Evolution in action: new plant species

[Peter Soderqvist]

TO BILL HOYT

To expand on this a bit...

There are three basic types of selection: stabilizing, directional and disruptive. I'll avoid the differential equations that define them rigorously and define them as follows:

o stabilizing - tending to maintain the status quo of the genome's allele frequencies

o directional - favoring one allele over others and shifting the genome's allele frequencies over time

o disruptive - forcing a divide in the population such that two different alleles become favored over all others.

Peter is describing directional selection, and Dr. Matt is describing disruptive selection. As a somewhat technical aside, in the directional selection case, selection doesn't eliminate alleles. Selection can only reduce alleles as far as the mutation-selection equilibrium value, which is always non-zero. A random force, genetic drift, is responsible for eliminating alleles. Even then, mutation can always reintroduce it from time to time.

Cheers,

"As a somewhat technical aside, in the directional selection case, selection doesn't eliminate alleles."

Soderqvist1: not truth!
Genes for longer legs and its alleles can be found everywhere in a species' gene-pool, the genome's half-life is one generation, because the offspring inherit 50% of his genes from his father, and 50% from his mother, and therefore these "slow running genes" tend to go extinct, because the slow running animals have a lower amount of "fast running genes" and end up as food, meanwhile the fast running animals makes more offspring! A home breeder can select traits, and let animals with these traits make the offspring, and the breeder can also "prevent animals with "bad traits to mate"!

Extended Phenotype: All effects of a gene upon the world. As always, 'effect' of a gene is understood as meaning in comparison with its alleles. The conventional phenotype is a special case in which the effects are regarded as being confined to the individual body in which the gene sits. In practice it is convenient to limit 'extended phenotype' to cases where the effects influence the survival chances of the gene, positively or negatively.
http://www.world-of-dawkins.com/Dawkins/Work/Books/extend.htm

The Blind Watchmaker
The thing that defines a species is that all members have the same addressing system for their DNA. DNA is ROM. It can be read millions of times over, but only written to once - when it is first assembled the birth of the cell in which it resides. ...Instead, what we find is that natural selection exerts a braking effect on evolution. ... This isn't really paradoxical. When we think about it carefully, we see that it couldn't be otherwise. Evolution by natural selection could not be faster than the mutation rate, for mutation is, ultimately, the only way in which new variation enters the species. All that natural selection can do is accept certain new variations, and reject others. The mutation rate is bound to place an upper limit on the rate at which evolution can proceed. As a matter of fact, most of natural selection is concerned with preventing evolutionary change rather than with driving it. This doesn't mean, I hasten to insist, that natural selection is a purely destructive process. It can construct too, in ways that Chapter 7 will explain.
http://www.world-of-dawkins.com/Dawkins/Work/Books/blind.htm

 

[Guest]

TO BILL HOYT


Soderqvist1: not truth!
Genes for longer legs and its alleles can be found everywhere in a species' gene-pool, the genome's half-life is one generation, because the offspring inherit 50% of his genes from his father, and 50% from his mother, and therefore these "slow running genes" tend to go extinct, because the slow running animals have a lower amount of "fast running genes" and end up as food, meanwhile the fast running animals makes more offspring! A home breeder can select traits, and let animals with these traits make the offspring, and the breeder can also "prevent animals with "bad traits to mate"!

Extended Phenotype: All effects of a gene upon the world. As always, 'effect' of a gene is understood as meaning in comparison with its alleles. The conventional phenotype is a special case in which the effects are regarded as being confined to the individual body in which the gene sits. In practice it is convenient to limit 'extended phenotype' to cases where the effects influence the survival chances of the gene, positively or negatively.
http://www.world-of-dawkins.com/Dawkins/Work/Books/extend.htm

