Forgot your password?
typodupeerror
Science

Gene MYH16: A Tasty New Jawbreaker 71

Posted by michael
from the chew-then-swallow dept.
kid_wonder writes "Jeremy Roenick take heart! Glass Joe take heart! Scientists discovered that humans owe their big brains to a single genetic mutation that weakened our jaw muscles about 2.4 million years ago. So I guess now we can call all those dopey muscle bound guys 'apes' with a clear conscience."
This discussion has been archived. No new comments can be posted.

Gene MYH16: A Tasty New Jawbreaker

Comments Filter:
  • Actually, no. (Score:4, Informative)

    by Romothecus (553103) on Thursday March 25, 2004 @01:57PM (#8670297)
    RTFA. Virtually every scientist who read their work was of the opinion that the explanation "mutation to smaller jaw means bigger brain" is incredibly simplistic and that the real explanation is probably far more complex. The change in jaw morphology is probably only one of many contributing factors.
  • "Discovered"? (Score:5, Insightful)

    by afabbro (33948) on Thursday March 25, 2004 @02:07PM (#8670448) Homepage
    "Discussed a new theory" is more accurate...
    • Re:"Discovered"? (Score:4, Insightful)

      by bugnuts (94678) on Thursday March 25, 2004 @02:18PM (#8670638) Journal
      Stop calling everything "theories" as if that word weakens the probability of it being true. That is the same lame tactic used by Creationists.

      Theories are developed hypotheses, that have withstood scientific examination. Some theories are stronger than others, such as evolution, which has extremely compelling and a wealth of strong evidence. Examining genes and doing the statistics on them is also extremely compelling. Everything you do with technology including the computer you're using now is supported completely by theories. Does that mean it's not true? Kind of like disproving Zeno's Paradox -- please stand in front of the arrow.

      So, sure, it's a theory as opposed to a proof. But you can probably bet your life on it.
      • He calls it a theory rightly, and it does weaken the probability of it being true. It is not known to be true! It is merely an idea.

        Paul Pettitt, speaking about the discovery in the article, uses qualifiers like could, potentially, plausible. This theory could be true, or it could equally not be true.

        Stop defending "theories" as if that word can assign some probability of it being true.
        • Well, yes. Technically, we *know* very, very little about the world around us. So far things fall down when you drop them, so we *think* gravity will keep operating tomorrow, but we don't really *know*.
        • Re:"Discovered"? (Score:3, Insightful)

          by Smidge204 (605297)
          I think the parent was commenting on how many people disregard ideas that are not compatible with their views (eg: Creation and Evolution) by saying "it's just a theory".

          A "theory" is usually given much more weight than a "belief", because theories are typically based on observation and experimentation, reviewed by peers, and have been used to make accurate, testable and verifiable predictions. Beliefs tend to be more based on emotion and hearsay. It is therefore reasonable to assume that a "theory" is clo
        • Re:"Discovered"? (Score:3, Insightful)

          by bugnuts (94678)
          This theory could be true, or it could equally not be true.

          Wrong. Simply because there are two choices between true/not-true, does not give it 50% chance of either.

          There are theories you bet your life on, every day. If they all had an equal chance of being true or false, you would be dead now. Try flipping a fair coin 100 times and getting all heads. Is there a chance you can do it? Yes, but is it likely? No.

          He calls it a theory rightly, and it does weaken the probability of it being true.

          You k
      • Re:"Discovered"? (Score:4, Insightful)

        by RevAaron (125240) <revaaron&hotmail,com> on Thursday March 25, 2004 @06:14PM (#8673923) Homepage
        Indeed. I hate it when people say this or that (usually "evolutionism"; -ism, heh) is "just" a theory. A theory is a big deal. Perhaps creationism is "just" an educated guess, but the definition of the word theory is not. In common usage, people use the word "theory" to mean just that- an educated guess, rather than a hypothesis backed up by a lot of evidence.

        And no, like you say, it's not a proof- but proofs really only exist in the world of mathematics. No scientist can say that a particular theory is 100% proven, ever. That is science, and the fact that science can adapt and grow with new information is one of its great strengths.

