Flight Evolution in Birds

[sayak83]

This thread is primarily a discussion thread with @Crossboard regarding evolution of flight in birds. The evidence for evolution and the plausibility of the process will be discussed. The proposition that I like to defend is the following (excerpt from an evolution textbook).

Birds evolved from small, bipedal, feathered theropods, which changed their structure as they changed their habitat.From land, small theropods first moved to trees for safety from hungry predators, then learned how to live in a three- dimensional world, acquiring balance and coordination. From trees, they took to the air in small baby steps, first by parachuting, then by gliding, and finally by flapping and maneuvering. Forelimbs that had been used for catching prey on the ground were modified for climbing vertical tree trunks with clawed fingers, eventually morphing into wings for flight. Brilliant downy feathers that evolved initially to attract a mate and for species recognition developed into stiff contour feathers that were co-opted for flight. Once started on an arboreal life, the theropod body was altered in more subtle ways. Climbing adaptation changed short forelimbs into elongated and powerful wings. The downy feathers that covered the body for insulation and sexual display were also gradually transformed, eventually becoming light, overlapping, stiff, and flexible contour feathers. The long theropod frame became a compact structure with a flexible neck, stiff trunk, strong ribcage and powerful shoulder girdle to support a body suspended from wings. Finally, in arboreal life, where coordination and sharp vision are crucial to survival in a three- dimensional world, the bird’s brain expanded in a lighter skull. The Jehol and Daohugou biota offers crucial insights about the ecology and the evolution of the skeleton of modern birds from that of their theropod ancestors.

Let the discussion begin!

 

[David T]

I don't see the term metamorphisis or symbiosis so while the narrative is valid it's also just self evident.

 

[sayak83]

@Crossboard

Skeleton of a modern bird

Dinosaur to bird wrists.

Evolution Of Modern Birds: How Dinosaurs Got Their Wings

Vargas showed how some dinosaurs went from having nine wrist bones to four wrist bones, the number of wrist bones in modern birds.

Aves are birds. Rest are dinosaurs. Maniraptors are feathered dinosaurs.


Also see,
How Dinosaurs Shrank and Became Birds

“A bird didn’t just evolve from a T. rex overnight, but rather the classic features of birds evolved one by one; first bipedal locomotion, then feathers, then a wishbone, then more complex feathers that look like quill-pen feathers, then wings,” Brusatte said. “The end result is a relatively seamless transition between dinosaurs and birds, so much so that you can’t just draw an easy line between these two groups.”

recent research suggests that a few simple change—among them the adoption of a more babylike skull shape into adulthood—likely played essential roles in the final push to bird-hood. Not only are birds much smaller than their dinosaur ancestors, they closely resemble dinosaur embryos.

Like other bird features, diminishing body size likely began long before the birds themselves evolved. A study published in Science last year found that the miniaturization process began much earlier than scientists had expected. Some coelurosaurs started shrinking as far back as 200 million years ago—50 million years before archaeopteryx emerged. At that time, most other dinosaur lineages were growing larger. “Miniaturization is unusual, especially among dinosaurs,” Benton said.

That shrinkage sped up once bird ancestors grew wings and began experimenting with gliding flight. Last year, Benton’s team showed that this dinosaur lineage, known as paraves, was shrinking 160 times faster than other dinosaur lineages were growing. “Other dinosaurs were getting bigger and uglier while this line was quietly getting smaller and smaller,” Benton said. “We believe that marked an event of intense selection going on at that point.”

Birds are effectively baby dinosaurs with some added features.

The first birds were almost identical to the late embryo from velociraptors,” Abzhanov said. “Modern birds became even more babylike and change even less from their embryonic form.” In short, birds resemble tiny, infantile dinosaurs that can reproduce.

This process, known as paedomorphosis, is an efficient evolutionary route. “Rather than coming up with something new, it takes something you already have and extends it,” said Nipam Patel, a developmental biologist at the University of California, Berkeley.

 

[shunyadragon]

@Crossboard

Skeleton of a modern bird

Dinosaur to bird wrists.

Evolution Of Modern Birds: How Dinosaurs Got Their Wings

Vargas showed how some dinosaurs went from having nine wrist bones to four wrist bones, the number of wrist bones in modern birds.

Aves are birds. Rest are dinosaurs. Maniraptors are feathered dinosaurs.


Also see,
How Dinosaurs Shrank and Became Birds

“A bird didn’t just evolve from a T. rex overnight, but rather the classic features of birds evolved one by one; first bipedal locomotion, then feathers, then a wishbone, then more complex feathers that look like quill-pen feathers, then wings,” Brusatte said. “The end result is a relatively seamless transition between dinosaurs and birds, so much so that you can’t just draw an easy line between these two groups.”

recent research suggests that a few simple change—among them the adoption of a more babylike skull shape into adulthood—likely played essential roles in the final push to bird-hood. Not only are birds much smaller than their dinosaur ancestors, they closely resemble dinosaur embryos.

