Feb 11 2013

The Evolution of Feathers

Published by under Evolution
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8 Responses to “The Evolution of Feathers”

  1. jugaon 11 Feb 2013 at 10:26 am

    A related question. Are all present day flightless birds thought to have evolved from flying birds? If not, studying the purpose of feathers in flightless birds might help understand their origin.

  2. Steven Novellaon 11 Feb 2013 at 10:34 am

    Yes – all flightless birds are descended from the common ancestor of birds that was flying. They are therefore not a perfect analogy to paraves species that could never fly.

  3. daedalus2uon 11 Feb 2013 at 12:04 pm

    Porcupines have quills that are quite feather-like in that they have a hollow shaft.

    Some horns are keratin and hence from the skin (cows and rhinos) rather than bone as in antlers.

  4. AndrewTysonon 11 Feb 2013 at 12:46 pm

    Do we have any examples of early feathers? The irreduceable complexity argument was pretty soundly countered with the example of the eye starting from a patch of light sensitive skin and slowly changing shape, each step of the way becoming more useful. While we might not know the use for an adaption of an early feather, do we know of an example of them existing. Would they have evolved from what we think of as a quill? How similar in structure is it?

  5. ZooPraxison 11 Feb 2013 at 1:40 pm

    I really enjoy these pedagogical posts and would even like tips on pronunciation.
    I don’t know if they bore or frustrate your more educated readers but as a layman with no background in science I find them really useful.
    Thanks.

  6. lfvvbon 12 Feb 2013 at 3:31 pm

    Indeed, the randomness and historical baggage is evidence of evolution. There is also the sexual selection hypothesis, since the paleobiologists could infere some of the fossil feathers colors.

  7. ccbowerson 13 Feb 2013 at 3:45 pm

    “Yes – all flightless birds are descended from the common ancestor of birds that was flying. They are therefore not a perfect analogy to paraves species that could never fly.”

    I wouldn’t necessarily view this as a flaw in the analogy for this discussion, because this fact demonstrates a major flaw in the irriducibly complex argument. Not only is it often an argument from incredulity, but this incredulity exists due to an assumption that the utility of the feather (or eye or whatever) remains constant over time.

    The fact that penguins do not fly, but have feathers that are vital for temperature regulation, yet these feathers come from an ancestor that used them to fly (and also perhaps temperature regulation), which in turn had ancestors that had protofeathers for other purposes other than flying really brings the point home that the concept of exaptation is essential to understanding these questions.

  8. a_haworthrobertson 14 Feb 2013 at 3:40 pm

    Steven

    You may have seen a recent anti-evolutionist blog post by Dr Jay Wile:
    http://blog.drwile.com/?p=9531

    Some of what he says seem fair enough (concerning a paper on Sinosauropteryx dating from 2012) but he also writes: “At university, I was taught as fact that feathers evolved from scales. However, we now know that there are several reasons why that isn’t possible”. He does not elaborate on this sweeping claim, and simply links to this article from 2003:
    http://www.scientificamerican.com/article.cfm?id=which-came-first–the-fea

    However – without subscribing – I cannot read this beyond the first two paragraphs. Perhaps you have read it? Of course reptile scales, like feathers, are made of keratin.

    I’ve also just read this 2011 National Geographic article (I expect you are familiar with it):
    http://ngm.nationalgeographic.com/2011/02/feathers/zimmer-text/1

    The article does not state that feathers evolving from scales isn’t possible. It does say:
    “The long, hollow filaments on theropods posed a puzzle. If they were early feathers, how had they evolved from flat scales? Fortunately, there are theropods with threadlike feathers alive today: baby birds. All the feathers on a developing chick begin as bristles rising up from its skin; only later do they split open into more complex shapes. In the bird embryo these bristles erupt from tiny patches of skin cells called placodes. A ring of fast-growing cells on the top of the placode builds a cylindrical wall that becomes a bristle.
    Reptiles have placodes too. But in a reptile embryo each placode switches on genes that cause only the skin cells on the back edge of the placode to grow, eventually forming scales.”

    It seems that creationists tend only to quote the most up-to-date papers or articles when their contents appear to be helpful to them.

    Ashley Haworth-Roberts

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