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A Problem With Evolutionary Theory


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#1 Guest_Calipithecus_*

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Posted 14 June 2005 - 10:29 AM

You guys have been good enough to put up with me even though I disagree with most of you on a lot of points. Discussions here have led me to approaching some ideas from angles I might never have considered on my own, and it seems only fitting that if as a result I find something about evolutionary theory that makes me uncomfortable, I share that here. Maybe arguing about it with you guys will help me clarify my thoughts. It's happened before.

The catalyst was this comment by 92g:

Engineering is an intellectual activity.

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The English language is a teleological minefield. But the problem to which the above statement led me is much worse than a problem with language.

When we speak of a person's intentions, we tacitly acknowledge that such matters can get a bit complicated: a person's actions are not a simple matter of him doing what he wants, but reflect the greasing of the squeakiest wheel among an internal cacophony of various urges and counter-urges. Humans often demonstrate a phenomenal ability to make accurate guesses about which situations will cause another person's wheels to start squeaking, and which ones he is most likely to grease first. It is a skill that confers an advantage in the singles bar and the corporate boardroom alike; in some environments (such as the ancestral African savannah, the prison yard, or certain streets in most any large city), it is absolutely critical for survival.

Because it is so important, a considerable portion of our cognitive resources are dedicated to this task (one need only consider what percentage of the total bandwidth consumed by discussions about creation vs evolution are directed to the motives of a poster rather than to the content of his posts). I am convinced that high priority given to the performance of this task, and high reproductive reward for success was, directly or indirectly, a major driving force behind the evolution of the human brain.

Our brains leap instantly at the slightest hint of motive, and once they think they've got it, they don't like to let go. It is not surprising then that we always have an eye out for 'designs', and when we spot one, our minds immediately go to work formulating guesses about the designer and his intentions. If this practice is error-prone, the biologist may be the worst offender. Substituting "natural selection" for "designer", he points to the utter lack of purpose or direction in evolution, thinking that this is enough to free him of all hidden teleological assumptions. "Traits exist because they were selected for", he says, perhaps without appreciating the breadth of the leap he has just made. (Okay, maybe the evolutionary psychologist would be the worst offender.)

One problem is highlighted by the results of the recently completed human genome project: there simply are not enough functional genes to explicitly code for everything the biologist might like to refer to as a 'trait'. Apparently, the situation is even more complex than we thought, with a great deal taking place implicitly, or by side-effect; 'traits' (at least a lot of them) being emergent features of that complexity. Gould introduced his metaphor of the "spandrel" to explain the evolution of some features as the co-opting of side-effects of earlier features. Like many others, I have always found something vaguely unsatisfying about that explanation, but it serves at least to get us into the neighborhood of what I'm trying to express.

In his audaciously titled book, "Consciousness Explained", the philosopher Daniel Dennett proposed (for purposes tangential to this discussion) that among the properties which might be considered 'design features' of a 'designed object' (or, say, an organism) is its center of gravity. That's the sort of thing I'm talking about. If one were to consider that as a 'trait', where on the genome would one begin looking for the nucleotide sequences which produce it? How many other 'traits' might prove as elusive? Do we have mathematical models adequate to sufficiently isolate such 'traits' so as to even attempt to measure them in terms of 'absolute fitness', or 'relative fitness'?

What has been described as the "Central Dogma" of evolutionary biology is this mapping: DNA=> RNA=> Amino Acid=> Protein. There are nuances of that process enough to keep biochemists working for quite some time, but it does not seem as mysterious to me as it did when I was first introduced to it. Usually omitted, however, though tacitly presupposed, is one last mapping: Protein=> Trait. This I still find absolutely mind-boggling. It seems to me that reconstructing those mappings accurately enough to permit full appreciation of their evolutionary implications may not always be possible even in principle, a difficulty which often appears to be overlooked. Perhaps this is part of what inspired Gould to repeat the cliché that evolutionary reasoning is just "cocktail-party speculation".

At the very least, a lot of empirical work remains to be done in this area, especially with regard to proposals made by the most ambitious of theorists. If I were looking for a chink in the armour of evolutionary theory (and loyalty to the highest standards of scientific inquiry seem to demand that I do so), I think I'd start there.

