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Author Topic:   What drove bird evolution?
PaulK
Member
Posts: 17822
Joined: 01-10-2003
Member Rating: 2.3


Message 31 of 145 (124436)
07-14-2004 9:57 AM
Reply to: Message 26 by arachnophilia
07-14-2004 12:33 AM


Re: Birds Evolving??
I suspect that the "system birds use to rotate flight feathers on upstrokes" may refer to the swivelling wrist joint which is found in no other living vertebrates. It is however found in the Maniraptoran dinosaurs and is one of the major lines of evidence supporting the dinosaurian ancestry of birds.

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redwolf
Member (Idle past 5790 days)
Posts: 185
From: alexandria va usa
Joined: 04-13-2004


Message 32 of 145 (124438)
07-14-2004 10:03 AM
Reply to: Message 30 by Wounded King
07-14-2004 9:47 AM


Re: flow through hearts and lungs...
Bats aren't a counterexample. They don't fly anywhere near as fast, as far, or as high as birds do.
The basic reality is that birds need the kinds of hearts and lungs they have, and no other creature seems to have them. How are you going to evolve something like that? Why and how would anything which didn't fly end up with them and how would anything which did fly (the way birds do) function without them? Flight feathers same thing, beaks same thing, tail feathers same thing, light bone structure, same thing.....

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Replies to this message:
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crashfrog
Member (Idle past 1466 days)
Posts: 19762
From: Silver Spring, MD
Joined: 03-20-2003


Message 33 of 145 (124439)
07-14-2004 10:07 AM
Reply to: Message 32 by redwolf
07-14-2004 10:03 AM


Why and how would anything which didn't fly end up with them and how would anything which did fly (the way birds do) function without them?
Why do flightless birds have them, then?
beaks same thing
Not same thing. Not all birds have beaks, remember?

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Wounded King
Member
Posts: 4149
From: Cincinnati, Ohio, USA
Joined: 04-09-2003


Message 34 of 145 (124456)
07-14-2004 11:40 AM
Reply to: Message 32 by redwolf
07-14-2004 10:03 AM


Re: flow through hearts and lungs...
redwolf writes:
Bats aren't a counterexample. They don't fly anywhere near as fast, as far, or as high as birds do.
And yet they do fly, so flight itself doesn't require these elements. The flight of modern birds may require them, but this poses no problem for them being absent in their present forms in an ancestral bird which may also not have flown as high, fast or far as modern birds.
This seems to be pretty much baseless assertion, do you have any evidence that all of these things are absoloute prerequisites for flight and have no use in a non-flight context. Beaks seem a particularly strange as a choice given, as has already been mentioned, the number of non birds which have them.
TTFN,
WK

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coffee_addict
Member (Idle past 476 days)
Posts: 3645
From: Indianapolis, IN
Joined: 03-29-2004


Message 35 of 145 (124461)
07-14-2004 12:10 PM
Reply to: Message 34 by Wounded King
07-14-2004 11:40 AM


Re: flow through hearts and lungs...
Wounded King, I have to ask. What the heck is in that jar (your avatar). I thought it was brain but it doesn't look like brain.

The Laminator

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redwolf
Member (Idle past 5790 days)
Posts: 185
From: alexandria va usa
Joined: 04-13-2004


Message 36 of 145 (124495)
07-14-2004 2:39 PM
Reply to: Message 33 by crashfrog
07-14-2004 10:07 AM


quote:
Why do flightless birds have them, then?
beaks same thing
Flightless birds have evolved/devolved from flying birds. That is microevolution, which nobody disputes. (Micro) Evolution is good at LOSING features and complex capabilities; it is not good at producing them. Sort of like cutting hair; it's easy to cut it off, and much harder to put it back on if you cut off too much.
In the cases of the ostrich, moa, and other larger flightless birds, in the ones which survived the changes in gravity which killed off the larger dinosaurs, they had gotten too heavy to fly (~30-lb limit in our present world) and the wings became vestigial.
In real life, you not only cannot evolve a complex capability, but having lost the tiniest bit of such a capability, you can't ever even get the tiny bit back.
Thus in the case of the domestic chicken we observe a 2-lb forest bird having been bred into a 6 - 8 lb domestic bird which still has the wings for a 2-lb bird, and can fly just well enough to hop up into trees and over fences. Now, with all the billions of chickens around, with them not having been kept in fences or cages untill very recently and with all the billions of such which must have escaped and become feral over the millenia, if there was anything to evolution at all, you'd think that some small number of those would have retaken the air, that you'd look overhead, and there their progeny would all be.
As I noted however, having lost even part of the ability to fly, in real life, it doesn't come back.
Now, the coelurosaur/bird ancestor needed flight feathers, wings, and a baker's dozen things he didn't have, while the escaped chicken HAS all of those things and lacks only the tiniest iota of whatever is involved in full flying capabilities. Moreover, the coelurosaur bird-wannabes would have been starting from a microscopic numeric base while the escaped chicken is working from a base of billions.
If the chicken can't make it that final quarter inch, how is the "bird ancestor" supposed to make it the thousand miles??

