malookiemaloo

Oriecat, who started this thread, did make an interesting point re creation evidence-one which I had never considered before.

If God created the world as told in Genesis, in what way would our world be different to what it is now?


m

MyKell

I don't know if this is supposed to be an evidence for creation, but if so it's pretty lame...
If God had created the world according to the story in Genesis, we would not have the fossil record we have. Why would there be fossils of Trilobites, Dinosaurs, etc... that happens to have existed long before the appearance of the first human.

malookiemaloo

No, it was not a defence of creation. I can't do that as my scientific knowledge is zilch. I just wondered that's all.

Thanks.


m

Selsaral

Yeah the entire geologic record would be different. Not only fossils (there basically wouldn't be any), but all of the sedimentary rock record (which has been precisely mapped out and which spans hundreds of millions of years) wouldn't exist. Sedimentary rocks wouldn't exist at all (unless they were designed specifically to fool us into thinking grand time scales and other processes were at work), since they are simply cemented minerals and chunks of eroded igneous rocks. Limestone wouldn't exist at all, unless god specifically wanted to make us think grand time scales and the shells of small marine organisms cement together naturally. The mapping of plate techtonics which shows the continents have moved quite a bit over the history of planet would show no movement at all (or it was designed to look like it had moved when it hadn't). Landform analysis shows clear evidence of recent glaciation, so that couldn't exist either (or was placed purposely to mess with us). The genetic similarities between organisms wouldn't exist either, unless they were designed specifically to fool us into thinking we shared common ancestors. Features of organisms, such as torsion in gastropods, or the fetal development of organisms would be radically different, or would have been designed specifically to fool us into thinking the creator was on crack or another system (evolution through natural selection) was at work. Archaeological evidence that shows human beings have existed far longer than six thousand years wouldn't exist.

I could go on and on, and this is just my rudimentary understanding of geology. A real scientist could write volumes on this. Basically either the entire world would be different, or we would have to accept it was created to fool us into thinking natural processes are at work.

Jayjay

Hmm, I wonder if anyone has ever asked a creationist the reverse of that question: how would they expect the world to be different if evolution were true? (My guess is that most creationists would just say "evolution is impossible blah blah" or something to that effect though.)

Lobstrosity

Or they'll say that evolution is untestable, just like creationism (this delusion makes them feel better about the fact that creationism isn't a valid "theory" in the true sense of the word) and hence anything could be expected under the theory of evolution. Basically, it's the same argument we make about the predictions of creationism, except that their application of this argument is not valid. Evolution has clear predictions and some of the ways it could be refuted I have listed in my earlier posts.

Lobstrosity

For my own edification, would it be possible for you to explain this in a little bit more detail? What is currently wrong with the torsion in gastropods and how could it be fixed?

Selsaral

I don't mean to call torsion a 'problem' or something 'wrong', but it is an extremely interesting feature of their development that has powerful implications. I'd also argue it flies in the face of 'intelligent' design theory. Either the design is so 'intelligent' that we cannot possibly comprehend its purpose, or it wasn't 'designed'. I must refer you to sources who can explain it better than me. I'd prime these by saying that how body forms position the mouth and anus are of critical importance (contaminating your food with your own waste is bad), and that the process by which some gastropods twist and then un-twist their bodies during their larval stage is the key issue. I hope I am not breaking any copywrite rules in how I present these. These were quick links google.com gave me. The first, at http://comenius.susqu.edu/bi/322/IZLecture27.htm, reads:

"Gastropods initially have a basic bilateral symmetry like most mobile animals. The mouth sits at one end anteriorly and the anus sits at the other end posteriorly. During development however, the digestive system and the rest of the internal organs turn-sometimes 90 degrees, sometimes up to 180 degrees so that the anus is then situated over the mouth.

This process occurs early in development in most cases and usually occurs in two steps.

A foot retractor muscle develops and at a certain stage in development, this retractor muscle is pulled and the internal body organs and digestive tract turn 90 degrees in a counterclockwise fashion. This turn usually occurs within a few minutes or hours.

The second 90 degrees usually takes much longer and occurs through another mechanism-differential growth of the left and right sides of the gastropod.

Some gastropods during development rearrange their organs again and become "detorted" while others remain "torted" throughout their lives.

Detorsion may be 90 degrees or less, or in some cases a full 180 degrees again.





