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Talk:Counterexamples to Evolution (view source)
Revision as of 16:24, November 15, 2008
, 16:24, November 15, 2008no edit summary
: I've reinstated the whale and giraffe examples. It is nonsense to claim that common descent is not in dispute. And I've explained at the top of this page why evolution can't explain the giraffe. [[User:Philip J. Rayment|Philip J. Rayment]] 04:25, 15 November 2008 (EST)
: I've reinstated the whale and giraffe examples. It is nonsense to claim that common descent is not in dispute. And I've explained at the top of this page why evolution can't explain the giraffe. [[User:Philip J. Rayment|Philip J. Rayment]] 04:25, 15 November 2008 (EST)
::Common descent is not ''scientifically'' in dispute. The only attacks to common descent come from without the scientific realm. That doesn't invalidate those attacks, per se, but in order for this article to use scientific reasons for the "rejection" of evolution, it has to be subject to scientific reasoning. And the fact of the matter is that no reputable scientist who has looked at the evidence rejects common descent.
::The neck of the giraffe is a result of what we would call "runaway sexual selection". If you observe giraffes in their natural environment, you might notice that the neck is far, far longer than any shrubs or trees which they eat. So, the neck is obviously not adaptive in that way, because natural selection dis-favors anything that expends energy without need. However, the ancestral giraffe (which is conjectured to look somthing like the Okapi) had a much shorter neck. Although we cannot quite be sure what the environment looked like millions of years ago when these selections took place, it is not much of a stretch to assume that giraffes with longer necks (and we're not talking about a significant difference here) had a higher fitness, so natural selection favored longer necks. At the same time, however, males were competing for access to receptive females. It should be obvious that better competitors were able to reproduce more, and that they would pass on whatever heritable trait allowed them to compete better. In the case of giraffes (anc yes! we can test this!), males with longer necks are more effective competitors, so they produce more children with long necks, and the end result is a net shift of the population distribution. Most importantly, the length comes from increasing the length of individual neck bones, rathering than gaining new structures. It's a perfect example of evolutionary homology!
::Now the next part becomes a little more complicated, and I expect a number of people might not be able to follow it (I'm drawing on some relatively high-level biology). The neck ''valves'' of the giraffe do pose a bit more of an obstacle. The explanation requires accepting common descent, but since I'm sticking to science, I'll go ahead and make that jump. If you know your evolutionary history, you know that all terrestrial chordates are derived from an ancestral fish-like organism. This organism had valves in its ventral aorta for just the same reason as giraffes (prevent back-flow). That's information bit number one. Information bit number two is that the vast majority of our genetic code is inert. It must be "turned on" to work. As the last information bit, remember that natural selection acts against anything which expends unneccessary energy. As the circulatory system of chordates evolved, the original requirement for aortic valves diminished, so natural selection favored those organisms which lost the structure. But wait! '''Losing a structure is not the same as losing the genes for that structure!''' Indeed, the genes were there the whole time: they are part of the ''hox'' complex that controls body plans, and this complex is very heavily conserved. Thus when the need arose for pressure control in the aorta again, it was but a small step to reactivate those genes in the giraffe.
::I can see how that becomes a "chicken or the egg" problem, and I think I may change the point to reflect that. Evolution does a great job of explaining how the neck became long, but people might take issue with the potentiation argument for the valves. I guess it's sort of an irreducible complexity argument.
::Reinstating the whale example shouldn't have been done. The question posed by this article is "can these phenomena be explained in the framework of Darwinian evolution?" The resounding answer for the case of the whale is '''YES!''' That's because one of the main tenets of evolution is common descent, and it's also one very, very strongly supported by evidence. So, scientifically, there is no basis for the inclusion of the whale as a counter-example to evolutionary theory. And please note, when we apply the type of scrutiny we're applying, we must first "pretend," if you will, to accept the theory as a whole and see if it does not provide explanations. That's how speculative science works.
::So with that in mind, I will once again remove the whale example. There's simply no scientific reason to include it. To do so would require attacking common descent first, which has been attempted numerous times and has yet to succeed in empirically-based scientific study.
::If we want to throw out the requirement of scientific scrutiny for a scientific article, that's the perogative of the admins. But we should be honest about the worldview lens through which we're viewing reality. That would save everyone a lot of time, because then we could focus on the source of discord itself.--[[User:Thinker|Thinker]] 11:24, 15 November 2008 (EST)