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?
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.
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.
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.
Apparently koala pouches are not upside down as such:
"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'."
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!