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Education Science

Evolution of Mammals Re-evaluated 249

Posted by ScuttleMonkey from the shaking-the-tree-to-see-what-falls-out dept.
AaxelB writes "A study described in the New York Times rethinks mammalian evolution. Specifically, that the mass extinction of the dinosaurs had relatively little impact on mammals and that the steps in mammals' evolution happened well before and long after the dinosaurs' death."
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Evolution of Mammals Re-evaluated More

Evolution of Mammals Re-evaluated

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  • What About the Other Dinosaurs? (Score:4, Funny)

    by Anonymous Coward on Wednesday March 28, 2007 @03:20PM (#18519863)

    Most paleontologists now think that birds descended from dinosaurs. So in a sense, even dinosaurs in one form escaped the calamity.
    Don't forget varanus komodoensis [wikipedia.org] ... and Strom Thurman [wikipedia.org], he died out only four years ago and was the most prominent organism to escape the icy grasp of natural selection!

    • Re:What About the Other Dinosaurs? (Score:4, Funny)

      by Anonymous Coward on Wednesday March 28, 2007 @04:15PM (#18520607)
      "...Dinosaurs were created on day 6 of the creation week approximately 6,000 years ago, along with other land animals, and therefore co-existed with humans."

      "...Dinosaurs lived in harmony with other animals, (probably including in the Garden of Eden) eating only plants;" and "pairs of each dinosaur kind were taken onto Noah's Ark during the Great Flood and were preserved from drowning."

      "Dinosaur bones originated during the mass killing of the Flood;" and "some descendants of those dinosaurs taken aboard the Ark still roam the earth today."

      And you can look that up! [conservapedia.com]
      • And you can look that up!

        "Conservapedia". That's a good one. Of course, I had to go to an authoritative source [wikipedia.org] to find out more facts about this aberration.

  • Alternate theory (Score:5, Funny)

    by Average_Joe_Sixpack ( 534373 ) on Wednesday March 28, 2007 @03:29PM (#18520005)
    Most sensible explanation [youtube.com]
    • A magic man done it! [youtube.com] With "forcey forces" of coursey.
      • That dude is hilarious. I saw him on Never Mind the Buzzcocks, the ep with the guy from Torchwood.

    • Re:Alternate theory (Score:5, Funny)

      by franksands ( 938435 ) on Wednesday March 28, 2007 @07:15PM (#18522849) Homepage Journal

      Sorry for the comment abuse, but I just had to post this comment from youtube:

      evilc27 (2 hours ago)
      The fact that we are born babies and evolve into people is evidence enough to dispel the myth of evolution. If we were born monkeys, then there would be billions of monkeys in the world as there are billions of people. This does not equate. People have called me stupid for expressing my facts, but I am far from stupid. I took an IQ test at my church school, and I scored 95. You cannot get more than 100% and so I am in the top 5% of the smartest people in the world. chew on that disbelievers.

      This just made my day.

      • Gah!

        Oh my god, I don't believe I've ever seen such unbridled stupid!

        Honestly. With the mostly well assembled gramer and proper punctuation, I have to assume that was satire; you'd have to have an IQ below 75 to say that shit.
  • I had thought this point was actually a point of disagreement between Gould and Dawkins, with Dawkins pointing out that the cambrian explosion wasn't as sudden as Gould had pointed out. I think this particular point was discussed in Bryson's "A Brief History of Nearly Everything". I didn't think anyone still held this viewpoint about mammalian evolution anymore.

    • Re: (Score:2)

      by AJWM ( 19027 )
      What the hell does the cambrian explosion have to do with mammalian evolution? There's a several hundred million year time span between the two, and that's just to the beginning of the mammal line with the synapsids like dimetrodon. Add another hundred million or two before we get to anything that most people would consider mammalian.

    • Re: (Score:3, Informative)

      by victorvodka ( 597971 )
      Dude you said "cambrian" - there was a cambrian explosion too and perhaps that's what you mean. But here we're talking about the Cretaceous, 65 Million years ago instead of 600 Million years ago.

