Mr Stillwater wrote:I don't think you have quite grasped that the driving force of natural selection is that the species is always looking for a 'best fit' to the conditions that are currently present, not anticipating events that will occur in geological time.
I haven't suggested that any "anticipation" is involved, only that a particular mutation might generate a "tendency" for change from one generation to the next. In other words, that the focus of a mutation might not be on a specific morphological trait, but rather on the genetic replication event which affects that gene which results in that morphological trait. Natural selection would still work against the results.
Hi Brandon,
You're restating the standard theory. I understand the standard theory and I agree with its basic tenets, but I think there may be more to it.
When Darwin proposed Evolution by means of natural selection, he described a pretty fundamental process in which variation fed the force of selection. But Darwin didn't know about the types of variation which could occur or why. He also didn't know about Genetics, though his theory preducted that such a mechanism should be there (prediction of this type is a hallmark of good science theory).
Unlike Darwin, today we know about Genetic Drift and Gene flow as additional factors in variation. I'm looking for another factor in genetic variation which might give selection more to work with.
When you recite standard theory in answer to my question, it seems to imply that you think standard theory answers all questions, and yet, there are still things we don't understand about evolution. We don't know what causes Punctuated Equilibria for example. We know that there seem to be patches of accelerated change within certain lines, and we know that there are other groups which remain relatively unchaged for Eons (Sharks, Horseshoe Crabs, Nautilus, Cockroaches, Dragonflies). We also don't know why there seems to be an increase in complexity. We know about the Red Queen principle, but knowing about it doesn't give us all that many answers. It almost gives us more questions.
I think everyone would agree that there is more to Evolution than we currently know (and it's nothing supernatural). Even professional in the field know that the process isn't completely understood yet.
Natural Selection by itself is kind of a no brainer; it's a mathematic certainty. Variation seems to be where it's at, and as time goes by, modern theories have incorporated more mechanisms of variation. I think there are still more to go.
rosborne979 wrote:...We know that there seem to be patches of accelerated change within certain lines, and we know that there are other groups which remain relatively unchaged for Eons (Sharks, Horseshoe Crabs, Nautilus, Cockroaches, Dragonflies). We also don't know why there seems to be an increase in complexity.
I think everyone would agree that there is more to Evolution than we currently know (and it's nothing supernatural).
Actually, everyone wouldn't agree. It seems to me that the basic mechanism is sufficient to produce the evolution that we observe. It seems perfectly understandable to me that complexity increases, since the goal of evolution is to produce an animal more effective in surviving predators, surviving disease, surviving intra-species competition, finding mates, attracting mates, etc., and, generally, to make a better machine, you have to make a more complex machine.
Some species, particularly very simple ones, may be relatively static evolutionarily because they fit their evolutionary niche well. Other variations I would think would be due to evolutionary pressures to adapt to something.
There may be additional, unknown principles, but the basic ones seem to me to be sufficient. Not being in the field of genetics, I feel no pressing reason to look for problems with the basic theory of evolution by natural selection and mutation.
Brandon9000 wrote:Not being in the field of genetics, I feel no pressing reason to look for problems with the basic theory of evolution by natural selection and mutation.
Ok, that's fair enough. I just feel differently. I feel that the existing mechanisms described in the theory are not sufficient to explain everything we see in morphological development.
In this particular case, the part that seemed unlikely to me was the need for a repetition of mutation within the genes which control tooth size (which is how the basic theory would explain things). The seeming requirement for repetitive mutation of that Gene with the relative stability of genes around it, seems unlikely to me.
However, Fishin points out that other Genes may also be changing, but that selection is pruning everything except the one that changes canine tooth size. While I agree that this may be a possibility, it still doesn't seem likely.
Other posts seem to suggest that there is a much more fluid aspect to the genetic morphology of a population, and that so much variation is occuring all the time that multiple changes in tooth size within a population is inevitible; limited only by the point at which the beneficial trait reaches a point of diminishing returns. I'm still considering this because it's harder to break down into steps to understand.
