# Natural Selection



## Gel (Oct 3, 2013)

Hi all,

Not too sure if this is the right forum but it seemed to be the best place for it.

I have a very basic understanding of evolution so my question below may be due to a lack of understanding.

I understand that organisms really do not consciously adapt or evolve to their environment, rather a mutation causing a beneficial trait increases the survivability of the organism so that it is able to reproduce and pass on that mutation while those that didn't have this mutation die off.

I guess I'll use an example to get my questions across. It is an example I used a while back in an older thread.

At some point I'd imagine spiders or a distant relative of spiders mutated with the ability to spin silk. Did these spiders with this mutation instinctively know that by spinning this silk and lining the walls of their burrow with it would serve in reinforcing the burrow walls?

Or did they just arbitrarily start spinning the web for no reason and it just ended up being something beneficial which allowed them to survive and pass on their genes.

Is there some sort of intelligence that drives organisms to realize that using this mutation is beneficial and to continue doing it?

Would it be like us all of a sudden waking up with a tool and an instruction manual implanted in our brain on how to use this tool?

Or would it be like us waking up with the tool and having to figure out how it can be of benefit to us, which is driven by intelligence?

Hope my questions somewhat makes sense.

Thanks,


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## The Snark (Oct 3, 2013)

Please understand I'm not being flippant or curt here. Your questions are certainly viable and significant. It appears that you need an expanded background on evolution and environment interaction. To this end I would quote a professor on day 1 of his biology class:
"Mr. Darwin spent about 5 years on his voyage, delving into the natural history of this planet. I expect this class to spend about 5 months getting a rudimentary grasp of what he wrote."
Your question about spider silk is something of intrigue but you aren't taking into account the vast scope of both environments and the time line. The (most likely) tens of thousands of evolutionary dead ends and failed 'experiments'. 
And the inevitable. Get your hands on Darwin's 'On the origin of the Species' and start digging. What he wrote about for the most part is exactly what you are asking. His bibliography: https://en.wikipedia.org/wiki/Charles_Darwin_bibliography

Interestingly, what you wrote, "Would it be like us all of a sudden waking up with a tool and an instruction manual implanted in our brain on how to use this tool?" is precisely what ends up happening. An evolutionary experiment worked and was passed on to the progeny. The genes rewritten with each following generation and the successful progeny spreading, modifying and adding to this information with both the 'operators manual' and the tools themselves.

The pre frontal lobe crowd came in pretty late in the opera, just before the fat lady sings, according to some.

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## Gel (Oct 4, 2013)

Thank you for your post The Snark.

I guess the part I'm having problem with is understanding if the first organism or line of organisms with the ability to spin web intelligently knew that laying down web was reinforcing their burrows. As a result more of them survived and passed on their genes with the written "manual" that their offspring could make use of. In other words was their a first organism or group of organisms who (and I'm using Anthropomorphism to get my question across) said, "Hey! This web is really useful to reinforce my burrow with. I'm gonna make a note of this!).

As you mentioned, "An evolutionary experiment worked and was passed on to the progeny." So as I understand it, theoretically, the first few organisms who were able to spin web and line their burrows were doing so without realizing the benefits. They then passed it on to their offspring along with the instruction manual they didn't even realize they were writing. Once this experiment was perfected, did their offspring intelligently know that what they were doing was useful? Or was the "instruction manual" and it's use by the offspring just instinct?

I will check out Darwin's book. 

Thank you,


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## bugmankeith (Oct 4, 2013)

Chimps never knew to use rocks to crack nuts, it was by accident one saw it break and learned to do it themselves, but that is learnt evolution. I wonder if baby spiders using silk for wind to carry them was a learnt trait?

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## RakuenVI (Oct 4, 2013)

Further reading!

> The of behaviour in the evolution of spiders, silk and webs (article in .PDF)

> Craig C. L., 1997. "Evolution of arthropod silk." Annual Review of Entomology. 42: 231-67.

> Same author as above,  "Spiderwebs and silk: Tracing Evolution From Molecules to Genes to Phenotypes;" ( click here for the book on google books).

> Brunetta L., Craig C. L., 2010. "Spider Silk: Evolution and 400 Million Years of Spinning, Waiting, Snagging and Mating." CSIRO Publishing. (click for .pdf)

Though this is vaguely like wings in insects. Insects went from wingless to winged in the fossil record without many records of what happened in between - same for silk and spiders. The oldest spiders we know of already had silk, but the glands were undifferentiated and they had little control over where their silk went (i.e. they only used it to line their burrows/etc, no webs yet). So, we can only guess at the origins really.

