In “The spandrels of San Marco and the Panglossian paradigm: a critique of the adaptationist programme.” (Proc. R. Soc. Lond. B. 205:581-98) Gould and Lewontin offer the “competing notion” (to the “adaptionist program”) that organisms should be analyzed as integrated wholes.
In support of their argument the authors describe the European approach, divided into “strong” and “weak” forms, which involves the concept of “Bauplan” (Bodyplan). Natural Selection is recognized in both cases but is generally considered inadequate to account for construction of the bauplan itself, or for the transitions between them.
Gould and Lewontin disassociate themselves, however, from speculation over any internal mechanism saying: “We believe that English Biologists have been right in rejecting this strong form as close to an appeal to mysticism”
Are there any objections to an internal mechanism beyond the three listed below?
“Populations evolve, individuals don’t” (I’m not sure why this phrase is invoked but I’ve encountered it a few times now).
Weismann’s experiment in which he chopped the tails off of succeeding generations of rats/mice (doesn’t stand up to close scrutiny)
The “Weismann Barrier” (appears to presume there would have to be a linear, or direct, relationship between, say, the liver cells and their associated genes in the germ cells).
My interest is not connected to any form of Lamarckianism and I would be appreciative of any serious replies.
I’m not familiar enough with the works you’ve cited to answer anything but this.
This phrase deals with a common misconception about what “evolution” means. The scientific definition is that evolution is a change in allele frequencies over time. This is why individuals can’t evolve–no matter what I do, my alleles are either present or not, so the frequencies can’t change. On the other hand, the percentage of individuals in a population with a given allele can change over time.
That’s what people mean when they say that populations evolve but individuals don’t.
I’m not so sure individuals don’t evolve.
What I’m thinking of in particular is the blind fish found in caves. A fish lays eggs upstream of the cave, the eggs follow the water into the cracks underground and lodge in the deeper parts of the cave. Now do they grow up normally, with big eyes? Or shriveled, dinky dead eyes? If the former, since eyes are no threat to reproduction, they would remain eyed creatures.
Well, given the scientific definition of evolution, it’s really impossible for individuals to evolve. But that aside, let’s look for a moment at a possible scenario for the development of eyeless fish. It’s particularly interesting to see that eyes can be considered a threat to reproduction.
So there’s this fish with eyes, like you said, that lays its eggs upstream and goes about its business. Its children grow up in the cave, and assuming they can find food, they grow up and have fish children of their own. These children survive to reproduce, and so on and so forth.
Now let’s suppose that one day, one of these fish children has a mutation that causes it to not grow eyes. This fish can find food as well as any other fish in the cave, but there’s a crucial difference between it and its sighted cousins: whatever energy the regular fish would’ve used to help its eyes grow is available for other purposes in the sightless fish. So this new sightless fish can reproduce more on the same amount of food. This gives its descendants quite an edge in having descendants of their own, and eventually the sightless fish wipe out the sighted ones.
Of course, I don’t know if this actually happened; it’s just a thought experiment. But the point is, none of the individuals evolved. Their genes were fixed at the moment the gametes that became them were formed.
Are you sure you don’t mean “semi-comprehensible”?
Which, along with crying “absurd!”, is how a number of Galileo’s comtemporaries reacted to the heliocentric theory?
(grin)
That’s pretty much my understanding too and the reason why I wrote “I’m not sure why this phrase is invoked”.
Populations are made up of non-evolving individuals and an internal mechanism, whereby evolutionary changes would appear in succeeding generations, contains no direct contradiction to “Populations evolve…(etc.)”. I’m just trying to see whether there’s anything I’m missing concerning this objection.
With regard to the definition of evolution, do you think the following would be a reasonable analogy?:
If the individual members of a population are equated to the individual pieces of glass in a kaliedoscope then the pattern seen looking into it is the “gene pool”.
As time passes and new pieces of glass/individuals appear then this will produce the “changes in allele frequencies over time” when viewed from the outside.