The Blind Watchmaker
The thing that defines a species is that all members have the same addressing system for their DNA. DNA is ROM. It can be read millions of times over, but only written to once - when it is first assembled the birth of the cell in which it resides. ...Instead, what we find is that natural selection exerts a braking effect on evolution. ... This isn't really paradoxical. When we think about it carefully, we see that it couldn't be otherwise. Evolution by natural selection could not be faster than the mutation rate, for mutation is, ultimately, the only way in which new variation enters the species. All that natural selection can do is accept certain new variations, and reject others. The mutation rate is bound to place an upper limit on the rate at which evolution can proceed. As a matter of fact, most of natural selection is concerned with preventing evolutionary change rather than with driving it. This doesn't mean, I hasten to insist, that natural selection is a purely destructive process. It can construct too, in ways that Chapter 7 will explain.
http://www.world-of-dawkins.com/Dawkins/Work/Books/blind.htm

Soderquist,

Your explanation is what is usually presented at a non-theoretical level. The underlying theory of population genetics is where you need to go to get this information.

The differential equation describing directional selection shows a rate of decline that itself declines as the alleles are pulled out of the genome. That is, as fewer of the less fit alleles are left, the rate of selection drops. On the other side of the equation, mutation is replacing those alleles at a certain rate. The unfit alleles keep getting inserted back into the population. The net effect is that the two forces reach the mutation-selection equilibrium.

In small populations, a third force often takes over. This force is random drift, sometimes called random genetic drift or genetic drift. These are fluctuations in allele frequencies unrelated to fitness. Only this drift can take an allele frequency to 0 (or, conversely, to 1). Over time, however, mutation will again replace it.

Does this make sense? If you'd like to see the equations for a deeper understanding of this, I will accomodate you.

Cheers,

 

[Peter Soderqvist]

TO BILLY HOYT

You wrote on page 3, 02-24-2003 11:56 AM: Your explanation is what is usually presented at a non-theoretical level. The underlying theory of population genetics is where you need to go to get this information. The differential equation describing directional selection shows a rate of decline that itself declines as the alleles are pulled out of the genome. That is, as fewer of the less fit alleles are left, the rate of selection drops. On the other side of the equation, mutation is replacing those alleles at a certain rate. The unfit alleles keep getting inserted back into the population. The net effect is that the two forces reach the mutation-selection equilibrium.

Soderqvist1: It appears to me as back to the starting point again, hence equilibrium!
But if that is the case, a Pekinese should be back again as wolf too! But Dawkins has not said anything about that, instead he has said in the Blind Watchmaker chapter 9, Puncturing Punctuationism, something like that; home breeders reach an end when all the old variation in the species is used, it needs new mutation in order to go further! I will reread Dawkins about it when I get home!

In small populations, a third force often takes over. This force is random drift, sometimes called random genetic drift or genetic drift. These are fluctuations in allele frequencies unrelated to fitness. Only this drift can take an allele frequency to 0 (or, conversely, to 1). Over time, however, mutation will again replace it.

Soderqvist1: Genetic drift is connected with allopatric speciation!

Does this make sense? If you'd like to see the equations for a deeper understanding of this, I will accommodate you.

Soderqvist1: It doesn't make sense for the moment, but probably afterwards when we have sorted out this dispute! Btw, are you a geneticist by profession?

Best regards

 

[hammegk]

I'll bet you read the only post in which I gave a bit of bio, didn't you?

No I haven't, but would like to. Would someone provide the location of that post?

Thanks.

 

[Guest]

It appears to me as back to the starting point again, hence equilibrium!
But if that is the case, a Pekinese should be back again as wolf too! But Dawkins has not said anything about that, instead he has said in the Blind Watchmaker chapter 9, Puncturing Punctuationism, something like that; home breeders reach an end when all the old variation in the species is used, it needs new mutation in order to go further! I will reread Dawkins about it when I get home!

The phrase you're searching for is "punctuated equilibrium." But no, a Pekinese "shouldn't" turn back into a wolf again. A Pekinese, allowed to mate freely with a large number of other breeds, would become more wolf-like over time, however. Dogs and wolves are the same species (Canis lupus familiaris = dog; Canis lupus = wolf)

Genetic drift is connected with allopatric speciation!

Yes it is. It is a weak force, however, that only serves to eliminate or fix alleles one the frequencies are at the margins.

