Freethought & Rationalism Archive

Oolon Colluphid · 12-30-2001, 11:04 AM

...And anyone who doubts that feathers would be good for insulation should throw out their duvet...

Cheers, Oolon

Christopher Lord · 12-30-2001, 11:16 AM

To me, feathers look a lot like what one would expect scales to turn into if a scaled creature needed to be a bit warmer. Air spaces between each proto-feather, and then between filiments of the proto-feather.

Flight feathers can then be developed from these.

bluefugue · 12-30-2001, 11:18 AM

faded_glory:

Quote:

See? Who needs Douglas? I can do the whole bloody debate on my own

If you find yourself short on cash, you might want to publish a book called "Demolishing the Lies of Evolution" or somesuch. It'd take you about 3 hours to write, and you'd probably make a pretty penny. Then you could write another book refuting yourself and make even more money!

faded_Glory · 12-30-2001, 01:57 PM

What makes you think I haven't done this already?

Duane.

uh... I mean fG.

[ December 30, 2001: Message edited by: faded_Glory ]</p>

Quetzal · 12-30-2001, 10:03 PM

As usual, Douglas's arguments show a fairly limited understanding of the subject he is denying. In the first place, he needs to define which kind of feather he is referring to: there are seven modern feather designs, only one of which has his famous barbs. The rest range from something that looks mostly like a hair (could be maybe evolved from the same structure?, i.e., scales - duhoh) to the fluffy down insulator.

Even the hook and barb structure is fairly easy to explain via evolution if you understand that feathers probably started out as insulation and only later were found to be useful for flight (another of the VERY common unintended consequences of evolution). Given the variation in the hook and barb system (from round barbules that sort of link to near hook-and-eye) it is pretty obvious that even a slight capability to link together provides a substantial increase in the thermal insulation properties of the feather integument.

Once again, Douglas needs to go back to school. Or at least get some new arguments.

Quetzal · 12-31-2001, 04:43 AM

And in yet another example of Douglas’s complete lack of scientific knowledge, he posted the following poser:

Quote:

Bird Navigation By the Stars
Also, how could birds "microevolve" the apparently innate ability to navigate by the stars? According to John MacArthur, in his book, "The Battle for the Beginning" (page 131),
Most birds that migrate long distances fly mostly at night. They do this because one of the main ways they navigate is by the stars. Studies have shown [no footnotes or references] that even birds raised entirely indoors can orient themselves properly the first time they see the stars. Tests done in planetariums [again, no footnotes or references] show that birds know which direction to fly even in an artificial sky if the stars are properly placed. But when the star alignment in the planetarium is confused, the birds are confused as well.
What would be the "random mutation plus natural selection" scenario which would explain this phenomenon? (Assuming Mr. MacArthur is correct.)

Anyone who’s bothered to look at even the least amount of research on bird navigation could see the problems with this spurious quotation. The easy answer is: stellar navigation IS NOT THE MOST IMPORTANT NAVIGATION TOOL USED BY MIGRANT BIRDS. Sorry for shouting. Douglas's question is pointless because the basic premise behind it - birds navigate by stars - is wrong.

Birds use a multiplicity of navigational tools to get from point A to point B. These tools include:

Quote:

Visual Landmarks - It is widely believed that migrating birds will follow topographical features like coastlines, rivers or mountain ranges. This would be particularly useful for birds that are able to make their first journey with their parents, and thus learn their route.

Sun Compass - One of the earliest navigational mechanisms studied was the "sun compass". By observing the sun's position in the sky and calibrating it against their own internal clock starlings were able to orient consistently in experimental situations. Altering the position of the "sun" for caged birds caused them to change their orientation.

Celestial Navigation - Cornell scientist Steve Emlen demonstrated an ability to navigate by a celestial compass in Indigo Buntings. In an elegant experiment Emlen divided juvenile buntings into three test groups with no exposure to a daily point source of light and placed them nightly in the Cornell planetarium. One group was exposed to the normal pattern of night stars, with the pole star Polaris in the proper position. For the second group Emlen created an artificial night sky by putting the bright star Betelgeuse in the pole position. The third group was exposed to no celestial clues. When tested in the fall migratory period members of the third group showed no directional preferences at all. Birds exposed to the normal night sky oriented toward the south. The birds that were exposed to a fictitious sky oriented to a "south" that corresponded to the south in their artificial sky.