Like other bird features, diminishing body size likely began long before the birds themselves evolved. A study published in Science last year found that the miniaturization process began much earlier than scientists had expected. Some coelurosaurs started shrinking as far back as 200 million years ago—50 million years before archaeopteryx emerged. At that time, most other dinosaur lineages were growing larger. “Miniaturization is unusual, especially among dinosaurs,” Benton said.

That shrinkage sped up once bird ancestors grew wings and began experimenting with gliding flight. Last year, Benton’s team showed that this dinosaur lineage, known as paraves, was shrinking 160 times faster than other dinosaur lineages were growing. “Other dinosaurs were getting bigger and uglier while this line was quietly getting smaller and smaller,” Benton said. “We believe that marked an event of intense selection going on at that point.”

Birds are effectively baby dinosaurs with some added features.

The first birds were almost identical to the late embryo from velociraptors,” Abzhanov said. “Modern birds became even more babylike and change even less from their embryonic form.” In short, birds resemble tiny, infantile dinosaurs that can reproduce.

This process, known as paedomorphosis, is an efficient evolutionary route. “Rather than coming up with something new, it takes something you already have and extends it,” said Nipam Patel, a developmental biologist at the University of California, Berkeley.

I am not sure I buy the shrinking argument totally. There always have been small versions of the larger Dinosaurs. I believe they have common ancestors, but I believe that birds evolved from lineages of smaller dinosaurs.

 

[Crossboard]

This thread is primarily a discussion thread with @Crossboard regarding evolution of flight in birds. The evidence for evolution and the plausibility of the process will be discussed. The proposition that I like to defend is the following (excerpt from an evolution textbook).

Birds evolved from small, bipedal, feathered theropods, which changed their structure as they changed their habitat.From land, small theropods first moved to trees for safety from hungry predators, then learned how to live in a three- dimensional world, acquiring balance and coordination. From trees, they took to the air in small baby steps, first by parachuting, then by gliding, and finally by flapping and maneuvering. Forelimbs that had been used for catching prey on the ground were modified for climbing vertical tree trunks with clawed fingers, eventually morphing into wings for flight. Brilliant downy feathers that evolved initially to attract a mate and for species recognition developed into stiff contour feathers that were co-opted for flight. Once started on an arboreal life, the theropod body was altered in more subtle ways. Climbing adaptation changed short forelimbs into elongated and powerful wings. The downy feathers that covered the body for insulation and sexual display were also gradually transformed, eventually becoming light, overlapping, stiff, and flexible contour feathers. The long theropod frame became a compact structure with a flexible neck, stiff trunk, strong ribcage and powerful shoulder girdle to support a body suspended from wings. Finally, in arboreal life, where coordination and sharp vision are crucial to survival in a three- dimensional world, the bird’s brain expanded in a lighter skull. The Jehol and Daohugou biota offers crucial insights about the ecology and the evolution of the skeleton of modern birds from that of their theropod ancestors.

Let the discussion begin!

Thanks Sayak! You’re kind to open this thread. I’m rather new to the forum, and honestly don’t use the “reply/quote” tools like you experts. But I’ll do my best.

I actually just stumbled upon this thread today. For some reason, email notification didn’t come to me, but maybe it will do so after this reply.

Gotta say, I’m quite busier with my work than I had been when I first jumped on this forum, so my responses may be slower than even I would prefer.

I’ll read through your info, and will try to provide my angle as best I can. In touch...

 

[shunyadragon]

I am not sure I buy the shrinking argument totally. There always have been small versions of the larger Dinosaurs. I believe they have common ancestors, but I believe that birds evolved from lineages of smaller dinosaurs.

To add Many of the velocirapter species that were discussed in the article are much smaller than the picture (1.5 m and smaller) shows a rather larger Tyranosaurus like dinosaur. which may be misleading. The larger Velocirapters max was about 10 feet.

 

[sayak83]

To add Many of the velocirapter species that were discussed in the article are much smaller than the picture (1.5 m and smaller) shows a rather larger Tyranosaurus like dinosaur. which may be misleading. The larger Velocirapters max was about 10 feet.

I will check the original paper on this.

 

[Polymath257]

I am not sure I buy the shrinking argument totally. There always have been small versions of the larger Dinosaurs. I believe they have common ancestors, but I believe that birds evolved from lineages of smaller dinosaurs.

Well, one article pointed to mentions that the ancestral neotheropod weighed about 200 kg and that there were at least 12 stepwise decreases in size to the early birds.

So, the obvious question is what drove the decrease in size for the lineage leading to birds? Once they started going into trees, I can see why smaller size would be selected, but it isn't clear what was going on prior to that.

Any ideas?

 

[columbus]

The evidence for evolution and the plausibility of the process will be discussed.

So how did bats become birds?
Hunh?

Can't answer that can ya, brainiac? You may have four eyes, but you just won't see.

Tom

 

[It Aint Necessarily So]

Well, one article pointed to mentions that the ancestral neotheropod weighed about 200 kg and that there were at least 12 stepwise decreases in size to the early birds.

So, the obvious question is what drove the decrease in size for the lineage leading to birds? Once they started going into trees, I can see why smaller size would be selected, but it isn't clear what was going on prior to that.

