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Author Topic:   How did Evolution produce Symmetry?
defenderofthefaith
Inactive Member


Message 1 of 73 (62079)
10-22-2003 4:23 AM


It is an interesting fact that out of the vast variety of multicelled creatures, most are entirely symmetrical - especially the vertebrates. How could a random process of evolution produce animals that are completely and perfectly symmetrical, instead of having two heads with three eyes on one and none on the other... or invertebrates with an uneven amount of legs? Most creatures adhere to the laws of symmetry.
Could anyone here provide a hypothesis as to how evolution would produce such perfectly crafted creatures?

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rokit
Inactive Member


Message 2 of 73 (62091)
10-22-2003 5:20 AM
Reply to: Message 1 by defenderofthefaith
10-22-2003 4:23 AM


An interesting subject. I've never really looked into it, but here's an article I googled: http://www.nimr.mrc.ac.uk/MillHillEssays/1999/handedness.htm.
It seems to say that bilateral symmetry started early in the evolutionary tree. Why and how it started is what I'm not clear about. I think you would have to deduce that bilateral symmetry posed some type of advantage in the process of natural selection by enabling animals to work more efficiently. Ex: It could swim faster with fins on two sides, and a symmetrical body shape.
I think there may be a deeper reason at the cellular level. Similar cells may tend to grow as close together as possible for efficiency, but at the same time provide room for the optimal function of other cells. Two ears on either side of our head probably provide the most efficient internal wiring, while making room for other cells.
Another idea, which is probably less true would have occured later in the evolutionary timeline. Greater sex appeal for animals with greater external bilateral symmetry may have helped shape the evolutionary process. It's true for me at least...
I'm no expert, but just wanted to throw some ideas out. I'd be interested in learning more about it.

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Dr Jack
Member
Posts: 3514
From: Immigrant in the land of Deutsch
Joined: 07-14-2003
Member Rating: 8.7


Message 3 of 73 (62092)
10-22-2003 5:25 AM
Reply to: Message 1 by defenderofthefaith
10-22-2003 4:23 AM


It's not true that animals are perfectly symmetrical. Only the external organs are (approximately anyway). This makes good functional sense, a fish with one side more developed than the other would swim best in circles, a spider with six legs on one side and two on the other wouldn't walk so well, a fish with two eyes on one side and none on the other would be vulnerable to attack from the side with no eyes, and unable to forage effectively on that side.
You'll note that external symmetry is broadly true of man-made vehicles too, look at a car, a bike and a plane for example.
How could a random process of evolution
Incidently, this is a strawman - evolution is not a random process, although it does have random elements.

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sidelined
Member (Idle past 5908 days)
Posts: 3435
From: Edmonton Alberta Canada
Joined: 08-30-2003


Message 4 of 73 (62094)
10-22-2003 5:35 AM
Reply to: Message 1 by defenderofthefaith
10-22-2003 4:23 AM


DOF
These animals are symetrical yes but not perfectly so. Under close enough scrutiny they too have imbalances which are to be expected since they are subject to enviroments which alter the forces prevalent upon them in random ways.

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Philip
Member (Idle past 4722 days)
Posts: 656
From: Albertville, AL, USA
Joined: 03-10-2002


Message 5 of 73 (62103)
10-22-2003 6:50 AM
Reply to: Message 1 by defenderofthefaith
10-22-2003 4:23 AM


Harmony, Symmetry, Proportion
Your question might be broadened to:
How could random events (or elements) produce harmony, symmetry, and proportion, PER SE?
True, propagations and rebirths (micro-ToE events) should aide somewhat in maintaining these excellencies on biological levels as per your ToE speculators.
But speaking PER SE on cosmic excellencies of symmetry, harmony, and proportion does beg (strongly infer) awesome design (ID) to be sure, so that it seems pointless to argue the matter.
Most of us infer that a potter fashions the pottery, an artist the painting, etc. How much more might I (we) infer an excellent universe, quantum chemical science, life-form, and/or person to be directly fashioned by an awesome Maker.
Albeit doubts and fears must always taunt me (us) in this matter. A real curse of sin and blindness in my (our) mind(s) which repeatedly refuses to acknowledge the glorious truth of cosmic design.