#2 chance

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Posted 14 June 2005 - 02:17 PM

In his audaciously titled book, "Consciousness Explained", the philosopher Daniel Dennett proposed (for purposes tangential to this discussion) that among the properties which might be considered 'design features' of a 'designed object' (or, say, an organism) is its center of gravity.

I would consider centre of gravity, to be a product of every other trait with no specific DNA controlling it. A bird for example mutates with a longer tail (better flight control, but more cumbersome when perched). Survivability, or reproductive success is determined by the sum of the traits.

At the very least, a lot of empirical work remains to be done in this area

Protein=> Trait. This I still find absolutely mind-boggling. It seems to me that reconstructing those mappings accurately enough to permit full appreciation of their evolutionary implications may not always be possible even in principle

if I understand, you are implying that the job at hand is complex and large and sometimes impossible. Can you give an example of one of these impossibilities? Must admit that I’m not quite sure of the point you are making.

#3 Guest_92g_*

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Posted 14 June 2005 - 04:00 PM

The reason I pointed out your use of the word "Engineering" is that I find that to be an unconcious admission of design(no offense intended), sort of a Fruedian slip....

It always cracks me up to watch an evolutionary documentary, and hear the narrator say "by a stroke of evolutionary genious".

The thoughts about proteins -> traits is an interesting point. I think its even more mind-boggling when you try to suggest that the mental charachteristics of living beings are encoded into DNA.

E.g. the foraging dance of the honey bee.

Its already a stretch to imagine the information system of DNA evolving on its own, but to imagine the information required to program a living being such that it can can communicate direction and distance symbolically. That's really amazing....

Then, somehow, if the mental characheristics can be traced to functional proteins, then for those mental charachteriscs to evolve at the same time as a phsyical charachteristics such that the two can function together. That's really really amazing....

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Posted 14 June 2005 - 11:00 PM

I would consider centre of gravity, to be a product of every other trait with no specific DNA controlling it. 

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I would too. The problem is that the DNA controlling those other traits would be specific; it's just that it would be specific with regard to those other traits, and non-specific to center of gravity -- a property which, in this case, is assumed to be an important factor determining reproductive success. And at the same time, those specific sequences would also have to be non-specifically producing any of the other emergent traits we might care to posit; not just any of them; all of them. All at once. It just seems like a bit much (to indulge in a bit of argument from personal incredulity).

We also wouldn't expect to find the center of gravity of an automobile to be explicitly specified anywhere in the complete set of its blueprints -- its top speed, braking distance, or turn radius, either. Yet it is not necessary to posit that these properties are the result of anything other than what is specified in the blueprints.

Now, a human designer can make calculations (or guesses) as to what specifications might need to be changed in order to bring these properties within some desired range, but because these properties are determined by a sum total of every explicit specification (or at least some large number of them), he would be wise to keep an eye toward what other consequences such changes might produce.

This activity would certainly deserve to be called: "engineering", and it differs from biological evolution in two important respects. One is that the engineer is able to anticipate the effect that some change might have for some emergent property of the vehicle as a whole, and the other is that his considering such changes is a reflection of his goals. Again, because our language does not offer graceful ways to express an idea like: "engineered, but without an engineer other than the laws of probability", biologists often do simply invoke terms like "engineered" without including the disclaimer that they are intended in a metaphorical sense; that is assumed to be understood. Evolutionary theory, proposing random mutation and natural selection as its mechanisms, implicitly denies any hint of genuine teleology by neither requiring it nor offerring any way for such a thing to exert an effect.

There appears to me to be an enormous gap between what is known about how proteins are formed and what is known about how the formation of proteins results in various emergent properties at the level of the complete organism. I predict (intuit, whatever -- which proteins enable me to do this?) that better understanding of this will not reflect kindly upon much of what is currently presented (somewhat overconfidently, I fear) as fresh insight. Hardly a week goes by without some new announcement of the discovery of a genetic component for some feature of human behavior like H*m*s*xuality or alcoholism or fundamentalism or what-have-you, the inference being that all that remains is the filling in of a few details. I'm not actually sure whether to regard that job as merely complex, hopelessly complex, or merely hopeless, but I do think a bit more caution is warranted. The elegance of evolutionary theory seems to have a way of going to some people's heads.

