Gene MYH16: A Tasty New Jawbreaker

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."

Comments

Actually, no.

[Romothecus]

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.

Re:Actually, no.

[woohoodonuts]

So I guess now we can call all those dopey muscle bound guys 'apes' with a clear conscience

I realize this comment is in jest--and that my response is way offtopic-- but the world is changing, damnit... I played Division IA college football, and yes--I'm posting on Slashdot... The Geek/Tech/Nerd stigma/prejudice/expectation is deeply ingrained as someone single/pimply/bug-eyed... but someone is dopey just because they workout? wtf?
Mod this Offtopic, but shouldn't the intelligent crowd be the first ones to try and change this persona... try and accept the fact that technology now appeals to more than just typical Geeks and not everyone who posts on this site is male/single/pimply?

On that note, were you aware that Harvard is the nations largest Div I athletics program... Looks like some of those geeky kids up in Boston do a little bit more than study.

And here's this just for the heck of it.

Bored at the Big H? Hows this for a few things to try?

Re:Actually, no.

[Anonymous Coward]

On that note, were you aware that Harvard is the nations largest Div I athletics program ... Looks like some of those geeky kids up in Boston do a little bit more than study.

You played D1 football? Except for their hockey team (which is genuinely really good), I assure you that you could stuff any of their jocks into a locker.

Re:Actually, no.

[WyerByter]

A little lesson in sentence construction for you. "All those dopey muscle bound guys" does not necessarily refer to all muscle bound guys. Only the ones that are dopey.

Let me ask. Are you a little insecure?

Re:Actually, no.

[AS400 Hacker]

Obviously you must have a massive jaw so I'll repeat the main points to you v e r y s l o w l y. .... 1) A single mutation allowed for a smaller jaw, which left room for brain growth. .... 2) Brain good.

Re:Actually, no.

[Anonymous Coward]

This is automatic flamebait but it is fair to question: what exactly makes you think that just because you are posting here in Slashdot it automatically means you are intelligent?

Re:Actually, no.

[Romothecus]

Again, NO. Read a more informative version of the article, like the one at the NY Times. Free registration required for more accurate reporting. :)

"Discovered"?

[afabbro]

"Discussed a new theory" is more accurate...

Re:"Discovered"?

[bugnuts]

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.

Re:"Discovered"?

[TwistedKestrel]

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.

Re:"Discovered"?

[0x0d0a]

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"?

[Ayaress]

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.

Re:"Discovered"?

[Smidge204]

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 closer to reality than a belief, if only in a practical sense.

Moreover, theories are seldom touted as absolute facts, and most credible scientists will admit their theory wrong/flawed when given sufficient evidence.
=Smidge=

Re:"Discovered"?

[Anonymous Coward]

Hypothesis -> Theory -> Law

To which of these steps does gravity belong?

Everyone should turn off NPR for a few minutes periodically and review basic science and mathematics.

Re:"Discovered"?

[b-baggins]

This isn't even a theory. It's a hypothesis. It requires experimental verification before you can call it a theory.

Re:"Discovered"?

[RevAaron]

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"?

[bugnuts]

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 know nothing about probability. He could call it a yellow elephant with handlebars, but that doesn't affect the probability of it being true or not. But he would want you to believe that.

It is a theory, rightly, but he does not call it a theory rightly. He calls it a theory as if that somehow makes it less likely to be true. They're all theories and all scientists know this, but he was simply using misleading rhetoric and calling it a theory wrongly.

Re:"Discovered"?

[0x0d0a]

Hypothesis -> Theory -> Law

No. Hypothesis does go to theory, but a law is a very basic observation that always happens as far as we've seen. A theory is an "explanation". See here for details.

No scientist would say that a law is written in stone, in any event. You can find something that breaks a law -- perhaps on Mars, gravity operates differently. Doesn't seem real likely, but nothing preventing it from happening.

Re:"Discovered"?

[aug24]

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 back to science vs religion, the biggest weakness with claiming 'this is the word of God' is when it become inconvenient or clearly wrong. Consider Galileo - 'nough said!

Of course, allowing re-interpretation doesn't help whene there are believers involved. For example, right at the start, Moses was told "Thou shalt not kill". Immediately after that, he was told to go to land of Canaan and kill everyone there, thus enabling every religious leader since then from Mohammed to David Koresh to interpret "Thou shalt not kill" in his own way, as its most obvious interpretation clearly wasn't God's intent - or the Canaanites would still be around!

Justin.

Re:"Discovered"?

[Jagasian]

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, you get a different math with different semantics and possibly the ability to prove different things.

For example, truth in some forms of math means "can be proven". Hence things can be proven to be true in said types of math.

So sorry to burst your overly simplistic view of "mathematics", but there is such a thing as true proof.

Don't be surprised that you were taught mathematics in a heavily biased way that most likely only presented some form of Platonic formal mathematics, which proves the existence of mathematics objects that are presupposed to exist in an ideal realm. Don't tell me that you took the rigor of the math you were taught based on trust or faith?