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## Bill Myers (Oct 4, 2013)

Gel said:


> Would it be like us all of a sudden waking up with a tool and an instruction manual implanted in our brain on how to use this tool?
> 
> Or would it be like us waking up with the tool and having to figure out how it can be of benefit to us, which is driven by intelligence?


A little of both.  

Consider the Argiope aurantia:  They have a web which is distinguishable from other species of Orbweavers due to its zippered, zig-zag pattern vertically going through the center of the web.  See image here:

http://bugguide.net/images/raw/GZ0L...ZQL4ZGHEZHL1HPHYH6HWZGLBZ0LVHMH1H8H1H5HBH.jpg

Obviously, that zig-zag pattern is genetically encoded somewhere along the way in their fused ganglia, or something.  So, I guess you could consider that genetic encoding an "instruction manual implant."  

However, the younger, juvenile Argiope aurantia spiders seem to have a learning curve when trying to make that elegant, vertical zig-zag pattern.  In fact, they seem to overdo it to the extreme!  See image here:

http://bugguide.net/images/cache/EL...HSZOLKZHH8RLHQZALFLBLIZ0HGRRHPRSHXZRHMZ1L.jpg

So, it's obvious (to me, at least) that they also need to learn how to actually use their webbing tool.

Ergo, my statement, "a little of both."

Cheers

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## Stan Schultz (Oct 6, 2013)

Gel said:


> ... I have a very basic understanding of evolution so my question below may be due to a lack of understanding. ...


You can, if you've a strong enough interest, download and read a free copy of the first edition of Charles Darwin's *Origin of Species...*http://darwin-online.org.uk/content/frameset?itemID=F373&viewtype=text&pageseq=1http://darwin-online.org.uk/content/frameset?itemID=F373&viewtype=text&pageseq=1, the book that started the whole shebang.

Go ahead! Try it. It certainly isn't going to hurt you, and if you have the patience and stamina to wade through his gargantuan, run-on sentences you'll be head and shoulders above 99% of the rest of the people on this forum.



Gel said:


> ... I understand that organisms really do not consciously adapt or evolve to their environment, rather a mutation causing a beneficial trait increases the survivability of the organism so that it is able to reproduce and pass on that mutation while those that didn't have this mutation die off. ...


The reverse is much more common. Most mutations are either inconsequential or deleterious. (Think about randomly changing or removing one small part from an otherwise smoothly working automobile engine. What are the chances that it'll do any good? What are the chances that it'll stop the engine dead?) The rule is that organisms inheriting deleterious mutations may or may not be at a disadvantage in the struggle for survival and reproduction, and the mutation may or may not survive very long. It's much more complicated than that.

This is where the concepts behind genetics come into play. Before proceeding, I must remind you that most animals possess pairs of chromosomes (the fundamental carriers of DNA) and therefore pairs of genes. One member of each pair is inherited from the female parent, the other from the male. (Note that this is the usual, textbook situation. There are lots of variations and outright violations of these rules. Biology can be maddeningly variable and complex.)

Most mutations are "recessive" (e.g., the damaged gene merely no longer works) which means that they are masked behind the original, non-mutated, "dominant," functional gene, and therefore the mutated gene most frequently never displays itself. Thus, they are inherited generation after generation without being selected against ... except in the relatively rare instance where inbreeding at some level manages to recombine a copy of the mutated, recessive gene from both parents. In that unique set of circumstances the offspring ends up with two copies of the mutated gene, and no non-mutated version to hide them. And, the afflicted offspring displays whatever characteristic the mutated gene causes (assuming the offspring even survives at all), and thereby the mutation may be "selected against" (i.e., "weeded out") *IN THAT INDIVIDUAL ONLY*. But, while the offspring that got the double dose of the mutated gene may fall by the wayside, all its siblings that inherited a mixed set (i.e., one mutated and one normal gene) will continue to breed and pass the mutation on to their offspring with no natural selection.

[Note that this is the big reason that the 1950s era science fiction, "creature feature" movies starring "things" mutated by atomic radiation (*Godzilla*http://en.wikipedia.org/wiki/Godzillahttp://en.wikipedia.org/wiki/Godzilla being among the worst!) are so silly and completely unbelievably. It is highly improbably that even one mutated gene would occur in the gametes (sex cells, either ova or sperm). It is even less probable that the mutated gene would not be recessive and therefore display itself immediately. And it is much, *MUCH* more improbable that a whole galaxy of such mutations occur at the same time to produce a new kind of organism in only one generation. There's a whole lot of inbreeding and natural selection, not to mention dozens, hundreds or thousands of generations required to produce something like Godzilla, or any other of the hypothetical monsters in those movies. Trust me. The producers, writers and directors of such movies failed biology!]

