Why can't we fly?

[pcwilkins]

I just thought, in prehistoric times (so-called) man's greatest predators would presumably have been sabre-tooth tigers for example, or other men maybe. If a man could have flown, he would have had a huge advantage, not only in that respect, but also in hunting. So how come we're still ground based?

May seem silly question (in fact it is) but surely (if you believe in evolution) there must have been a time when birds couldn't fly, and they might have had the same discussion then - so is there a chance that in a few years time, I might see a man with wings tucked behind his back? Why hasn't it happened already?

Please don't turn this thread into a "evolution is true!"/"no it isn't" thread! Thanks.

Peter

 

[notto]

Evolution happens in two steps.
1) random mutation happens to certain individuals within a population creating diversity.
2) Natural selection selects from that diversity and those in a population who have characteristics that allow them to survive better or cause them to be selected for sexual activity at a higher rate produce more offspring than others and the traits they have are passed on to a higher percentage of the population in the next generation.

If random mutations don't happen that can lead to a particular trait, then that trait won't be expressed.

In your example, we can assume that because we can't fly, that there have not been random mutations that would lead us that way.

Now, if we look at the populations of dinosaurs that we find in the fossil record, we can find populations that did have mutations that lead to flight - namely, scales turning into feathers (which may have aided in survival AND sexual selection) and bipedal locamotion that allowed their feathered arms and tails to aid in balance, control, and lift when running or gliding from predators - over time, additional mutations led to flight.

Any questions?

 

[PhantomLlama]

Well, for one thing the wingspan required for a creature of our size to fly is around 8 meters, and our chests would have to be about twice the size they are now to accomodate the extra muscle mass needed to lift us off the ground.

Also, unless we gain a new pair of limbs (which would necessitate a major change in the entire mammalian/avian/reptilian body structure that has been constant for more than a hundred million years) we would have to convert our existing arms into wings, which would mean we lose their utility as hands and precise manipulators, meaning no more spears, sharp rocks, etc.

To summarise, being able to fly would be useful, but it is impractical for a creature our size, and would require either major changes in body plan that are several tens of millions of years of evolution away or more, or the loss of our arms in exchange for wings.

 

[Nathan David]

May seem silly question (in fact it is) but surely (if you believe in evolution) there must have been a time when birds couldn't fly, and they might have had the same discussion then

Birds don't have discussions.

 

[Sanguine]

I just thought, in prehistoric times (so-called) man's greatest predators would presumably have been sabre-tooth tigers for example, or other men maybe. If a man could have flown, he would have had a huge advantage, not only in that respect, but also in hunting. So how come we're still ground based?

I don't know that it would have been such a huge advantage. Flight is incredibly hard work even for birds, having a human frame would only make matters worse. This flying man would need to consume a ridiculous amount of food to function. Any advantage gained with flight would likely be offset by the incessant need to hunt and the fact that the flightless humans are doing just fine in the same niche only with considerably less effort.

May seem silly question (in fact it is) but surely (if you believe in evolution) there must have been a time when birds couldn't fly, and they might have had the same discussion then - so is there a chance that in a few years time, I might see a man with wings tucked behind his back? Why hasn't it happened already?

Flight isn't simply a matter of having wings, it takes number of structures to make it not only possible, but viable. For example birds have hollow bones to reduce weight, and a two cycle breathing process to maintain their high metabolic rates.

 

[Hydra009]

I just thought, in prehistoric times (so-called) man's greatest predators would presumably have been sabre-tooth tigers for example, or other men maybe. If a man could have flown, he would have had a huge advantage, not only in that respect, but also in hunting. So how come we're still ground based?

Because our ancestors could probably survive most of these attacks by simply evading predators, probably by climbing trees. In more recent times, they could use primitive weapons (spears, torches, etc) as well as domesticated dogs to defend ourselves against man-eating animals.

May seem silly question (in fact it is) but surely (if you believe in evolution) there must have been a time when birds couldn't fly, and they might have had the same discussion then - so is there a chance that in a few years time, I might see a man with wings tucked behind his back?

That would take one heck of a mutation.

Why hasn't it happened already?

Because it isn't practical for a creature our size to develop flight. I heard a long time ago that an average-sized human would have to have a wingspan of 12ft in order to have any hope of becoming airborne.

 

[Logic]

Monkeys don't have scales. Monkeys (humans for sure, most of them at least) don'tfind scales, feathers, or protruding bones sticking out of someone's back to be sexually appealing.