#5 Mariner Fan

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Posted 15 June 2005 - 08:47 AM

Its already a stretch to imagine the information system of DNA evolving on its own, but to imagine the information required to program a living being such that it can can communicate direction and distance symbolically.  That's really amazing....


It is, but we all have to be careful about what can and can't be "imagined". Both sides of the debate are guilty of this, but it is faulty logic to demand that reality conform to our human imagination.

I think this is what Chance was talking about. Geneticists expected many more genes, or actively transcribed regions, in the human genome to be much higher than the final tally. However, this has led to a new field within genetics, the study of transcription factors. The thinking is starting to shift from the gene sequence being the most important factor to a new paradigm where gene expression and the timing of expression is as important or even more important than the gene sequence itself. The sequencing of the human genome was supposed to clear up a lot of issues but it has only muddied the waters.

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Posted 15 June 2005 - 11:29 AM

...it is faulty logic to demand that reality conform to our human imagination.

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That expresses very nicely what I'm getting at. We cannot simply wave the magic wand of selection and expect to create rigorous explanations for everything we think we see.


The thinking is starting to shift from the gene sequence being the most important factor to a new paradigm where gene expression and the timing of expression is as important or even more important than the gene sequence itself.


Right. In other words, there are two (very simplified) ways to look at the process. One is to consider the DNA to be using proteins to make cells, and the other is to consider the cells to be using the DNA to make proteins. I would say that there is a third, which is to consider both to be happening at once; but there is a great temptation to at least sort of postpone grappling with the complexity that incurs, by pointing to DNA as the origin of the cells in the first place, thereby subsuming the second approach under the first.

A nice metaphor for this is to consider what is contained in the DNA to be analogous to a list of words, and gene expression analogous to using words from the list to create a story. This idea goes a long way toward explaining why there is so much similarity in the genomes of organisms so dissimilar in morphology -- but it also helps in appreciating how vital to the process are the histories of the cells themselves, as components in the cellular colonies we refer to as: "organisms". Just as English-speaking authors with personal histories as different as Mark Twain and Charles Dickens produce very different stories from (very nearly) the same words, cells with different histories produce very different protein structures from the same DNA.

But the history of a cell does not begin at the onset of embryonic development; that history includes the histories of all the cells of which it is only the latest in an unbroken succession reaching back to the origin of cellular forms (a topic for another thread... I hope).

Not only is gene expression and the timing of expression as important or even more important than the gene sequence itself, which sequence gets expressed when is as much a function of the history of the cell in which the action is taking place as it is of anything on the DNA itself. It's just an absolute mess.

#7 chance

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Posted 15 June 2005 - 02:02 PM

I would too. The problem is that the DNA controlling those other traits would be specific; it's just that it would be specific with regard to those other traits, and non-specific to center of gravity -- a property which, in this case, is assumed to be an important factor determining reproductive success.

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Agreed. But the reproductive success has always been 'in the eyes of the beholder’ so to speak. For example, lets suppose Superman was the product of a rather large series of mutations from a human mother. But unlike the comic books he has the looks ‘only a mother could love’ and the personal hygiene of drunken pig! He’s also not very savvy and thus poor as a church mouse, cant see the female of our species beating a path to his door, Yes? So with all those advantages, he’s extinct. I think what you have actually described is a limitation on evolution. Sometimes better is not better.


We also wouldn't expect to find the center of gravity of an automobile to be explicitly specified anywhere in the complete set of its blueprints


I cant speak for cars, but you most certainly do for aircraft. The point being, it is a conscious decision to consider the centre of gravity, and thus all the contributing design features are addressed before production. Quite different from evolution where centre of gravity is still a product of many other features, but no conscious considerations of what will work. A poor adaptation is very quickly weeded out. Consider a clutch of hatchlings one of the birds has a much higher bone density in the skull, so it matures with the others. However when it comes to flying, it expends a lot of energy in comparison to the others, thus there is a very good chance it wont survive to adulthood.