There is another facet of genetics that is poorly understood even by geneticists, much less by laymen. Not all changes in an evolving species are the direct result of mutations. The ways that genes express themselves are modulated and controlled by a host of other processes, organic compounds (mostly proteins, geneticists think) and even environmental factors. And these modulations apparently often express themselves as smooth, analogue-like gradations rather than the "digital" increments that we expect from genes. And with this topic I am way out beyond my level of expertise in genetics! If you need to know more, talk to a geneticist at a university. Or better yet, go back to school!

I'm sorry I cannot give you a primer course in genetics here. Genetics 101 is a 16 week, college level course that requires Basic Statistics 101 and either Zoology 101, Botany 101, or both. Sorry.

[In an interesting side note, the man who is credited with laying the foundation for modern genetics, *Gregor Mendel*http://en.wikipedia.org/wiki/Gregor_mendelhttp://en.wikipedia.org/wiki/Gregor_mendel, and *Charles Darwin*http://en.wikipedia.org/wiki/Charles_Darwinhttp://en.wikipedia.org/wiki/Charles_Darwin were contemporaries. The irony is that Mendel published his *seminal work on heredity*http://www.esp.org/foundations/genetics/classical/gm-65.pdfhttp://www.esp.org/foundations/genetics/classical/gm-65.pdf in 1866, only seven years after Darwin's first edition of the _Origin of Species..._ was published, and before the publication of the last two editions (the 5th in 1869 and the *6th in 1872*http://www.digital.library.upenn.edu/webbin/gutbook/lookup?num=2009http://www.digital.library.upenn.edu/webbin/gutbook/lookup?num=2009). And, Darwin apparently had a copy of Mendel's paper in his library but never read it. (This is entirely understandable since literally *EVERYBODY* who published a natural history paper in the 1860s or 1870s sent a copy to Darwin in the hopes that he would read it and mention it in a lecture, paper or book. Darwin had far, *FAR* too many fish to fry!) One can hardly imagine what the outcome would have been had he read Mendel's work and integrated it into those last two editions of _Origin of Species..._.]



Gel said:


> ... At some point I'd imagine spiders or a distant relative of spiders mutated with the ability to spin silk. Did these spiders with this mutation instinctively know that by spinning this silk and lining the walls of their burrow with it would serve in reinforcing the burrow walls? ...


What you're talking about here is the evolution of both an inheritable, physical characteristic *AND* an inheritable, behavioral pattern (putatively, "instinct"). It is generally assumed among biologists that they evolve together, each being affected by the other as the generations progress. The organisms that integrate the two forces best, survive better than their cohorts. And, their offspring not only inherit both the better versions of the "hardware," but also the better versions of the "software." These qualities are then fine tuned even more and more, either through genetics or the "analogue-like" processes I alluded to above with each succeeding generation. Again, this is a poorly understood, gray area that's often hotly debated at genetics and evolution symposia and conferences. While we know how albinism and skin color, for instance, are inherited in humans, we have no clue as to how complex behavioral patterns (e.g., courting and mating, the "fight or flight" reaction, migrations) can be inherited in other animals. *"Here be dragons."*http://en.wikipedia.org/wiki/Here_be_dragonshttp://en.wikipedia.org/wiki/Here_be_dragons



Gel said:


> ... Or did they just arbitrarily start spinning the web for no reason and it just ended up being something beneficial which allowed them to survive and pass on their genes.  ...


If you want a fairy tale, I can give you a fairy tale as long as you don't repeat it as the king's truth. One of the major functions of living tissues in multicellular organisms is the secretion of chemical compounds and mixtures of such compounds. These include such things as mucous from certain kinds of tissues, e.g., the epithelial linings of our digestive tracts from our mouths all the way to our anus, body sweat, fluids (perhaps lubricating or digestive) from arachnids' coxal glands, silk, and venom to name a few. If these secretory cells are lumped together into a definable body (as opposed to being spread more or less uniformly over a surface or throughout an organism), we call them "glands." (Otherwise they may be termed "glandular tissue," or "glandular cells.")