 

[nyjbarnes]

What are the chances that a random mutation would ever result in a benefit for a particular situation?

Consider this,

If my situation is such that in order for my race to survive a certain predator I need to be able to fly (this is a given and accepted part of the story, no other contravention will suffice) in order to survive being hunted, and I have enough in my species that even at a normal rate of decay it would take millions of years for this predator to wipe my species out. Is is fair to state that your answer would be, you would grow wings?

Doesn't this ask for the conciouss mind to have part of this process?
Considering that it was a given fact as stated in the OPR that "random mutation" was necessary...don't you think we would have a lot more extinct species?

 

[Ishmael Borg]

What are the chances that a random mutation would ever result in a benefit for a particular situation?

1:1. It has happeed.

Consider this,

If my situation is such that in order for my race to survive a certain predator I need to be able to fly (this is a given and accepted part of the story, no other contravention will suffice) in order to survive being hunted, and I have enough in my species that even at a normal rate of decay it would take millions of years for this predator to wipe my species out. Is is fair to state that your answer would be, you would grow wings?

A false scenario. You need a lot more assumptions to make this one fly. In what scenario would aerial assault be the only selective pressure?

Doesn't this ask for the conciouss mind to have part of this process?
Considering that it was a given fact as stated in the OPR that "random mutation" was necessary...don't you think we would have a lot more extinct species?

We have a great many extinct species.

 

[Sanguine]

don't you think we would have a lot more extinct species?

99% of all species that ever existed not enough?

 

[michabo]

Some mammals have developed limited forms of flight, such as bats and flying squirels. As has been pointed out, size is a huge factor, but so too is the way an organism lives. If we were arboreal and spent much time leaping from tree to tree, then some minor body changes to allow changing direction in flight might be beneficial, but then we wouldn't be humans: we would be bats or flying squirrels.

The real answer to why we are what we are is that:
1) we are what we are and
2) if we were different then we would be different, but would still say (1)

 

[billwald]

Consider the phrase, "bird brain." <G>

 

[Phred]

May seem silly question (in fact it is) but surely (if you believe in evolution) there must have been a time when birds couldn't fly, and they might have had the same discussion then - so is there a chance that in a few years time, I might see a man with wings tucked behind his back? Why hasn't it happened already?

Wasn't worth trading our arms for. (ask a silly question... )

 

[pcwilkins]

Hmm, thanks for your responses, I'm still not convinced. I'm still going to concentrate on growing those 12ft wings.

Peter

 

[Obertray]

Hmm, thanks for your responses, I'm still not convinced. I'm still going to concentrate on growing those 12ft wings.

Hey, if you're going to try evolution over one generation, why don't you draw me one of those 4-sided circles while you're at it?

 

[pcwilkins]

All circles have four sides. They just have an infinite number of other sides, too...

 

[Ryal Kane]

Why can't we fly?

For the same reason that prayer doesn't cure all illness:

We're not trying hard enough!

Ryal Kane

 

[ThePhoenix]

We can't fly because we're at the past the "point of no return." Basically, at the human body's current mass there is no wingspan at which we could fly. The mass of the wings and the muscle needed to lift the wings would exceed the lift generated by the wings.

 

[pcwilkins]

Yes yes, all very well but nobody has really given a satisfactory answer. Just because we're big makes no difference - a bird might have looked at a bee and said, "Well, I'll never be able to fly, those wings wouldn't work at my size". Ok so maybe we can't fly using the mechanism that birds use, but why not evolve a new mechanism? Like integrated jet packs or something, someone somewhere must be able to evolve something, surely! A 747 flies, and that's heavier than me (just). Are we saying that the mechanism to enable us to fly would just be too complex to evolve? That holds no water either, a bird might have said the same, but they managed to evolve nice feathery wings, allegedly!

What is this "point of no return"? Who says we can't return? I claim the ability to evolve backwards (devolve?) as a basic human right!

Peter

 

[Tomk80]

Like integrated jet packs or something, someone somewhere must be able to evolve something, surely!

Just working out a little hunch after reading the above sentence

Everytime I fart I feel myself lifted up in the air just a little bit. Now, what if our stomachs would evolve in big gas chamber, so we could lift ourselves up in the air with our intestinal gasses. We wouldn't become heavier, although aerodynamics might be a problem this way. If we'd also evolve some wings between our arms and chests (as with bats), it might just be possible. Stinky business, but we might evolve so we appreciate the biggest stinkers.