Magnetic Field - How do birds detect the earth's magnetic field? A form of iron oxide known as magnetite that was used by early mariners in early compasses has been found in the brains of pigeons as well as some other animals. It has been theorized that this magnetite deposit is involved in sensing the earth's lines of magnetic force. Robins in Germany showed an ability to orient correctly in a darkened room with no access to solar or celestial clues. When the magnetic field around their cages was disrupted experimentally their orientation shifted accordingly.

Polarized Light - Birds have shown an ability to detect polarization of light that is invisible to the human eye. Detecting polarization would enable birds using a solar compass to work out the sun's position even on mostly overcast days.

Smell - Some experiments with homing pigeons have shown that they can orient themselves with the use of "smell landmarks". However, other researchers have been unable to replicate these results. Shearwaters returning to land from foraging trips at sea are able to locate their own burrows by scent.

Sound - Theories have been proposed that birds navigate by following patterns of infra-sounds, sound waves that our well below our human threshold of hearing. Infra-sounds can carry for a great distance and are generated by major topographical features such as mountain ranges or breaking waves on a shore. Proponents of infra-sound as a navigational tool cannot explain how the birds manage to filter these sounds out of a background of ambient noise.

(From <a href="http://natzoo.si.edu/Animals/Birdfacts/navigation.htm" target="_blank"> National Zoo Birdfacts site.</a>)

The dominance of one tool over another in a particular migratory species depends on environment and the particular problems the species faces. Which of course, is entirely consistent with evolutionary theories and natural selection.

For example, the bobolink (Dolichonyx oryzivorus), a North American songbird, migrates 7000 miles annually from Alaska to Argentina. It uses two different magnetic sensors (magnetite and chemical photoreceptors in its eyes), and celestial navigation (to occasionally re-calibrate its magnetic compass). It does not, however, need to worry about magnetic declination (i.e. east-west variation). Experiments such as the one on <a href="http://www.nwf.org/nationalwildlife/1999/compass.html" target="_blank"> this site </a> show that bobolinks deprived of their magnetic sensing ability and provided ONLY with stars for navigation, get completely turned around. On the other hand, ornithologists Kenneth and Mary Able, both of the State University of New York at Albany, have found that Savannah sparrows (Passerculus sandwichensis beldingi), who migrate substantially less distance, rely more on celestial cues to make adjustments to their magnetic compass and compensate for the changes in declination, since their migration, although shorter, has a significant east-west component. See <a href="http://www.nwf.org/nationalwildlife/1999/compass.html" target="_blank"> “Navigating with a Built in Compass” </a> for more details.

In addition, for those who would like more information on magnetic sensing in animals, not just birds, see <a href="http://www.ks.uiuc.edu/~ritz/RESEARCH/MS/ms.html" target="_blank"> this article </a> or <a href="http://serendip.brynmawr.edu/bb/neuro/neuro00/web1/MathraniVand.html" target="_blank"> this one.</a>

Someday we will have a creationist on this board who knows what they’re talking about. Of course, I’m an incurable optimist.

[edited 'cause I invariably mess up url links]

[ December 31, 2001: Message edited by: Morpho ]</p>

MrDarwin · 12-31-2001, 05:11 AM

Quote:

Also, how could birds "microevolve" the apparently innate ability to navigate by the stars? According to John MacArthur, in his book, "The Battle for the Beginning" (page 131)

<a href="http://www.amazon.com/exec/obidos/ASIN/0849916259/qid=1009807985/sr=1-1/ref=sr_1_6_1/002-9711128-2644819" target="_blank">Battle for the Beginning</a>

Douglas isn't going to get very far if he continues to try to make evolutionary arguments by quoting other creationists. Ironically, Douglas doesn't even seem to realize why this kind of debate tactic is self-defeating.

[ December 31, 2001: Message edited by: MrDarwin ]</p>

Asha'man · 01-01-2002, 12:47 PM

Hmm, I was going to ask about the survival value of transitional forms of feathers, but the question seems to have been answered. Sharp group here.

However, it does bring up a larger question, one that Douglas might want to consider if he is going to really address the debate topic of microevolution vs macroevolution.

It is easy to see the increased survival value of some gradual mutations, such as the lengthening of a giraffe's neck. But are there any transitional mutations where the intermediate form appears to have no value?

