Why can't we fly?

pcwilkins · #1 3rd September 2004, 09:26 AM

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 · #2 3rd September 2004, 09:38 AM

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 · #3 3rd September 2004, 09:40 AM

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 · #4 3rd September 2004, 09:47 AM

Originally Posted by pcwilkins

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 · #5 3rd September 2004, 09:52 AM

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 · #6 3rd September 2004, 12:31 PM

Originally Posted by 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?

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 · #7 3rd September 2004, 04:27 PM

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 · #8 3rd September 2004, 07:18 PM

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 · #9 3rd September 2004, 07:29 PM

Originally Posted by nyjbarnes

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 · #10 3rd September 2004, 07:41 PM

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

99% of all species that ever existed not enough?