        *sigh*
        • Re:"Discovered"? (Score:2, Insightful)

          by aug24 (38229)

          proofs really only exist in the world of mathematics

          And all of those rely on 'axioms' aka assumptions too. Admittedly there aren't many of them (five arithmetic and eight geometric if I remember my first year), but still, nothing is provably 'true' on its own merits.

          By way of example, one of the axioms is that parallel lines never meet. We don't actually know if that's true, but it's pretty close. If we do turn out to live in a curved universe, we'll have to throw away some bits of maths.

          Popping

          • And all of those rely on 'axioms' aka assumptions too. Admittedly there aren't many of them (five arithmetic and eight geometric if I remember my first year), but still, nothing is provably 'true' on its own merits.

            Math is a little more sophisticated than that. Classical formlist mathematics relies on axioms. Many constructive varients of mathematics do not rely on theories. I guess my point is that there is not one mathematics. Depending on the philosophical foundation you take for mathematics, y

            • /me still laughing:

              I have a first class degree in Maths, and a lower second in Physics too. My post was intended to be understood by anyone, rather than representing what you called my 'overly simplistic view'. Try not to be so patronising in future till you know whom you are addressing.

              Anyway, while there are internally self-consistent theories ("a=>b=>a"), there is no such thing as a proof without axioms. I'd love to hear one, if you claim to know of one. <thinks> The last person who t

              • Go read a text on foundations of mathematics, which presents such things as Intuitionism and other constructive forms of mathematics. Intuitionism, for example, doesn't rely on formal axioms... and therefore isn't bothered by incompleteness phenonmenon such as is the case with Hilbert-style math.

                Your degree seems to have only taught you classical formalism of the Hilbert type, i.e. axiomatic.

                Interesting that schools teach such a narrow and biased view of "mathematics". Only presenting classical formal a
                • As I thought: philosophy of mathematics. Not useful for physics or engineering, but a great way to spend an afternoon in the sun with a beer.

                  J.
              • By way of example, one of the axioms is that parallel lines never meet. We don't actually know if that's true, but it's pretty close. If we do turn out to live in a curved universe, we'll have to throw away some bits of maths.

                I have a first class degree in Maths, and a lower second in Physics too.

                It's hard to believe you managed to do both without learning anything about either non-Euclidean geometry [wikipedia.org] or the geometry of the universe (for the curious: yes, it is curved [uoregon.edu]). It's even harder to believe th

                • If you'd read my reply, you'd have noticed that I said I was attempting to make a point for the layman. This is /. not a maths group.

                  Firstly, of course I did non-euclidean, at A-level initially. I didn't appeal to my own authority to debate a mathematical point, just to suggest that he should be less patronising. Finally, the branch of maths he is referring to is not mainstream maths, it's "philosophy of maths" and personally I don't think much of it. YMMV, of course.

                  J.
          • Re:"Discovered"? (Score:2, Informative)

            by joebok (457904)
            By way of example, one of the axioms is that parallel lines never meet. We don't actually know if that's true, but it's pretty close. If we do turn out to live in a curved universe, we'll have to throw away some bits of maths.

            You are correct that math and logic require basic unproven assertions that "nothing is provably 'true' on its own merits". But math is not about truth. No piece of math will ever have to be thrown away!

            Geomoetries in which the parallel postulate you mention are different than the
            • Forgive me, it was not meant as a literal truth, rather a comment about the nature of 'truth'! Your point is entirely correct.

              J.
      • Everything you do with technology including the computer you're using now is supported completely by theories.

        No. Everything I'm doing now is supported completely by the sort of things that theories are made about. The theories are just our best guesses as to why these things work.

        Creationists, and other non-mainstream avenues of thought, often bring up the "only a theory" argument not because they think it improperly weakens the weight of a theory, but because they want to debunk theories being treate
    • Re:"Discovered"? (Score:5, Insightful)

      by Ayaress (662020) on Thursday March 25, 2004 @02:59PM (#8671172) Journal
      I'm pretty sure I've posted this exact reply to the exact parent a dozen times over.

      In science, Theory is the highest level of understanding. Law and observation are, in fact, much lower on the heirarchy.