For example, in the transition from land mammal to whale, the tail and forelimbs grow, but the rear legs dissapear. However, after a while, I don't see any advantage to smaller rear legs. Once they cease to produce hydrodynamic drag, they should stop shrinking, right? Unless they are a liability for some other reason...

If a clear example can be found where microevolution and natural selection are not sufficient to explain a change, then a new mechanism for that specific change would be needed.

scigirl, do you know of any such troublesome transitions? Anyone else? I'm sure that most can be explained with some thought, but a single solid example could cast some doubt on the issue.

(I don't believe there are any, but figuring out some tough ones might be an interesting excercise in reasoning.)

Christopher Lord · 01-01-2002, 02:36 PM

Quote:

For example, in the transition from land mammal to whale, the tail and forelimbs grow, but the rear legs dissapear. However, after a while, I don't see any advantage to smaller rear legs. Once they cease to produce hydrodynamic drag, they should stop shrinking, right? Unless they are a liability for some other reason...

Limbs would act as radiators of heat in addition to causing drag. A Mammal needs to keep its heat, so that would be pressure against stub-limbs, even if they where streamlined. Eventually everything that is not needed on a whale should be selected against, since it is such a difficult transition to make. Every bit of optimization will yeild better whales and thus faster evolution.

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12-30-2001, 11:04 AM	#141
Oolon Colluphid Contributor Join Date: Sep 2000 Location: Alibi: ego ipse hinc extermino Posts: 12,591	...And anyone who doubts that feathers would be good for insulation should throw out their duvet... Cheers, Oolon

12-30-2001, 11:16 AM	#142
Christopher Lord Senior Member Join Date: Feb 2001 Location: Toronto Posts: 808	To me, feathers look a lot like what one would expect scales to turn into if a scaled creature needed to be a bit warmer. Air spaces between each proto-feather, and then between filiments of the proto-feather. Flight feathers can then be developed from these.

12-30-2001, 01:57 PM	#144
faded_Glory Veteran Member Join Date: Jul 2000 Location: Cairo, Egypt Posts: 1,128	What makes you think I haven't done this already? Duane. uh... I mean fG. [ December 30, 2001: Message edited by: faded_Glory ]</p>

12-30-2001, 10:03 PM	#145
Quetzal Senior Member Join Date: Nov 2001 Location: Ecuador Posts: 738	As usual, Douglas's arguments show a fairly limited understanding of the subject he is denying. In the first place, he needs to define which kind of feather he is referring to: there are seven modern feather designs, only one of which has his famous barbs. The rest range from something that looks mostly like a hair (could be maybe evolved from the same structure?, i.e., scales - duhoh) to the fluffy down insulator. Even the hook and barb structure is fairly easy to explain via evolution if you understand that feathers probably started out as insulation and only later were found to be useful for flight (another of the VERY common unintended consequences of evolution). Given the variation in the hook and barb system (from round barbules that sort of link to near hook-and-eye) it is pretty obvious that even a slight capability to link together provides a substantial increase in the thermal insulation properties of the feather integument. Once again, Douglas needs to go back to school. Or at least get some new arguments.

01-01-2002, 12:47 PM	#148
Asha'man Veteran Member Join Date: Dec 2001 Location: southeast Posts: 2,526	Hmm, I was going to ask about the survival value of transitional forms of feathers, but the question seems to have been answered. Sharp group here. However, it does bring up a larger question, one that Douglas might want to consider if he is going to really address the debate topic of microevolution vs macroevolution. It is easy to see the increased survival value of some gradual mutations, such as the lengthening of a giraffe's neck. But are there any transitional mutations where the intermediate form appears to have no value? For example, in the transition from land mammal to whale, the tail and forelimbs grow, but the rear legs dissapear. However, after a while, I don't see any advantage to smaller rear legs. Once they cease to produce hydrodynamic drag, they should stop shrinking, right? Unless they are a liability for some other reason... If a clear example can be found where microevolution and natural selection are not sufficient to explain a change, then a new mechanism for that specific change would be needed. scigirl, do you know of any such troublesome transitions? Anyone else? I'm sure that most can be explained with some thought, but a single solid example could cast some doubt on the issue. (I don't believe there are any, but figuring out some tough ones might be an interesting excercise in reasoning.)

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