As for Complexity, that's a whole other subject which I've spend time researching in the past. I think I have another thread on it... yes, here it is:
http://www.able2know.com/forums/viewtopic.php?t=7600&start=0&postdays=0&postorder=asc&highlight=
Best Regards,
Rosborne-I beleieve that youre falling into a comfort zone that sez, "Any phenotypic expression, sufficiently bizarre, must be a mutation"
Ever since evolutionary science has become the principal toolbox of the geneticists and only with backup assistance by paleontologists has the unscrambling of the implications of geneteic structures been understood.
the very genetic makeup differs from each related species very little. AND, as Mayr has stated and Voilard had shown, a packet of genes has an unlimited range of variability and can express a huge differential in the phenotype, and, converesely, there are only a few 'basic body styles" that can be expressed by the compliment of genes. If you look at the smilodons, you will see that there were a bunch of other animals that developed long dagger like teeth and these werent even placentals, let alone felines, demonstrating that , through convergent evolution, there arent a whole bunch of body solutions to an "aptation " (Goulds word for adaptation) problem.
Look up thylacosmilus, It was a marsupial that , separated from all the Barbouirofelis stock of pre-sabre toothies, became the sabre tooth"possum" of South America (which hadnt even connected to North America yet)
Gould created another word -exaptation , in order to drop the 1970s thinking that " adaptations is a term everyone used to say that any body feature that worked was an adaptation'" Some fit intoa bag of evolutionary tricks that, like feathers on a dinonychus (who would never ever think of flying) were a universal phenotypic option, whether or not it served any purpose at the time it first appeared. so, in short terms,in the case of a sabretooths teeth a stock phenotypic expression mayhave always been there in the genome of mammals in general not just felis.
"Pre adaptation" as a term grew out of favor because it gave a deterministic view to a phenotypic expression, but, as a concept, it has been often demonstrated that phenotypic expressionsmay lie in reserve until an environmental opportunity presents itself, for that phenotype to present itself and even grow to the statistical end point of expression.then , if the environmental circumstance that made that expression work, no longer presents itself, the animal must further evolve or die.
The sort of evidence to this with respect to smilodons , is , that when an environmental change occured (the total body plan for Smilodons was a huge barrel chested , no tailed , long toothed, pouncer), the Smilodons and the Sabre tooth possum friends , just crashed. Their red queen option was to die off quickly in the latest interglacial stage.
What I did mean to say re: mutation is that, statistical endpoints of phenotypic expression can get culled for until they are no longer end points but norms. the dNA of pygmymammoths and Columbian mammoths were essentially the same (theres some STR differences in the Junk which is useful to geographically locate a population) but essentially these were 2 end points of a same species.The expression of body size (pygmy elephants v standard) is not that of genetic mutation but of selection for existing variability.
Now, dont get me wrong, we all recognize that coding abberartions like doubling or reversal of a coding section and mutationcertainly are ways to pack more gross changes into a phenotype when it buds off the parental line and coupling that with the generational time afforded so random mutations can accumulate sufficiently, we will certainly get into apparent saltation or " punctuated equilibria".
All Im saying is that we dont have to run to mutation as the "only way" species develop major differences such as the sabretooths body plan in the phenotype.
I agree with satt in that the time dimension is "what keeps everything from happening at once" , it , converesely, its presence is merely a blacboard upon whichthings get "properly(or improperly) sorted out'
rosborne979 wrote:In this particular case, the part that seemed unlikely to me was the need for a repetition of mutation within the genes which control tooth size (which is how the basic theory would explain things). The seeming requirement for repetitive mutation of that Gene with the relative stability of genes around it, seems unlikely to me.
This is completely wrong. The other traits are changing as well during the same time period. We're just looking at tooth size.
Based on what you say, you don't seem to understand me. All sorts of mutations are occurring all the time, most of them harmful. In a large population over millions of years, every once in a while some particular child is born with slightly larger than usual teeth, and he has a better chance of survival than others of his species with smaller teeth.
All sorts of other mutations are occurring in the same population during the same time period.
Quote: It seems perfectly understandable to me that complexity increases, since the goal of evolution is to produce an animal more effective in surviving predators, surviving disease, surviving intra-species competition, finding mates, attracting mates, etc., and, generally, to make a better machine, you have to make a more complex machine.
Not true at all. The louse, for instance, has done very well for itself by a significant reduction in complexity. Similar with the echinoderms (seastars et al): they have evolved (or devolved, if you please) toward radial symmetry from what was likely a bilaterally symmetrical ancestor.