It appears from at least a superficial overview, that arthropods in general, arachnids in particular, and spiders specifically are capable of evolving secretory glands just about anywhere on or in their bodies, and that these can produce just about any useful substance or mixture. There are rules about this however. For instance, once a particular gland is evolved in a particular place to produce a particular concoction, its size, shape, position and function apparently change only with great difficulty and as the result of great evolutionary pressure.

But, the genetic information for producing a gland and it producing some substance is common to every cell in the animal's body that has a nucleus. So, in theory at least, any cell in the spider's body has the potential to become a glandular cell, and possesses the potential for producing just about any material defined by any snippet of the spider's genetic code. (This, by the way, is also true of almost all other multicellular organisms including humans.)

So we can spin the story that the far distant precursors of spiders, 600,000,000 years ago or so, may have had some sort of secretory glands appear on some of their appendages as a developmental defect or mutation that allowed it to hold onto the underlying surface better than our primal creature's cohorts. (This would be especially true in a terrestrial - as opposed to an aquatic or marine - environment.) This may have allowed them to run faster in more precarious places to elude predators or chase down prey more efficiently. Over several thousands or millions of generations the quality and quantity of the sticky substance changed, as did its delivery method and even the nature of the appendages that possessed the glands. Those primal creatures that evolved silk spinning appendages on their rear ends eventually became known as spiders by a much later, much younger, less evolved, less sophisticated species. Some of those primal creatures evolved along a different path and developed the silk glands on their pedipalps instead, and much later became known as pseudoscorpions.

So, no. It wasn't arbitrary although a lot of variation and pure, dumb luck played a large part in its evolution. And it entailed a horrendous mortality rate among those that weren't both very, very good at what they did, and very, very lucky.



Gel said:


> ... Is there some sort of intelligence that drives organisms to realize that using this mutation is beneficial and to continue doing it? ...


If you're referring to the organism's intelligence, I've already gotten into some "intense" debates with others on the nature of intelligence and whether or not something like a spider can possess it or even possess the ability to learn. The results of such discussions were unilaterally unproductive because we all walked away with little additional learning, and our personal opinions held fast. Short answer: <shrug> <dumb look>

If you're talking about some divine Überintelligence, this is where I check out. Your question smacks strongly of that uniquely human, absolutely irrational and insane endeavor, religion. And, this is the wrong forum for such a discussion.



Gel said:


> ... Would it be like us all of a sudden waking up with a tool and an instruction manual implanted in our brain on how to use this tool? ...


Yes. And such is called (supposedly) instinct, an inheritable behavioral pattern developed simultaneously, in parallel with the physical hardware.



Gel said:


> ... Or would it be like us waking up with the tool and having to figure out how it can be of benefit to us, which is driven by intelligence? ...


If this were the case, the *99% rule*http://people.ucalgary.ca/~schultz/NaturalAndOrganic.html#mortalityhttp://people.ucalgary.ca/~schultz/NaturalAndOrganic.html#mortality would have instead been called the 100% rule! (And there's a subtle, irrational, irony there. Can you spot it?)


Where are you in Canada?

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## ShredderEmp (Oct 6, 2013)

I like how the super long answer ends with "Where are you in Canada?"

I read "The Origin of Species" a while ago, but it was too advanced for my 10 year old brain to comprehend. I want to read it again, but I never have time during the school year and always forget during the summer, but I still have it. I don't remember very much, but I did find it very interesting, even though I couldn't understand most of the words due to my age. So instead of making me a head and shoulders above 99% if the people on here, I would be above more like 50%? Haha.

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## The Snark (Oct 7, 2013)

Pikaia, you have the makings of a very nice dissertation there. The synopsis is very well thought out and covers the subject admirably.
One way of summing up the opposing aspects as the OP mentioned is the perpetual argument between a friend of mines' parents; one a double doc of microbiology and chemistry, the other a double doc of psychology and sociology. The eternal debate is of course all mental aberrations are a product of the environment and genetics vs all mental abnormalities will eventually link back to and be explained by chemical reactions and interactions. Read, irresistible force vs immovable object.

Good luck with Origin. A permanent memory unfortunately embedded forever in my ganglia is a certain professor holding up said book with a nasty grin and intoning, "Let's try again."

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## Stan Schultz (Oct 7, 2013)

ShredderEmp said:


> I like how the super long answer ends with "Where are you in Canada?" ...


Well, I had to break the catatonia somehow, eh?



ShredderEmp said:


> ... I read "The Origin of Species" a while ago, but it was too advanced for my 10 year old brain to comprehend. I want to read it again, but I never have time during the school year and always forget during the summer, but I still have it. I don't remember very much, but I did find it very interesting, even though I couldn't understand most of the words due to my age. So instead of making me a head and shoulders above 99% if the people on here, ...


