Wombat Pouch

My point is that not only do you have no clue what symmetry and asymmetry mean in biology, you are also incapable of doing basic research about the subject before spouting off and showing your ignorance.

Shame there is no block/ignore feature here.

Think of the colon. Internally it's asymmetric but it attaches to the rectum and the anus which appear symmetric externally. The birthing canal is similarly asymmetric internally but the pouch appears as symmetric externally.If you have ever written software code you will know that it is generally good practice to hide the gory implementation details behind a more structured and friendlier interface. You have unwittingly presented your strongest argument for design over blind chance. Well done!

Like I said, asymmetric on the inside, symmetric on the outside. Which is why, as we observe, random mutations which affect the outside of a bilaterian produce symmetry without even natural selection needing to get involved, let alone "design". I have written computer code, and have a degree in Math & Computer Science. This is nothing like that. Mammals are not externally symmetrical in order to be user-friendly. Er ... not only have I not presented such an argument, but nor, so far as I can see, have you. Where do you think you did so?Edited by Dr Adequate, : No reason given.

Do you want to make a claim about symmetry in biology that supports your argument? Or are you just going to whine because you got called out on spouting crap?

Perhaps your point is, stop me if I'm wrong, that the external symmetry of bilaterians reminds you vaguely of the interfaces of software, and the latter are designed.This is a very vague resemblance, since interfaces are not symmetrical and bilaterians are not user-friendly (with the possible exception of dogs).But what it resembles far more is what random mutations observably do to the external form of bilaterians. The mutation that gives fruit flies an extra pair of wings gives them an extra pair of wings. The mutation that gives an American Curl cat curly ears makes both ears curly. Here we have a mechanism that produces bilaterally symmetrical features in bilaterians without design, without even the operation of natural or artificial selection. So if the wombat pouch was produced by evolution we would expect the wombat pouch to be symmetrical even if there were no selective pressures (i.e. no good functional reason) for it to be so.What would we expect if it was produced by design? Well if, as you claim, there is no functional reason for it to be symmetrical, then we might expect anything. The designer could have given it a stylish rakish tilt for aesthetic reasons. Or not. Who knows what a creator of wombats would find aesthetically pleasing? But we would expect evolution to produce symmetry in such a case, because this is what random mutations do.Edited by Dr Adequate, : No reason given.Edited by Dr Adequate, : No reason given.

Look, I myself can't figure out exactly what point you're trying to make with your quotation from WP about symmetry. And I am, as you know, quite smart. If even I can't figure out what your point is, then you haven't made your point very well, and it may not be Big Al's problem if he doesn't get it.

Symmetry in biology does not mean that an animal is a mirror image internally.Maybe I misunderstood the point he was trying to make.

I'm not sure what point you're trying to make as we only have one anus, one mouth, etc not a pair.

Yeah, but they're still bilaterally symmetric. Since they fall on the axis of symmetry, there's only one of each.My point is that when a mutation happens that affects the exterior of a bilaterally symmetric animal, it almost always does so in a bilaterally symmetrical way. We expect evolution affecting the outsides of bilaterians (including wombats) to be bilaterally symmetric, because the mutations that form the raw material of evolution have bilaterally symmetric results when they affect the outsides of bilaterians. There's no mystery here --- that's a complete explanation. It's when we see a bilaterian with external asymmetry that we have to wonder how it came about.Fiddler crabs, for example, might puzzle us: What is the biochemical mechanism that breaks the symmetry, and how did that evolve? I have no idea. (Possibly someone does, I've not researched it.) But I absolutely know why marsupial pouches are symmetric --- that happens by default. Wondering how that evolved is kind of like wondering how so many species have evolved to not be able to fly. That one's easy.Edited by Dr Adequate, : No reason given.

Well, he actually said that himself (post #57). Also, when he thought that I didn't know that (same post), he was much more gracious in the way he said so.I myself am sometimes spiteful and rebarbative, but I like to think that I only do that when it's called for. Big Al, to his credit, is a perfectly decent guy, no matter how wrong he is about biology. I think we should treat him well until and unless he himself behaves badly.

My bad.Thank you for calling me out when I am inappropriate.ABEAlso,
Big Al I apologize for being an ass.Edited by Theodoric, : No reason given.

Thanks for the vote of confidence. I never expected any acknowledgement on these forums and with my measly 200 posts to your 11000 I had taken my rejection on the chin. I had infact, for the greater part, forsaken EVC. Don't worry though I'm not looking for a slap on the back. I will however continue to make my points, whatever those might be at the time.Still getting back to the subject, I should point out examples of cleft palate which can have environmental or genetic factors. If you view pictures of these defects you will see that a mutation in this area generally does not have a symmetrical outcome.

This is true, though I don't know what proportion of these defects are genetic, rather than developmental, or what proportion of those that are genetic are symmetric. Nor do you.However, it is still true that most mutations that affect the exterior form of bilaterians are bilaterally symmetric. We know this just by cataloging actual mutations. The fruit fly has been used as a model for genetics for the last 100 years or so. How many mutations affecting the external form of the fruit fly can you come up with which are asymmetric?If the answer is "not very many", then I stand pat. I did say, after all "almost all", as you can see by reading my post. It is not necessary to my argument that it is an unbreakable rule, merely that it should be a very general one. Well, you're welcome. So long as you're discussing biology then we're doing the thing that these forums are here for. Unfortunately, these discussions often degenerate into slanging matches about which of us is more like Hitler. (Hint: neither of us is particularly like Hitler, 'cos of neither of us perpetrating genocide.) So long as we're exchanging views about biology, then even if you're completely wrong (which you are) then talking to people like you is exactly why I joined these forums in the first place.Edited by Dr Adequate, : No reason given.Edited by Dr Adequate, : No reason given.

d.p.Edited by Dr Adequate, : No reason given.