Freethought & Rationalism Archive

tgamble · 02-08-2002, 04:19 PM

Quote:

Originally posted by rafe gutman:
tgamble, that response does not make any sense whatsoever. it is as though someone randomly pieced together a series of words and phrases.

Didn't make much sense to me either.

Quote:

i think it would be better to discuss the actual claims of the article, as opposed to the claims made by a summary of that article. here's the last paragraph of the original nature article:

Is the article available online in full?

Valentine Pontifex · 02-08-2002, 05:10 PM

More links:

<a href="http://www.answersingenesis.org/docs2002/0208Prelim_evolution_gene.asp" target="_blank">AiG's First Response</a>

(Is it evil to hope that they eventually repeat Well's remark referencing the original paper?)

<a href="http://www-acs.ucsd.edu/~idea/wellsshrimp.htm" target="_blank">IDEA Club Response</a>

<a href="http://abcnews.go.com/sections/scitech/DailyNews/darwingene020207.html" target="_blank">ABC News Article with AiG/ICR and Wells comments</a>

[ February 08, 2002: Message edited by: LordValentine ]

tgamble · 02-08-2002, 05:24 PM

Quote:

Originally posted by LordValentine:
[QB]More links:

<a href="http://www.answersingenesis.org/docs2002/0208Prelim_evolution_gene.asp" target="_blank">AiG's First Response</a>

huh? So it caused a "loss of information". Wouldn't it be more accurate to call it a change of information content thus causing a new body plan.

oh well, when has AIG ever been accurate?

Coragyps · 02-08-2002, 05:36 PM

From the IDEA Club article:

Quote:

Does this prove that they weren't designed, or that common ancestry must be responsible for the similarities? Not at all. From an intelligent design perspective, it is entirely possible that both insects and crustaceans have similar developmental pathways since they are both built upon the arthropod body plan. The fact that their genes are similar, and in some ways somewhat compatable could just as easily testify to common design as it could testify to similarities due to common ancestry.

And I presume that since humans aren't built upon the arthropod body plan, we must have a different designer than shrimps do?

BTW, tgamble - it appears that the article is available from nature.org, but at a charge of $15 US. Too rich for my non-crustacean blood.

[ February 08, 2002: Message edited by: Coragyps ]

lpetrich · 02-09-2002, 12:03 PM

I'm sorry if I seem underwhelmed by this discovery, but to me, this result is simply the confirmation of something that has been suspected for a long time.

Some background:

Arthropod limbs are a good example of "serial homology", a homology between body parts in different places, especially different-looking parts. Arthropod limbs often receive various specializations, such as the outer two segments becoming a claw or some limbs being turned into mouthparts or antennae, but their overall construction is the same.

Serial homology is further supported by the existence of "homeotic mutations", in which a body part develops like one in another place. Some famous ones first discovered in Drosophila fruit flies are antennapedia and proboscipedia, in which antennae and mouthparts develop like walking limbs.

The genes whose mutations cause such out-of-place development have been named the homeobox genes, or Hox genes for short. These genes are expressed in regions of an embryo in a front-to-back order that is always the same wherever these genes are found. And these genes have been found in many species; consider <a href="http://www.people.virginia.edu/~rjh9u/homeo.html" target="_blank">this comparison between fruit-fly and mouse Hox genes</a>. The mouse set of these genes is 4 copies of the fruit-fly set, but with dropouts here and there.

And what these UCSD researchers had found was there there is a crucial difference between species in one of the rearward homeobox genes -- a difference that suppresses rearward legs in insects but not in shrimp.

[ February 09, 2002: Message edited by: lpetrich ]

lpetrich · 02-09-2002, 11:12 PM

This work is a success in evolutionary developmental biology, evo-devo for short. Here are some more interesting curiosities:

Serial homology is very apparent if one studies the parts of flowers -- petals and sepals look much like the leaves of the plant that produces them.

Also, Geoffroy St. Hilaire had noted in the early 19th cy. that vertebrate internal organs are upside-down relative to arthropod and annelid ones; arthropods and annelids have arrangement:

ventral - main nerves - digestive - heart - dorsal

while vertebrates have arrangement:

ventral - heart - digestive - main nerves - dorsal

The St. Hilaire inversion was not taken very seriously for a long time; every few decades, someone would "rediscover" it, and other comparative anatomists would explain why they found these similarities less-than-convincing -- there are numerous differences as well as similarities.

That was until about 5 years ago, when it was discovered that the genes that control overall dorsoventral patterning in fruit flies match onto those that cause that patterning in frogs -- if one reverses the direction! So the St. Hilaire inversion has gone the way of continental drift -- gone from a marginal sort of theory to a mainstream one, as a result of some dramatic discoveries.

Here's a nice illustration:

Valentine Pontifex · 02-10-2002, 06:47 AM

Quote:

Originally posted by lpetrich:

...Also, Geoffroy St. Hilaire had noted in the early 19th cy. that vertebrate internal organs are upside-down relative to arthropod and annelid ones; arthropods and annelids have arrangement:

...

