Wing evolution

[ecoli]

Wing evolution in dinosaurs... A professor of mine (philosophy, not evolution) said he had heard a hypothesis that wing evolution could have arisen to aid in body cooling (to literally fan the body). A student proposed the opposite... that wing expansion could have helped early bird-like creatures to expand the body surface area to collect more sun. Whatever the origin, bird wing evolution is a case of co-opting anatomy for other tasks.

 

What I've heard though, is that early wings were merely meant for gliding.

 

So, are any of these ideas correct?

[PhDP]

For insects, it's pretty clear that thermoregulation was the first purpose. I think it's not as clear for dinosaurs and the origins of birds.

[ecoli]

perhaps my professor confused his animals, then.

[lucaspa]

What I've heard though, is that early wings were merely meant for gliding.

 

So, are any of these ideas correct?

 

As PhD stated, there is considerable data that insect wings evolved as thermoregulators: JG Kingsolver and MAR Koehl "Aerodynamics, thermoregulation, and the evolution of insect wings: differential scaling and evolutionary change", Evolution, 1985.

 

Now, feathers first arose as modified scales for mating displays and then were exapted for insulation. That may be what the prof was trying to say.

 

For bird wings, there are 2 theories. You stated one: the forelimbs were used for gliding.

 

However, recently a new theory has been advanced that wings are an exaptation from running. A study done on hatchlings with feathers but without flight feather showed that flapping a forelimb enables the bird to run up inclines that it would normally not be able to do. In fact, at its best, the "wing" and flapping will allow the bird to run up a 100° slope! More than vertical!

 

So, since birds evolved from small theropod dinos, it is easy to infer a situation where the feathered dino either uses the wing to chase prey up vertical surfaces (trees) and/or runs away up vertical surfaces to get to a refuge away from even bigger predators. At the point where the "wings" are best for running up those vertical surfaces, they are also just at the point where they start to lift the animal off the ground. Voila! Instant flight.

3. Kenneth P.Dial, Wing-Assisted Incline Running and the Evolution of Flight. Science, 299: 402-405, Jan 17, 2003.

[Protoart]

Now, feathers first arose as modified scales for mating displays and then were exapted for insulation. That may be what the prof was trying to say.

 

Who says or where's your evidence that feathers arose for mating displays.

It's far more likely that feathers were for thermal protection for small endothermic bodies. These are fluffy "down" type feathers and are not flight feathers!

[ecoli]

Who says or where's your evidence that feathers arose for mating displays.

Well there's certainly no doubt that they were co-opted for mating displays, if that wasn't the 'purpose' of their evolution.

[Protoart]

Well there's certainly no doubt that they were co-opted for mating displays, if that wasn't the 'purpose' of their evolution.

 

Of course, feathers, scales, fur or external color or pattern are needed for species recognition and mating display. But, these are visual in nature and not immediatly functional enough to benefit survival. "Form follows function."

[cre8ivmind]

I'm sure transitional species between non-flight and flight must have been gliders. Is that true with Archaeopteryx?

 

I keep flying squirrels. They don't truly fly; they glide. They have a fleshy bone-like protrusion on their forearms that separate from the elbow and remain attached to the wrist. Does anyone supposed more of these will evolve in the next few million years, and flying squirrels will evolve true flight?

 

Sorry if these questions seem dumb or silly.

[lucaspa]

Who says or where's your evidence that feathers arose for mating displays.

It's far more likely that feathers were for thermal protection for small endothermic bodies. These are fluffy "down" type feathers and are not flight feathers!

 

The first known feathers are very sparse on the body -- not enough for thermal protection.

6 M Nowell First came feathers.  Natural History 107: 33, Sept. 1998 Summary of recent discoveries in China.  Sinosauropteryx did not have true feathers; intermediates between scales and feathers.

 

There seems to have been 2 exaptations of feathers: 1 from mating display to thermal and one from thermal to flight.

 

I'm sure transitional species between non-flight and flight must have been gliders. Is that true with Archaeopteryx?

 

Go back and look at my earlier post. The transition may have been from runners to flight. There is disagreement about how well Archeopteryx could fly. However, it does appear that it did fly and not glide.

 

Of course, feathers, scales, fur or external color or pattern are needed for species recognition and mating display. But, these are visual in nature and not immediatly functional enough to benefit survival. "Form follows function."

 

They are functional for sexual selection. And that benefits differential reproductive success: the individuals with the best mating displays get mates.