Pharyngula

More mammal macroevolution

I strongly recommend Larry Moran’s analysis of the paper on mammalian macroevolution that I briefly described earlier today.

Comments

  1. #1 bennet
    March 30, 2007

    Just curious — how does macroevolution happen when there’s no such thing as a random mutation that adds a new, novel body part? And since organisms are individually adaptive to the environment(environmentally-induced gene expression, horizontal gene transfer, phenotypic plasticity, etc ) what is the point of natural selection adapting them?

  2. #2 Loren Petrich
    March 30, 2007

    What “new body parts” do you believe must have been added?

    Be careful about the examples you select, because there are remarkably many features that can be shown to be modifications of existing features.

    The wings of flying animals do not pop out of nowhere, in the fashion of pegasus and angel wings, but are modifications of existing body parts. Bird, bat, and pterosaur wings are very clearly modified front limba, and insect wings are gills.

    The limbs of land vertebrates are modified side fins; one can even follow the transformation in the fossil record with such fossils as Tiktaalik.

    Flower parts — sepals, petals, stamens, and carpels — are modified leaves.

    Etc. etc. etc. — this is rather elementary evolutionary biology.

  3. #3 David Marjanovi?
    March 30, 2007

    Frankly, I don’t recommend it. Never accept molecular divergence date estimates at face value, always study the method and the calibration points…

    bennet, what is your definition of “macroevolution”? There are lots of definitions out there, and under some of them there may not be any macroevolution in the whole mammal tree, whereas under another the origin of every species is called macroevolution. Like MartinC I find the term rather useless.

    most biologists, notwithstanding Goulds punctuated equilibrium ideas, tend to see all mammalian body plans being the result of the gradual modification of the original ancestral mammalian structures.

    The punctuations only appear if you look very closely, at quite small timescales (and even then not always). From a bit farther away it’s all as gradual as ever.

  4. #4 David Marjanovi?
    March 30, 2007

    Frankly, I don’t recommend it. Never accept molecular divergence date estimates at face value, always study the method and the calibration points…

    bennet, what is your definition of “macroevolution”? There are lots of definitions out there, and under some of them there may not be any macroevolution in the whole mammal tree, whereas under another the origin of every species is called macroevolution. Like MartinC I find the term rather useless.

    most biologists, notwithstanding Goulds punctuated equilibrium ideas, tend to see all mammalian body plans being the result of the gradual modification of the original ancestral mammalian structures.

    The punctuations only appear if you look very closely, at quite small timescales (and even then not always). From a bit farther away it’s all as gradual as ever.

  5. #5 David Marjanovi?
    April 1, 2007

    Also, what about horns / antlers? What tissues / structures are they derived from?

    Outgrowths of the frontal bones.

    They aren’t homologous, right?

    AFAIK they are (remember giraffe horns), but that’s not my specialty.

    Is there (was there) any animal with both?

    No.

  6. #6 David Marjanovi?
    April 1, 2007

    Also, what about horns / antlers? What tissues / structures are they derived from?

    Outgrowths of the frontal bones.

    They aren’t homologous, right?

    AFAIK they are (remember giraffe horns), but that’s not my specialty.

    Is there (was there) any animal with both?

    No.