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Darwin's Terrier
Inactive Member


Message 6 of 73 (62104)
10-22-2003 7:19 AM


I'd have thought bilateral symmetry was obvious. If you want to go somewhere in particular -- rather than wander aimlessly -- the route you will take will be a version of a straight line. A straight line with directionality (one way or the other) is an arrow.
So the bit of you that gets somewhere -- whereverthehell you're going -- first is the best place to put sense organs -- it's no good finding out that you're going to hit a rock after you've already done so -- and this gives you a head end. The rest, that which trails behind and gets 'there' later, is the remainder of your body.
All that remains is for there to be a left and a right, rather than being tube-like and any-way-up. But 'up' is the other clue: gravity will tend to define a top and a bottom. The side of the body that is in contact with the ground (or whatever) is the best place to put whatever makes you move along; 'up' and 'down' are useful variables too, so it makes sense to diversify your body plan into a top and a bottom, a dorsal and a ventral side. This could also come about from embryology-development: gravity will tend to have effects on embryological processes, setting for instance grading of hormones (as with bootstrapping of early 'advanced' embryos).
And voila, bilateral symmetry, from nothing more complex than 'needing to go somewhere in an environment with gravity'.
But the alternative, having sense organs all the way round, also works too, producing radial symmetry -- and plenty of animals have gone that way, such as echinoderms. But since evolution is constrained by history, once a lineage went down one route, it was stuck with it. It might be useful to have eyes in th eback of your head, but we just can’t have 'em!
Cheers, DT

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Darwin's Terrier
Inactive Member


Message 7 of 73 (62105)
10-22-2003 7:29 AM
Reply to: Message 5 by Philip
10-22-2003 6:50 AM


Harmony, Symmetry, Proportion my arse
quote:
Originally posted by Philip:
But speaking PER SE on cosmic excellencies of symmetry, harmony, and proportion does beg (strongly infer) awesome design (ID) to be sure, so that it seems pointless to argue the matter.
Most of us infer that a potter fashions the pottery, an artist the painting, etc. How much more might I (we) infer an excellent universe, quantum chemical science, life-form, and/or person to be directly fashioned by an awesome Maker.
Albeit doubts and fears must always taunt me (us) in this matter. A real curse of sin and blindness in my (our) mind(s) which repeatedly refuses to acknowledge the glorious truth of cosmic design.

Oh yes Philip, I entirely concur. I freely accept that design "strongly infers" an "awesome Maker". The only problem is that the designer strongly inferred it is an incompetent idiot and a sadistic bastard. That, matey, is the "glorious truth" about this designer.
TTFN, DT

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Darwin's Terrier
Inactive Member


Message 8 of 73 (62115)
10-22-2003 10:44 AM
Reply to: Message 1 by defenderofthefaith
10-22-2003 4:23 AM


Oh yeah, DOTF... "... perfectly crafted creatures... ", eh? See my first link above.
DT

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Rei
Member (Idle past 7013 days)
Posts: 1546
From: Iowa City, IA
Joined: 09-03-2003


Message 9 of 73 (62154)
10-22-2003 2:15 PM
Reply to: Message 1 by defenderofthefaith
10-22-2003 4:23 AM


quote:
How could a random process of evolution produce animals that are completely and perfectly symmetrical, instead of having two heads with three eyes on one and none on the other...
Download and run Framsticks for a while, and you'll understand.
------------------
"Illuminant light,
illuminate me."

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Loudmouth
Inactive Member


Message 10 of 73 (62174)
10-22-2003 3:40 PM
Reply to: Message 5 by Philip
10-22-2003 6:50 AM


Re: Harmony, Symmetry, Proportion
How could random events (or elements) produce harmony, symmetry, and proportion, PER SE?
True, propagations and rebirths (micro-ToE events) should aide somewhat in maintaining these excellencies on biological levels as per your ToE speculators.
How about flatfish. They lose bilateral symmetry during development. Proof of NO DESIGNER, since symmetry is lacking?
Oh, and it might help us if you provide evidence of a designer that is more explanatory than the supposed speculative Theory of Evolution. You could also supply evidence that order and symmetry can not come about due to chance and physical laws.

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zephyr
Member (Idle past 4550 days)
Posts: 821
From: FOB Taji, Iraq
Joined: 04-22-2003


Message 11 of 73 (62185)
10-22-2003 4:33 PM
Reply to: Message 7 by Darwin's Terrier
10-22-2003 7:29 AM


Re: Harmony, Symmetry, Proportion my arse
quote:
Oh yes Philip, I entirely concur. I freely accept that design "strongly infers" an "awesome Maker". The only problem is that the designer strongly inferred it is an incompetent idiot and a sadistic bastard. That, matey, is the "glorious truth" about this designer.
WOW.
Had a lot of fun reading those, especially the second.

