Slashdot Mirror
Racing Dinosaurs with Spoilers
PhilHibbs writes "The BBC is reporting a new theory - dinosaurs flapped their proto-wings to generate downforce for added traction when running up-hill. Another one to add to the many theories of the evolution of flight."
Since evolution is still happening all around us, we can look at some of the "proto-wings" we see today and make some inferences.
We have squirrels that glide out of trees by stretching the skin between their legs.
We have snakes that do something similar.
We have flightless birds that still flap their wings when they run.
We have lizards that stretch membranes much like the flying squirrel. Some of them do it to glide, while others do it to control their temperature.
If feathers were only for flight, the flightless birds wouldn't have them, and flighted birds would only have them on their wings and tails. We use down for insulation in ski jackets for the same reason the goose made it in the first place.
A small, warm blooded dinosaur would need insulation. Insulation is lightweight for its bulk, so it would lower the density of the animal as a whole. This would protect the animal from falls, but it would also make it difficult to run, due to the air resistance overcoming the available traction.
Streamlining would be selected for. Small animals would experience higher Reynolds numbers (the air would seem thicker to them) and so flapping their feathered arms would get them more benefit than a larger animal would get.
It would not surprise me to find out that flight developed in several dinosaurs in parallel, given that we see it evolving in several quite different critters today (insects, reptiles, mammals, fish).
Your idea that flight developed as a side effect of temperature control mechanisms doesn't seem far-fetched to me at all. In fact, one might call it near-fletched, if one were a punning fellow.
Free book: Science Toys You Can Make
Logically, evidence for the first case is not evidence for the second. It's a bit like any inductive proof, proving for n still leaves the proof for n+1. In evolution, we know micro-evolutionary changes through DNA mutations are possible. But that the process of mutations can be extended indefinitely back to a common ancestor is a seperate issue.
Like I said, I'm not an expert on evidence for the common ancestor theories. That said, while microchanges and adaptions through mutation may not by itself be evidence enough to satisfy, when combined with the DNA/RNA/Protein sequence evidence , it becomes rather compelling, IMO. (once again, I'm a bit out of my area)
It comes down to two options, an intelligent agent (god, aliens, etc) could have created the species' with DNA sequences that fit a mutational model quite well, or every organism could have a common ancestor and these sequences evolved naturally through mutation. If an intelligent agent created the species, why would it engineer the DNA/RNA/Protein sequences such that they looked exactly like they would if they got that way by eons of mutation? Occam's razor would tell you that natural evolution of those sequences is a far, far simpler and more likely explanation, especially in light of the fact that microchanges happen spontaneously and are commonly observed in the laboratory.
-Sean
> I've yet to see a single pair of fossils that
are close enough to one another to be a single mutation apart
You and your parents are several mutations apart. You won't find that minimal quantum jump in the fossil record.
> We should see all kinds of creatures and
evidence of past creatures that are similar, with relatively smooth transitions from one form to another. The just isn't any evidence of that.
No one is going to make you believe the results of scientific enquiry if you don't want to, but if you want to sound like an informed critic you're going to have to get informed first. There is absolutely nothing in the theory of evolution that implies that we should have the collection of fossils you are demanding to see.
Sheesh, evil *and* a jerk. -- Jade