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 Message 43 by Gary, posted 07-14-2004 6:56 PM redwolf has not replied
 Message 50 by arachnophilia, posted 07-15-2004 2:10 AM redwolf has not replied
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1.61803
Member (Idle past 1503 days)
Posts: 2928
From: Lone Star State USA
Joined: 02-19-2004


Message 37 of 145 (124500)
07-14-2004 2:49 PM
Reply to: Message 36 by redwolf
07-14-2004 2:39 PM


changes in gravity ???
redwolf writes:
In the cases of the ostrich, moa, and other larger flightless birds, in the ones which survived the changes in gravity which killed off the larger dinosaurs, they had gotten too heavy to fly..
Umm...I thought this changes in gravity theory was previously discussed in another thread and the consensus was that it was NOT a scientific verifiable fact. *edit typos.
This message has been edited by 1.61803, 07-14-2004 01:53 PM

"One is punished most for ones virtues" Fredrick Neitzche

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Wounded King
Member
Posts: 4149
From: Cincinnati, Ohio, USA
Joined: 04-09-2003


Message 38 of 145 (124506)
07-14-2004 3:02 PM
Reply to: Message 35 by coffee_addict
07-14-2004 12:10 PM


Re: what's in the jar.
Its a beluga whale embryo, naturally.

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1.61803
Member (Idle past 1503 days)
Posts: 2928
From: Lone Star State USA
Joined: 02-19-2004


Message 39 of 145 (124508)
07-14-2004 3:10 PM
Reply to: Message 38 by Wounded King
07-14-2004 3:02 PM


Re: what's in the jar.
And I thought that most people just eat beluga caviar..

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crashfrog
Member (Idle past 1466 days)
Posts: 19762
From: Silver Spring, MD
Joined: 03-20-2003


Message 40 of 145 (124519)
07-14-2004 3:49 PM
Reply to: Message 36 by redwolf
07-14-2004 2:39 PM


In real life, you not only cannot evolve a complex capability, but having lost the tiniest bit of such a capability, you can't ever even get the tiny bit back.
How about those stick insects, that evolved wings, lost them, and then evolved them again?
If the chicken can't make it that final quarter inch, how is the "bird ancestor" supposed to make it the thousand miles??
I wasn't aware there was a selection pressure on chickens for flight.
How about that beak thing? You keep ignoring the fact that not all birds had beaks.
Oh, and if you're going to talk about that ridiculous fiction of "changing gravity", do you suppose that you could address my standing rebuttals in the thread in which we discussed it? Thanks...
This message has been edited by crashfrog, 07-14-2004 02:50 PM

This message is a reply to:
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redwolf
Member (Idle past 5790 days)
Posts: 185
From: alexandria va usa
Joined: 04-13-2004


Message 41 of 145 (124548)
07-14-2004 6:34 PM
Reply to: Message 40 by crashfrog
07-14-2004 3:49 PM


quote:
How about those stick insects, that evolved wings, lost them, and then evolved them again?
Kind of sounds like there might have originally been flightless versions and flying versions. It's not obvous how fossils could show the difference.
quote:
I wasn't aware there was a selection pressure on chickens for flight.
The advantage to chickens (of being able to fly better) would be immense: better access to more distant feeding areas, easier escape from predators, ability to move to optimal climates by season, you name it.
quote:
How about that beak thing? You keep ignoring the fact that not all birds had beaks.
Sorry, but I never saw one that didn't and google searches on "beakless bird" don't turn up anything meaningful or anything indicating that such actually exist.
quote:
Oh, and if you're going to talk about that ridiculous fiction of "changing gravity"...
Basically, you've probably still got a handful of geniuses on talk.origins who would still tell you that the idea of a gravity change was ridiculous, nonetheless they've already lost the war on that one and they don't even know it. A google search on dinosaurs and gravity will turn up 40K hits or more, one of the directors of Los Alamos has told me that the topic is a now a safe one there, and when serious scholars went to put together a documentary on the topic last winter, they came to me and not to the geniuses at talk.origins. How about that?
Japanese Office Workers Viewing
The basic reality is that the question is no longer even about whether or not gravity changed, but over what caused it. A lot of the web sites which discuss gravity change argue for an expanding earth theory of one stripe or another. My own little book argues against that.
http://www.bearfabrique.org/books/books.html