  • Hrmm... (Score:5, Funny)

    by grub ( 11606 ) <slashdot@grub.net> on Wednesday March 28, 2007 @03:30PM (#18520031) Homepage Journal

    But can they shoehorn it into the framework of a 6000 year old Earth?

    • Re: (Score:2)

      by mark-t ( 151149 )

      Well, that all depends how you measure age.

      If by *all* appearances something appears fully mature, is it? What if it was merely created to look that way so that it would be functional immediately, rather than waiting for however long it takes to be viable.

      Of course, the anti-creationist might be inclined to criticize such a remark with the reflection that if that were so with the universe, how would we know that everything was not, for example, merely created yesterday, complete with all apparent hist

  • How could it be true otherwise?

    Here's an interesting question: how long did it take for creatures to speciate after the Permian extinction? I wonder if there was the same amount of lag-time after that disaster...

    RS

  • well, duh. (Score:3)

    by Triv ( 181010 ) on Wednesday March 28, 2007 @03:43PM (#18520197) Journal

    I've known about this since Sunday [youtube.com].



    Triv

  • Shamelessly off-topic, but must be done... (Score:3, Interesting)

    by jeevesbond ( 1066726 ) on Wednesday March 28, 2007 @03:44PM (#18520217) Homepage

    From Conservapedia [conservapedia.com]:

    The Theory of evolution is a materialist explanation of the history of life on earth. Despite being the scientific standard, in the United States, there are a significant number of lay people who do not accept evolution. According to a CBS poll, only 13% of American adults believe humans evolved without divine guidance.

    A CBS survey said there's no evolution! If 87% of people say there's no evolution then this article is a sham sir!

    Back on-topic, what interests me is:

    But the researchers conceded that much more research would be required to explain the delayed rise of present-day mammals.

    If it wasn't the dinosaurs stopping the evolution of mammals (i.e. dinosaurs dominating the habitat), then what did? Could it be that the available habitats were just better suited to dinosaurs vs. mammals? That's the first thing that springs to mind (although am no paleontologist). As ever with this sort of thing, the finding raises more questions than it answers!

    • Re: (Score:2)

      by geek ( 5680 )
      Well, I may be corrected on this but I'll say it anyway since it's what I was taught in college. The median world temp around the peek of the dinosaurs was very high, somewhere around 130 to 140 degrees and there was a much larger amount of CO2 in the air. I would have assumed that as this changed mammals were given their chance at the top of the food chain.

      I always interpreted mammalian evolution to be parallel with climate change. I suspect however many people would disagree.

      • The higher temperature of the Cretaceous has already been referred to. Estimates suggest that at the beginning of the Cretaceous, the Global Mean Surface Temperature (GMST) was around 20C (about 5 hotter than today's value of 15C), and was about the same at the period's end - but peaked to a high of 25C in the Upper Cretaceous.

        From http://www.bbm.me.uk/portsdown/PH_130_Envmnt.htm#t empr [bbm.me.uk]

    • Re: (Score:2)

      by E++99 ( 880734 )

      According to a CBS poll, only 13% of American adults believe humans evolved without divine guidance.

      A CBS survey said there's no evolution! If 87% of people say there's no evolution then this article is a sham sir!

      There is no 87% saying there's no evolution. They are saying there's no MATERIALISTIC evolution. It's probably the 87% of us who believe that life itself has divine guidance. Whether evolution or anything else is random/mechanical or divine-influenced is a purely philosophical one, not a scien

      • Re:Shamelessly off-topic, but must be done... (Score:5, Informative)

        by Daniel Dvorkin ( 106857 ) * on Wednesday March 28, 2007 @06:43PM (#18522543) Homepage Journal
        There is obviously no evidence that the mutations which gave rise to speciations were "random" and not in some way directed, naturally or supernaturally, or otherwise forced in some particular direction.

        "Obvious" if you ignore pretty much all work in molecular genetics at least since Watson and Crick.

        Once we arrive at a better understanding of how DNA works, perhaps it will be possible to form mathematical models to determine whether or not the "random mutation" theory is feasible.

        You mean, the way bioinformaticists and statistical geneticists do all the time, right now, and have been for years?

