The Theory of Evolution: Defined

[xianghua]

You mean "feather-like structures." Otherwise you're committing a category error.

so this is eye like structure or just eye?:

convergent evolution eye‏ - חיפוש ב-Google:

 

[Speedwell]

so this is eye like structure or just eye?:

convergent evolution eye‏ - חיפוש ב-Google:

They are the same only in that they are organs of vision. "Eye" is nothing but convenient generalization.

I asked you once before if you were a Platonist, but go no response. It would explain a lot. You see, there is difference between the feathers that birds have now and any feather-like structures mammals may evolve later as a result of convergent evolution. Mammals can never evolve bird feathers.

 

[xianghua]

. Mammals can never evolve bird feathers.

why not? if it evolved once it can evolve twice. unless you have a calculation to prove othehrwise?

 

[Speedwell]

why not? if it evolved once it can evolve twice. unless you have a calculation to prove othehrwise?

Calculation? LOL!.
No, if mammals evolved feather-like structures they would be mammal feathers, not bird feathers. They might look very similar, but they would be morphologically and genetically distinct.
I see you are still confusing "similar in form and function" with "identical." No wonder you don't understand convergent evolution.

 

[xianghua]

Calculation? LOL!.
No, if mammals evolved feather-like structures they would be mammal feathers, not bird feathers.

false. if they both feathers they both feathers. you cant play with it. so you dont have any logical explanation why a mammal cant evolve a bird feathers. interesting. thanks for proving my point.

 

[Speedwell]

false. if they both feathers they both feathers. you cant play with it. so you dont have any logical explanation why a mammal cant evolve a bird feathers. interesting. thanks for proving my point.

You are a Platonist. I knew it.

Tell me this: Do you think bats have bird's wings? Or is it birds that have bat's wings?

 

[PsychoSarah]

its actually very easy sarah. if we will find a mammal fossil with feathers we can claim for convergent evolution of feathers. after all, if eyes evolved about 50 times why feathers cant evolve twice?

No, you cannot claim convergent evolution for identical structure, only for similar structure in organisms which are not closely related. And as I said before, mammals have fur, there would be no selective pressures to even develop a similar structure to feathers because the fur and hair already perform the same basic task of feathers.

Feathers can't evolve twice because the exact same structure can't evolve twice. Eyes can evolve independently multiple times, but the resulting eyes have distinct structural differences from each other. New structures that perform the same basic function, but none of the independently evolved structures are identical. For mammals to develop feathers defies evolution entirely, demanding that a redundant, lesser structure somehow be promoted in mammals with near identical mutations to form an identical structure with another one that evolved independently. This does not happen in evolution, not ever.

why not? here is one example of a similar trait as the result of convergent evolution:

What is Convergent Evolution?

Similar, not the same, never the same. The distinctions between feathers and hair/fur are already very specific in terms of structure. As in, there are fewer structural differences between feathers and hair/fur than there are between horns and antlers. Basically, hair/fur and feathers are near identical, aside from shape. Feathers use more keratin types, but both hair/fur are made of keratin.

You could argue that some mammals could develop hair that appeared similar to feathers perhaps, but there would be structural distinctions and the mutations behind it would separate the structures from feathers even more. You. Can't. Get. Feathers. Twice.

 

[xianghua]

No, you cannot claim convergent evolution for identical structure, only for similar structure in organisms which are not closely related.

so convnergent evolution is only about general similarity but not an identical one? first: we also find examples of convergent even in the genetic level. so convnergent evolution can also means identical structure by theory. also remmember that there are different shapes of feathers. and you still believe that they all evolved from a common feathers even when they are different. so how do you know that all those feathers kinds arent the result of a convergent evolution too?

And as I said before, mammals have fur, there would be no selective pressures to even develop a similar structure to feathers because the fur and hair already perform the same basic task of feathers.

im sure that if we will find such a fossil scientists will have no problem to explain it. as for many structures in nature that seems strange in the first time.

Basically, hair/fur and feathers are near identical, aside from shape. Feathers use more keratin types, but both hair/fur are made of keratin.

so if they are almost identical where is the problem actually?

 

[Jimmy D]

where is the problem actually?

I was wondering that myself.

 

[PsychoSarah]

so convnergent evolution is only about general similarity but not an identical one?

