the creationist claim of a "species barrier" depends on, is the demonstration that every single one of these pathways is impossible. If even 99% of the pathways, or 99.9%, or 99.999% are non-viable, that still leaves such an enormous number of possible candidate pathways, that the creationist claim is clearly untenable. Quite simply, they have no way of arguing that this "species barrier" actually exists, short of working out every single possible mutational pathway to a common ancestral genome, and specifically demonstrating why each one of these could not have occurred in real life.

So get to it, creationists....