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Author Topic:   Wombat Pouch
InGodITrust
Member (Idle past 2394 days)
Posts: 53
From: Reno, Nevada, USA
Joined: 05-02-2009


(1)
Message 1 of 85 (615538)
05-13-2011 3:25 PM


One of the best creationist arguments I have heard concerns the "backward" pouch of the wombat. Opposite to most marsupial pouches, the wombat's opens to the rear, which is valuable to it, as a burrowing animal, for keeping dirt out of the pouch. But how could the pouch turn around by natural selction?

When I first heard about this problem, I thought that the answer that would satisfy natural selection would be that the wobat evolved its pouch seperatly from marsupials that evolved front-opening pouches. But I just saw a TV show that said all of the world's marsupials have a common ancestor: a rat-like animal that lived in China.

So is there a well known solution to this probalem that I have missed? I searched the web and the EVC forums for discussion on it, but found none. Could the pouch have flipped around in one fell swoop, with a single genetic mutation? If so, wouldn't other simultateous mutations have had to occur to make the new pouch work? And if the pouch transitioned in a series of small steps, what would that have looked like?

IGIT


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Message 2 of 85 (615540)
05-14-2011 6:26 AM


Thread Copied from Proposed New Topics Forum
Thread copied here from the Wombat Pouch thread in the Proposed New Topics forum.
    
Dr Jack
Member (Idle past 179 days)
Posts: 3507
From: Leicester, England
Joined: 07-14-2003


Message 3 of 85 (615541)
05-14-2011 6:53 AM


The difference between the two pouches is not rotation, it's the position of the opening relative to the front and rear of the pouch. The common ancestor likely had a small pouch with a rearward opening, in Kangaroos the pouch lengthened with the opening sitting to the front, in wombats it lengthened with opening remaining rearward.

Probably.


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Percy
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Posts: 18307
From: New Hampshire
Joined: 12-23-2000
Member Rating: 3.2


Message 4 of 85 (615542)
05-14-2011 7:29 AM
Reply to: Message 3 by Dr Jack
05-14-2011 6:53 AM


The opening post assume that the pouch rotated and asked how that could happen with gradual stepwise evolution.

You answer that it wasn't the pouch that rotated but the opening that moved from rear to front. How does that happen with gradual stepwise evolution?

--Percy


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Dr Jack
Member (Idle past 179 days)
Posts: 3507
From: Leicester, England
Joined: 07-14-2003


Message 5 of 85 (615543)
05-14-2011 7:54 AM
Reply to: Message 4 by Percy
05-14-2011 7:29 AM


Percy writes:

You answer that it wasn't the pouch that rotated but the opening that moved from rear to front. How does that happen with gradual stepwise evolution?

By stepwise changes in the growth rate/time of the sections that form the front and rear flaps of the pouch, of course.


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Percy
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Posts: 18307
From: New Hampshire
Joined: 12-23-2000
Member Rating: 3.2


(1)
Message 6 of 85 (615549)
05-14-2011 8:47 AM
Reply to: Message 5 by Dr Jack
05-14-2011 7:54 AM


One of us is missing the obvious.

--Percy


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Modulous
Member (Idle past 178 days)
Posts: 7789
From: Manchester, UK
Joined: 05-01-2005


Message 7 of 85 (615553)
05-14-2011 9:27 AM
Reply to: Message 6 by Percy
05-14-2011 8:47 AM


One of those key cognitive difficulties with evolution is our tendency to view animals as final products, as opposed to things which were developed. I assume Mr Jack is suggesting that minor changes in early development can potentially have much larger ramifications later on in the wombat's development. Rather than developing a pouch and then having to invert it, a minor alteration in the timings of growth surrounding the rear and front flaps is potentially all that is needed.

Ive never really looked into wombat pouches a great deal before. I would hesitate to call it an argument for creation, its more of an interesting question for developmental biologists. But I guess creationists have difficulty discriminating between the two.


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Percy
Member
Posts: 18307
From: New Hampshire
Joined: 12-23-2000
Member Rating: 3.2


(1)
Message 8 of 85 (615557)
05-14-2011 9:48 AM
Reply to: Message 7 by Modulous
05-14-2011 9:27 AM


I see unexplained conundrums no matter which way you turn.

