tgamble

In a discussion with another creationist he demanded examples of speciation which I gave. One of the links I gave is addressed below. and yes, I did give the links at talkorigins. :=)

<a href="http://forums.sympatico.ca/WebX?14@170.aNL8aBH1tDX^4@.eeb50e7/37436" target="_blank">http://forums.sympatico.ca/WebX?14@170.aNL8aBH1tDX^4@.eeb50e7/37436</a>

Homer [that's me] and pl [another poster], before I go to the Airport, I note that Homer's showcase link (to which pl draws double emphasis) is:

<a href="http://biomed.brown.edu/Courses/BIO48/23.Cases.HTML" target="_blank">http://biomed.brown.edu/Courses/BIO48/23.Cases.HTML</a>

pl claims that this link provides many "indisputable" examples of speciation events, and then pl waxes bold beyond his understanding when he ventures to state with certainty, "So there's your proof. Speciation does occur..."

What "proof"?

Imagine my disapointment, upon clicking on to this site, to find one of the first and showcase examples of this so-called "proof" of speciation to be none other than Darwin's Finches.

Well, well, well! This is a deep subject.

The link specifically states, as an example,

"Darwin's Finches. Morphological and genetic studies indicate that they are derived from single ancestral finch, i.e., are monophyletic. There has been dramatic specialization in ecological roles, each species having distinct morphologies and associated food items (beak size and shape associated with seed size, grub feeding, tool use, etc.)."


Homer, when was this link last up-dated???

First of all, this example provides no indication that there is a huge difference between mere variation of an organ, and the creation of new types of complex organs or body plans.

Second, what the author of the link apparently has not been brought up-to-date on is that the famous textbook examples of variation in the beaks of finches on the Galapagos Islands involve only back-and-forth variation within a fundamentally stable species. No new features appear, and there is no directional change of any kind.

Nevertheless, these modest examples are repeatedly used as so-called proof of the actual transformation of one species into another, and that therefore, the changes needed to transform a bacterium into a human being can also occur over the course of many millions of years.

Now we have even the National Academy's Guidebook, on page l9, describing one of the most frequently cited examples of evolution, in a section titled, "Ongoing Evolution Among Darwin's Finches."

Here is the complete text:
[/QUOTE]
"A particularly interesting example of contemporary evolution involves the 13 species of finches studied by Darwin on the Galapagos Islands, now known as Darwin's finches. A research group led by Peter and Rosemary Grant of Princeton University, has shown that a single year of drought on the islands can drive evolutionary changes in the finches.

"Drought diminishes supplies of easily cracked nuts but perhaps the survival of plants that produce larger, tougher nuts. Drought thus favors birds with strong, wide beaks that can break these tougher seeds, producing populations of birds with these traits. The Grants have estimated that if droughts occur about once every l0 years on the islands, a new species of finch might arise in only about 200 years."
[/QUOTE]

Ho! Ho! Ho!

A good science teacher might employ humor to illustrate the fallacy of extrapolation here. "If the average length of finch beaks in a population increases five per cent following drought years, and droughts occur every ten years, how long will it take the beaks to grow from an average of one inch in length to ten feet, or for finches to become eagles?"

It is no wonder that the Guidebook's authors did not quote the title of the Grant's 1987 paper in Nature, "Oscillating Selection in Darwin's Finches," because that would have signaled to teachers, and perhaps also to bright students, that the finch-beak example involves no continuing directional change at all. The drought in question was followed a few years later by floods, and the average beak size promptly went back to normal.

But even if finches did grow steadily larger for a time, would this show that they can change into something completely different???

But even if finches did grow steadily larger for a time, This example is not taken out of context, nor is it atypical. It follows the thesis of The Beak of thke Finch, by Jonathan Weiner, a book that won the Pulitzer Prize in 1995 and has been enthuaiastically recommended to the public by leading authorities, including the president of the national Academy of Sciences.

It is easy to see why the Darwinists feel they have to present evidence in a selective and slanted manner. Under any kind of objective analysis, it would become apparent that the Darwinists have never discovered a mechanism capable of creating new complex organs, or changing one kind of body plan into another.

(The finch-beak example is given top billing in the textbooks precisely because the other known examples of observed natural selection are even less impressive.)

The Darwinist educators appear to be, or seem to be determined to persuade rather than to educate, and so their textbooks have to bluff.

Homer and pl, I expected more than this from you. Surely you can do better than this.

No wonder you just give general links as "proof" and show a reluctance to defend any one example in your own posts.

What pl calls "proof" turns out to be a "spoof."

===============

My own response that I've come up with makes the following points:

New species would not include complex organs or body plans. New body plans come with new phyla, not species!

Since when is direction change required? There may be variation within one of the species there but that's not the point. The point is that there are several different species, with more differences than beak size, on the island that are obviously related.

Why would a beak grow up to ten feet? Why would anyone claim that eagles are directly descended from finches? this is absurd.

Larger finches aren't the only differences and something "completely different" wouldn't be just a new species, but a new genus that would involve much greater change that any reasonable person would expect to observe in a single lifetime.

Comments? Suggestions? Corrections? Thanks!