Uh oh, am I pointing out that the entire foundation of your science AND your math is religious in nature?

You do know that there is another popular name for the Platonic ideal realm... Christians call it "heaven". Everything is perfect there.

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 won't even begin to touch on the fact that the axioms of the math you studied are not based on assumptions about the physical world, but I guess if you pervert the Platonic ideal an extreme you could end up with a mathematics whose truth depends on the existence of things in the immediate physical world instead of a Platonic deal realm.

Re:"Discovered"?

[aug24]

/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 tried to claim that to me was a philosophy student... what are you? I'm betting on a Christian</thinks>

For example, even logical standards such as "a==b && b==c => a==c" actually rely on underlying axioms, it's just that very few people realise that we are using some pre-existing part of the mind to make that leap, rather than pure mathematical logic. I would tell you the name of the ancient greek who realised that, if I could just remember it.

With regard to the stuff about 'heaven' and 'not in the physical world', I follow the school of the computational theory of mind which suggests that geometry, integer maths etc is all a part of the physical world we inhabit. In other words, the mind of any animal evolved in this universe will find 1+1=2, rather than that relationship being an arbitrary choice of any kind.

Finally: Uh oh, am I pointing out that the entire foundation of your science AND your math is religious in nature?

Sure it is. Cos maths hasn't been tested (proved!) at all, unlike God. Ha ha, right!

J.

Re:"Discovered"?

[joebok]

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 Euclidean are just as consistent and logical as those with different ones. They can even be useful:

If, given a line and a point not on that line, you have exactly one line through that point which is parallel to the first, you are dealing with a Euclidean plain. Architects and Engineers love this one. Alternately, if there is more than one line through that point parallel to the first, then we are in a hyperbolic space. Physicists and Astronomers tend to like this one, but whether the universe is Euclidean or hyperbolic it does not in any way invalidate these geometric notions. In fact, if you take the axiom where there are NO parallel lines you are in a "spherical" geometry which is really handy for navigation.

Re:"Discovered"?

[aug24]

Forgive me, it was not meant as a literal truth, rather a comment about the nature of 'truth'! Your point is entirely correct.

J.

Re:"Discovered"?

[Planesdragon]

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 treated as Gospel truth.

We probably evolved from an apelike ancestor through natural selection. The universe looks like it arose from a Big Bang fourteen billion years ago.

Science is not religion, and it doesn't give definite answers--because every claim it makes is eternally subject to review and refutation, and many of the theories that contradict someone's religious beliefs are untestable.

Re:"Discovered"?

[Jagasian]

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 axiomatic mathematics is not a good thing if you want train sophisticated mathematicians.

Re:"Discovered"?

[aug24]

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.

Re:"Discovered"?

[voodoo1man]

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 or the geometry of the universe (for the curious: yes, it is curved). It's even harder to believe that someone with a degree in math would use appeal to authority (his own authority no less!) to debate mathematical points. The poster to whom you are replying makes some valid (and quite interesting) points; you are just making an ass out of yourself.

Re:"Discovered"?

[aug24]

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.

Silly protozoa!

[Jerf]

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!

[Otter]

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.

Re:Silly protozoa!

[Jerf]

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 without it?"

There's obviously some fuzziness inherited from the definition of "modern human that we'd consider a modern human", but for one that's clearly not on this critical path, one can see that we didn't "need" green eyes vs. blue eyes vs. brown eyes. On the other hand, it is plausible we needed this jaw loosening.

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. (Establishing whether this is on the path or not is science; it's the emphasis and the spin, not the work, I object to.)

(And to forstall another object, note I'm defining "critical path" explicitly as the path to humanity; there are other paths to other hypothetical intelligent beings, but as humans, we pretty much only care about how we got to where we are. At least for now.)

Re:Silly protozoa!

[drinkypoo]

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.

Re:Silly protozoa!

[Otter]

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 a smaller skull. At least to my mind, it's a much more fascinating issue than some new point mutation in a GABA receptor 5000 years ago.

Good news for Louisiana

[bugnuts]

Slack-jawed yokels have bigger brains!

All those jaw muscles...

[Mr. Darl McBride]

Once again, this just goes to show that the guys who never tire of talking are the ones who have the least to say.

big brains?

[whathappenedtomonday]

"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.

Re:big brains?

[azbot]

and Gods chances of existing are over 50% what does this all mean?

Don't buy into the hype

[spin2cool]

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 . . . didn't hold the cranial bones tightly together? I may stop chewing tonite!"

An appropriate quip, I think.

Re:Don't buy into the hype

[Ayaress]

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 sense. A gorrila has a very large head, but it's mostly jaw muscle. The ridge on the top of the skull is the attachment point for the muscles, and shows just how much of their head is muscle. Humans, on the other hand, have their jaw muscles attached lower down their head, at the top of the temples, and are much thinner. Despite having smaller heads, there's much more room for the brain case to expand from subsequent (or likely simultaneous) mutations.