      Observation is dumb: It's just what you see. "Oh, the sky is blue." "It hurts when I hit myself with this rock." "Look, there's another rat." That's observation.

      Law is also pretty dumb. It's just a set of rules derived from observation. e=mc^2 fits observation, and it has some interesting connotations, but it doesn't say anything about WHY the equation works, and it says even less about HOW matter and energy are interchangeable.

      Theory is an overarching collections of observations, laws derived from observation, and principles deduced from laws.

      Theory explains why laws work, and why observations are as they are.

      To be granted the distinction of 'theory' an idea must:
      1. Explain any and all laws and observations already explained by a previous theory (example: to be valid, Relativity had to encompas Newtonian mechanics);
      2. Explain such in an imperical manner (any forces involved must be identified and observed. This is why there is no theory regarding dark energy and dark matter - they have yet to be identified, observed, or quantified);
      3.a. Explain something not covered in the existing theory (Darwin's theory explained why rats with their tails cut off did not have tailless offspring, as Lamarck's theory said they shoudl);
      OR
      3.b. Explain the existing theory in simpler terms (such as the replacement of phlogiston theory and epicycle theory by their more advanced, but much simpler, successors).

      Now, by calling an observation a Theory, you are, in your misguided attempt to discredit it, in fact exaulting it to a much higher status than it claims to hold already.
      • then shouldn't this be +5 redundant, but still insightful?
      • My students always have a mental block when it comes to teaching the distinction between theory and law. Although I state clearly several times that a "law describes, and a theory explains", many students have it firmly fixed in their minds that the progression of the scientific method is

        Observation --> hypothesis --> theory --> law

        instead of the correct

        Observation --> law --> hypothesis --> theory

        By the middle of the year, when we start talking about Boyle's Law and other gas l
        • That subject-object metaphysics will bite you in the ass every time.

          (By the way, a hint: there is nothing but values.)

          This moment of Quality brought to you by Zen and the Art of Motorcycle Maintenance.

          • I recognize that Quine and others have denied the existence of the subject-object distinction. I also recognize that observer-observed interactions make observations challenging. That said, I don't agree that it's helpful to toss the distinction between observations and inferences out. It is legitimate to ask oneself "Am I observing, or am I hypothesizing?", if only as a way to identify bias. My high-school students will have ample opportunity in college to probe the problems with that question, but unt
            • MoQ (Pirsig) doesn't "deny" subjects and objects, it redefines them as values (Quality) and leaves Quality undefined (it defines everything else.)

              There are always biases. Even if one were to able to completely set aside one's innate drive to interpret the senses, there are biases built into the senses themselves. For example our vision doesn't see infrared, yet important and useful information about the thing being seen (it's heat profile) is found there.

              The difference between observing and hypothesizing
              • I'm intrigued by the discussion; theory of knowledge is one of my interests. Thanks for the tip on Pirsig; I'll have to read him.

                I'm skeptical (ignorantly so, obviously) about redefining reality as Values. I'm fairly committed to the objective existence of both objects and people, while recognizing that there are difficult boundary questions. The problem comes when asking basic questions like "are there other people besides me out there?" If my only answer to that is that I value my sense experience sa
    • Re:"Discovered"? (Score:3, Insightful)

      by b-baggins (610215)
      This isn't even a theory. It's a hypothesis. It requires experimental verification before you can call it a theory.
  • Silly protozoa! (Score:3, Informative)

    by Jerf (17166) on Thursday March 25, 2004 @02:09PM (#8670479) Journal
    Silly protozoa, if only you had known that this one gene would be responsible for super intelligence, you could have mutated billions of years ago and beats humans to the punch!

    What? You say you're missing thousands of other necessary genes and you can't assign responsibility for such large changes on one single change? However will I then write misleading science stories, and even more misleading Slashdot article intros?

    That's not bad commentary, for a protozoa. Pity the article author isn't that smart.
    • Re:Silly protozoa! (Score:4, Interesting)

      by Otter (3800) on Thursday March 25, 2004 @02:27PM (#8670747) Journal
      What? You say you're missing thousands of other necessary genes and you can't assign responsibility for such large changes on one single change?