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Loudmouth
Inactive Member


Message 42 of 145 (124552)
07-14-2004 6:51 PM
Reply to: Message 36 by redwolf
07-14-2004 2:39 PM


quote:
Thus in the case of the domestic chicken we observe a 2-lb forest bird having been bred into a 6 - 8 lb domestic bird which still has the wings for a 2-lb bird, and can fly just well enough to hop up into trees and over fences. Now, with all the billions of chickens around, with them not having been kept in fences or cages untill very recently and with all the billions of such which must have escaped and become feral over the millenia, if there was anything to evolution at all, you'd think that some small number of those would have retaken the air, that you'd look overhead, and there their progeny would all be.
I think you pretty much answered your own questions. I will try and help you along a bit. First of all, humans selected for size, not ability to fly. The ability to fly is still there but it is hampered by the increase in muscle mass, a three to four fold increase in overall weight. Just as an experiment, triple our quadruple your overall weight and see if you can still run.
For chickens to fly it would necessitate a reduction in size, something that farmers breed against. Secondly, there is not a selective pressure for flight among domesticated chickens. Given their present mass, it would take several morphological steps for them to fly free once more. In the wild each small step would mean be advantageous, but within their domesticated environment each mutation towards flight is not spread through the population through selective pressures.
Thirdly, the mutations necessary for flight would probably take a long time anyway, much longer than the time they have been domesticated. Recently, it has been shown that increased muscle mass can be the result of one mutation in the myostatin gene, so an increase in size within the time frame of domestication is not surprising. What would be surprising is seeing the wing from a 2 lb bird evolve into a wing able to support a larger bird in the same time period without selective pressures.

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Gary
Inactive Member


Message 43 of 145 (124554)
07-14-2004 6:56 PM
Reply to: Message 36 by redwolf
07-14-2004 2:39 PM


No one wants chickens to be able to fly well. People want them to be fat, easy to keep in one area, and tasty. Therefore, they breed the fat, tasty, manageable ones. Chickens may have been able to fly a couple thousand years ago but they can't now because humans have selectively bred them.
It might be better for an individual chicken's health for it to be able to fly, and therefore escape being slaughtered, but evolution doesn't work like that. The chickens carrying genes that people like are the ones that have been allowed to survive long enough to breed, so useful chickens are all that's left. Selective breeding is just an extension of natural selection - those that humans deem fittest to eat and sell are the ones that have offspring.
Feral chickens might get back their ability to fly if there was selective pressure to do so. If chickens with larger, more usable wings were more likely to breed, then those individuals would have more offspring than others and might be able to regain flight in a matter of a few centuries. Keep in mind though, that these chickens get eaten too, whether by humans or by other predators. I don't think a slightly larger wing would help them much, chickens would have difficulty getting over that hump to become able to fly again.
Bird/dinosaur transitional fossils lack many characteristics that modern birds have. They might have evolved large feathers for a variety of reasons other than for flight, to get mates, to keep warm, or for whatever reason. Early birds couldn't fly like most modern birds can either, they could only glide, much like flying squirrels do.

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1.61803
Member (Idle past 1503 days)
Posts: 2928
From: Lone Star State USA
Joined: 02-19-2004


Message 44 of 145 (124572)
07-14-2004 9:40 PM
Reply to: Message 41 by redwolf
07-14-2004 6:34 PM


redwolf writes:
The advantage of chickens (being able to fly better would be immense:
except one problem, humans bred them to stay put.

"One is punished most for ones virtues" Fredrick Neitzche

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redwolf
Member (Idle past 5790 days)
Posts: 185
From: alexandria va usa
Joined: 04-13-2004


Message 45 of 145 (124587)
07-14-2004 10:45 PM


Humans never bred chickens to "stay put". We bred them to lay eggs and taste good. Until very recently they were never kept in cages and often ran loose, often becoming feral with feral chickens living for some generations in various areas.
Moreover any other non-flying creature which you might suppose to be evolving into a flying bird would have no plausible way of ending up with wings of the "right size". Evolution would have to take care of that for them and, if that were possible, it would have happened in the case of the escaped chicken long since.

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