It doesn't make sense for the moment, but probably afterwards when we have sorted out this dispute!

The equation for directional selection is:

dq_s = -spq²/(1-sq²)

As q -> 0, (1-sq²) -> 1 and this equation simplifies to:

dq_s = -spq²

The rate of removal of q declines as q declines. Let's set the selection coefficient (s) to 1. Then the rate at which q is removed from the population rests solely on p and q. Let's simplify further and say p and q are the only two alleles at this locus. Then p = 1 - q, and the equation becomes:

dq_s = q³ - q²

So, as q falls, the removal rate falls. It never reaches 0 for effectively large population sizes.

Btw, are you a geneticist by profession?

Sorry, Peter, I generally choose not to answer such questions. Nothing personal, it is just that part of my mission is to help people here learn critical thinking. Whatever "white coat" I may or may not wear is immaterial to the truth-value of my assertions. I prefer to provide evidence rather than to even broach upon "I'm trained in so-and-so, so I know!"

 

[Guest]

No I haven't, but would like to. Would someone provide the location of that post?

Thanks.

It looks like that post was lost in the database glitch this past summer. That's fine with me. It was way too long and done in sheer frustration with someone who had accused me of "posing." As I said to Peter, I prefer not to enter into anything broaching "argument from authority."

It will have to remain a mystery.

Cheers,

 

[hammegk]

I prefer not to enter into anything broaching "argument from authority."

It will have to remain a mystery.

Cheers,

No problem, we will just continue to speculate whether your doctorate is used in furthering the world of academe, or if you are more directly involved in basic research.

Did you notice my earlier thought on potential fruits of viral research?

Cheers back at ya.....

 

[Guest]

Did you notice my earlier thought on potential fruits of viral research?

Cheers back at ya.....

Yes I did. I ignored it. Since you seem about to insist, however:

I mentioned I'm onboard evolution from an Idealist perspective, which can and does provide some logic for what the record is interpreted to depict. I.E. LIFE strives towards organisms that support higher & higher consciousness (human the best we know of at the moment). No problem with the first male/female pair for each new critter which has apparently happened here a very large number of times -- other than time, randomness, and luck. And yes dropsila may well evolve -- but, a fly is a fly is a fly.

Life doesn't strive toward consciousness. It strives to continue to exist and to reproduce. Period. Your "fly is a fly" bit is a restatement of the "kinds" position taken by creationists. The fact that we have yet to produce "in the laboratory" and have yet to directly observe "in the field" the transition from one genus to another doesn't argue against the fact that this has happened over and over again in geologic and evolutionary time. We have that record available to guide us. We have created and have observed the creation of new species. Over two dozen times already, if I recall correctly. Amazingly, this has happened in less than 100 years. Contrast that with geologic and evolutionary time scales.

For us my main thought for the next "oops" will come from genetic engineering; damn, who thought we could come up with a virus that kills a human in minutes, lives forever in all conditions, and infects yet is benign in every other lifeform on the planet.

Are you really going to trot out this tired confounding of science with technology? The uses to which we put knowledge have no impact on the knowledge itself. This is a deflection (again) from the central subject here.

Cheers,

 

[hammegk]

Life doesn't strive toward consciousness. It strives to continue to exist and to reproduce. Period.

Yes, your certainty for those assertions is at 100%; my certainty is a bit less, that's all.

This is a deflection (again) from the central subject here.
Cheers,

As you prefer to define the central subject, that's true.

Regards, and Thank You for your kind response.

 

[Guest]

Yes, your certainty for those assertions is at 100%; my certainty is a bit less, that's all.

We've been through this before. Please desist from this straw man, sir. We have discussed the concept of provisional truth and the concept of a continuum of "certainty."

Cheers,

 

[hammegk]

We have discussed the concept of provisional truth and the concept of a continuum of "certainty."

Cheers,

True, but it's also been noted that the axioms of a logical system must lie unproved by that system. (Or words to that basic thought).

