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It seems to me, that every part we have now, could be traced back through one pathway atleast. A kind of reversal process, to show how systems like the blood - could live without aortas and such.
Blood and circulatory systems are very ancient. They are even seen in earthworms, for example, where the mucous covered epidermis of the earthworm acts as a lung. The very first circulatory systems may have been used for waste management, a way to move metabolic waste into a central location where it is either recycled or excreted. Also, there are several solutions for getting oxygen to cells. In insects there are tubes that lead from central locations (spiracles) to the tissues, eliminating the need for a circulatory system. The bigger question should be why we ended up with the type of circulatory system we have instead of a different system.
The other thing that Behe seems to overlook is that even a very rudimentary circulation system is more beneficial than no circ. system whatsoever. Again, in a kingdom of the blind the one eyed man is king. Therefore, small increments will always be selected for, no matter how ineffecient they are. For example, if a very crude circulatory system increased tissue oxygenation by 5% it would be selected for (given the right environment). It is very possible that the first circulatory systems were a secondary system. Once the circulatory system became much more effecient then the primary oxygenation system was removed through mutation. **If you only read a section of my post, the last two sentences are the most important**
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Yes, I suppose I can imagine a rudimentary system building on what it has - but can ever living organism - throughout all of history - be relied on as having all the systems coming together - by chance, - hearts, lungs - ears, eyes, etc. What were all the previous systems? Can they be shown from some parts of a system?
Let's look at how the mudskipper "breathes" air. The mudskipper is a fish that can move freely on the shore of lakes, streams, etc. It needs access to mud in order to keep it's gills wet, however. What the mudskipper does is store air in pouches, much like lungs. However, these pseudo-lungs do not absorbe oxygen. Instead, these pseudo-lungs push air over the wet gills allowing for gas exchange. As you can well imagine, if these pseudo-lungs developed the ability to absorb small amounts of oxygen then this trait may be selected for. Each subsequent mutation that increased the effectiveness and effeciency of these pseudo-lungs would also be selected for. After a while, gills would no longer be needed for moving about on land. Therefore, if this species also became specialized for surviving on land (eg improvement of limbs) then mutations that removed the gills would not be selected against.
You might ask "why doesn't the mudskipper evolve lungs". Well, the land is already full of terrestrial animals, so competition is quite high on land. This wasn't true for the first tetrapods moving on to land. The mudskipper gives us a hint at how the transfer from water to land occured.
Firstly, do you agree that my mudskipper scenario is a legitimate explanation on how lungs could have evolved? Do you have any problems with it?
Also, this type of scenario causes problems for Behe's ideas. For Behe to suggest that these types of IC systems came about in "one fell swoop" he must have a documented history of all the other sub-systems that existed. Also, he must document all the systems that may have acted in the same role as the one he is studying. Take flagella, for example. It may be very possible that bacteria used to have very simple and ineffecient methods of locomotion. The flagella may have started as a simple system unrelated to locomotion, such as in ion transport. At some point, the pre-flagella structures acquired the ability to add to that locomotion in some sense through the mutation of one of it's proteins. As the new flagella became more effecient the old system was no longer needed and so it disappeared. Subsequent mutations increased the effeciency of the flagella over time which resulted in the system we see today. What Behe needs is an actual history of how the flagella developed. Without this history he is not able to claim that the flagella had to come about in "one fell swoop", nor can he argue that there were other methods of locomotion before the current flagellar system evolved.
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