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Brad McFall
Member (Idle past 5032 days)
Posts: 3428
From: Ithaca,NY, USA
Joined: 12-20-2001


Message 12 of 73 (62201)
10-22-2003 6:07 PM
Reply to: Message 6 by Darwin's Terrier
10-22-2003 7:19 AM


a cell is not a cell is not a cell
So then you would presume "to know" if then that plants ARE NOT going to the same places as animals? If so, would you be kind enough to try your sense at this question, "When a seed falls does it fall to the Earth or the Sun or some other Inertial System?" For thinking this way it is impossible to tell which way the psychology went and I see not reason to think that leaves didnt some how cut them self out of this arrow called the stem invert their "tail" end in your sense and provide the animals a convertable front and back at will of the higher clade seperation level. At least the variation in amphipods is not depauperated on this thought. The problem is that bilateral symeetry was used by Kant to show God's hand in his time and I see no reason this should not be found in plants if so well as well. Instead you have descended to vulgar or common language in your linkage of filiation.
I do not think it occurs by a formula Weyl tried to use of lattice points + metric but I also do not think like Wolfram that Gould's selection on different levels can not be found. I have often wondered if Pasteur's grand asymmetry undelay biological symmetry much as an arrow could but Maxwell used the figure as well for nonorganic matter so I am matterially torn but not unthinking on the matter. Some people try to find chiralty as cause but the effect of Wolfram's program could indeed see Gould's biology trump any universality common in this to both plants and animals as well as the others.
[This message has been edited by Brad McFall, 10-22-2003]

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Philip
Member (Idle past 4722 days)
Posts: 656
From: Albertville, AL, USA
Joined: 03-10-2002


Message 13 of 73 (62257)
10-23-2003 12:47 AM
Reply to: Message 10 by Loudmouth
10-22-2003 3:40 PM


Re: Harmony, Symmetry, Proportion
Can't engage in these clowning incoherent responses; its dreadfully and fearfully clear to me, redemptive-ID being responsible for all the cursed yet complex excellencies being derided at.
If you want to deride these excellencies, I'm out of here (fast).
Philip

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defenderofthefaith
Inactive Member


Message 14 of 73 (62295)
10-23-2003 5:06 AM


Further thought will be required by all. I've never heard this topic actually broached before. But it seems clear that, while some symmetry is good for survival, much is not. An extra eye on one side of our head would be asymmetrical and probably beneficial as well. Why is it then that if you divide the shape of a human body in half you get bilateral symmetry? Ten fingers (2*5), two arms (2*1), two eyes, ears, and a nose precisely in the middle. Sounds simple but it's actually quite perplexing from an evolutionary standpoint. For example, if eyes evolved from light-sensitive cells, why didn't these cells pop up all over the place? What we have is two perfectly aligned eyes pointing forwards.
And of course there are the decorations, such as completely symmetrical designs on butterfly wings. How did evolution come up with that?

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Dr Jack
Member
Posts: 3514
From: Immigrant in the land of Deutsch
Joined: 07-14-2003
Member Rating: 8.7


Message 15 of 73 (62301)
10-23-2003 5:46 AM
Reply to: Message 14 by defenderofthefaith
10-23-2003 5:06 AM


An extra eye on one side of our head would be asymmetrical and probably beneficial as well.
How so?
Ten fingers (2*5)
Pentadactyl limbs are believed to be an evolutionary 'accident'. As to why we have two hands, see below:
two arms (2*1)
We evolved from four legged animals, four legs is the minimum number for easy walking (since you can maintain a stable tripod at all times - which is what the earliest known land animals seem to have done). Symmetry is the best for easy movement.
two eyes, ears
Two is the minimum number required for stereoscopic sensing.
and a nose precisely in the middle.
If you've got a body plan based on two of things, where is the logical place for something you only need one of? That's right, in the middle. Otherwise you'd de-balance the body plan, with the resultant constructive and mechanical difficulties.
And of course there are the decorations, such as completely symmetrical designs on butterfly wings. How did evolution come up with that?
Symmetry is almost universally attractive among animal species (including humans). Butterfly decrorative patterns are generally either display, or eye-mimic patterns. Display patterns will want to be symmetrical for the above mentioned reason, eye-mimic patterns need to match the eyes of those they mimic.
There is a good reason for the attractiveness of symetrry, perfect symmetry (as opposed to near-perfect symmetry) is very difficult to build, it otherwords it's energetically expensive, while being functionally minimally advantagous. Thus successful mate material will be able to spare the energy required for symmetry while less fit organisms will not.

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