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Science

Dinosaur Evolution Comes Into Focus 52

Posted by timothy from the first-small-then-big dept.
nickynicky9doors writes: "National Geographic has an article celebrating the work of dinosaur hunter Paul Sereno and his colleagues. New Thinking On Dino Evolution provides an overview of the recent discoveries and the conclusions and questions that follow the discoveries. One of the lines of inquiry asks how the breakup of the SuperContenient Pangaea impacted the evolution of the dinosaurs."
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Dinosaur Evolution Comes Into Focus More

Dinosaur Evolution Comes Into Focus

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  • Questions: (Score:2, Interesting)

    by gartogg ( 317481 )
    "For one thing, that the breakup of the ancient supercontinent Pangaea was not rapid, as widely believed, but slow enough to drastically limit dinosaur evolution in the region. "

    I beleive that geographic isolation (punctuated equilibrium) differentiated species after a long (the longer the better) period of mutation. Are there any biology/ecology people out there who can correct me?

    The article repeatedly discusses the amazing radiation, yet they wonder how it occurred as they ask about how the supercontinent broke up?

    "In a 1999 report in the journal Science, Sereno said: 'I think there was some kind of a tenuous land bridge [linking Europe and Africa] for several million years' after initial breakup of Pangaea. 'That land mass prevented the evolution, in isolation, of a unique southern dinosaur fauna.'"

    Is it absolutely crazt to think that with the same pressures, and starting from the same genetic base, the two continents would develop similar dinosaurs?

    Does the article explain this that badly (I assume) or are these scientists just dumb?
    • I beleive that geographic isolation (punctuated equilibrium) differentiated species after a long (the longer the better) period of mutation. Are there any biology/ecology people out there who can correct me?

      I'm not sure what you're trying to say, but punctuated equilibrium is an aspect of evolution that posits that evolution occurs in accelerated spurts rather than continually and gradually. Geographic isolation would seem to tend to slow evolution rather than encourage it, as evolution depends on competition for its impetus.

      Is it absolutely crazt to think that with the same pressures, and starting from the same genetic base, the two continents would develop similar dinosaurs?

      Er yes, it is pretty crazy, unless you're being very loose with your definition of similar. The two continents would likely have very different climates, which would affect the developing dinosaurs directly, as well as providing completely different vegetation and even bacteria surrounding the two different groups of dinosaurs.
      • "yes, it is pretty crazy, unless you're being very loose with your definition of similar. The two continents would likely have very different climates, which would affect the developing dinosaurs directly, as well as providing completely different vegetation and even bacteria surrounding the two different groups of dinosaurs."

        The problem I have with this is that the bacteria and vegetation are the same, all coming from the bacteria and vegetation on pangaea. Also, the climate didn't differe very much, because of the slow rate of movement of the continents. The exact timing (couple dozen million years) of when there was a land bridge shouldn't matter that much.

        Anyways, I don't think the article explains it well, because it makes very little sense.
        • The only problem I have here is "the bacteria and vegetation are the same, all coming from the bacteria and vegetation on pangaea." Just take a look at North america for an example of why this isn't necessarily valid. We have dramatically different climates all over North America. If it were to break up, the local climate would push for whatever is best best suited for the area. Before you may have had some immigration and other outside forces, but now, with the contitent segmented, this wouldn't happen as much.

          So each subcontinent of Pangaea wouldn't be "the same." The different climates would already have created some differentiation.

    • Re:Questions: (Score:3, Insightful)

      by TheGreenLantern ( 537864 )
      Keep in mind that, if you buy into evolution, in theory very small changes could have very drastic effects down the road.

      This is all completely hypothetical, but let's say you have Pangea, starting to break apart. At this time they have pretty much the same animals wandering around. Now, when they finally do become seperated and start drifting apart, one of the new continents begins to see average temperatures a few degrees lower than on the others. These few degrees perhaps has a negative effect on the incubation periods of several key predators eggs, resulting in a mini-mass extinction of certain predators on the "colder" new land mass.

      With a bunch of predators gone, there is suddenly a gap, which predators who were previously lower on the food chain can exploit. Or perhaps prey start dominating the landscape for a while, growing tremendously in size. The process just continues to domino effect from there on.

      The point being that there are so many factors that could send evolution branching in so many different ways, it's very unlikely that dinosaurs would have continued to evolve in much the same way on seperated landmasses. Hence the idea that the breakup took a very long time, and the possibilities of "land bridges".

    • I beleive that geographic isolation (punctuated equilibrium) differentiated species after a long (the longer the better) period of mutation. Are there any biology/ecology people out there who can correct me?

      I believe that traditional evolutionary theories point toward the idea that isolated populations develop more rapidly. The example of Drawin's finches, usualy widely in high school textbooks, illustrates (among other things) that the isolated populations evolved more rapidly than their continental ancestors/contemporaries.

      The selection pressures from living on small islands with limited food resources, a single (helpful) trait among an isolated finch population would most likely to be expressed. If these finches with a new trait were still on the mainland, the presence of so many other "unaltered" finches would eventaully "dilute" that genetic variation, because there is no selection pressure on the mainland for that trait, individuals with and without the modification survive.

      However, on an island, there is a natural selection pressure for said trait to have an advantage over "unaltered" finches. These finches would not survive, leaving the new birds to multiply.

      • Half of the worlds landmass isn't really "isolated."

        Any evolution that occurs would be on such a large timescale that it seems as though a landbridge for a couple million years wouldn't matter.
    • I beleive that geographic isolation (punctuated equilibrium) differentiated species after a long (the longer the better) period of mutation. Are there any biology/ecology people out there who can correct me?

      As much as I revel in correcting others, (When being corrected I tend toward covering my ears and yelling: "I can't hear you!"), the material requires something more than my amateur handling. Try the following: Jeffrey H. Schwartz "Sudden origins: fossils, genes, and the emergence of species" New York Wiley 1999

  • the SuperContenient Pangaea

    this sounds too much like an anime title.

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