Thread: Doubting Dinosaur Bird Connection

Awwww, but I really like the birdosaur theory

I'm wondering about the evidence of birds predating the therapods, and dinosaurs generally. The therapods were around for a long, long time--quite possibly long enough for birds to diverge from that line. And I'm not sure why the OSU researchers consider it unlikely for the fixed-thigh to have evolved from fast runners and evenutally gliders in the therapod family rather than some earlier form.

It also fails to address the fact that therapods have been found with feathers. Feathers are a pretty complicated thing to have evolved twice.

Originally Posted by PhilosopherStoned

It also fails to address the fact that therapods have been found with feathers. Feathers are a pretty complicated thing to have evolved twice.

meh, I could see birds diverging before feathered dinos, and the scale-->feather bit repeating itself, conferring benefits of insulation, glide time, or both.

Hell, even if the adult animal doesn't benefit from feathers, it might bring more eggs to term in a feather-lined nest.

Originally Posted by Taosaur

meh, I could see birds diverging before feathered dinos, and the scale-->feather bit repeating itself, conferring benefits of insulation, glide time, or both.

It still seems like the simpler solution is that the fixed femur evolved in late stage gliders and that feathers evolved once. They're pretty complicated and the likely hood of the sequence of mutations occuring twice is, imo, much less than that of there being gaps in the fossil record to make it appear as if birds were around before feathered therapods.

I think that it's gonna take a little more than this to knock the 'birdosour' (love that word) theory down.

Originally Posted by DeathCell

http://www.astrobio.net/news/index.p...ticle&sid=3163


Interesting read, especially when it mentions birds perhaps being older than dinosaurs.. and evolving alongside them.

My bible picture book could have told you that.......Dinousaurs walked along side man and birds saw the whole thing happen in the skies. Just like in ma piktur book

Originally Posted by PhilosopherStoned

It still seems like the simpler solution is that the fixed femur evolved in late stage gliders and that feathers evolved once. They're pretty complicated and the likely hood of the sequence of mutations occuring twice is, imo, much less than that of there being gaps in the fossil record to make it appear as if birds were around before feathered therapods.

I think that it's gonna take a little more than this to knock the 'birdosour' (love that word) theory down.

Mutations don't really occur twice. Don't you forget evolution is not about species generating others, but about a species differentiating into two new one - a species doesn't end as a new one begins. Who knows for how long birds and feathered therapods (or any other species for that matter) lived together.

Why exactly couldn't the same mutation happen twice, I understand the likely hood is less but what theory of evolution says this?

It could. Perhaps not the same mutation because you would be dealing with a different genotype but nature has some non-trivial examples of it occuring. It's just that is has way more examples of incomplete fossil records.

Originally Posted by DeathCell

Why exactly couldn't the same mutation happen twice, I understand the likely hood is less but what theory of evolution says this?

No theory saying tis. But the chance of a mutation happening is already low: twice the same mutation is unlikely².

Using some other peoples arguments that would mean it's likely to happen, though you probably didn't pay attention to that thread...

For structures to develop independently in two divergent lineages does not necessarily require "the same mutation happening twice." The same environmental pressures acting on creatures pursuing the same ecological niche may well bring about similar structures by different means. People stressing mutation often overlook the transformative power of selection pressures guiding natural, sexual recombination over many generations.

Originally Posted by Taosaur

For structures to develop independently in two divergent lineages does not necessarily require "the same mutation happening twice."

Granted, I was being lazy. Like I said, they wouldn't be the 'same' mutations because they would be occuring in two separate genotypes. On the flip side, people stressing selection pressures often assume the availability of raw genetic material for selection and recombination to work upon in the first place. While I could surely stand to know more about this field, it seems that scales evolving into feathers will occur as the consequence of mutations and the always present recombination rather than recombination alone. So it comes back to a sequence of mutations leading from scales to feathers occuring twice.