Yes. Convergent evolution refers to situations in which two species are compared and have one or more similar physiological trait that was not present in their nearest shared ancestor. Thus, it outwardly give the illusion that the two species are more closely related than they actually are. However, it is worth noting that you can notice a case of convergent evolution without necessarily requiring genetic comparisons, thanks to the fact that as the structural similarities are not caused by identical genes, the underlying bones and tissue configurations are not nearly as similar as the outer observations would imply. For example, dolphin fore fins and shark fore fins may outwardly look similar, but the underlying structures of the two are entirely different (dolphins have bones, sharks do not).

first: we also find examples of convergent even in the genetic level. so convnergent evolution can also means identical structure by theory.

Recognize convergent, again. The genes in convergent evolution are not identical to each other, though some may be identical in terms of effect thanks to the redundancy of codons (for example, the condons TCT and TCA result in the same amino acid being added to a protein product, even though the sequences themselves are NOT identical). The genes that result in the physical traits of convergent evolution also aren't usually in the same location on chromosomes or in the same number (most genes are present on DNA multiple times).

also remmember that there are different shapes of feathers. and you still believe that they all evolved from a common feathers even when they are different. so how do you know that all those feathers kinds arent the result of a convergent evolution too?

Genetic analysis. The same basic genes for feather development are pretty consistent between all modern birds. The variations in feather shape and purpose of course are genetically present as well and not shared between all bird species, but of course when the basic variations of birds split off from each other on the evolutionary timeline varies. Some of the similarities in feather shape and size between individual bird species can be a result of convergent evolution, however, it would be illogical to conclude that the presence of feathers at all is a result of convergent evolution, as all bird feathers share key similarities in terms of structure and genes that contribute to them.

Bird feathers are too consistent between all bird species, both structurally and genetically, to view them as the result of convergent evolution. Same applies to mammalian hair.

im sure that if we will find such a fossil scientists will have no problem to explain it. as for many structures in nature that seems strange in the first time.

The only explanation for a mammal fossil with feathers that wouldn't deal a huge blow to modern evolutionary theory is that the fossil is fake or misidentified as a mammal fossil (or what was perceived as feathers weren't feathers but an unrelated pattern in the fossil rock, something along those lines). Notice that all of those allowable explanations basically mean what has been found wasn't actually a mammal with feathers.

so if they are almost identical where is the problem actually?

Again, the "almost" in "almost identical" is key. The exact same thing never happens in evolution twice, just because of how statistically improbable that would be (especially considering that the genomes between different species aren't the same size or have all the genes that provide similar function in the same place without sharing an ancestor that had those genes).

That being said, similar traits can be selected for in two, distantly related populations if the environments they live in happen to be very similar, and the two populations do NOT intermingle or compete with each other. Similar, but never identical.

 

[xianghua]

Recognize convergent, again. The genes in convergent evolution are not identical to each other, though some may be identical in terms of effect thanks to the redundancy of codons (for example, the condons TCT and TCA result in the same amino acid being added to a protein product, even though the sequences themselves are NOT identical). The genes that result in the physical traits of convergent evolution also aren't usually in the same location on chromosomes or in the same number (most genes are present on DNA multiple times).

there are some cases with about 20 identical amino acids that suppose to evolve by convergent evolution. its equal to about 50 identical DNA bases (from chance prespective). so there is no problem for evolution to evolve even the same gene twice.

Bird feathers are too consistent between all bird species, both structurally and genetically, to view them as the result of convergent evolution. Same applies to mammalian hair.

not sure. first; some scientists clamining for convergent evolution in proto-feathers too:

Evolution of dinosaur epidermal structures | Biology Letters

"Rare occurrences of ornithischian filamentous integument might represent independent acquisitions of novel epidermal structures that are not homologous with theropod feathers."

"The origins of ‘protofeathers’ and ‘quills’ outside Theropoda are ambiguous: interpretations of their homology should be correspondingly cautious, especially in those ornithodirans phylogenetically distant from birds"

so again we can see that even according to evolution there is no problem to claim for convergent.

secondly: we cant get a DNA from the old birds fossils like the archaeopteryx. so you cant test it in the genetic level so you cant know if those feathers are also the result of convergent .