How can evolution explain body symmetry?

Perhaps you could give an example of an external, asymmetrical mutation in man that you think would not be selected against (and while sexual selection has been shown to do this you may ignore that for the moment)?Do you think we would do well with the configuration of a side-hill gouger? That is, one leg longer than the other. Would an extra eye on one side of our head offer an advantage? What did you have in mind?After you've found a couple of those then you need to suggest some evolutionary pathways to get to them. Not all advantages configurations can be reached throught evolutionary processes.Now there is one more point that I think has been mentioned. I'm not sure of this so it may take a bit of digging but I think that our symetrical features are not the result of "left-genes" and "right genes" but one gene for both sides with expression controled by other mechanisms.

The "hardly" present refers to the "sea". I take this as a marine environment. There are some marine insects but not, I think, many. There are, of course, many fresh water examples. However, I don't see why the lack of them in the current "seas" is a big problem.

A sea squirt ??

In the sciences this is always a possible outcome and, in fact, is rather frequent. The process is designed to work through this.The individuals publish, in very, very great detail their reasoning. Then others critisize it and it is corrected.Unfortunately, the proponents of ID seem to want to go directly to the public and, at least in what I've seen ignore critism. The mathematical probability arguments still seem to be put forward even though it is pretty easy to show they flaws in them.Why is that? Yes, but so far the process has been shown to (slowly perhaps) correct when things are wrong.You can speculate about such problems all you want. All that really counts is that you show where it has gone wrong. The ID folks don't seem to be doing a great job of that so far.