Evolution is really whatever works, survives. One could also take the position that evolution is terribly inefficient, as opposed to elegant.

#8 chance

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Posted 15 June 2005 - 02:07 PM

Geneticists expected many more genes, or actively transcribed regions, in the human genome to be much higher than the final tally.  However, this has led to a new field within genetics, the study of transcription factors.  The thinking is starting to shift from the gene sequence being the most important factor to a new paradigm where gene expression and the timing of expression is as important or even more important than the gene sequence itself.  The sequencing of the human genome was supposed to clear up a lot of issues but it has only muddied the waters.

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Sounds interesting, do you have a link (preferably in layman’s terms).

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Posted 15 June 2005 - 03:46 PM

It is, but we all have to be careful about what can and can't be "imagined".  Both sides of the debate are guilty of this, but it is faulty logic to demand that reality conform to our human imagination.


I agree, but its not just imagination that's involved, its understanding how things work, and consequently the huge contradiction to what is known about information it is to believe that information, and information processing systems can evolve on their own by purely materialistic processes.

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#10 Mariner Fan

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Posted 15 June 2005 - 04:51 PM

I agree, but its not just imagination that's involved, its understanding how things work, and consequently the huge contradiction to what is known about information it is to believe that information, and information processing systems can evolve on their own by purely materialistic processes.

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Well, we would then have to understand exactly how an information processing system COULD evolve. This would then give us an idea of what natural (not materialistic) processes need to be involved. We would also need to understand what other information systems could evolve other than the DNA/RNA/protein system found in life on earth.

Secondly, we could go on and on about the definition of information but I hardly think this is the place. But you did catch us in the fact that the word "engineering" is used loosely. This happens often in scientific literature.

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Posted 15 June 2005 - 05:51 PM

I cant speak for cars, but you most certainly do for aircraft.  The point being, it is a conscious decision to consider the centre of gravity, and thus all the contributing design features are addressed before production.

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But you know, going in, that center of gravity is one of the things the designer was considering, so working backwards from there is a piece of cake. The evolutionary theorist seems to have little choice but to attempt to do basically the same thing: starting with the assumption that some aspect of an organism's design must be important, he works backwards from there to explain what is happening on the genome.

To be fair, there are a lot of obvious cases in which this seems like a safe enough bet, but I'd be concerned that this practice could also result in a lot of time wasted considering something that was just a figment of some biologist's imagination (after all, one thing nearly everybody seems to agree on is that scientists in general and biologists in particular have much more fertile imaginations than the average person).

There just seem to be so many possibilities for error in presuming to second-guess the intentions of an engineer when that engineer is natural selection. A low center of gravity might be what was being selected for, one possible solution to the problem being big feet. It might then appear quite obvious that big feet conferred some advantage, and just a short hop from there to the conclusion that big feet were an end in themselves, rather than just one among a multitude of possible means to the same end -- and that end might be the last thing the biologist was actually considering.


One could also take the position that evolution is terribly inefficient, as opposed to elegant.

Oh, I absolutely agree. By elegant, I was referring to the theory, not the process. The process is hideously inefficient by human standards of engineering.

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Posted 15 June 2005 - 10:35 PM

Oh, I absolutely agree. By elegant, I was referring to the theory, not the process. The process is hideously inefficient by human standards of engineering.

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The process may be inelegant and ineffecient but the results are exquisitely elegant. Take for instance FPGA's, circuit boards that can be used to create unique circuits using random variation and selection. This type of circuit array was used to create a voice recognition circuit that was used fewer cells than anyone had ever dreamed of through teleologic, human engineering. That's right, a voice recognition circuit formed by chance, as creationists often view the process of evolution. The full story below (from http://www.talkorigi...les:electrical).

A field-programmable gate array, or FPGA for short, is a special type of circuit board with an array of logic cells, each of which can act as any type of logic gate, connected by flexible interlinks which can connect cells. Both of these functions are controlled by software, so merely by loading a special program into the board, it can be altered on the fly to perform the functions of any one of a vast variety of hardware devices.

