Logically, then, Sal is an Icelander, since he jumped the shark long ago.
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Well, you gave me my homework. I trust that you enjoyed the Schweitzer paper on the molecular evolution of feathers. Here is more I managed to dig up without requiring an academic account.
As you suggest:
Comparative transcriptome analyses demonstrate that 26 Ī±-keratins and 102 Ī²-keratins are differentially expressed in chicken scales and feathers during embryonic development.
Where it gets funky is:
This analysis showed extreme variation in copy number for birds with the barn owl having only 6 Ī²-keratins and the zebra finch having a maximum of 149 complete genes
So barn owls, having only 6 Ī²-keratin genes to service feather, beak, scale, and claw, seem to fly fine, whereas the zebra finch is over indulged. In the end, for 48 species in the study:
we found that the mean number of Ī²-keratins in birds was 33.81.
There is more discussion in there concerning duplication and divergence for which you can read the link.
Here is a paper with a pretty thorough treatment of keratin proteins, both alpha and beta.
Interesting tidbit in relation to complexity is, in the Ī²-keratin of the emu feather, only 32 amino acids form the central rod domain, 23 amino acids form the head domain and 47 amino acids form the tail domainā¦
The MWs of Ī²-keratins in scale-forming cells range from 17 to 20 kDa and those of Ī²-keratins in feather-forming cells range from 10 kDa to 14 kDa
ā¦so feather Ī²-keratin is not especially complex.
To finish off, two papers laying out some of the genetic conservation and variation distinguishing Ī²-keratins
Evolutionary relationships among copies of feather beta (Ī²) keratin genes from several avian orders
and if you can access it:
Nucleotide Sequences of Pigeon Feather Keratin Genes
RIEKO TAKAHASHI*, KISO AKAHANE and KUNIO ARAI
So there is no need for a aeronautically inclined dinosaur to submit a requisition for 60000 exactly ordered nucleotides to take to the air, the typical duplication and variation kludging along seems to work just fine. The fossil record for feathers shows a step wise, incremental development, and the molecular data is entirely compatible with that. As usual, evolution works with what it has; and it is not as if nature was in a hurry, feathers took their time. For RMNS to produce feathers, to take the catch phrase from the movie pitch guy, is super easy, barely an inconvenience.
https://www.cell.com/trends/ecology-evolution/fulltext/S0169-5347(19)30140-5?rss=yes
There are close connections in terms of genomic regulation between numerous regularly arrayed structures in the epidermis, including denticles in sharks, dermal scales in teleost fish, epidermal scales in reptiles, feathers in birds, and hairs in mammals.
The discovery that genes specific to the production of feathers evolved at the base of Archosauria rather than the base of Aves or Avialae (birds) is matched by fossil evidence that feathers were widespread among dinosaurs and pterosaurs, the flying reptiles.
I hadnāt known of feathered pterosaurs until now.
Not only did the pycnofibers cover almost all of the pterosaursā bodies, but they consisted of four distinct types of feathers. There are simple, hair-like filaments; brush-like bunches that split at the ends; filaments that have a little tuft about halfway down the length; and soft, downy feathers like those on modern bird chicks.
I understand that paid TAs and undergrads looking for extra credit do the bulk of the work in online courses. People like Joe are the celebrity hosts.
Self-study is great, but online courses have the advantage of forums where the one can raise questions about each lecture and have others or TAs answer them.
My original post was on this was only an admitted dream about what knowledgeable people could do with the time they now spend making the same points over and over to recalcitrant IDistsā¦
This is why ID is so important. You have an idea here based on putting together data and speculating on that data. The alternative hypothesis is ID. How do you go from here and empirically support your hypothesis vs just claiming you are right based on speculation.
If you can do this you will have eliminated ID for the origin of the flight feather however as @Joe_Felsenstein stated we are not quite ready to create a model or a test for the evolution of the flight feather.
But this must occur from the first cell to the first flight and the evolutionary resources required for ordering of the DNA by random change to lead to flight is most likely more than 150 bits of the total evolutionary resources available.
ID-Creationism is only important to a handful of religious zealots who are trying to force their religious origin views back into public schools. As a scientific explanation ID-Creationism is totally impotent. IDC canāt even come up with a testable hypothesis.
Hereās what colewd said I said:
@Joe_Felsenstein stated we are not quite ready to create a model or a test for the evolution of the flight feather.
But what I actually said was:
to actually model in realistic detail the genotypic and phenotypic changes that led, say, to the development of feathers in dinosaurs, we would need to have a comprehensive understanding of what all genes in the dinosaur did, what mutations could occur in them, and weād have to know a lot about the dinosaurās environment.
The emphasis is on āin realistic detailā.
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It would be a bit like reconstructing Latin from modern languages only. There would surely be things we get wrong, but that wouldnāt cast doubt on the common origin for the Romance languages.
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