2.4 million years is also more in line with the progress from man-like-ape to ape-like-man than with the original divergence, since that divergence probably lies furthur back in history.

Re:Don't buy into the hype

[spin2cool]

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 not eb attributed solely to this mutation, as the article suggests.

Re:Don't buy into the hype

[Ayaress]

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"

Re:Don't buy into the hype

[spin2cool]

Heh. I'm not arguing with that. Damn media...

Re:Don't buy into the hype

[Descartes]

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 mutation.

This reminds me of something I saw on the discovery channel about dogs. The scientists couldn't figure out why dogs have so many traits that seperate them from wolves (e.g. mottled fur, droopy ears). By breeding wild foxes based solely on their tameness they found multiple dog traits appeared in a single generation. It turns out that the traits were related to adrenaline production not unique genetic markers.

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.

Re:Don't buy into the hype

[Urkki]

• 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 apes have been for millions of years, only humans being able to advance beyond that).

It could have been a chain reaction, something like, change in jaw muscles gave more room to the brain, and at the same time gave evolutionary advantage to increased intelligence (compensating for weaker jaws). Without it, human intelligence might not have appeared at all, no matter what other mutations would have happened. With some other mutations in addition to that one, there would be different "humans" than us, but without that one mutation, there might be nobody.

Sure, the conclusion may be wrong because, well, that's not how it happened, but not because it's somehow not possible for single mutation to be critical. So as far as I can see, it can easily be completely true, too.

Re:Don't buy into the hype

[Urkki]

• 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's sonar (make it almost deaf) from birth, then give it reason to be smart, and stimulate it's intelligence to human direction. Could it learn to talk, for example through computer with dolphin "speech" recognition? Ie it would be taught to communicate with human language, reading text from screen (or with "speech" synthesis) and entering it by "speaking" (dolphin sounds, but human language).

(And then the porn industry learns about this, and the next thing you know, there are real live hot dolphin sex chats in the internet, with live image feed... ;-)

Re:Don't buy into the hype

[Descartes]

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.

not just roenick....

[jeffy124]

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. 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?

Re:not just roenick....

[Anonymous Coward]

So?

Can you feel the tension?

[azbot]

Well looks like you chalk one more up for evolution... And now God's chances of existing are more than 50%. I wonder which is going to win...

Uncertain cause and effect

[Chilltowner]

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.

Re:Uncertain cause and effect

[Ayaress]

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.

Re:Uncertain cause and effect

[b-baggins]

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.

Re:Uncertain cause and effect

[Chilltowner]

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.

p4?

[E1v!$]

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

Apes

[AllenChristopher]

"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.

Prove it

[jmpoast]

It should be easy enough to prove. Just genetically engineer the same mutation into another primate and see what happens.

weakened jaw muscles?

[BallPeenHammer]

I guess we've made up for that.

A DOZEN TIMES?

[way2trivial]

then shouldn't this be +5 redundant, but still insightful?

One muscle over another

[kyoko21]

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.

Application of this new knowledge?

[Jtheletter]

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 starts mucking about with superstrong mammals?
Imagine a trained attack dog with the strength of a horse. (shudder)

I for one do not welcome our new tiny-brained, hypermuscular overlords.

Re:Application of this new knowledge?

[Anonymous Coward]

I for one do not welcome our new tiny-brained, hypermuscular overlords.

Yeah, it'd be just like high school all over again.

Which came first....

[Stephen Samuel]

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.

Actual Nature Article

[mike3411]

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

"Theory" is a hard concept to teach

[cagle_.25]

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 laws being explained by the Kinetic Theory, some students start to get straightened out.

I'm not sure why this is so difficult for them, but my hypothesis is that it has something to do with their underlying thought structure. The reason (I believe) that students believe that theory comes before law is that they themselves have trouble distinguishing what they SEE with their BELIEFS about what they see. Therefore, they see no need to distinguish laws from theories. My $.02

Re:"Theory" is a hard concept to teach

[dvd_tude]

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.

Re:"Theory" is a hard concept to teach

[cagle_.25]

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 until they learn to actually ASK it, they aren't anywhere.

Regards,
Jeff Cagle

Re:"Theory" is a hard concept to teach

[dvd_tude]

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 is the overt attempt to apply a value-set to the phenomenon being seen. But that's the only difference.

Bias is everywhere... the trick to taming it is to allow dynamic things to challenge it.

Re:"Theory" is a hard concept to teach

[cagle_.25]

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 saying "yes", then I come dangerously close to denying other people existence independent of my values. That seems -- arrogant. And foolish, since when I die, I would not expect everyone to stop existing! But perhaps I don't understand the theory.

In a similar vein, if one thinks of people as only one's perception of them, without granting them an indepedent, objective existence outside oneself, then the tendency is to treat people behavioristically.

But again, I'm thinking out loud without having read Pirsig. Still and all, my suspicion is that he trades one set of problems for another.

Regards,
Jeff Cagle

Let's make smart apes!

[hoggoth]

So, can we put the same mutation into Apes and watch the resulting hilarity?