Of course the obvious question is why would a gastropod rearrange its digestive system and other organs-including gills and nerves, so that its anus is above its head. This doesn’t seem to be a good adaptation to anything.

Besides the hygiene considerations, it also limits growth since the body is doubled over on itself, and nerves are bent into a figure eight. The result is the visceral hump prevalent in most gastropods.

What is the adaptive advantage of torsion? Is it an adaptation?

First I’d like to say something-

This is one of the great unanswered questions in invertebrate zoology.

But lets consider some of the clues about what the function may be--

Most slug-like gastropods-gastropods without shells, have undergone detorsion.

This suggests that whatever value torsion has it probably has something to do with carrying a shell-with one opening only.

It is also worth noting that the veliger larva can retract its head after torsion, but cannot prior to it.

The fact that veligers can retract the head prompted the hypothesis that it was an adaptation of larvae to avoid predators

Veligers when disturbed retract their heads into the shell and sink to the bottom.

Although this idea makes sense for planktonic predators-most bigger animals like fish eat them whole.

Pennington and Chia tested Garstang’s hypothesis using torted and untorted veligers and found that even small planktonic predators ate both types of veligers with equal frequency.

Another possibility is that torsion is an adult adaptation. Torsion allows for better retraction of the head in adult gastropods too.

When the digestive system is turned, the gills are also turned allowing better sensing of chemicals in the water current by the osphradium, and oncoming water for the gills.

Another possibility has to do with another process that gastropods exhibit-coiling.

This is the spiraling of the shell.

Primitively, the shell coils in a manner such that each turn is within the same axis as the turn before it. Very quickly this results in a tall, ungainly shell with a high center of gravity and poses difficulty in movement.

The evolved solution to this problem is asymmetrical coiling around a central axis (called a columella). This allows a stronger and more stable shell.

It has been suggested that one of the adaptive values of torsion is to better exploit the available space in an asymmetrical coiled shell-since the direction of the torsion event is usually in line with the direction the shell is off center.

I would like to point out that torsion and coiling are separate evolutionary events.

All evidence suggests that coiling preceded torsion which is a necessary prerequisite for torsion to be adaptive for taking advantage of space created by asymmetrical coiling.

In either case, it is important to realize that coiling is spiraling of the shell.

Torsion is twisting of the internal body parts of the gastropod.

Whatever the adaptive significance of torsion-the result is to move the gills, gonopore and excretory pore into the mantle cavity-a position consistent with the other mollusc taxa."

And the second, much shorter is at http://bioweb.uwlax.edu/zoolab/Table...tropoda_01.htm and reads:

"The Class Gastropoda ("belly foots") is the largest and most diverse group of molluscs, containing over 40,000 living species of snails, slugs, limpets, whelks, conchs, periwinkles, etc. Most (but not all) have a single shell (valve) that is usually coiled. When threatened by predators or the possibility of desiccation, can withdraw their bodies into the shell and seal the entrance with a tough, horny plate called an operculum on the back of the foot. Gastropods are distinguished from all other molluscs by a 180E twisting of the visceral mass called torsion that occurs during development in the veliger larva. This twisting is brought about by uneven growth of the right and left muscles that attach the shell to the head-foot. As a consequence, torsion brings the anus and mantle cavity forward to a position above the head. Some gastropods even show detorsion where the anus opens to the right side or even to the posterior. In addition to torsion, many gastropods also undergo the separate process of coiling in the development of the visceral mass and shell. Coiling is one way that a shell can grow along with the animal without becoming so long that it impedes locomotion. "

Why would this mollusc that was designed (by god) to be exactly how it is, display features of its ancestor (initial torsion event) during the larval stage, then undo that torsion (second, detortion event)? The detorsion, as noted, is advantageous for molluscs without shells. This detorsion shows exactly what you'd see if evolution were taking place...the modification of previous designs. An intelligently designed mollusc would develop to its current form..not to its ancestor's form and then back. (Or the design is just too 'intelligent').

Lobstrosity

I see. Thank you very much for going through the trouble to explain all that to me!

Selsaral

That was a hell of a question too, I hadn't studied this for years (since my paleontology courses in college). I remembered the basics but that was about it. I had to edit my post several times....I am hoping a real paleontologist will come here and make more sense than me. Thanks.