      It's not obvious to me that your spin is more correct than his, though. Does a single mutation take you from a chimp to a reality show contestant in one jump? Of course not. As you say, there are thousands of other changes involved.

      But what's being proposed here is precisely that a single mutation radically changed primate head morphology and changed the selective constraints on all those other intelligence-enhancing mutations. Is it true? Who knows? But that does seem to be what's being argued.

      • But what's being proposed here is precisely that a single mutation radically changed primate head morphology and changed the selective constraints on all those other intelligence-enhancing mutations. Is it true? Who knows? But that does seem to be what's being argued.

        One can imagine a "critical path" of mutations to get from that first single-cell to where we are today. I definite whether a gene/mutations is on that critical path as "could we have gotten a modern human that we'd consider a modern human w
        • My point is that maybe this is on the critical path, maybe not. But there are thousands (millions?) of other things on that path. Promoting this one mutation above others isn't science, it's grandstanding, either by the journalist, the scientist, or both.

          I dunno -- if the mechanism proposed is correct (and I have no idea whether that's true, or even plausible), it deserves to be considered a big deal, and certainly promoted "above" subsequent mutations that would have had no or negative selective value in

      • Does a single mutation take you from a chimp to a reality show contestant in one jump?

        Arguably, you don't need to have any mutation to go from one to the other. The two are generally freely interchangable.

        Especially on Fox.

  • by bugnuts (94678) on Thursday March 25, 2004 @02:10PM (#8670504) Journal
    Slack-jawed yokels have bigger brains!
  • Once again, this just goes to show that the guys who never tire of talking are the ones who have the least to say.
  • "humans owe their big brains to a single genetic mutation"

    well, that explaines a lot. browse /. at -1 and see what we're doing with those big brains! I want my tree back.

  • The conclusion that this mutation was responsible for the divergence of humans and apes is just plain wrong.

    It is, however, one of the many hundreds of mutations that led to the differentiation of us from primate brethren. In that respect, it's an interesting find.

    It's good to note that the scientific community isn't buying into the media hype though. In response to these claims, Tim White, a respected researcher of human evolution at UC Berkeley said: "We got big brains because little muscles . . .

    • It doesn't really its responsible for the divergence of humans and apes. Obviously, no amount of related rates of growth will make our thumbs opposable by weakening our jaws, and many other differences that are probably more important towards speciation than our brain size (as conceited as we like to be about our intellect).

      It said that this mutation allowed our brains to grow bigger. This is a much less significant suggestion than tagging this muation as the speciation event, and it also makes logical sen
      • I agree completely. My problem is with the original article, which states in the first sentence:

        "Humans owe their big brains and sophisticated culture to a single genetic mutation that weakened our jaw muscles about 2.4 million years ago, a new study suggests."

        I'm just pointing out that this statement draws an incredibly overbroad conclusion. Yes, it's possible that this mutatation left room for larger brains, but the process of developing those brains and our sophisticated culture can absolutely no

        • by Ayaress (662020) on Thursday March 25, 2004 @03:06PM (#8671242) Journal
          Yes, but this comes down to the constant issue with any scientific literiture. There are several versions of every story:

          1. What the scientists actually think (what I was addressing in my post).
          2. What they tell the people they get their grant money from (to make it sound more profitable)
          3. What the damned journalists say when they get ahold of it.

          For example, take last week's discovery of sediments on Mars precipitated from salt water:

          1. What NASA thinks: "Well, there's the proof of the sea we were looking for. Pity it's not there anymore"
          2. What NASA says: "Hey look at this, there used to be water on Mars! And water doesn't just disappear, you know. Imagine what could be done with that much water!"
          3. What the journalists say: "OMG OMG OMG TEHER WERE LIFE ON MARZ OMFG!!!111oneone"
      • Uh dude, apes have opposable thumbs, four of them (hands & feet). I'm pretty sure that is one of the things that distinguishes apes from monkeys.