Dr. Adrian Thompson has exploited this device, in conjunction with the principles of evolution, to produce a prototype voice-recognition circuit that can distinguish between and respond to spoken commands using only 37 logic gates - a task that would have been considered impossible for any human engineer. He generated random bit strings of 0s and 1s and used them as configurations for the FPGA, selecting the fittest individuals from each generation, reproducing and randomly mutating them, swapping sections of their code and passing them on to another round of selection. His goal was to evolve a device that could at first discriminate between tones of different frequencies (1 and 10 kilohertz), then distinguish between the spoken words "go" and "stop".

This aim was achieved within 3000 generations, but the success was even greater than had been anticipated. The evolved system uses far fewer cells than anything a human engineer could have designed, and it does not even need the most critical component of human-built systems - a clock. How does it work? Thompson has no idea, though he has traced the input signal through a complex arrangement of feedback loops within the evolved circuit. In fact, out of the 37 logic gates the final product uses, five of them are not even connected to the rest of the circuit in any way - yet if their power supply is removed, the circuit stops working. It seems that evolution has exploited some subtle electromagnetic effect of these cells to come up with its solution, yet the exact workings of the complex and intricate evolved structure remain a mystery (Davidson 1997).



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Posted 16 June 2005 - 10:00 AM

Yes, and the only way we know if it is possible is by trying to make one evolve, not by sitting in an armchair and proclaiming it to be impossible.

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How about sitting in an armchair and trying to make one evolve?

Go-moku is sort of like a little brother to the Japanese game of Go, in the same sense that checkers is to chess. Played on a Go board (a grid of lines, usually 19 x 19), the rules are only slightly more complicated than tic-tac-toe (I believe it's "naughts and crosses" to you Brits and Strines), the main difference being that winning requires placing five tokens in a row instead of only three (in Go/Gomoku, the tokens are called "stones"; in good quality sets, the black ones actually are made of stone, the white ones of shell). I think the game is available on some cell phones now.

Years ago, I hardcoded a gomoku AI that plays a strong enough game to trounce every human who's ever tried it for at least the first ten or so games, including some who were fairly experienced players. It still beats me about half the time. But I thought it would be more interesting to write an evolving AI for it. Here (simplified for brevity) is how that works:

On every turn, each cell is examined as a potential candidate for the next move, and assigned a 'weight'. Starting from the cell being evaluated, the cells out to a distance of five cells, in eight directions (four orthogonal, four diagonal) are examined, and the results saved in a string. Cells containing a friendly stone are designated "1", hostiles "2", and empty cells "0" (a sample scan: "110020"). The decimal equivalent of the base-three value of this string is used as an index into a table of 'weights' (the 'population'), which are initialized with random values. At the beginning of a match, two sets of weights are assembled by randomly selecting weights from the table; these weights are used for the duration of that match only. At the end of each match, the loser's weights are adjusted (some, randomly selected, are overwritten with the corresponding weights from the winner's set, others are incremented or decremented, still others left unchanged). The winner's weights are, naturally, left unchanged (if it ain't broke...).

I would love to be able to report that the results have been stunningly clear confirmation of the way an 'information processing system' (if you like) could emerge as the result of a process of natural selection operating on random mutation. I understand that others have achieved such results, and I was hoping to experience that too. Unfortunately, though there is marked improvement during the early hours of a run, beyond a certain point (and long before it rises significantly above the level of idiotic) the play ceases to improve. I have let it run for weeks at a time, with matches being resolved at an average rate of less than ten seconds per match.

I regard my results as inconclusive. Possibilities I have considered:

1) Due to my mediocre abilities as a programmer, the program contains logic errors that prevent it from working properly.

2) Due to my mediocre abilities as a critical thinker, I have failed to capture the essential properties of an evolving system.

3) It works fine, but evolving strong play would take years rather than weeks (and if it required happy accidents of an extremely rare nature, maybe decades or centuries).

4) The creationists are right, and it was a fool's errand to begin with.

It probably goes without saying that Number 3 is the possibility I find most attractive. Numbers 1 and 2 are the ones I consider most likely, about equally so. Number 4 is included just to be thorough.

