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Why do chickens lay eggs?

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Why do chickens lay eggs?
J. Random Hacker
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Posted 05/13/09 - 07:27 PM:
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ying wrote:
Yeah, that's an ad hoc argument or an after the facts explanation.


Should it be before the facts?
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Posted 05/13/09 - 07:34 PM:
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J. Random Hacker wrote:


Should it be before the facts?


If we wish to establish A, then "A because B" is valid ("B" being a cause of "A"). But if we want to establish B, then "A because B" isn't ("A" being an effect of "B").

http://www.infidels.org/library/modern/mathew/logic.html#adhoc

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J. Random Hacker
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Posted 05/13/09 - 07:39 PM:
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ying wrote:


If we wish to establish A, then "A because B" is valid. But if we want to establish B, then "A because B" isn't.

http://www.infidels.org/library/mo...w/logic.html#adhoc[/quote]

http://en.wikipedia.org/wiki/Retrodiction
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Posted 05/13/09 - 07:48 PM:
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J. Random Hacker wrote:


http://en.wikipedia.org/wiki/Retrodiction[/quote]

Yeah, just re-read your post (#6). You weren't responding to Unenlighteneds first post. My bad. shocked

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Posted 05/13/09 - 09:43 PM:
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Maybe not so much an external application; but in part the origins might derive from whichever type of bacteria the complex life started from. The form of cell division combined with the type of existing materials may have determined the solidity of the external wall.

A more solid outer membrane may have given rise to a higher survivability during the early years of life.


Of course; that makes the general assumption that different single cell bacteria takes the same amount of time (figuratively) to evolve to a viable multi-cell platform.

Edited by Cadrache on 05/13/09 - 09:49 PM. Reason: missed a word

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Posted 05/13/09 - 11:24 PM:
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Is it 'after the fact'? It seems to be an explanation why laying eggs early has relative survival value: the bird can lay more eggs and get around more easily. So genes that determine later egg-laying would tend to be selected out, because the phenotypes would lay fewer eggs and be less mobile.
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Posted 05/13/09 - 11:58 PM:
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Cuthbert wrote:
Is it 'after the fact'? It seems to be an explanation why laying eggs early has relative survival value: the bird can lay more eggs and get around more easily. So genes that determine later egg-laying would tend to be selected out, because the phenotypes would lay fewer eggs and be less mobile.


It is, if the question is why chickens lay eggs. That's not what JRH was responding to though. He was responding to post #4 of Unenlightened, who stated:

Unenlightened wrote:
...we should come up with some speculative advantage to laying your eggs and sitting on them as opposed to keeping them within the body.


... Which I didn't bother to read the first round through...

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Posted 05/20/09 - 05:25 PM:
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ying wrote:
"What came first, the chicken or the egg?"
Both. Laying eggs is a characteristic of species and not of individual birds. sticking out tongue

Yeah, that's an ad hoc argument or an after the facts explanation.

Science, especially historical science, is loaded with these. I don't even think causation can be established with certainty. There are so many possible "environmental" factors all of which need to be ruled out to be sure.

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Posted 08/07/09 - 07:28 PM:
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There is a paper by Steven J. Gould about the spandrels of San Marco and the adaptationist paradigm. In short, the San Marco cathedral has a bunch of pretty spandrels where the arches meet, and they are decorated and look intentional. We might ask, why are those spandrels there? We could easily come up with the answer that they are a designed architectural element; the spandrels were put there because they are aesthetically pleasing. In fact, spandrels are just what happens when you stick two arches next to each other. Arches are necessary, spandrels are just the result of arches.

The adaptationist paradigm attempts to come up with an evolutionary reason for every trait. The fact is, much of evolution is dependent on historical contingency and constraint. Constraints may be trade-offs, or just historical legacy, phylogenetic constraint.

Birds lay eggs because it works. Birds lay eggs because their ancestors laid eggs and passed their egg laying genes on. If a bird lays slightly smaller eggs, or keeps them inside for slightly longer, or whatever, and that results in more genes being passed on disproportionately more than other genes, before long, that will become the norm. Birds have been enormously successful laying eggs. Every egg-laying bird carries genes with a lineage going back over 3 billion years. Those egg-laying genes could not have been more successful. Evolution is pass-fail. Egg laying passes.

We might also ask why don't humans have wings like birds, wouldn't being able to fly be better than not being able to fly? Again, we don't have the evolutionary history of wing development. We don't have the developmental pathways for growing wings. We don't have the skeletal and muscular structure necessary for wings. Birds don't have the placenta or the mammary glands we do. And if it ain't broke, don't fix it. We have a greater than 3 billion year ancestry also. That doesn't mean we are optimized in every respect. It means we have what it takes to survive and reproduce.

Incidentally, another example is the explanation that fingers evolved to type on keyboards, seeing as how they are so good at it. This is obviously not true, but the point is that we use what we evolved to accomplish our goals. Birds use eggs to reproduce because they are good for reproducing. We use fingers to type because they are good for typing. That doesn't mean they were adapted for it.
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Posted 08/10/09 - 10:05 AM:
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What else would a chicken lay?
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