And, you just reminded me that I need to review the first edition, then read the sixth. I know there were changes, but I never knew what they were. Light, Saturday afternoon reading, no?



ShredderEmp said:


> ...  I would be above more like 50%? Haha. ...


Still not too shabby, not too shabby at all for a 10 year old!

If any of the rest of you need a subject for a book report or just a very interesting natural history read, check out Darwin's *The Voyage of the Beagle*. You can download free copies of it *here* and *here*. *I REALLY ENJOYED THIS BOOK.* You will too!

---------- Post added 10-07-2013 at 02:11 PM ----------




The Snark said:


> ... A permanent memory unfortunately embedded forever in my ganglia is a certain professor holding up said book with a nasty grin and intoning, "Let's try again."


You had him too? Wow!

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## ShredderEmp (Oct 7, 2013)

Pikaia said:


> Still not too shabby, not too shabby at all for a 10 year old!


Yay me!

BTW: Not sure if you meant as a ten year old, but I'm 15 now. I'm hoping I still qualify as not too shabby.

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## Kazaam (Oct 7, 2013)

ShredderEmp said:


> Not sure if you meant as a ten year old, but I'm 15 now


When you're his age that makes no difference.

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## Gel (Oct 7, 2013)

I came back to check on my thread and was so pleased with all the great responses. Thank you to everybody and keep the conversation going!

I will have to cerebrally digest all of this and if I have any questions I will do my best to post them.





Pikaia said:


> If you're talking about some divine Überintelligence, this is where I check out. Your question smacks strongly of that uniquely human, absolutely irrational and insane endeavor, religion. And, this is the wrong forum for such a discussion.


I apologize if my question seemed to have hinted at a metaphysical, divine intelligence; it couldn't have been further from what I intended. I was referring to the capability of an organism like a spider to "learn".

I was born into a conservative religious faith; I believed in creationism and microevolution at most. 

I am now what could best be defined as agnostic and am highly interested in and believe in the subject of evolution.

My education on this topic is at an introductory, high-school, biology class level.

As I learn more about natural selection, my brain is infused with many exciting questions.

I greatly appreciate everybody's responses.



P.S. I'm from Ontario 

P.P.S. I have a copy of the Tarantula Keeper's Guide. Thank you for writing such a great resource!


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## Stan Schultz (Oct 8, 2013)

ShredderEmp said:


> Yay me!
> 
> BTW: Not sure if you meant as a ten year old, but I'm 15 now. I'm hoping I still qualify as not too shabby.


Fifteen ain't too shabby either! Age thirty wouldn't be too shabby!

Where in Illinois?

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Gel said:


> ... I apologize if my question seemed to have hinted at a metaphysical, divine intelligence; it couldn't have been further from what I intended. I was referring to the capability of an organism like a spider to "learn". ...


No apology necessary! I just get flamed ("torched" or "incinerated" might be better terms!) every time I get involved in a religious discussion. My comment was just a warning that I wasn't going to participate. Too many scars!



Gel said:


> ... As I learn more about natural selection, my brain is infused with many exciting questions. ...


Natural selection is only a small part of evolution. You really should read *Origin of Species*.



Gel said:


> ... P.S. I'm from Ontario  ...


I grew up in Michigan, just next door. Ended up in Calgary by way of Tampa, Florida, and much later Galveston, Texas.



Gel said:


> ... P.P.S. I have a copy of the Tarantula Keeper's Guide. Thank you for writing such a great resource!


Bless you my child! Do you know about the *Addenda and Errata sheet*? Good reading for a cold, dark, Canadian, Winter's eve!

:biggrin:

And thanks for the good words!


Sheesh! I get no respect!

Why is it that every time I make a firm statement about tarantulas, one of the little beggars proves me wrong?


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## ShredderEmp (Oct 8, 2013)

Pikaia said:


> Fifteen ain't too shabby either! Age thirty wouldn't be too shabby!
> 
> Where in Illinois?


I'm from the western suburbs of Chicago. If you want even more a precise location, email me, I don't want to tell all the people where I live. My email is rmmchugh97@gmail.com.


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## Gel (Oct 8, 2013)

Pikaia said:


> Natural selection is only a small part of evolution. You really should read *Origin of Species*.
> 
> 
> 
> ...