        I'm curious what would happend to an ape if we altered those two bases to match our genes (no I don't mean slice human and ape genes). It seems like everyone here is operating on the assumption that it took several generations for our ancestors to mutate larger brains. Maybe if you raise an ape with a weak jaw he'll develop a larger brain without further mu
          • With that in mind imagine the mutant ape with a small jaw, suddenly the physical barrier that stops normal ape brain growth is removed and the brain keeps growing all in a single generation. I'm sure we had more brain evolution to do, but it seems possible that there could be enough of an advantage to offset the weaker jaw.

          I wonder if the same thing could be applied to a dolphin, that already has a big brain, which I believe is mostly to process sound, to make their sonar to work.

          So take away a dolphin'

          • Although I think this would be terrible for the dolphin, because it would render it deaf and blind (sonar), I imagine it could probably speak with a normal human voice. Dolphins are incredibly adept at making sounds, I imagine they could learn to mimic humans in the same way that parrots do.
    • Apes (Score:3, Insightful)

      "The conclusion that this mutation was responsible for the divergence of humans and apes is just plain wrong."

      It's just plain wrong in another way. Humans are both apes and primates. The divergence is rather far down the taxonomic tree. We and our proto-human relatives are in sub-family Homininae, as distinct from the other members of Hominidae. The Hylobatidae are also apes.

      • The conclusion that this mutation was responsible for the divergence of humans and apes is just plain wrong.

        It is, however, one of the many hundreds of mutations that led to the differentiation of us from primate brethren. In that respect, it's an interesting find.

      One of the many yes, but perhaps the crucial one, meaning that without it, with different mutations but not just that one, there would have been just another species of apes, no technological civilization (above sticks and stones, the level ap

  • his new teammate Vladimir Malakhov (sp?) (who hasn't even played with J.R. yet) has also been victimized by a puck to the jaw [philly.com]. Thankfully, for VM, the shot had been deflected and rapidly losing speed, so it didnt shatter anything as it did JR, nor did it give him a concussion (the main reason Roenick has missed so many games).

    btw - is that the first time Sports Illustrated has a link on a slashdot story?
  • by Chilltowner (647305) on Thursday March 25, 2004 @02:46PM (#8671014) Homepage Journal
    While it's true that Australopithecus species had much smaller brains than anatomically modern humans and other of the Homo genus, this isn't the gene that separates us from the apes--earlier species made that division.

    It also seems to me that they may be putting the cart before the horse here. Depending on the feeding habits of our Homo genus ancestors, a smaller jaw could be a decidedly large disadvantage, limiting the kinds of foods that could be eaten by a scavenger species such as our ancestors. It seems possible, and even likely, in this case, that our already advanced brains provided a large enough offset against the loss of powerful jaw muscles. This might mean that we were well on our way toward advanced thinking before the loss of muscle mass in the jaw.

    Anatomical structures always pretty tricky, especially when it comes to judging cognitive development and other tangential related adaptations. The kinds of mutations that make us human (smaller jaws, larger heads, versatile voiceboxes) also tend to cause of a lot of potential problems (restricted diet, difficult birth, tendency to choke). Weighing the value of one change over another become enormously difficult.

    Not to knock their work, though--this is pretty amazing stuff and will definitely be another piece of the puzzle for anthropologists to consider. My only concerns are that we not look at this as a) the great divide between us and the other apes or b) the silver bullet that made us the brainy folks we are today.
    • by Ayaress (662020) on Thursday March 25, 2004 @03:14PM (#8671326) Journal
      It seems possible, and even likely, in this case, that our already advanced brains provided a large enough offset against the loss of powerful jaw muscles

      Take a look at most simain brains. The jaw muscles of a chimp, gorrilla, or even an Australopithescene, attach at the very peak of the skull, and are very thick, comprising the bulk of the head.

      There's just not room to expand the brain with ape-like jaw muscles. You're right on one thing, though: Weak jaws are a severe handicap without expanded brains.

      There are three ways the two changes could have come: Brain, then jaw; jaw, then brain; both in parallel.
      The brain can't expand against simian jaw muscles, so the first one's out.
      Weak jaw and small brain are a severe handicap, and the remaining strong-jawed humans would have outcompeted their slackjawed relatives, and the weak-jawed strain would have been bred into extinction.

