The Lone Ranger

Actually, some birds are known to echolocate -- notably, cave-nesting swiftlets and oilbirds. Their echolocation abilities aren't nearly as impressive as are those of bats, however.

Cheers,

Michael

Charles Darwin

No, I don't doubt that instances of microevolution are observed. Nor do I doubt that instances of macroevolution are observed.

The equivocation comes in when you say the evolution is a fact because instances of microevolution are observed. Some moths changed color, therefore it is a fact that fish evolved into giraffes.

Regarding your ideas of why evolution is a fact, I assume that you mean 'public' fact, not 'private' fact. That is, you intend that this fact is objective, for all to see, not your own private inspiration. If I'm on track here, then I utterly fail to track your logic. How did evolution create the adaptation machine that produces microevolution that you now claim as evidence for your theory? And the same for the developmental programs?

I hope you understand my questions are rhetorical. I have no doubt you can provide speculations on these questions. My point is that the evidence you are citing that evolution is a fact does not support evolution in the way you seem to think it does.

On to the fossil record. How does that help to combine with the other evidences to arrive at telling us evolution is a fact? You mean that species appear out of nowhere? Emm, no, that's probably not what you're referring to. You mean that species don't change once they appear? Emm, no, can't be that. You mean that there are similar species in the fossil record? OK, where does that get you?

Do you see my point? To prove evolution to be a (public) fact, we need more than a jumble of evidences which can be interpreted in various ways (including contra evolution).

Even granting you favorable interpretations of these evidences, why do they prove evolution to be a fact?

The Lone Ranger

Whoa, hang on there a moment.

Evolution is changes in populations of organisms over time, specifically, genetic changes. Period. End of statement.

It is an observed fact that populations of organisms change over time, as you note. Therefore, it is a fact that evolution occurs.

When you're talking about the evolution of giraffes from fish (via quite a few intermediaries), you're talking about common descent. Theories of evolution explain this.

This is why we distinguish between the fact that evolution occurs and evolutionary theory which seeks to explain such things as the apparent fact that all organisms share common ancestry.

Cheers,

Michael

Doubting Didymus

When a biologist attempts to construct a phylogenetic tree, they are basically drawing a diagram of how species are related. By 'relationship' here, we aren't talking about the vague colloquial sense (early 1900s church music is 'related' to jazz of the same period, by bent of sharing characteristics). We mean related in the specific sense of family relationships. I am related to my sister, and to my cousin, by blood.

So when a biologist builds a tree of species relationships based on something (morphology, DNA, etc), it's not just an effort in saying "these species look the most alike" but a hypothesis about the lineage relationships. If the tree places humans and chimps on more recently diverging lines than cats, its making a hypothesis about when the ancestors of these species diverged.

Now, if that hypothesis is false, and humans and chimps don't share an ancestor, and neither of us shares an ancestor with cats, then we don't expect the tree we drew based on morphology to agree with our genomes. Our nucleotide sequences shouldn't build a tree that agrees with the hypothesis that certain species are more or less related (again, related in the sense of lineage). It could be anything, building a wildly different tree.

Now, a common objection to this is that there might indeed be a good reason to expect an animals genes to agree with the tree, even if they were never related. Perhaps, goes the argument, animals that just happen to be similar because of the taste of the creator would naturally share more genes with species they look more like, and less than those that don't. The genes would agree with the morphology tree, just because they are more similar in shape to that species. If two cakes taste alike they should have similar recipes, and as the cake becomes less like the first, the recipe should slowly change accordingly. That doesn't mean that all caes are descended from the first cake.

Unfortunately, that argument doesn't hold water for a number of reasons. First, we could test areas of the genome that aren't used: genes that don't make anything, and see if the tree is still produced the same way. It does.

Second, we should then be able to take two species that have similar morphology and expect there to be a consistantly higher genetic similarity. We should expect dolphins to have swimming-thing-with-fins-that-eats-fish genomes that are more similar to sharks than to walking-around-a-field-chewing-grass genomes like elephants. But they don't. We should expect the flying suirrel to be more genetically like an australian flying marsupial possum than to, say, a dog. They don't.

Thus, being able to build the same phylogenetic tree over and over, no matter what method we use, is strong evidence that the hypotheses that the tree generates (i.e. that species are related by lineage) are correct.

Charles Darwin

So does the failure of endogenous retrovial insertions to confirm pre established trees disprove evolution? If so, then you should drop evolution as they are all over the map. For instance, there is the HERV that shows up in gorillas and chimps but not humans. In general:

"As has been the case with numerous nuclear DNA markers, there was no consensus among the HERV trees for the relationship among humans, chimpanzees, and gorillas (30). The remaining trees displayed interesting deviations from the predicted separation of the 5' and 3' LTR sequences." PNAS, 96:10254, 1999.

If the failure of endogenous retrovial insertions to confirm pre established trees does not disprove evolution, then how does it tell us that evolution is a fact?

Duvenoy

Thanks Ranger. Now that you've said it, I get a little nudge in the back of my mind that I read it somewhere. I should'a looked.

Echolocation is no more big a deal than the ever-growing incisors of rodents or the lure possesed by angler fish. It is just another trait that some organisms evolved to give a slight survival advantage.

Here�s another link, on fossils (not bats), one might find interesting:

http://www.gcssepm.org/special/cuffey_05.htm

doov

Doubting Didymus

Here is the full text of the article referenced by Charles:

Constructing primate phylogenies from ancient retrovirus sequences

Note that the overwhelming finding of the study found that ERVs support the long standing phylogenetic tree of the old world primates.

An example of findings from this article that support the standard phylogenetic tree:

Also note the following paragraph from the papers conclusion:

The exceptions noted by my emphasis above are, of course, discussed in the article. Evolution does not predict that something so mutable and error-prone as the genome should perfectly preserve every retrovirus it ever includes. we should expect there to be explainations when data is imperfect, which this article devotes some time to doing. I do not believe that a fair reading of this article can lead one to the conclusion that ERVs have "failed" to confirm pre established trees. They overwhelmingly do, and the few exeptions are not mysterious.

God Fearing Atheist

For everyones sake, lets try quoting the whole passage:

Does that make more sense now?

Let's also note Johnson & Coffin's conclusion:

The full text is available here.

-GFA

Doubting Didymus

Beat you by one minute, GFA.

God Fearing Atheist

dag-nabbit DD!



-GFA