I stayed in Michigan and have passed through numerous times. Flights from Detroit can be considerably cheaper so many make the drive down and fly out. I like Michigan. It reminds me of home but just across the border. I've never been to Western Canada but would love to some day. Florida has a special place in my heart; it was our vacation spot when I was a kid and we always drove through Detroit on our way there. Texas is another place on my wish list to visit as well. The people from Texas I've met have been very friendly, I hear they have great BBQ, and Aphonopelmas too!

I will definitely check it out Origin of Species.

I will also check out the Addenda and Errata sheet.

I've heard it will be a harsher winter than last so it should keep me busy. 

Thank you!


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## JadeWilliamson (Oct 9, 2013)

I love reading Stan's writing.  I really need TKG!



Pikaia said:


> If you're referring to the organism's intelligence, I've already gotten into some "intense" debates with others on the nature of intelligence and whether or not something like a spider can possess it or even possess the ability to learn. The results of such discussions were unilaterally unproductive because we all walked away with little additional learning, and our personal opinions held fast. Short answer: <shrug> <dumb look>
> 
> If you're talking about some divine Überintelligence, this is where I check out. Your question smacks strongly of that uniquely human, absolutely irrational and insane endeavor, religion. And, this is the wrong forum for such a discussion.


Favorite part.


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## PlaidJaguar (Oct 9, 2013)

On the topic of intelligence, I've been told by many experienced keepers that arboreal Ts will stop building webs on the lid of their enclosures after it's been opened and destroyed a few times.  That sounds distinctly like learning to me.

I find it difficult to imagine the arachnid group could have been so massively successful for so many millions of years without at least some capacity for adaptive learning.

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## Stan Schultz (Oct 9, 2013)

PlaidJaguar said:


> On the topic of intelligence, I've been told by many experienced keepers that arboreal Ts will stop building webs on the lid of their enclosures after it's been opened and destroyed a few times.  That sounds distinctly like learning to me.
> 
> I find it difficult to imagine the arachnid group could have been so massively successful for so many millions of years without at least some capacity for adaptive learning.


*ONE AND ALL -*

See? Another convert. I'm thinking of starting my own original religion. Things with 8 legs. I'll be the Pope.

:roflmao:

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## The Snark (Oct 9, 2013)

Introduce a jumper to your hand. It will shy. When it finally jumps on you it learns and loses the fear, taking your anatomy as just another stalking ground. Let it cruise several people without frightening it from that moment on it won't have any fear of humans until a different learning situation is encountered.

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## Thistles (Oct 10, 2013)

Pikaia said:


> *ONE AND ALL -*
> 
> See? Another convert. I'm thinking of starting my own original religion. Things with 8 legs. I'll be the Pope.
> 
> :roflmao:


It won't be a proper religion unless you incorporate some way to profit from it. I say you require an income-based tithe and an annual donation of 5 tarantulas.

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## Stan Schultz (Oct 11, 2013)

Thistles said:


> It won't be a proper religion unless you incorporate some way to profit from it. I say you require an income-based tithe and an annual donation of 5 tarantulas.


EVERYBODY TAKE NOTE -----

*I DIDN'T SAY THAT!*


:biggrin:


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## jecraque (Oct 14, 2013)

Late to the party but wanted to add a thing or two...

On _the Origin_--if you read the free version, the first edition is best to start. A number of changes were made in later editions that can serve to make it even more confusing. To those with unpleasant memories of muddling through it in school or on their own, a really thorough annotated version* (_The Annotated Origin_) came out a few years ago and it is well worth picking up if you've got the spare change. 

If you're into learning about evolution and not sure where to start, an excellent resource is Berkeley's Evolution 101 site. You sound like you're on the right track so far, and the previous comments are helping!


Lastly, and more along the lines of the original questions, spider silk is probably something that happened waaaay back in the lineage (think 400mya or earlier), before there was anything recognizable as an araneomorph spider. I'm no expert, and I'll try to keep the technical stuff to a minimum, but my understanding of the current literature is that silk was initially associated with appendages (like Stan pointed out), and that spinnerets are evolved from appendages (think forked legs like in horseshoe crabs). Not just that, but the segmented plates on the undersides of early arachnids are not evolutionarily the same as the abdominal plates you see on roaches and other insects, but fused appendages as well. Weird, right? 

