Gene Mutation Said Linked to Evolution

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

[Junior]

Did you catch the message to humanity at the end of the 2010 movie? Straight out of the Book of Genesis. Clark always liked to tie religious themes into his works. Childhood's End (not one of his better books, in my opinion) had aliens that were dead ringers for the classic "devil" (horns, pointy tail, the works).

[RightWingAtheist]

Clarke has made it very clear that he does not believe in this "imperialist-colonialist" message some have read into the book.

[RightWingAtheist]

Have you seen this?:

[Agnes Heep]

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.

I suspect you're quite right. If we had to rely on spot mutations, there would probably be no life on earth, because there's no guarantee that a mutation will crop up in exactly the right place exactly when you need it.

This is also why sexual reproduction is so important. If there were no need for genetic diversity to facilitate adaptation, there would be no reason why we couldn't all be carbon copies of one another.

[js1138]

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.

I first saw this theory applied to porpoises. It doesn't take a huge brain to live in the ocean and catch fish. Other fish manage this with peabrains.

But porpoises engage in elaborate mating games, and it ain't necessarily the biggest and strongest that leave the most offspring.

[Junior]

Yes, except I saw it as Five Million Years to Earth.

[explodingspleen]

Some apes were born with a defective jaw-strength gene that nonetheless had no lesser probability of reproduction but that had a much enhanced probability of developing larger brains.

That is precisely my objection. If a weaker jaw provides no less probability of reproduction then a strong jaw should never have evolved in the first place.

The larger brains concomitant to the weaker jaw over time carried both traits into prevalence. It's not that complicated.

Actually, it is quite complicated. First of all, having a larger brain doesn't do you a squat of good unless you are equipped to use it. Do you think that we can make a monkey smarter by surgically incorporating additional brain matter? Of course not; it would not do any more good for the monkey than it would do you to attach an extra arm. There are all kinds of complicated neural pathways and receptors that must be in place or else it's just junk tissue. Further, as I tender you would agree, the increase in intelligence cannot be slight because the advantage it confers on the creature must surpass the detriment it suffers from the weakened jaw which would impair its capacity for self defence and possibly restrict its diet. So there is no gradual evolution--it has to happen all at once. I think that does indeed make it a quite complicated arrangement.

[Junior]

If a weaker jaw provides no less probability of reproduction then a strong jaw should never have evolved in the first place.

Unless the stronger jaw evolved in an environment wherein the food available was tougher and required such. The weaker jaw only appeared after the food supply had changed to softer foods.

[js1138]

Clarke has made it very clear that he does not believe in this "imperialist-colonialist" message some have read into the book.

I didn't imply anything about imperialism. Clarke's aliens just step in with their butterfly effect, doing the tinest tweaks to insure that intellignce has a chance. In the book 2001, they save a dying race by giving them the idea of weapons. In 2010, they give Europa a sun. (which come to think of it, isn't a tiny tweak.)

I just resent the implication that evolution doesn't work.

[Junior]

First of all, having a larger brain doesn't do you a squat of good unless you are equipped to use it.

The extra brain matter didn't show up all at once. The species had generations to evolve intelligence, with each generation being a skosh more clever than the last, but not orders of magnitude so.

[js1138]

Childhood's End is another book where mama alien helps us along. the implication is that the horned aliens had visited earlier and left us with a visual meme.

[Agnes Heep]

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.

Back in the days when I used to care about these things, I would refer to this as "social selection." Consider it this way: if it's just "survival of the fittest," you're going to have weeded out of the population individuals who are either too young to pass on their traits, or individuals so old that they've already passed them on. Neither one facilitates adaptation. The younger individual who gets selected out may have traits that are really useful; the older one may have passed on traits that are positively harmful. Add to that the further complication that some individuals may have a combination of traits that are both useful and harmful. Social selection takes all the factors into account because an individual's rank in the mating order will be a function of the totality of all his attributes.

[explodingspleen]

"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?

I don't think I have ever suggested that selective pressure causes mutations. What it does do, however, is determine whether a mutation is propagated to an entire population or if it is isolated and eventually eliminated. With large changes that represent the accumulation of many different mutations, it makes much more sense to ascribe the development of the characteristic to natural selection than to mutation.

[DannyTN]

Well except for the following holes in your selection process religion:

• That many mutations in a short amount of time (even the evolutionary time frame is short for that many successful mutations)
• Mutations that increase information instead of lose it.
• Sexual reproduction which tends to stabelize the gene pool and reduce genetic drift.

[explodingspleen]

The extra brain matter didn't show up all at once. The species had generations to evolve intelligence, with each generation being a skosh more clever than the last, but not orders of magnitude so.

I quoth myself:
"the increase in intelligence cannot be slight because the advantage it confers on the creature must surpass the detriment it suffers from the weakened jaw which would impair its capacity for self defence and possibly restrict its diet. So there is no gradual evolution--it has to happen all at once."

[js1138]

I suppose, if you are uncomfortable with the phrase sexual selection. Most mate selection is done by the womenfolk.

[CobaltBlue]

I think it was the women who wised up first, and quit picking "bad" guys who wouldn't stick around and help raise the kids.;^)

[js1138]

Information is provided by selection. That is what selection means. There is no such thing as information in the absense of context and selection is the context.

[Junior]

1) The mutation may have been kicking around in the population for quite some time before selection pressures (bigger brains) brought it to the fore. We've been over this on this thread.

2) "Information" is present everywhere. If you mean an increase in the size of the genome, that was not required for this particular mutation/selection cycle, but it does happen in other instances. Replication errors, viral insertions, etc., increase the size of the genome and allow for increased genetic experimentation. Of course, you already knew this because this has been brought up on numerous crevo threads where you have been a participant. That you refuse to learn anything from these threads reflects more upon you than upon the state of the science.

3) Not necessarily. Take, for instance, the peacock. Sexual selection has driven male peacocks a long way away from their plainer ancestors. In the case of human beings, sexual selection has led to everything from larger brains, to hairlessness to blond hair and blue eyes.

[Doctor Stochastic]

Didn't the Monolith merely show apes how to use a blunt instrument?