My fundamental assumption is that it is possible for selection to operate on multiple factors at the same time, including some which (like center of gravity) would clearly be emergent properties of a system as a whole. This is what achieving five-in-a-row would be, since the 'weights' don't 'know' anything about what they're supposed to be doing -- and the selective mechanism doesn't 'know' (or 'care') how they're doing what they're doing; it looks at only one thing, that being whether or not a set of weights has produced a winning position.

This is an idea I have a little trouble really wrapping my head around. Dawkins made it sound compelling enough:

It is possible to imagine a compatible combination of genes as being selected together as a unit... Suppose it is important in a really successful crew that the rowers should coordinate their activities by means of speech... Because of the importance of communication, a mixed crew will tend to win fewer races than either a pure English crew or a pure German crew. The coach does not realize this. All he does is shuffle his men around, giving credit points to individuals in winning boats, marking down individuals in losing boats. What will emerge as the overall best crew will be one of the two stable states--pure English or pure German, but not mixed. Superficially, it looks as though the coach is selecting whole language groups as units. This is not what he is doing. He is selecting individual oarsmen for their apparent ability to win races... Selection at the low level of the single gene can give the impression of selection at some higher level. The Selfish Gene, Oxford, 1989, p. 84-5.



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Posted 16 June 2005 - 06:41 PM

The process may be inelegant and ineffecient but the results are exquisitely elegant.  Take for instance FPGA's, circuit boards that can be used to create unique circuits using random variation and selection.  This type of circuit array was used to create a voice recognition circuit that was used fewer cells than anyone had ever dreamed of through teleologic, human engineering.  That's right, a voice recognition circuit formed by chance, as creationists often view the process of evolution.


This is a genetic algorithm applied to electronic HW. A genetic algorithm is just a human guided seach algorithm. Human guided search algorithms implemented in a system where a solution exists will most always produce a solution, wether the concept is correct or not.

Admittedly, this is a clever application of the concept of Neo-Dawinian Evolution, but the task of differentiating between 1khz and 10khz, and activating the output to its limits, 5V, or 0V is not very impressive. This is essentially a low pass filter, and to call it a tone discriminator, looks to be really glorifiying a not very impressive result.

It may have some function with less cells than a human designer would have come up with, but the human design would not be temperature, or circuit limited. So, which one is really better?????

We see design in nature, and rightly so. IMO,.........,examples such as this that do not exhibit design, they said they can't figure out how it works, are more of an argument against Neo-Darwinian Evolution producing what we see in nature than it is for it.

Terry

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Posted 17 June 2005 - 07:27 AM

A genetic algorithm is just a human guided seach algorithm. 

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You acknowledge a difference between 'human guided' and 'human designed', and I'm inclined to go along with that. To me, 'human designed' means that some human has attended to every detail, making deliberate choices intended to achieve some goal. As you noted, this clearly is not the case with the FPGA example, since: "the exact workings of the complex and intricate evolved structure remain a mystery". The human defines the goal parameters, and in doing so, assumes a guiding role analogous to natural selection in biological evolution: "this tree is top-heavy, and will fall to the ground at this time", says natural selection, without knowing or caring about the details.


examples such as this that do not exhibit design

I'm not sure what your basis is for this -- unless you're saying that because they are not designed by humans (or some other intelligent agent), they are not designed at all. This looks to me like either a quibble about semantics, or a deeply philosophical argument (one which I think I could counter if I felt the discussion would be a positive contribution to this thread -- which I don't).

What if we were to refer to such examples as: "functionally equivalent to structures exhibiting design"?


this is a clever application of the concept of Neo-Dawinian Evolution

Now, that I agree with.

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Posted 19 June 2005 - 05:29 AM

I'm not sure what your basis is for this  -- unless you're saying that because they are not designed by humans (or some other intelligent agent), they are not designed at all.


To me its very simple, if we take a look at a biological machine/system, and can see a discrete logical implementation of components that make it functional, as we would expect a human mind, or other intelligent being, to do it, then that biological machine/system exhibits design characteristics.

E.g. The Bombadier Beetle which expels a hot gaseous mixture out of its tail for defense. It uses 2 chemicals stored in seperate chamber that are mixed in a reaction chamber with a catalyst to get the reaction going. It can then spray that mixture very accurately at it's attacker.

