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.

"Discovered"?

[afabbro]

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

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.

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.