So here's where it gets interesting--in the earliest spiders, silk isn't associated with spinnerets (that we know of) but comes straight out of spigots on those belly plates. Google _Attercopus_ or check out the links posted by RakuenVI for more. If you know anything about _hox_ genes, it's easy to make the leap in thinking about the position of silk production moving from one part of the body to another, or in this case, from covering a large area to a smaller, more focused/flexible location. Flexibility and the increased accuracy that comes with it would definitely have been a major selection pressure in more modern spiders with spinnerets on the end of the abdomen.

Unfortunately, _Attercopus_ already had silk--in one fossil fragment there's even a strand coming out of a spigot--so the origin of silk, like others have said, is still under debate. I've heard of a couple of ideas in the literature, but basically, all agree it would have happened on dry land, so we have a general idea of the timing (which is where the 400mya estimate comes in). One idea is that pre-silk was a covering for the gills (before book lungs) that allowed for movement on land with no drying out of your essential oxygen-getting equipment; another is that pre-silk was a protective covering for eggs. I've also heard the burrow-lining thing, but I'm pretty sure this is thought to be a secondary use.

As for learning and behavior... we may never know, beyond what we can glean from living spider species. Interesting questions though!

*Full disclosure: the annotator is a lovely fellow who I'd consider a mentor (but the book is really good, you guys).

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## Kaimetsu (Oct 16, 2013)

On the origin of species is one of the most important books in the history of science and a must have for any collection, but I don't recommend using it to learn about evolution.  For one thing the victorian era wordy writing is difficult to get through, and we know infinitely more about evolution today then what Darwin knew, he didn't even know how heredity worked or anything.
If your really interested in how amazing evolution, natural selection, genetics, and the history of life on earth is their are tons of amazing modern books on the topic.  One introduction to evolution that I enjoyed was Evolution: the triumph of an idea by Carl Zimmer.  For a much more involved book that details how natural selection truly works by altering how an embryo develops and how similar all living animals are to each other I recommend Endless Forms Most Beautiful by Sean Carroll.
Also if your interested in really heavy informative reads you can't go wrong with Richard Dawkins, you don't have to agree with his views on religion to enjoy his books on evolution, although hes definitely right about religion!  My favorite book of his is the Ancestors Tail, which tells the story of the history of life starting with humans and tracking the family tree back in time to the last common ancestor of all life.  The Selfish Gene is great for explaining how the unit that natural selection acts on is really individual gene's in DNA rather than just a species, population, or individual, and the Blind Watchmaker does a good job of explaining how natural selection can create complex ordered structures like living things through accumulated small changes over time.

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## Stan Schultz (Oct 16, 2013)

jecraque said:


> ... but the segmented plates on the undersides of early arachnids are not evolutionarily the same as the abdominal plates you see on roaches and other insects, but fused appendages as well. Weird, right? ...


References please?



jecraque said:


> ... all agree it would have happened on dry land, ...


I wonder from where "they" made this leap of faith? Given that so many arthropods (e.g., *caddisflies*) make silk underwater (even several spiders, see *Diving Bell Spiders* and possibly some species of the family *Pisauridae*), I find it equally likely that silk production preceded land/air living. I can spin (Sorry. Bad pun) as likely a story that silk was evolved by aquatic arthropods as holdfasts and safety lines in water currents, and later became adopted to a terrestrial/air existence as the arthropods eventually adapted to that new environment.

Just stirring the pot a little...


"The magnitude of our ignorance [about tarantulas] is staggering."
- S. A. Schultz, *TKG3*

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## jecraque (Oct 16, 2013)

Pikaia said:


> References please?


Dunlop, J.A. 1998. The origins of tetrapulmonate book lungs and their significance for chelicerate phylogeny. In _Proceedings of the 17th European Colloquium of Arachnology_, P.A. Selden, ed. (Edinburgh, Scotland), pp. 9–16. PDF here
Selden, P.A., W.A. Shear & M.D. Sutton 2008. Fossil evidence for the origin of spider spinnerets, and a proposed arachnid order. _Proceedings of the National Academy of Sciences_ 105 (52): 20781–20785. PDF here

You know, having studied caddisflies pretty extensively I also wondered the same thing--why not an underwater ancestor for the first silk-producer? I'm afraid I don't know enough about the physiology of silk production to speculate, but it does seem strange that it's often taken for granted that silk was a post-land adaptation. Good point and not one I can readily account for.


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## Stan Schultz (Oct 17, 2013)

jecraque said:


> Dunlop, J.A. 1998. The origins of tetrapulmonate book lungs and their significance for chelicerate phylogeny. In _Proceedings of the 17th European Colloquium of Arachnology_, P.A. Selden, ed. (Edinburgh, Scotland), pp. 9–16. PDF here
> Selden, P.A., W.A. Shear & M.D. Sutton 2008. Fossil evidence for the origin of spider spinnerets, and a proposed arachnid order. _Proceedings of the National Academy of Sciences_ 105 (52): 20781–20785. PDF here ...


