Let me start off by saying I am in no way a creationist. I just have a question about the “survival of the fittest” theory.
I understand the principals behind a taller offspring being able to get more food than a shorter one, or a certain colored insect being less prone to be consumed by a predator.
What I’m specifically wondering about is birds. Obviously wings didn’t develop with a single mutation. How is it that the presence of what were probably small, useless appendages allow the forefathers of birds to evolve into getting wings? What survival mechanism did they posses?
The forelimbs were probably not useless, and even if they were (vestigial) anytime a creature starts using a feature for something new, that’s when evolution starts happening.
Flying squirrels are able to get mobility benefits out of a body design that can be viewed as having crude precursors of wings. Perhaps in a few hundred thousand years their descendants will start to look bat-like.
Evolution doesn’t create new structures out of nothing. Evolution takes existing structures, which already are serving a useful role, and gradually modifies them to eventually meet a new goal. The whole time along, the structure never stops being useful. Wings didn’t start out as small useless structures. They started out as forelimbs, useful for running, climbing, and/or catching prey. As they became useful for gliding they didn’t stop being useful for their previous roles.
Unlikely. Do you have any idea how long they’ve already been around as gliders? Not to mention that there are over a dozen Genera of FSs w/ many more different species. You are, even if just subconsciously, making the mistake of assuming that gliding must eventually lead to flying. That gliding is some sort of way station on the way to flying. It’s quite possible that flying squirrels will lose their ability to glide, depending on the environmental pressures they meet up with.
As for the OP, we really don’t know. We assume that temperature regulation (or maybe courtship rituals) were the original driving force behind feathers. From there, it could be gliding or flapping as a way of assisted tree climbing, or something else entirely that lead to flight.
We have a much better fossil record showing us how cetaceans evolved from land mammals, btw. It is really remarkable, and something that has only come to light in the last few decades.
Watching how ducklings use their wings are a good demonstration of how small, “useless” appendages could have allowed the forefathers of birds to evolve into getting wings. The answer is that even though they couldn’t fly, their wings weren’t useless. Ducklings can’t fly, but they make good use of their undeveloped wings to much more effectively jump uphill, or over obstacles, than they could with just their puny little legs.
I once saw a flying fish fly at least 100 yards. They do appear to flap a bit and I have speculated that perhaps in 10 million years they will evolve to a fish that really can fly.
It seems clear that they fly to avoid predators. I can just picture one flying into the mouth of a pelican. But there are no pelicans where I have seen them.
Again, there are dozens of species of “flying fish”, so it all depends on the environment and the species. It would astounding if all of them evolved to true flight. And depending on what you mean by “true flight”, they would have to evolve some type of lungs, too.
There’s something fascinating in that cite - it says “gonadal hypertrophy” reduces weight?! “Gonadal hypertrophy” sounds to me like enlarged sex organs :eek:. Haven’t seen any “well hung” birds flying around recently.
Well, what Xema said isn’t incorrect, though it is prone to misinterpretation. It certainly is possible that flying squirrels might eventually evolve into something like bats. After all, bats evolved in the first place from ancestors that were something like flying squirrels. The key, of course, is that just because it’s possible, doesn’t mean it must happen.
What Chronos said. Perhaps is a long way from Must.
My basic point is that flying squirrels show how even extremely crude “wings” can confer an adaptive advantage. The argument that wings must be fully formed to be useful is unsound.
We really have no idea what bats evolved from, or how. Their origin is even more mysterious and implausible than that of birds. Bats really do appear fully formed in the fossil record. We don’t have anything like a bat equivalent of Archaeopteryx, all we have are perfectly functional, insectivorous, echolocating bats.
The idea of a flying animal evolving form a gliding animal is extremely problematic for two reasons. The first is the one that John Mace gave: gliding is a dead end. An animal that can glide is on a path to becoming a better glider, and their is no plausible path from glider to flyer. At some point on the path to flying a gliding animals must pass though a stage where the forelimbs are utterly incapable of providing powered flight, yet almost completely useless for climbing as well. That would seem to be an insurmountable problem for a transition from gliding to flying.
With bats we have a few other problems as well, such as the inability of a non-flying animal to echolocate for energetic reasons while simultaneously it is impossible for a non-echolocating bat to compete with birds. It’s a hell of a Catch 22. A gliding bat can’t echolocate, and a non-echolocating bat can’t fly.
These and a dozen other problems mean that we really have no what bats evolved from, but it almost certainly wasn’t anything like a flying squirrel. More likely it was something akin to a bushbaby. A leaping insectivore that never had any real ability glide, rather making a direct transition from leaping to powered flight.
Flap running may have been a precursor to flight, it’s a technique that enables birds to climb steep slopes but requires much less muscle power (10%) than actual flight. Flightless birds may have found it useful to evade predators and reach food sources. Half, or even one tenth of a wing can be functionally useful. That doesn’t explain why there were long feathers on the forelimbs in the first place, but display is one possibility.
Not sure I understand this. In what way would a non-flying animal of the same size have less energy for echolocation than a flying one? It seems to me that flying is a more energy intensive mode of movement than walking/running, so a ground animal should have more surplus energy for echolocation. No doubt you meant “energetic” in some other meaning.
I’m no expert, but I don’t see why. Even modern bats can still climb with the “thumb” claws on their wings. They have to be able to climb, since they are generally unable to take off from level ground like birds can. And some bats (vampires) have to climb around on their prey.
Speaking of vampire bats, they don’t need echolocation, nor do they have to compete with birds. Fruit bats, same deal.