--Percy


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Percy
Member
Posts: 18307
From: New Hampshire
Joined: 12-23-2000
Member Rating: 3.2


Message 9 of 85 (615558)
05-14-2011 9:55 AM
Reply to: Message 7 by Modulous
05-14-2011 9:27 AM


Here's an interesting fact - the koala bear's pouch is also inverted. So much for the connection
with burrowing.

AbE: Tasmanian devil, inverted pouch, burrowing animal.

--Percy

Edited by Percy, : Add another detail.


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frako
Member
Posts: 2813
From: slovenija
Joined: 09-04-2010


Message 10 of 85 (615562)
05-14-2011 10:34 AM
Reply to: Message 1 by InGodITrust
05-13-2011 3:25 PM


i dont think the "rotation" of the pouch had to be gradual, it could have been a single mutation like when people get a mutation that makes their legs face backwards.

The question is advantage of a backward facing pouch or disadvantage of a forward facing pouch. And what came first? And from what it evolved?

My guess and its a guess i dint read up on it is that the pouch was originally backwards orientated evolving from sexual organs or something similar in the back part of the body.

A ken-guru with a pouch facing backwards would probably have a big problem holding on to his young while jumping around. So my guess is the freedom of jumping around was first enabled by the rotation of the pouch giving the animal more speed while carrying their young giving it a better chance for survival.

All the back pouch facing marsupials never had any selective pressure to turn their pouch around so their pouches stayed facing backwards or at some point even had selective pressures to keep their pouch facing backwards like digging and getting their pouch messy in the process.

This argument is pulled out of my arse so it might be wrong.


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Straggler
Member
Posts: 10284
From: London England
Joined: 09-30-2006


Message 11 of 85 (615563)
05-14-2011 11:03 AM
Reply to: Message 9 by Percy
05-14-2011 9:55 AM


Percy writes:

Here's an interesting fact - the koala bear's pouch is also inverted. So much for the connection
with burrowing.

An animal that climbs trees with it's belly dragging across the surface of the tree arguably has much the same reasons for an inverted pouch as a burrowing animal.

Or koalas are descended from burrowing animals and evolution was incapable of inverting a fully formed pouch?

The inverted pouch question is more interesting than it first appears.........


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Replies to this message:
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Straggler
Member
Posts: 10284
From: London England
Joined: 09-30-2006


Message 12 of 85 (615566)
05-14-2011 11:24 AM


Koala Pouches
Apparently koala pouches are not upside down as such:

Link writes:

"Female koalas have been described as having a ‘backward-opening’ pouch, in common with wombats and in contrast to an upward-opening pouch like kangaroos. However, that's not strictly true. When a female koala first gives birth to young her pouch opening faces neither up nor down, although it is located towards the bottom of the pouch rather than at the top. It faces straight outwards rather than 'backwards'. It sometimes appears to be ‘backward-facing’ because when the joey is older and leans out of the pouch, this pulls the pouch downwards or 'backwards'."

Koalas


  
jar
Member
Posts: 30934
From: Texas!!
Joined: 04-20-2004


Message 13 of 85 (615567)
05-14-2011 11:44 AM


passing the plate
Would infants killed because they were smothered in dirt while in their mothers pouch pass on their genes?


Anyone so limited that they can only spell a word one way is severely handicapped!
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Straggler
Member
Posts: 10284
From: London England
Joined: 09-30-2006


Message 14 of 85 (615570)
05-14-2011 11:53 AM
Reply to: Message 13 by jar
05-14-2011 11:44 AM


Re: passing the plate
jar writes:

Would infants killed because they were smothered in dirt while in their mothers pouch pass on their genes?

Obviously not. Which explains why the wombat pouch isn't the same as that of a kangaroo. But how this difference in pouch orientation occurred remains a valid question.


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jar
Member
Posts: 30934
From: Texas!!
Joined: 04-20-2004


Message 15 of 85 (615572)
05-14-2011 11:59 AM
Reply to: Message 14 by Straggler
05-14-2011 11:53 AM


Re: passing the plate
So would the genes from the mothers who just happened to have a pouch opening that protected the infant more get passed on?


Anyone so limited that they can only spell a word one way is severely handicapped!
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