| Topic: |
Religions > Atheism |
| User: |
"david ford" |
| Date: |
01 Jan 2004 05:19:00 PM |
| Object: |
Similarities & Common Descent |
What, if anything, is wrong with the following claim?:
If 2 organisms have similar body structures, then they obtained those
similar structures from a common ancestor-- the similarities in the
structures are attributable to common descent from a common ancestor
that had the original version of the structure(s) in question.
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| User: "gen2rev" |
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| Title: Re: Similarities & Common Descent |
02 Jan 2004 08:51:12 AM |
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On Fri, 2 Jan 2004 05:50:26 +0000 (UTC), "Penny Nickels"
<5cents@bellsouth.net> wrote in
<M96Jb.3894$wW5.1019@bignews6.bellsouth.net>:
"gen2rev" <gen2rev@crosswinds.net> wrote in message
news:24d9vv4tmcg4nvv29mstrdbq7ajnla4bp4@4ax.com...
On Thu, 1 Jan 2004 23:19:00 +0000 (UTC), (david ford)
wrote in <b1c67abe.0401011520.5d1f4671@posting.google.com>:
What, if anything, is wrong with the following claim?:
If 2 organisms have similar body structures, then they obtained those
similar structures from a common ancestor-- the similarities in the
structures are attributable to common descent from a common ancestor
that had the original version of the structure(s) in question.
gen2rev wrote:
Nothing that I can see. Of course, it all depends on what you mean by
"similar" Are bat wings and bird wings similar? They certainly have
similar functions, but no one is going to claim that their common
ancestor had wings.
Penny writes:
Since similar structure is evidence of common descent from a
common ancestor, one must conclude that the wings of a bat
a bird and the flying reptiles which share common aerodynamic
prosperities must have a common ancestor from which they
descended. A flying reptile, no doubt an ancestor of the pterosaur
must also be the ancestor of both bats and birds.
Actually, the wings of birds, pterosaurs, and bats are quite different
from each other and don't indicate a common ancestor that could fly.
Birds wings incorporate the 1st, 2nd, and 3rd digits, and there's a lot
of fusion of bones to form a new bone called the carpometacarpus.
Pterosaur wings are composed of a membrane of skin between an extremely
enlarged 4th digit and the legs.
Bat wings are made up of membranes of skin between the 2nd, 3rd, 4th,
and 5th digits and the legs.
More info can be found at
http://www.ucmp.berkeley.edu/vertebrates/flight/converge.html
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| User: "Mike Ruskai" |
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| Title: Re: Similarities & Common Descent |
03 Jan 2004 02:42:56 AM |
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On Thu, 1 Jan 2004 23:19:00 +0000 (UTC), david ford wrote:
What, if anything, is wrong with the following claim?:
If 2 organisms have similar body structures, then they obtained those
similar structures from a common ancestor-- the similarities in the
structures are attributable to common descent from a common ancestor
that had the original version of the structure(s) in question.
It ignores convergence. Something as vague as "similar body structures"
can easily be caused by two widely separated lineages (which, of course,
ultimately do have a common ancestor, but not one which provided the
"structures" in question) adapting to the same living conditions.
Typically, the ways in which the two organisms differ will be more
revealing than how they are similar, because of convergence (e.g. look at
respiratory systems rather than locomotive appendages in whales and fish).
Though some specific things (such as spines) are distinctive enough
solutions to imply common ancestry as the source of similarities, rather
than convergence.
In this day and age, however, DNA can clarify the issue without the
guesswork.
--
- Mike
Remove 'spambegone.net' and reverse to send e-mail.
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| User: "John Popelish" |
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| Title: Re: Similarities & Common Descent |
01 Jan 2004 11:50:05 PM |
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david ford wrote:
What, if anything, is wrong with the following claim?:
If 2 organisms have similar body structures, then they obtained those
similar structures from a common ancestor-- the similarities in the
structures are attributable to common descent from a common ancestor
that had the original version of the structure(s) in question.