Edited to fix link. It was to the wrong post.

[ July 05, 2002: Message edited by: tgamble ]</p>

lpetrich

One problem here is that there are already several species of Galapagos finch, and an emerging new species would go into competition with an existing one.

However, when new niches open up, there is evidence that new species emerge to fill them. Thus, the apple-maggot fly, Rhagoletis pomonella, looks like it's dividing into two species: one that feeds on its original diet, hawthorn trees, and one that feeds on apple trees, which were introduced by European settlers.

A 10-foot beak is rather unlikely, but one can expect the evolution of some big bird from some small bird given enough time and some suitably-rich ecological niche for a big bird to occupy, such as there being plenty of food for a population of several thousand. In fact, that has actually happened on some oceanic islands; consider the now-extinct dodo of Mauritius.

That's reasonable.

The emergence of such structures would not happen in one typical human lifetime, of course. Such structures require several changes -- and one can sometimes see evidence of partial changes, either among organisms that have kept them, fossil evidence, or developmental relics.

One simple way for great complexity to emerge is specialization of different segments; arthropods have excellent examples of this "serial homology". Early arthropods had had most of their segments looking much like each other, with little specialization; trilobites are a good example. Later arthropods often have a variety of specializations, such as segments being grouped (three groups in insects, two groups in spiders) and different limbs having very different functions, such as mouthparts, walking legs, and so forth -- when they are present.

Vertebrate skeletons show evidence of similar specialization. Fish vertebrae typically look very much like each other, while land-vertebrate ones often have more variation -- including some vertebrae being fused with some hindlimb bones. Likewise, the limbs and their digits may get specialized in different directions; consider the wings of birds, bats, and pterodactyls, which are all modified front limbs.

And among plants, flower parts are essentially specialized leaves. That is obvious for sepals, a bit less so for petals, and not very for stamens and carpels (pistil parts). But certain genes have mutations that make one flower part look like another -- or like a leaf.

As to the emergence of body plans, that requires having a very simple, unspecialized ancestor -- which is why most easily-fossilized phyla had emerged in the Cambrian or shortly after. It would take a really big mass extinction to allow phylum-level body-plan features to evolve again, as a result of clearing away the competition.

RufusAtticus

This is my favorite example of speciation in human time.

<a href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?cmd=Retrieve&db=PubMed&list_uids=102000 79&dopt=Abstract" target="_blank">Culex pipiens in London Underground tunnels: differentiation between surface and subterranean populations</a>

I keep a pdf on my system to send to creationists as evidence for evolution.

~~RvFvS~~

KC

The problem with the learned pl's response is all too typical-- it is probably based on a second-hand, poor assessement of the Grant's work, most likely the shamefully inadequate hatchet job of Jonathan Wells. The argument reeks of Wells.

What the creato-weenies want the general public to think is a grossly distorted pictutre of what actually is going on. Wells and his ilk want the public to think that no speciation has occurred there. They do this primarily by playing games with the concept of species.

They usually try and say the diversity of these birds is merely variation within a species. Sorry, Jack. By any criterion, as the Grants point out, the populations of birds are species. THey are morphologically distinct, and they do not, except in extremely rare cases, interbreed.It is true that they are capable of producing fertile hybrids, but these hybrids do not mate with each other to produce an F2 generation. Instead, they almost always introgressively hybridize with birds of the parental stocks. The reason for this is ethological-- birds mate with birds resembling parents (primarily by beak shape, also by song).Since the Biological Species Concept as proposed by Mayr and others re;lies on reproductive isolation, NOT infertility, these pop7uloations qualify as species. Many creationists are somehow convinced that populations must be incapable of producing viable, fertile hybrids in order to be considered species. This, of course, is incorrect.

What makes the Grants work so fascinating is that they show how character displacement for beak size between sympatric populations of birds produce greater and greater differences in beak morphology on islands where the birds coexist. This in turn reinforces the reproductive isolation between the populations, driving speciation even harder. Their main contention is that speciation in these birds is driven far more by ecological factors, and reinforced by ethological ones. Since ecology is one subject creationists, in my experience, tend to avoid like the plague, it's not surprising they grasp neither the significance nor the subtleties of the Grant's work. As a result, they are easily duped by slick creationists with PhD's who conveniently refuse to discuss the crux of the relative data.

I dont have time to address all of the weaknesses of pl's argument, but I hope this helps. What you might also want to do is familiarize yourself with the primary literature from the Grants themselves. The most in-depth source is Peter Grant's Ecology and Evolution of Darwin's Finches, (the 1999 edition). An excellent survey paper of their work can be found relatively easily in the March-April 2002 issue of the journal American Scientist, "Adaptive Radiation of Darwin's Finches'.

Cheers,

KC

[ July 05, 2002: Message edited by: KCdgw ]</p>

tgamble

Hold on! Just to set the record straight, pl is NOT a creationist. He's as much as creationist as Richard Dawkins. The rejection of speciation was another poster.

thanks for your response.

[ July 05, 2002: Message edited by: tgamble ]</p>

KC

Ok. It was tough figuring out just who said what the way the post was presented.

Cheers,

KC