Gene Mutation Said Linked to Evolution

Science - AP ^ | 2004-03-24 | JOSEPH B. VERRENGIA

[Agnes Heep]

Why would this have to be caused by a mutation? There was probably enough diversity in jaw sizes to accommodate a shift without any major genetic changes, just as there is in the present human population. Just look at how many different varieties of canis familiaris there are ... all arising from the same set of genes.

[LiteKeeper]

To go from one species to another requires a radical change in information. Since there can not be "self-generated" information in the DNA, the information that makes Homo Sapiens what they are had to have been in the DNA before the "split." If it was there before the "split" why don't the chimps have the exact same body as we have?

[PatrickHenry]

Without the strong bands of muscle constraining the skull, the Penn researchers said the Homo skull changed shape and grew to accommodate a much larger brain, while the Australopithicine skulls did not.

This makes a bit of sense. Observe this chimp skull:

Without the need for all that extra materal up there to hold the massive jaw muscles, a different -- and separate -- mutation for a larger brain case would then be able to survive. It could pass through the birth canal without killing the baby. One mutation, the relatively trivial one for a smaller jaw, makes the other mutation able to survive.

[kkindt]

In the first place there is no proof this is actually a mutation. We have a gene that is similar to that of an animal. But there is a difference. So the difference is chalked up as a mutation??? What kind of thinking is that? Not logical thinking but ideological with the built in assumption that a similar gene must have resulted from a mutation. No actual observation of this happening but because evolution MUST have happened then that's the onlyh explanation there can be for a similar gene existing in one kind of being compared to another.

[tcuoohjohn]

We ALL know that guy...Deacon Cletus Annoyance

[AntiGuv]

To go from one species to another requires a radical change in information.

Yes, that's why the process frequently takes millions of years.

Since there can not be "self-generated" information in the DNA, the information that makes Homo Sapiens what they are had to have been in the DNA before the "split."

One can say that it was.

If it was there before the "split" why don't the chimps have the exact same body as we have?

Because they express different parts of the information than we do. Think of it this way. HTML includes all the information expressed in this thread. It also includes all the information expressed in this thread. The two threads are not the exact same.

[AntiGuv]

See my posts #25 and #26.

[js1138]

"It only would've become fixed if it coincided with mutations that reduced tooth size, jaw size and increased brain size. What are the chances of that?"

I don't know the answer to that, but sometimes one mutation has broad spectrum of effects.

[hc87]

Survival of the adequate? Actually, I see your point. If no other mutations were to ever occur, the primates with the stronger jaws would probably outlast the primates with the weaker jaw, over a number of generations. However, since other mutations do occur, the primates with the weaker jaws are in a position to profit from them, in the genetic long-run.

Another way to think about it is that all sorts of mutations occur and have no effect on Dariwinian fitness of the species until the environment changes and the mutation then confers an evolutionary advantage on its holders. A good example of a mutation which is just there and has yet to confer an evolutionary advantage (or disadvantage) is the ability to roll one's tongue. Some people have it, other don't and it doesn't seem confer a any kind of evolutionary advantage either way. Until an environmental change happens that favors (or disfavors) individuals with that ability, it just continues along in the genome.

By the way, the loosed jaw mutation wouldn't necessarily confer an evolutionary disadvantage on individuals with it in an environment with abundent "soft" food. If there was already a genetic pre-disposition in primates for larger brain growth, the occurrence of the jaw loosening could have been the key that unlocked the door to bigger brains in a relatively short timespan. That, in turn, would have conferred a significant advantage on the proto-humans.

[adam_az]

But nonhuman primates — including our closest animal relative, the chimpanzee — still carry the original big-jaw gene and thanks to stout muscles attached to the tops of their heads, they can bite and grind the toughest foods.

This article explains a whole lot.

[js1138]

One may also posit that since increased intelligence is such an obvious evolutionary advantage...

There are folks who belive that big brains in mammals are a result of sexual selection, which is to say that smarter guys get more chicks. Consider your brain to be equivalent to a rack of antlers. Or in the case of democrats, a flaming red butt.

[CobaltBlue]

"Selective pressure" doesn't cause mutations. Mutations happen all the time, every day. And if the mutation is heritable, then the offspring will inherit it. So the only question is, does any given mutation make it less or more likely that the offspring will survive?

If it is a trait which makes survival easier, then more of the offspring will survive than otherwise.

If it is a trait which makes survival more difficult, then fewer of the offspring will survive than otherwise.

But if it's merely neutral in effect, it won't have any particular effect on the offspring.

[Junior]

Where does the variation in jaw sizes come from? From minor mutations in the genes for jaw size. A gene gets turned off or turned on, a nucleotide base gets replaced, deleted or added in (the latter through such processes as replication errors or viral insertions) and voila! You have a minor variation in jaw size that can hang around in a population for generations before a situation pops up -- for instance, the need for brain space -- that brings this variation to the fore.

[hc87]

Well, if that applies here then how did the jaws evolve that way in the first place? According to what you have said, there should be no selective pressure to develop such a jaw. But if there is selective pressure, then the original contention is justified.

You can't have your cake and eat it too.

Simple. Environments change. A trait which confers an advantage in one environment may have no effect, or may be detrimental in another environment. For example, the human body's ability to efficiently convert calories to fat and store it and then slowly burn it off is a great trait in an environment which has abundant food supplies during the summer and little food during the winter. The same trait will cause obesity and heart disease in an environment with abundant high calorie food all year long.

[Junior]

But there is a difference. So the difference is chalked up as a mutation???

The difference arose because of a change (mutation) in the genes. Mutations are not gross changes. Rather, they can be as simple as a flip-flopped gene, or a gene that's been turned off (such as our Vitamin C synthesizing gene), turned on, added to or deleted.

[onedoug]

I'm one.

I've long been curious whether cosmic rays could mutate even a protein in a gene's structure in ways that might alter the replication of subsequent genes. Hence, evolution.

'Don't see any conflict in this with The Bible.

[Physicist]

Igniting a scientific furor, scientists say they may have found the genetic mutation that first separated the earliest humans from their apelike ancestors.

First? The hominids had been walking upright for a couple million years before this mutation came along. And their jaws had been smaller than chimp jaws for a long time, too, without any great increase in brain size.

I'm not saying that they haven't uncovered a significant step on the road from ape to man, but it looks like just one out of many.

[js1138]

The monolith only turned a thigh bone into a spacestation (while playing the Blue Danube Waltz).

One of two or three times in a move where I have shed tears. Of course I saw it on the big screen, before anyone knew it would be a classic. I think there were ten other people in the theater.

[Junior]

Bigger brains do indicate an increased ability to plan and be more successful in bringing home the bacon, so I can see how sexual selection could lead to larger brains.

[js1138]

I always wanted to meet Clarke and have a chat with him about the implied necessity of having aliens jumpstart humanity. And then punch him in the nose.