Such similarities certainly suggest that common ancestry might be an
explanation, but many useful structures have evolved in parallel in
different lines, so common ancestry is not a certainty. Other
evidence is needed to make a reasonable decision. The more detailed
and numerous the similarities, the stronger the support for the common
ancestry explanation.
--
John Popelish
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| User: "Lenny Flank" |
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| Title: Re: Similarities & Common Descent |
01 Jan 2004 05:54:55 PM |
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david ford wrote:
What, if anything, is wrong with the following claim?:
If 2 organisms have similar body structures, then they obtained those
similar structures from a common ancestor-- the similarities in the
structures are attributable to common descent from a common ancestor
that had the original version of the structure(s) in question.
Show us how to test it. Let's take an example -------- humans and
chimps both have a broken vitamin C gene. Show us how to apply the
scientific method to your hypothesis "this broken gene is similar in
both species because of common design".
If you are like most creationists, you don't know what the scientific
method is. Let me help you out:
*ahem*
1. Observe some aspect of the universe.
OK, so we observe that humans and chimps share
unique genetic markers, including a broken vitamin C
gene.
2. Invent a tentative description, called a hypothesis,
that is consistent with what you have observed.
OK, your proposed hypothesis is "an intelligent
designer used a common design to produce both
chimps and humans, and that common design
included placing a broken vitamin C gene in both products."
3. Use the hypothesis to make predictions.
Here is your chance to shine. What
predictions can we make from your hypothesis. If an
Intelligent Designer used a common design to
produce both chimps and humans, then we would
also expect to see . . . . . . . . . . . .?
Fill in the blank.
And, to better help us test your hypothesis, it's most
useful to point out some negative predictions ---
things which, if found, would FALSIFY your
hypothesis and demonstrate conclusively that your
hypothesis is wrong. So, then --- if we find (fill in the
blank here), then the "common design"
hypothesis would have to be rejected.
4. Test those predictions by experiments or further
observations and modify the hypothesis in the light
of your results.
5. Repeat steps 3 and 4 until there are no
discrepancies between theory and experiment
and/or observation.
Well, we seem to be sort of stuck on step 3.
Help us out here. Give us some testible predictions
from your hypothesis. Tell us how to go about
testing them.
Or, would you rather than we just skip steps 3,4 and
5, and just take your religious word for it that your
hypothesis must be true. Is that, after all, what ID is
all about?
Take note here --- there are NO limits
imposed here on the nature of your predictions,
other than the simple ones indicated by steps 3,4
and 5 (whatever predictions you make must be
testible by experiments or further observations.) You
are entirely free to invoke whatever deities or
supernatural causes that you like, in whatever
number you like, so long as you follow along to steps
3,4 and 5 and tell us how we can test these deities
or causes using experiment or further observation.
Want to tell us that the Good Witch Glenda used her
magic non-naturalistic staff to POP these genetic
sequences into both chimps and humans? Fine ---
just tell us what experiment or observation we can
perform to test that. Want to tell us that God didn't
like humans very much and therefore decided to
design us with broken vitamin C genes? Hey, works
for me -- just as soon as you tell us what experiment
or observation we can perform to test it. Feel entirely
and totally free to use all the supernaturalistic
causes that you like. Just tell us what
experiment or observation we can perform to test
your predictions.
Let's throw methodological
materialism right out the window. Gone. Bye-bye.
Everything's fair game now. Ghosts, spirits,
demons, devils, cosmic enlightenment, elves, pixies,
magic star goats, whatever god-thing you like. Feel
free to include and invoke all of them. As many as
you need. Show us all how to apply the scientific
method to whatever non-naturalistic science you
choose to invoke in order to subject your hypothesis
"genetic similarities between chimps and humans
are the product of a common design" to the scientific
method.