        Maybe it's only feasible during intermittant radiation events that decimate populations by causing widespread mutations, leaving a few individuals with improvements, who go on to reproduce and build up populations again. Maybe it's not possible at all.

        Do you have any data, at all, that would support either one of these hypotheses? Or are you just cut'n'pasting from some ID site somewhere?

      • There is obviously no evidence that the mutations which gave rise to speciations were "random" and not in some way directed, naturally or supernaturally, or otherwise forced in some particular direction.

        Well, apparently you have your own definition about what is obvious. An *overwhelming* amount of evidence points to genetic mutations being random. Your claims have no scientific basis. None whatsoever. What you are saying is pure speculation, with absolutely no proof to back it up. Saying "sometime

  • Many mammalian lineages predate the K-T extinction (Score:5, Informative)

    by saforrest ( 184929 ) on Wednesday March 28, 2007 @03:53PM (#18520343) Journal
    If you read The Ancestor's Tale [amazon.com] by Richard Dawkins, you'll find that recent genetic evidence suggests that many of the distinct branches of modern mammals predate the K-T extinction.

    In particular, by the time of the K-T extinction, I believe that the primate lineage had already separated from rodents, as well as the laurasiatheres [wikipedia.org] (all hoofed mammals, lions, tigers, bears, etc.), xenarthrans [slashdot.org] (armadillos, sloths, etc.), and afrotheres [wikipedia.org] (elephants, manatees, anteaters, etc.).

    So, while most mammals in the Cretaceous may still have been tiny shrew-like creatures scurrying around in the underbrush, many of the modern lineages had already come into separate existence.

    It is also interesting to read, in the book, that our nearest non-primate relatives aside from the tree shrews are rodents. I can sort of see it: give a mouse a little more finger dexterity and it wouldn't not that different from a lemur. It also might explain why rodents are such good laboratory specimens.

    • Re: (Score:2)

      by rapett0 ( 92674 )
      While I am a programmer at heart I supposed, I do have a strong interest in biology (amongst other things). I just wanted to add to any geeks out there who have any interest at all in biology, read this book. I found it to be excellent on many levels. I am not here to do a book review, just wanted to say it comes highly recommened from someone *not* in the field. Also, if your in OC (SoCal), I think I saw a flyer that he gave a speech down in Laguna Beach a few months ago. Not sure if he is normally in
    • >It also might explain why rodents are such good laboratory specimens.
      See, you're actually assuming that they are good models, whereas it's not clear that they are.
      Indeed, regardless of how good a model they are, they are rather used because of their size,
      cost and fewer objections by laity. People want to save the cute bunnies (actually lagomorphs,
      close cousins of the rodents), but most don't care about the white mice in the cage next to it.
      And some people object to being compared to monkeys, apes or pig
      • See, you're actually assuming that they are good models, whereas it's not clear that they are.

        Yes, that's true.

        It may well be that any old mammal would do, and mice are merely good because they are small (and for breeding purposes, they have a very short generational cycle and large litters).

        I suppose what I was trying to suggest was that mice may be particularly good to compare for specific genetic reasons beyond the obvious ones I just mentioned. Though any argument about our particular closeness to mice

  • Yes, and.... (Score:3, Interesting)

    by Conspiracy_Of_Doves ( 236787 ) on Wednesday March 28, 2007 @03:58PM (#18520399)
    Specifically, that the mass extinction of the dinosaurs had relatively little impact on mammals and that the steps in mammals' evolution happened well before and long after the dinosaurs' death.

    Do they think that those steps ever could have taken place if the dinosaurs were still around?

    • Re: (Score:2)

      by jc42 ( 318812 )
      Do they think that those steps ever could have taken place if the dinosaurs were still around?

      Actually, Stephen Jay Gould wrote a fair amount on this topic, as part of his "contingency" hhypothesis. This is the idea that a fair part of evolutionary development is random and accidental, and if we could reset the clock to an earlier time, things would develop differently.

      He viewed the K-T extinction event as a "natural experiment" with this. Before it, there was wide diversity in both dinosaurs and mammals,
  • Evolution:
    x + 2 + 3 + 5 + 7 + y + 13 = 42

    Creationism:
    x^2 + 43 = 42

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