I suggest the axiom level of each of our world-views is the true basis in dispute.

Cheers also.

 

[Guest]

True, but it's also been noted that the axioms of a logical system must lie unproved by that system. (Or words to that basic thought).

I suggest the axiom level of each of our world-views is the true basis in dispute.

Cheers also.

No, that is not at the level of this discussion. The proposition you're discussing is that no system can exist without axioms. We've previously discussed the five axioms of science in other threads. Here we're discussing nothing about axioms. We're discussing the existence of evidence for evolution. We are also trying to discuss several of your assertions, including:

o there is no such evidence
o that evolution is teleological
o that evolutionary theory is speculative

etc., etc.

Any chance your deflections will stop and we have an opportunity to resolve these drive-bys?

Cheers,

 

[rwald]

If you think that evolution "strives towards consciousness," prove it. Which lines of evidence can we look at which show that consciousness is a goal which evolution has had since the beginning?

 

[FutileJester]

Any chance your deflections will stop and we have an opportunity to resolve these drive-bys?

Bears repeating. If you make an assertion, have the guts to back it up.

 

[hammegk]

If you think that evolution "strives towards consciousness," prove it.

No can do. It is only my comment on the fact we are having this discussion, and addresses only the "why".

Some materialists(& scientists?) here are adamant that teleological musing is meaningless. With them on that point, I also agree.

Please also recall my earlier comment that noted the evolutionary "how" that science theorizes over is not the point I'm discussing. I have no "proof" that the nuts & bolts of current materialistic/atheistic evolution theory is incorrect.

If ya'll think a new weed species is added "proof" for you, so be it.

 

[rwald]

No can do. It is only my comment on the fact we are having this discussion, and addresses only the "why".

Some materialists(& scientists?) here are adamant that teleological musing is meaningless. With them on that point, I also agree.

Please also recall my earlier comment that noted the evolutionary "how" that science theorizes over is not the point I'm discussing. I have no "proof" that the nuts & bolts of current materialistic/atheistic evolution theory is incorrect.

If ya'll think a new weed species is added "proof" for you, so be it.

So, you fully admit that the mechanisms of evolution are true? Your only complaint is that evolution isn't teleological enough for you?

Well, that's your problem. None of the evidence points towards teleology, and therefore scientists don't enter it into their theories. If you want to philosophize about a "greater purpose," have fun, but until you can find proof for your beliefs, know that they bear no resemblance to "science."

 

[Dymanic]

Life doesn't strive toward consciousness. It strives to continue to exist and to reproduce

Isn't it going a bit too far to say even that?
Organisms certainly strive to live and breed; explanations for this can be sought in their genetic makeup and the way it plays out on their cellular chemistry as they interact with their environment.

But are we to suppose that genes really care whether or not their hosts prosper, or whether they (the genes) become widespread in a population of organisms?


And:
Isn't there still considerable debate over the importance of drift?
Somebody...I wish I could remember...was it Kimura?... who postulated that random drift was the most significant factor in evolutionary change?

 

[hammegk]

So, you fully admit that the mechanisms of evolution are true?

Actually I said,

I have no "proof" that the nuts & bolts of current materialistic/atheistic evolution theory is incorrect.

If you take that as an admission "the mechanisms of evolution are true" so be it.

Will science ever erase the god-of-the-gaps? Not in my opinion. I especially like the definition of materialism that subsumes God if he interacts with the "material world".

Misquoting my betters(is that plagarism?):
Once you discuss a concept of "god" as a possible existent, that "god" no longer exists.

 

[rwald]

The way science works is that the best theory which explains all the evidence is assumed to be true, at least until a better theory comes along. If you agree that the theory of evolution explains the mechanisms of species diversity during the course of Earth's history better than any competing theory, than by definition you agree with evolution.

In science, there is no "absolute proof." There is only a preponderance of evidence.

 

[hammegk]

...there is no "absolute proof." There is only a preponderance of evidence.

Er, yes, that's what a number of us attempt to get materialists/atheists to agree to.

Their agreement makes them agnostics.