Any ideas?

I've learned that atmospheric oxygen concentration and mean ambient temperature correlate with size, warmer and lower oxygen tensions correlating with smaller size.

But I don't know what the conditions on earth were when these animals became smaller, so I can't comment on whether these were relevant factors at that time or not.

 

[Kelly of the Phoenix]

So, the obvious question is what drove the decrease in size for the lineage leading to birds?

Perhaps fewer resources leading to "runts"?

 

[Sapiens]

Neoteny is well documented in many lineages.

 

[Polymath257]

Neoteny is well documented in many lineages.

Including ours.

 

[Crossboard]

This thread is primarily a discussion thread with @Crossboard regarding evolution of flight in birds. The evidence for evolution and the plausibility of the process will be discussed. The proposition that I like to defend is the following (excerpt from an evolution textbook).

Birds evolved from small, bipedal, feathered theropods, which changed their structure as they changed their habitat.From land, small theropods first moved to trees for safety from hungry predators, then learned how to live in a three- dimensional world, acquiring balance and coordination. From trees, they took to the air in small baby steps, first by parachuting, then by gliding, and finally by flapping and maneuvering. Forelimbs that had been used for catching prey on the ground were modified for climbing vertical tree trunks with clawed fingers, eventually morphing into wings for flight. Brilliant downy feathers that evolved initially to attract a mate and for species recognition developed into stiff contour feathers that were co-opted for flight. Once started on an arboreal life, the theropod body was altered in more subtle ways. Climbing adaptation changed short forelimbs into elongated and powerful wings. The downy feathers that covered the body for insulation and sexual display were also gradually transformed, eventually becoming light, overlapping, stiff, and flexible contour feathers. The long theropod frame became a compact structure with a flexible neck, stiff trunk, strong ribcage and powerful shoulder girdle to support a body suspended from wings. Finally, in arboreal life, where coordination and sharp vision are crucial to survival in a three- dimensional world, the bird’s brain expanded in a lighter skull. The Jehol and Daohugou biota offers crucial insights about the ecology and the evolution of the skeleton of modern birds from that of their theropod ancestors.

Let the discussion begin!

A somewhat lengthy but interesting read about the marvel of bird flight.. might be worth a look.

Designed To Fly

 

[Jose Fly]

A somewhat lengthy but interesting read about the marvel of bird flight.. might be worth a look.

Designed To Fly

I'm curious....when it comes to the history of birds, do you see that as a scientific question?

 

[sayak83]

Designed To Fly

What do you want me to look in it? The information of flight behavior, I know already, and the objections against bird evolution are simply based on ignorance by the writer. For example, the early birds were very small, like the size of squirrels. Squirrels don't die if they fall from branches because their small bodies are quite light and fluffy. Same with bird chicks. So the cost of initial clumsy flight is not high at all for early birds. We know this by looking at bird chicks learning to fly today as well.

@Crossboard

 

[Crossboard]

I'm curious....when it comes to the history of birds, do you see that as a scientific question?

Not quite sure I follow, Jose. Are you asking... do I thinks it’s possible to study the history (or specifically, the evolution of) birds through scientific means?

 

[Jose Fly]

Not quite sure I follow, Jose. Are you asking... do I thinks it’s possible to study the history (or specifically, the evolution of) birds through scientific means?

It's basically.....you want to know how birds came to be. Do you see that as something we should answer via science, or some other means?

 

[Guy Threepwood]

Bird-from-dinosaur theory of evolution challenged: Was it the other way around?
https://www.sciencedaily.com/releases/2010/02/100209183335.htm

Scientists: Bird's Ancestors Likely Not Dinosaurs
Scientists: Bird's Ancestors Likely Not Dinosaurs

The assumption of birds from Dinos has been around since Victorian times, based today as then, mainly on superficial physical similarities- which has led to many erroneous assumptions.

We have learned that different animals can share common traits that are both useful to them, without demanding that one morphed from the other- i.e. form follows function more reliably than any hypothetical ancestors

If you simply want to design an animal that walks on two legs, but can also reach the ground with it's mouth... there are certain design constraints inherent in that, which Dinosaurs and Birds share, and not a whole lot else

Not to say it couldn't have happened, but the desire to build a case for evolution can, has often led to premature conclusions about an inherently speculative subject, I think this sums it up:

"Pesky new fossils...sharply at odds with conventional wisdom never seem to cease popping up," Ruben wrote in his PNAS commentary. "Given the vagaries of the fossil record, current notions of near resolution of many of the most basic questions about long-extinct forms should probably be regarded with caution."

 

[Crossboard]

It's basically.....you want to know how birds came to be. Do you see that as something we should answer via science, or some other means?

Yes, I would love to have a better understanding of how lots of animals came to be. But not everything can be “answered” by the scientific method.

You can tell me more about the “other means” you mentioned.

Scientific method is useful for some things, and best so when the subject of study can be critically tested - - taken into the laboratory, tested, repeated. Unfortunately, when we cannot apply those scientific means, things which occurred supposed eons ago have to be left to conjecture.