      However, both simultaneously makes the transition profitable and possible, but you're ignoring something important: Related growth rates.
      Just the act of lowering the point of connection of the jaw muscles (in the case of apes, this is a ridge on the very top of the skull - in the case of humans, it's the top of the temples, just behind the eyebrows) makes the braincase of the skull larger.
      • Two words: Bulging forehead.

        This hypothesis is such a load of just-so story, that I'm amazed anyone is taking it the least bit seriously.
      • by Chilltowner (647305) on Thursday March 25, 2004 @05:35PM (#8673496) Homepage Journal
        Excellent points!

        The problem I have, though, is that the article implies that the weak jaw is the result of a single mutation (or a small cluster of them). This would seem to point toward a very "punctuated" change in the strength of the jaw. The fact that it didn't do us any harm in the long run could indicate one of several things:

        1) the environment we were living in didn't require us to chew the kinds of plants that simians did (and do). Weak jaws were not maladaptive.

        2) it was better to be able to chew on plants that required a more simian jaw and dental arcade, but our brains carried us through. Weak jaw is potentially maladaptive, but less relevant.

        3) weak jaws were maladaptive, but other parts of our morphology (e.g. the attachment point of the muscle, different kinds of teeth) soften the blow long enough for the benefit of a weak jaw, larger potential cranial capacity, to come to the fore.

        I don't pretend to have the answer to any of this, but I think a lot these points support my main idea: the gene is not the silver bullet. There are other anatomical issues that have to resolve themselves before we get to modern humans (narrowed, flattened zygomatic arches, change in placement of key muscle anchors, smaller cheeks, reduced protusion of the lower face) as well as the onset of "culture"--i.e. at what point did habilis/rudofensis start using handaxes and other tools to the point where teeth were far less important to our survival than they might otherwise have been. Was there a "perfect storm"? Did we suddenly have weaker jaws at the right point where we could replace teeth with tools?

        We also have to figure out which of the Australopithicines was our ancestor--the more gracile species or the robust (which have the very large muscles you pointed out, extending up to the crest of the skull). That would impact on the severity of the change between this ancestor and the genus Homo.

        It's really fascinating stuff, and this discovery will probably play an important role in how we imagine the crossover from the Australopithicines. But, like I said, there's a lot more work to do and a lot more that needs explaining. There is no silver bullet, and I think the researchers would agree with that. The media, on the other hand, will probably stick to the hype--they seem to like simple, gene-based explanations these days. Ultimately, though, the question will be resolved by a confluence of ideas from geneticists and the stones-and-bones folks.
  • by E1v!$ (267945)
    This sounds abit like the P4 when it first came out...

    Performance wasn't so great, but the changes made for lots of 'headroom'....

    ehehe
  • It should be easy enough to prove. Just genetically engineer the same mutation into another primate and see what happens.
  • I guess we've made up for that.
  • As one muscle decreased strength, the other increased in size. And for this, the brain rewards us by making a better blender so that we do not need our jaws to eat. Perhaps this is Homer Simpson's dream come true: steak through a straw.... mmmm.... steakkkkk.
  • So now that we know which base pairs in certain muscle fiber genes are responsible for creating larger and more powerful muscles, could this be applied through genetic manipulation to create those atomic supermen we've been missing?
    Granted, genetics is a complicated and young field, but we are becoming quite adept at it. It seems every time there is a discovery about which gene creates what protein there's some scientist two months later growing potatoes or rats with that trait. Can it be long before DARPA
  • They surmise that the mutation might have been allowed by human precurosors going from eating leaves to eating meat, etc. and using tools (since both occurred at about the same time).

    I wonder, however, if it happened the other way 'round.... The mutation may have caused the 'mutants' to change their diet and their methods of obtaining food -- forcing proto-humanity into using tools.

    The rest,as they say, is (pre-)history.

  • For anyone interested in the actual research (as opposed to the New Scientist overview) it is published in this month's Nature. It's available at http://www.nature.com/cgi-taf/DynaPage.taf?file=/n ature/journal/v428/n6981/full/428373a_fs.html ... but i dont have a susciption
  • So, can we put the same mutation into Apes and watch the resulting hilarity?

How many Unix hacks does it take to change a light bulb? Let's see, can you use a shell script for that or does it need a C program?

Working...