===============================================
Lenny Flank
"There are no loose threads in the web of life"
Creation "Science" Debunked:
http://www.geocities.com/lflank
DebunkCreation Email list:
http://www.groups.yahoo.com/group/DebunkCreation
-----= Posted via Newsfeeds.Com, Uncensored Usenet News =-----
http://www.newsfeeds.com - The #1 Newsgroup Service in the World!
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| User: "William Barwell" |
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| Title: Re: Similarities & Common Descent |
01 Jan 2004 06:32:17 PM |
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david ford wrote:
What, if anything, is wrong with the following claim?:
If 2 organisms have similar body structures, then they obtained those
similar structures from a common ancestor-- the similarities in the
structures are attributable to common descent from a common ancestor
that had the original version of the structure(s) in question.
Everything?
Sometimes, body structure is the result of evolving to fit an given
enviroment.
Example, fish, dolphins and some aquatic dinosaurs had
similar bodies, evolved to be efficient in water.
Note sharks have no bones, yet are similar in shape to dolphines.
Far different evolutionary pathways. Yet similar shapes.
Eyes are useful, and have evolved at least five time sin differing
families. But the fact that crabs and grasshoppers have eyes does not
necessarily mean they evolved from a common ancestor that had eyes
similar to crabs or grasshoppers. They have eyes and crustaceans and
insects evolved seperately. Molluscs (squid and octopus) have complex
eyes, they did not evolve from a common ancestor with eyes that
gave us apes and squid with eyes.
--
Bush! Chimp or chump?
Cheerful Charlie
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| User: "Penny Nickels" |
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| Title: Re: Similarities & Common Descent |
01 Jan 2004 10:32:00 PM |
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"William Barwell" <wbarwell@mungged.mylinuxisp.com> wrote in message
news:3ff4b9fe$0$132$811e409b@news.mylinuxisp.com...
david ford wrote:
What, if anything, is wrong with the following claim?:
If 2 organisms have similar body structures, then they obtained those
similar structures from a common ancestor-- the similarities in the
structures are attributable to common descent from a common ancestor
that had the original version of the structure(s) in question.
Everything?
Sometimes, body structure is the result of evolving to fit an given
enviroment.
Example, fish, dolphins and some aquatic dinosaurs had
similar bodies, evolved to be efficient in water.
Note sharks have no bones, yet are similar in shape to dolphines.
Far different evolutionary pathways. Yet similar shapes.
Eyes are useful, and have evolved at least five time sin differing
families. But the fact that crabs and grasshoppers have eyes does not
necessarily mean they evolved from a common ancestor that had eyes
similar to crabs or grasshoppers. They have eyes and crustaceans and
insects evolved seperately. Molluscs (squid and octopus) have complex
eyes, they did not evolve from a common ancestor with eyes that
gave us apes and squid with eyes.
I can see how it is possible that eyes of apes, monkeys and man
are from a common ancestor, by the same token the eyes of shrimp,
lobsters, squid, crabs etc must have inhirited their eyes from a common
ancestor. The same must be true of grasshoppers, beetles, roaches
etc. They must have had a common ancestor.
--
Bush! Chimp or chump?
Cheerful Charlie
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| User: "John Harshman" |
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| Title: Re: Similarities & Common Descent |
01 Jan 2004 06:34:43 PM |
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david ford wrote:
What, if anything, is wrong with the following claim?:
If 2 organisms have similar body structures, then they obtained those
similar structures from a common ancestor-- the similarities in the
structures are attributable to common descent from a common ancestor
that had the original version of the structure(s) in question.
You already know what's wrong with it. What sort of rhetorical point are
you trying to make here?
We know that convergence is fairly common for individual
characteristics. What's quite rare is whole-organism convergence, such
that scientists are actually fooled about relationships, and this has
become reduced even more as a result of the vast expansion of the
available data coming from DNA sequences.
Your problem is that nobody actually makes the claim you discuss here.
It's a strawman that has nothing to do with actual inferences of common
descent made by real biologists. If you want to support a creationist
agenda, you will have to address the actual data and arguments.
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