The St. Hilaire inversion was not taken very seriously for a long time; every few decades, someone would "rediscover" it, and other comparative anatomists would explain why they found these similarities less-than-convincing -- there are numerous differences as well as similarities.

That was until about 5 years ago, when it was discovered that the genes that control overall dorsoventral patterning in fruit flies match onto those that cause that patterning in frogs -- if one reverses the direction! So the St. Hilaire inversion has gone the way of continental drift -- gone from a marginal sort of theory to a mainstream one, as a result of some dramatic discoveries.

...

Yet another strange idea gets very little notice UNTIL someone obtains evidence for it. Of course this is how it should be.

============================

There is another example of this sort of thing:

<a href="http://www.amazon.com/exec/obidos/ASIN/0198503113/nationalcenter02" target="_blank">The Variety of Life</a> tells us about echinoderms (starfish, etc.; a phylum related to our own):

Quote:

...How does an originally bilateral animal become a pentaradial animal?

Up until now, two main hypotheses have contested. The first says that the echinodermal ancestors were essentially like worms, and that in those ancestors the head joined up with the tail to form a kind of lifebelt or doughnut. Then (the idea has it) different sections of the doughnut grew arms; and five happened to be the favoured number (even though some modern types have multiples of five). The second notion says that the first bilaterally symmetrical echinoderm stood upright, like a little fat doll. But htis doll had a wide skirt, like a tutu: and this tutu was divided into sections. Then the doll become squashed, the head shoved down into the feet, leaving the tutu sticking out to form five arms.

Some marvellous molecular studies by Greg Wray at the State University of New York at Stony Brook now suggests, however, that both these hypotheseses are false. Once again, the required insight is supplied by the homeotic genes, which (broadly speaking) determine what each part of the developing animal ought to be. In fact, Wray focused on the gene known as engrailed, which is not itself a Hox gene but occompanies the Hox genes and, like them, is involved in laying out the sequence of appropriate tissues along the long axis of animals, from head to tail...Wray first 'fished out' (as he says) this gene from brittle stars. He was then able to apply markers to this gene, and shwo the regions in the developing brittle star which it is expressed. It transpired that the gene is expressed along each of the arms of the brittle star in the same way, as if each arm were a separate animal with its own axis. In other words, to put the matter crudely, the brittle star is not a worm coiled round with its head joined to its tail: it is like five coplete worms joined head to head. The mystery of echinoderm radiality seems solved, but the solution, as so often proves the case in nature, outstrips the imagination.

lpetrich · 02-10-2002, 11:52 AM

Quote:

LordValentine:

Yet another strange idea gets very little notice UNTIL someone obtains evidence for it. Of course this is how it should be.

However, evidence had earlier been known for both continental drift and the St. Hilaire arthropod-vertebrate inversion. However, the evidence was not judged strong enough for a long time.

Continental drift had the apparent absurdity of continents plowing their way through oceanic crust, and the "drifters" had only thought of some extremely unconvincing mechanisms. It was not until the discovery of seafloor spreading that this conundrum was resolved -- the continents do not plow through oceanic crust, but are instead carried with it.

The A-V inversion had the problem that the mouth must somehow change sides, not to mention the numerous differences in detail. Here are differences in the central nervous system:

Arthropods and annelids have two neural cords with a ganglion (little brain) on each one in each segment; each segment's two ganglia is connected by a nerve, resulting in a ladder-like appearance.

The brain is the frontmost ganglia, which are sometimes fused.

The vertebrate spinal cord, by contrast, is a hollow, fluid-filled tube that is essentially one long ganglion.

The brain is an enlargement of the front end of the spinal cord.

But here's a <a href="http://www.ucalgary.ca/UofC/eduweb/virtualembryo/D-V_drosophila.html" target="_blank">report on a demonstration of this inversion</a>. The fruit-fly gene sog will, when expressed, make a part develop like a ventral part. The frog gene chordin will, when expressed, make a part develop like a dorsal part. But put a chordin product into a fruit fly, and it will act like a sog product! And put a sog product into a frog, and it will act like a chordin product!

[ February 10, 2002: Message edited by: lpetrich ]

KeithHarwood · 02-10-2002, 04:45 PM

Quote:

Originally posted by Kevin Dorner:


I'm not much of a prophet... but I do envision a horde of very talented, very educated, and very angry biologists leaving the United States. (Come to Canada!)

What I had in mind was a little more long term. If high school students grow up thinking that science is a matter for personal choice in biology, they'll think it is in other disciplines as well and you'll end up with a generation of scientists who are at best lab technicians and at worst incompetent. A few more years and the engineers will follow suit. The only way you'll be able to keep a technological society is by importing your scientists and engineers from other countries where the creationists have no power.

Hmm, annecdotal evidence suggests that that is already happening.

But, for the moment, if you don't like the cold try Oz. It's a lot warmer than Canada.

tgamble · 02-11-2002, 02:55 PM

Here's another creationist response. Good for a laugh anyway.

