I’m reading a book called Stuffed Animals and Pickled Heads, which is a history of natural history museums. The author, in one of the early chapters, talks about how the similarities between a bird’s wing and bat’s wing are a homolog, but the similarities between a bird’s wing and a butterfly’s wing are an analog (i.e., a bird’s and bat’s wings are derived from the same structure (the forelegs) and a bird’s and butterfly’s wings are derived from different structures, but perform a similar purpose). But he doesn’t mention what that structure is in insects.
So my question is, from what body structure do insect wings derive? Did they develop from a pair of legs? Did they develop from…I don’t know. I’m not enough of an amateur entomologist to even come up with any other theories. I’m coming up to a cognitive blank wall on this one.
I vaguely remember a conversation I had about this. IIRC they is no analog, because an insects wings pretty well evolved from nothing, a few scales on the back. Something to do with originially cooling the body, or evaporation, or sumsuch. Sorry I can’t contribute more.
I had understood that the standard arthropod body plan had two appendages per body segment, and some of those appendages ended up evolving into legs, wings, antennae, mouthparts, etc., while groups of segments fused into larger-scale structures like the head, thorax, and abdomen seen in insects. Certainly you can tweak fruit flies into growing extra legs where their antennae should be, or the like.
This is commonly refuted (e.g. by Dawkins) by citing animals such as “flying” squirrels, which don’t really fly but can do some crude gliding using skin flaps that are very far from being wings. IOW, half a wing may allow some aerodynamic action that turns out to be rather useful.
Ditto for the notion that “half an eye” is of no use: even crude sensitivity to light can be very handy.
Well I think that that is po-ta-to po-tah-to territory and Myers is answering to a creationist talking point.
PZ Myers is not against Dawkins. He is indeed saying that the half wings will not function for **full **flight. This does not exclude that there are other advantages or functions that half a wing offers to insects.
They’re based in something called toolkit genes, and Will Wright did some research in the course of making the game. How to Build a Better Being from the pack-in DVD with Spore Galactic, it’s a NatGeo documentary.
I am not a creationist, I am in agreement with Richard Dawkins concerning just about everything we might conceivably agree on, and I am moderately familiar with some of the arguments that tend to pass back and forth between people who do and do not believe in creationism or ID.
However, I suspect you may be mis-representing the ‘half an eye’ debate and simplifying it. As I understand it, the argument put forward by the creationists or others who get involved in the ‘irreducible complexity’ argument it is not about degrees of light sensitivity. Everyone agrees that it can make sense to say some degree of light sensitivity is better than none, and the all the gradual stages from ‘single light-sensitive cell’ to ‘human eye’ might serve some purpose.
I believe the argument is that the eye mechanism doesn’t serve any purpose unless there is an optic nerve to connect it to the brain, and the brain has whatever ‘wiring and software’ is needed to make sense of the signal in a useful way; and that the optic nerve and the brain circuitry serve no purpose unless there is an eye to connect them to. The point the creationists and their ilk like to make is that there is no evolutionary advantage to either of these mechanisms unless the other is already in place.
It is not a valid argument, it is easy to refute and it is as sweetly deranged as the other rubbish that creationists like to spout. However, if we over-simplify or mis-state the (rotten) arguments they put forward, we are just giving them ammunition and an excuse to cry ‘Straw man!’ with tedious predictability.
I’ve also seen speculation that movable panels in the back of an insect would be useful for capturing solar heat even before they were useful for flying. Thus they might have been selected for increasing size and muscular control as adjustable solar panels, then later become useful in flight.
Similarly, although I can’t find a cite, I think I’ve seen a nature program showing some kind of dune beetle that raises its wing covers to catch dew or mist coming in off the ocean. Perhaps this was South Africa? The droplets condense on the wing covers and run down to the beetle.
The stonefly demonstrates that wings–even when they are quite small-- are very useful for locomotion among water-skimming insects. Water-skimmers whose wings are no larger than the gills on living and fossilized aquatic insects put them to good use in propelling themselves across the water, or even simply waiting for a breeze to sail them to shore.
So you don’t ever need to become airborne at all for wings to be of use.
Darkling beetles from Namibia and Western South Africa. Locally known as tok-tokkies for their knocking on wood with their abdomens (like deathwatch beetles do)
