Re: Evolution: A few questions

From: bivalve <>
Date: Mon Jun 14 2004 - 19:14:10 EDT

>I stumbled upon this site last night and it seems that there are quite a few theistic evolutionists here (or is this group for theistic evolutionists?)<

The ASA does not take any official position on evolution; it’s just that most (but not all) of those active on this discussion list accept a fair amount of evolution.

>1) Since evolution is not "conscious" how does it "know" that something is a benefit or a hinderance? The organism which experiences the change doesn't think, "Oh, wow, this <insert change> benefits my <insert feature> so I'm going to make sure I retain it!" And the process of evolution isn't isn't "conscious" so it doesn't consciously retain it, either.<

The only way for evolution to “know” that something is a benefit or hindance (or neutral) is experimentally. Mutations, interacting with varying environmental conditions, produce variation in success between different individuals. Whatever works well enough to survive and reproduce gets another chance.

>Or does it have to do more with the fact that the change isn't harmful to the organism (which would cause it to die without reproducing) therefore it's passed on? I imagine this is the case. If so, do we have any physical characteristics -- internal or external -- that developed by chance and that don't serve a purpose, but aren't harmful to survival, either so they're retained? I imagine organisms would randomly develop a number of these throughout the history of life.<

Most mutations are indeed neutral. One visible feature in humans that appears to be optional is the configuration of the nostrils. We, like apes and Old World monkeys, have nostrils pointing down. New World monkeys have nostrils pointing more sideways. Either one works just fine.

>2) What happens during the intermediary stages when a feature is evolving, but before it's fully functional? For example, I imagine it took an EXTREMELY long time before the wings of an insect or animal (which evolved from whatever they evolved from) were perfected and enabled them to fly. What happens during "however many generations" the organism exists with wings that were not yet functional? Wouldn't this be more detrimental thus causing the evolutionary process to drop the wings before they're useful?<

For flight, a partially developed wing (or even long hair, skin webbing, etc.) can help with gliding or parachuting, so a partial wing is useful. E.g., the “four-winged” dinosaur; “flying” squirrels, possums, frogs, snakes, lizards (all actually glide), etc. Such ability is quite useful for a small arboreal animal.

Contrary to some evolutionary and antievolutionary claims, the pressure to lose a useless feature may not necessarily be all that strong (though accumulating all but the last mutation for nice wings as useless mutations is indeed unlikely). For example, herbivores on the Great Barrier Reef love algae that have enough toxins to protect them from herbivores off California. Even though the toxins are now useless to the Australian algae, producing them does not seem to require enough effort to promote their loss.

Another complication is the fact that the first one to develop a new feature doesn’t have to do a great job to succeed. The first flying insects would only need to get off the ground/water to greatly improve their escape abilities from predatory arthropods or vertebrates. Likewise, the first pterosaurs would have had no competition. However, the success of the innovation produces pressure to improve it. E.g., as some of the insects took up catching each other in the air, greater maneuverability become more of an issue.

>3) My last question concerns non-theistic evolution -- the belief/theory that there's no God, that life occurred purely by chance, etc: The purpose of organisms is to survive and reproduce -- but why? If there's no purpose for existing and reproducing then what difference does it make if they do so or not? Why do organisms, from simple celled life-forms to plants to animals, have an innate need to survive and reproduce if there's no point to it?<

If organisms don’t survive and reproduce, they do not continue to exist. Thus, almost by definition, they must pursue those goals.

However, that is highly unsatisfying to humans as a meaning of life. Also, there’s nothing inherent in biological evolution (or science in general) that says that we should care about the survival of other organisms. Carelessness about the fate of other organisms may eventually endanger ourselves, but science cannot tell us that we ought to care about that, either. (Evolution does suggest that organisms that do “care” about their fate may have a better chance of survival. However, science cannot obligate me to care about my evolutionary success.)

>4) Ok, one last question :p . This is another one concerning non-theistic evolution and has to do with design -- specifically bodily symmetry. It's hard to understand how blind chance produced such a symmetrical body. Take the eyes for example. I followed a link from this list to . Under the progressive creationism section the article briefly describes how eyes may have evolved: "[A] few light-sensitive cells form an eyespot, the eyespot becomes recessed to increase the light-gathering area and to allow directional sense, the opening narrows to create a "pin-hole camera" eye, fluid fills the space for protection, the fluid becomes a lens." (the comment "the eyespot becomes recessed to increase the light-gathering area" makes it sound like it's a conscious decision, but I already asked about this in question 1). It's hard to understand how there just happened to be two areas containing light sensitive cells that w!
 ere so
symmetrically and "strategically" placed on the head. It seems more likely that organisms would have one eye on the side of the face, or two or three eyes placed randomly on the face. Another example are ears. I imagine the ears evolved in the same way the eyes did -- starting with an area of sound-sensitive cells. Again, though, it's so hard to imagine that two sound sensitive cell areas on the head happened to be so symmetrical -- being at the same distance from the center of the head, the same distance from the top of the head, that they both evolved the exact same way, etc. It seems more likely that blind chance would result bodies being more asymmetrical and random. Can anyone comment on this? <

There are at least two components. One is genetic. Key genes acting in animal development produce bilateral symmetry and anterior-posterior gradients (e.g., hox genes). A recent study (this year, I think) showed that such genetic mechanisms are at work even in bilaterally symmetrical cnidarians (a sea anemone). Having a relatively well-organized, successful genome makes major changes likely to be harmful, so there’s strong selective pressure to keep things working that way. Thus, animals are generally strongly programmed to be bilaterally symmetric.

Start with a simple motile animal. To efficiently move through water or sediment, it probably will be more or less worm shaped. As it’s moving, it mostly encounters things at the front end. Concentrating sense receptors there is a good idea. Thus, placing the light or other sensing areas on the head is likely. Some sense organs are single, some paired, but in mobile animals they are generally bilaterally symmetrical. One exception is owl ears, which are asymmetrical to enable precise location of a sound.

Another factor that affects symmetry is sexual selection. Asymmetric individuals are generally less appealing. This may reflect the potential for symmetry to be a visible proxy for genetic orderliness.

>Oh, finally, does anyone have testimonies online? I'd be interested in reading how believers dealt with and reconciled evolution and the Bible including the fall of man, the introduction of sin into the world causing the need for a savior, etc. Like I said above, I'm skeptical of evolution, but I do allow for the possibility of it so I want to hear some thoughts from Christian evolutionists.<

I’ll try to remember to post some of the ideas on this; I’m out of time for this evening.

> On a related matter, I recall a note that some insects (water striders ?)
> which could not fly used their wings to propel them rapidly across ponds.

H. and M. G. Kramer. 1994. Surface-skimming stoneflies - A possible intermediate stage in insect flight evolution. Science 266:427-430
Averof, M. and S. M. Cohen. 1997. Evolutionary origin of insect wings from
ancestral gills. Nature 385:627-630.

    Dr. David Campbell
    Old Seashells
    University of Alabama
    Biodiversity & Systematics
    Dept. Biological Sciences
    Box 870345
    Tuscaloosa, AL 35487-0345 USA

That is Uncle Joe, taken in the masonic regalia of a Grand Exalted Periwinkle of the Mystic Order of Whelks-P.G. Wodehouse, Romance at Droitgate Spa
Received on Mon Jun 14 22:56:57 2004

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