This is very similiar to a rocket engine which has two chemicals stored in chambers(tanks), e.g. keroseen, and oxygen, that are mixed together to produce a chemical reation whose product is expelled out an exhaust port.

The bombardier beetle's defense mechanism clearly exhibits mental design charachteristics.

What if we were to refer to such examples as: "functionally equivalent to structures exhibiting design"?

I suppose that's acceptable under warranted circumstances(I'm sure we'll see what it that really means down the road). IMO, the FPGA example is not one of them. It does something, but is so limited, and restricted in function, that to say that it really lives up to what the human mind is capable of creating is stretching things just a bit.

Terry

#17 chance

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Posted 19 June 2005 - 01:57 PM

There just seem to be so many possibilities for error in presuming to second-guess the intentions of an engineer when that engineer is natural selection. A low center of gravity might be what was being selected for, one possible solution to the problem being big feet. It might then appear quite obvious that big feet conferred some advantage, and just a short hop from there to the conclusion that big feet were an end in themselves, rather than just one among a multitude of possible means to the same end -- and that end might be the last thing the biologist was actually considering.

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I think you are looking at the problem the wrong way, e.g. if flight is good (what animal would not like to fly) what is preventing all animals from proceeding on an evolutionary path towards flight? Could not the question be rephrased so that, all non flying animals are ‘failures’?

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Posted 19 June 2005 - 04:57 PM

I think you are looking at the problem the wrong way

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I hate when that happens.

e.g. if flight is good (what animal would not like to fly) what is preventing all animals from proceeding on an evolutionary path towards flight? Could not the question be rephrased so that, all non flying animals are ‘failures’?

Yes, the taking on board of certain assumptions easily leads to error here: for a small, island-dwelling insect, flying might not consist of much more than simply being blown out to sea, and would almost certainly represent the end of an evolutionary path; not flying would be the emergent feature more likely to be selected for. During a hurricane, this factor could affect even larger ground-dwellers; would we say that this was natural selection operating on them as well?

But I thought I was speaking against the validity of such an approach, or at least of doing so without being very sensitive to the risk of error.

#19 chance

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Posted 19 June 2005 - 07:24 PM

I hate when that happens.

Yes, the taking on board of certain assumptions easily leads to error here: for a small, island-dwelling insect, flying might not consist of much more than simply being blown out to sea, and would almost certainly represent the end of an evolutionary path; not flying would be the emergent feature more likely to be selected for. During a hurricane, this factor could affect even larger ground-dwellers; would we say that this was natural selection operating on them as well?

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As a holistic factor I would say yes, i.e. a successful animal can find itself at the short end of bad circumstances, overspecialisation often leads to extinction, and the less glamorous animal is often the ‘long term winner’. Thus evolution is working on specifics and holistics at the same time. Given those handicaps it a wonder anything can evolve :)


But I thought I was speaking against the validity of such an approach, or at least of doing so without being very sensitive to the risk of error.

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Perhaps I have missed the thrust of your point then.

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Posted 19 June 2005 - 11:14 PM

Thus evolution is working on specifics and holistics at the same time.  Given those handicaps it a wonder anything can evolve.

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Yes. And, given awareness of those handicaps, it is a wonder that biologists can appear so confident about their ability to distinguish between the hypothetical and the intuitive in their observations regarding the action of selection upon this or that trait. The only recourse seems to be to resort to extrapolating backwards from observed forms, on the basis of the assumption if it exists, it must have been selected for (not to mention the assumption that if we observe it, it exists). This really does seem to involve an 'appeal to imagination' not entirely in keeping with the highest standards of scientific rigor.

The conclusion (though somewhat tentative) seems forced: this is a weakness in evolutionary theory -- or at least in the way evolutionary theorizing, as a human activity, is conducted.

Perhaps I have missed the thrust of your point then.

I started out not entirely sure if even I grasped my point, and (as I stated in the OP) started the thread hoping to get a little more clarity. When it comes to identifying the holes in my own knowledge, there's nothing quite like trying to explain things to someone else. I don't particularly like what this hole is filling up with, and believe me, I appreciate any effort you can make to talk me out of it.




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