Thanks. Now I have 14 unread pdfs on my desktop!

:laugh:



jecraque said:


> ... You know, having studied caddisflies pretty extensively I also wondered the same thing--why not an underwater ancestor for the first silk-producer? I'm afraid I don't know enough about the physiology of silk production to speculate, but it does seem strange that it's often taken for granted that silk was a post-land adaptation. Good point and not one I can readily account for.


That's so obvious an hypothesis that I'd be shocked if no one had ever thought of it before. The major problem seems to be  that no one has ever been able to demonstrate silk or silk spigots in fossils of aquatic arthropods. This is not too surprising given the fragility of silk, and its difficulty of recognition. Similarly, I wouldn't be too terribly surprised to hear of someone who went looking for evidence of it who would actually find it, perhaps as one of those enigmatic, unidentifiable fossils that litter every museum's shelves (or maybe thrown in the trash heap!), or misidentified as worm castings, leaf vein networks, crystalline formations, or something equally obscure.

Drat! Another line of research and another potential PhD thesis! Will it never end?

:roflmao:


“The difference between utility and utility plus beauty is the difference between telephone wires and the spider web.”
-- Edwin Way Teale


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## Gel (Oct 23, 2013)

Once again, thanks everybody for the great posts!

Keep the conversation going!


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## TomM (Oct 30, 2013)

You may want to read this book to get a better grasp of evolution:

http://www.amazon.com/The-Magic-Reality-Whats-Really/dp/1451675046

It is geared towards a younger audience, but is surprisingly helpful and does a great job of explaining things.

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## Gel (Nov 4, 2013)

TomM said:


> You may want to read this book to get a better grasp of evolution:
> 
> http://www.amazon.com/The-Magic-Reality-Whats-Really/dp/1451675046
> 
> It is geared towards a younger audience, but is surprisingly helpful and does a great job of explaining things.


Thank you. I will check it out


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## The Snark (Nov 5, 2013)

Pikaia said:


> Thanks. Now I have 14 unread pdfs on my desktop!
> 
> :laugh:
> 
> ...


Upon reflecting on this... Okay, first and foremost, the evidence of actual spider silk dates back to the early Cretaceous period with an actual fossil in amber identified. It has been theorized that spiders moved from the water to dry land during the early Devonian period. This was prior to the carboniferous period (no amber available to preserve webs) and there was no habitat suitable for a land based arachnid prior to that time. Therefore it can be assumed that aquatic arthropoda were the first to utilize webbing. This is as logical, or more so, than an eight legged critter crawling out of a swamp and going, 'Oh look! A tree! I think I'll squirt something out of my butt over it. So Pikaia's leap of faith is actually a very safe surmise. 

Re: Another line of research... Reminds me of a new advisor dragging me to his office to point out I appeared to be working on 5 different majors. I retorted that Albert got his start fiddling with refrigerators.


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## Micrathena (Dec 3, 2013)

Just to clarify, these zigzags that argiopes spin are called stabilimentae (stabilimentum singular) and they are to allow birds to see, and so avoid, the web. For more info, read Thomas Eisner's "For Love of Insects." I highly recommend that book.

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## jecraque (Dec 3, 2013)

Micrathena said:


> Just to clarify, these zigzags that argiopes spin are called stabilimentae (stabilimentum singular) and they are to allow birds to see, and so avoid, the web. For more info, read Thomas Eisner's "For Love of Insects." I highly recommend that book.


AFAIK the jury's still out on the bird thing. It doesn't make much sense to me and there are some competing hypotheses. My research-dad is pretty vehemently in Camp UV Patterning and anti-anti-bird-avoidance. I don't know enough about orb-webs to speculate much.

Funny you should mention the Eisner book. My partner is way into it right now (as in this week). I'll have to give it a read!


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## Stan Schultz (Dec 4, 2013)

jecraque said:


> AFAIK the jury's still out on the bird thing. It doesn't make much sense to me and there are some competing hypotheses. My research-dad is pretty vehemently in Camp UV Patterning and anti-anti-bird-avoidance. I don't know enough about orb-webs to speculate much. ...


What's wrong with the hypothesis that they just think it's cool to have that thing in the middle of the web? After all, *we do silly things like that*, why not them?

:biggrin:


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