Quote:

No. For 'body plans' to be affected in a major way as postulated by the theory of 'natural selection' and to have scientific support requires that such changes arise through a long series of mutations over millions and millions of years with no intelligent direction for the mutations. As Dr Spetner pointed out, mutations of 'represser genes' lose information along the way. Multiple mutations of the same gene over time will result in the loss of all information in repsect to that gene.

There's also the obsessive mantra that just because it happened in the lab "there's no reason to assume it happened naturally".

and this

Quote:

But it has been your mantra that complex organisms arise from simpler life forms. If you lose information with every mutation, you will eventually have lost all information. Your notion of evolutionary theory requires ADDITION of information, not LOSS.

jumping to the conclusion that whatever the experiment showed actually happened randomly in nature is false because it would be based on inadequate data

<img src="graemlins/boohoo.gif" border="0" alt="[Boo Hoo]" /> <img src="graemlins/boohoo.gif" border="0" alt="[Boo Hoo]" /> <img src="graemlins/banghead.gif" border="0" alt="[Bang Head]" /> <img src="graemlins/banghead.gif" border="0" alt="[Bang Head]" />

<a href="http://interact.cbc.ca/cgi-bin/WebX?14@11.LERuaOGIq7F^22@.ee8b8df/10228" target="_blank">http://interact.cbc.ca/cgi-bin/WebX?14@11.LERuaOGIq7F^22@.ee8b8df/10228</a>

02-08-2002, 05:10 PM	#22
Valentine Pontifex Veteran Member Join Date: Jul 2001 Location: Orion Arm of the Milky Way Galaxy Posts: 3,092	More links: <a href="http://www.answersingenesis.org/docs2002/0208Prelim_evolution_gene.asp" target="_blank">AiG's First Response</a> (Is it evil to hope that they eventually repeat Well's remark referencing the original paper?) <a href="http://www-acs.ucsd.edu/~idea/wellsshrimp.htm" target="_blank">IDEA Club Response</a> <a href="http://abcnews.go.com/sections/scitech/DailyNews/darwingene020207.html" target="_blank">ABC News Article with AiG/ICR and Wells comments</a> [ February 08, 2002: Message edited by: LordValentine ]</p>

02-09-2002, 12:03 PM	#25
lpetrich Contributor Join Date: Jul 2000 Location: Lebanon, OR, USA Posts: 16,829	I'm sorry if I seem underwhelmed by this discovery, but to me, this result is simply the confirmation of something that has been suspected for a long time. Some background: Arthropod limbs are a good example of "serial homology", a homology between body parts in different places, especially different-looking parts. Arthropod limbs often receive various specializations, such as the outer two segments becoming a claw or some limbs being turned into mouthparts or antennae, but their overall construction is the same. Serial homology is further supported by the existence of "homeotic mutations", in which a body part develops like one in another place. Some famous ones first discovered in Drosophila fruit flies are antennapedia and proboscipedia, in which antennae and mouthparts develop like walking limbs. The genes whose mutations cause such out-of-place development have been named the homeobox genes, or Hox genes for short. These genes are expressed in regions of an embryo in a front-to-back order that is always the same wherever these genes are found. And these genes have been found in many species; consider <a href="http://www.people.virginia.edu/~rjh9u/homeo.html" target="_blank">this comparison between fruit-fly and mouse Hox genes</a>. The mouse set of these genes is 4 copies of the fruit-fly set, but with dropouts here and there. And what these UCSD researchers had found was there there is a crucial difference between species in one of the rearward homeobox genes -- a difference that suppresses rearward legs in insects but not in shrimp. [ February 09, 2002: Message edited by: lpetrich ]</p>

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02-09-2002, 11:12 PM	#26
lpetrich Contributor Join Date: Jul 2000 Location: Lebanon, OR, USA Posts: 16,829	This work is a success in evolutionary developmental biology, evo-devo for short. Here are some more interesting curiosities: Serial homology is very apparent if one studies the parts of flowers -- petals and sepals look much like the leaves of the plant that produces them. Also, Geoffroy St. Hilaire had noted in the early 19th cy. that vertebrate internal organs are upside-down relative to arthropod and annelid ones; arthropods and annelids have arrangement: ventral - main nerves - digestive - heart - dorsal while vertebrates have arrangement: ventral - heart - digestive - main nerves - dorsal The St. Hilaire inversion was not taken very seriously for a long time; every few decades, someone would "rediscover" it, and other comparative anatomists would explain why they found these similarities less-than-convincing -- there are numerous differences as well as similarities. That was until about 5 years ago, when it was discovered that the genes that control overall dorsoventral patterning in fruit flies match onto those that cause that patterning in frogs -- if one reverses the direction! So the St. Hilaire inversion has gone the way of continental drift -- gone from a marginal sort of theory to a mainstream one, as a result of some dramatic discoveries. Here's a nice illustration:

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