I’m trying to find a way to differentiate between patterns and the actual reality (ie individuals) that produces them.
I don’t understand the question/problem.
Maybe if you stated it in a different way?
In response to your kaleidoscope analogy, however–
I don’t think it’s a helpful comparison, because of course as time passes we have different individuals, but the only way a change in allele frequencies could be accurately represented is if, over time, there were a noticeable change in the respective amounts of the different colors of glass (the glass pieces representing individuals with specific genotypes or alleles).
I’m not sure what is meant by an “internal mechanism” which facilitates evolution in successive generations; the only “mechanism” that I know of that influences evolution is the combination of environment and mutations, and whether or not a specific mutation benefits or disadvantages the individual.
Well, regardless, either your question is over my head (in other words, I am too lazy to look up in much depth what I know is an erroneous argument), or I just don’t know what you’re looking for. Either way, I’m not much help.
You may not know the answer, but isn’t it exciting to be a part of a message board that has questions like this posted with the actual expectation of an answer?
Why not try actually accomplishing something before comparing yourself to Galileo? Keep in mind that for every theory that has been called absurd and was then proven right, there have been umpteen million that were called absurd and later proven to be simply absurd.
Yep, they laughed at Galileo, they laughed at Columbus. But they also laughed at Bozo the Clown. Just because they laugh at you doesn’t mean you should compare yourself to Galileo. I would venture to say that the overwhelming majority of divergent thinkers that mainstream scientists have laughed at really deserved to be laughed at.
I think the problem with the kaliedoscope analogy is that no allele in that “population” can ever reach fixation. The glass of that color is simply not visible, instead of actually being absent from the population.
It’s been a while since I’ve read the Spandrels of San Marcos paper, could someone refresh my memory on what is meant by an “internal mechanism”? I suppose I probably still have a copy somewhere, but I don’t really want to go looking for it.
Finally, I don’t understand your comment on the Weismann barrier. The whole point of the concern over germ cells is that in a multicellular organism, it is the germ cell genes that are passed on to the offspring. Passing on mutations in somatic cells is problematic because somatic cells don’t make eggs or sperm.
The original post was simply looking for objections to an internal mechanism beyond those listed. In terms of “Populations evolve, individuals don’t” it would basically be a question of whether germ cell mutations are all truly random or could an unknown percentage be due to an indirect (and non-Lamarckian) internal mechanism.
I accept the kaliedoscope analogy may not work, I’m only online for a few minutes and will explain why I’m looking for such an analogy when I reply to wewet’s post later in the day.
“Populations are made up of non-evolving individuals and an internal mechanism, whereby evolutionary changes would appear in succeeding generations, contains no direct contradiction to “Populations evolve…(etc.)”. I’m just trying to see whether there’s anything I’m missing concerning this objection.” -Jorolat
What do you mean by “…internal mechanism, whereby evolutionary changes would appear in succeeding generations…”? Isn’t the method by which net changes (in allele frequency) appear over time known as “natural selection”, and the net result of many (usually small) changes known as “evolution”?
Also, what exactly is your aim here? are you trying to suggest that there is a process seperate from natural selection working to order body plans?
I made no such comparison
Nor would I want to
Galileo is dead!
The reason for mentioning him was to hopefully give some people pause for thought, to perhaps open their minds a little.
Einstein, also dead, said “Imagination is more important than knowledge”
He also said “It is a miracle that curiosity survives formal education”
Another quote:
“It has been my experience that when curiosity has been crushed it is replaced by a capacity for more negative responses” - John Latter
Ridicule, contempt, that kinda thing…
All the original post asked for was what objections, other than those listed, were there to the possible existence of an internal mechanism. Gould and Lewontin said the suggestion was close to an appeal to mysticism.
A moments reflection will (hopefully) bring the realization that such a mechanism would be testable. Consequently the charge of mysticism merely reflects reaction to the “novelty” of the concept rather than a testable reality would ever have such an attribute.