Which begs the question of what happened to sharks that didn't have this beneficial adaptation to start with.
They went extinct, or evolved into something else. Skin doesn't fossilize well, so we don't know when that adaptation came about - although it would have to be old enough to be found in all major branches of sharks. The fundamental shape of sharks is much older than sharks themselves - the basic body shape of sharks can be found in some of the first fish - Agnathans - which evolved 50-100 million years before sharks did.
I'd love to hear your explanation of the Wombat and how the upside down pouch was beneficial to burrowing underground.
It's not that complex - there is a group of marsupials (which includes wombats and koalas) who have backwards-facing pouches. In the case of wombats this is a good thing, as dirt doesn't get in. In the case of Koala's it makes little sense; it actually increases the risk of the young falling from a tree.
The reason for the pouch orientation is simple - that's what their ancestors had, and when they diverged they kept that adaptation; even though in the case of the koala it is a mild disadvantage.
As for where the first "backwards" pouch came from, no one knows. Pouches don't fossilize well, so there isn't any fossil record. Off the top of my head, I can think of three biologically plausable explanations as to how this occured:
1) Wombats/Koalas are "backwards", and evolved from a "forwards" predecessor. I don't know much about the developmental biology of marsupials, but assuming they're like the rest of the mammals, and that their pouch forms via the same invagination process that forms all the other organs, moving the opening would require nothing more than a single mutation in a morphogen's receptor.
2) "Backwards" pouches have been the first pouches, and its the rest of the marsupials which have it backwards. As above, this only requires a single mutation in a morphogen receptor.
I would add at this point that #'s 1 & 2 are the least likely, based on how mammals evolve, as morphogens tend to be used in many locations, so a mutation in a morphogens receptor would probably royally screw up the animal. That said, marsupials may have a dedicated morphogen for their pouch, at which point the above possibilities actually become the most likely.
Any experts on the developmental biology of marsupials out there?
3) Most likely, the orientation of the pouches are a result of divergent evolution from the pre-pouch form. For example, modern pouches may have started off as a flap of skin, or small hollow. In this case evolution, occurring of many generations could have deepend and altered the predecessor structure to the two different forms we see today.
Actually I'm quite confident in my beliefs and have stated them here before. I believe in Genesis 1:1...other miracles that occurred after that wouldn't surprise me. For example, God making an Earth like you see it today, fossils and all. As a scientist, you would see exactly what God wants you to and nothing more. Trickery? Only to those who seek empirical evidence to make God irrelevant.
It's been a while since I went to church, but if memory serves me, satan is the father of lies...
Any how, what about those of us who:
a) don't give a damn about god, and are simply exploring the universe in which we live (that would be me, btw), or
b) are devoutly Christian, and use science as a way of exploring gods universe?
Of course, you've been ignoring the fact that most Christian denominations accept evolution, and that many scientists are also Christians. Of course, I'm sure you'll rationalize that through the usual they are not "real christians" as they don't follow the very narrow interpretations of my faith...
Ultimately, its His creation and He has the authority to do do with it what he wants..right?
But what keeps him from using evolution? Or, for that matter, dumbing things down for sheppard's who don't have the educational background (or even language) to understand and intelligently discuss complex things like quarks, atoms, space-time continuum, abiogenesis and evolution...
Bryan