Quote: "Pre adaptation" as a term grew out of favor because it gave a deterministic view to a phenotypic expression, but, as a concept, it has been often demonstrated that phenotypic expressionsmay lie in reserve until an environmental opportunity presents itself, for that phenotype to present itself and even grow to the statistical end point of expression.then , if the environmental circumstance that made that expression work, no longer presents itself, the animal must further evolve or die.
This is really just a logical conclusion of genomic equivalence, isn't it? The constraints placed on phenotype by what is available in the genome also limit the changes that can take place.
*******
New thoughts, for the hell of it:
There's a tendency, it seems, to look at a gene as coding for a certain trait, but it's also the case that phenotype is largely the result of the timing of certain events during development. It's possible, then, for an allele of a single gene that controls some aspect of development -- say, switching off the expression of a receptor protein for a particular growth factor during tooth growth -- to mutate in such a way that the receptor is expressed for longer than it usually is. You could see a pronounced phenotypic change in a single generation. In fact, we see this all the time; it's just that these mutations are generally lethal. A big morphological change is not necessarily indicative of a big genomic change.
patiodog wrote:Quote: It seems perfectly understandable to me that complexity increases, since the goal of evolution is to produce an animal more effective in surviving predators, surviving disease, surviving intra-species competition, finding mates, attracting mates, etc., and, generally, to make a better machine, you have to make a more complex machine.
Not true at all. The louse, for instance, has done very well for itself by a significant reduction in complexity. Similar with the echinoderms (seastars et al): they have evolved (or devolved, if you please) toward radial symmetry from what was likely a bilaterally symmetrical ancestor.
That's why I said generally. Man, using his complex brain, has been able to eliminate the problem of predator animals, if not the problems of disease or aging. Our ability to reason has enabled us to put ourselves at the top of the food chain. In general, when a species faces some danger or mode of premature death, it is not surprising that evolution usually responds by adding a protective mechanism or by making an existing one more effective (which generally means more complex). For example, the immune system is an evolutionary response to disease (including infection). The fact that a few exceptions can be listed, doesn't mean that the principle is not
generally valid.
Aright, I see what you're saying. (Though evolution usually doesn't respond at all and the species dies out
)
patiodog wrote:Aright, I see what you're saying. (Though evolution usually doesn't respond at all and the species dies out
)
This may be true. Evolution is amazing, but not magical.
Thanks Farmerman, I think maybe I'm starting to see what you mean, but I need to challenge you on a couple of things to get more detail.... please bear with me, I'm still not sure where I'm losing this.
farmerman wrote:Rosborne-I beleieve that youre falling into a comfort zone that sez, "Any phenotypic expression, sufficiently bizarre, must be a mutation"
Ok, maybe this is the core of the problem. As far as I know, every phenotypic expression which gets selected against relates back to a gene (or group of genes which I think is called an allele). I agree that a given allele will give rise to variability, but if that allele remains the same across generations, then there will still be no change in its range of variability, and no particular trait would ever build up in the population. So, if what you're saying is correct, how does any given trait every become dominant in a population unless it's represented by a allele which is passing on its difference to successive generations?
farmerman wrote:The dNA of pygmymammoths and Columbian mammoths were essentially the same (theres some STR differences in the Junk which is useful to geographically locate a population) but essentially these were 2 end points of a same species.The expression of body size (pygmy elephants v standard) is not that of genetic mutation but of selection for existing variability.
I don't see how this can be possible, otherwise each generation of pygmy elephants would have an equal chance of producing non-pygmy offspring. There has to be some genetic representation for the morphology, or selection would lead nowhere.
farmerman wrote:All Im saying is that we dont have to run to mutation as the "only way" species develop major differences such as the sabretooths body plan in the phenotype.
Maybe I'm using the idea of "Mutation" differently than you are. To me, a mutation is any change in a gene whether it be from copying errors, or crossover or cosmic radiation.
I need to think about this more... I'll be back later.
Thanks everyone,
By the way, the definition of evolution I am working from is this:
"Evolution can be precisely defined as any change in the frequency of alleles within a gene pool from one generation to the next."
- Helena Curtis and N. Sue Barnes, Biology, 5th ed. 1989 Worth Publishers, p.974
It's from the
www.talkorigins.org archive.
Specifically:
http://www.talkorigins.org/faqs/evolution-definition.html
Ok, I found this:
[The modern theory of the mechanism of evolution differs from Darwinism in three important respects:
It recognizes several mechanisms of evolution in addition to natural selection. One of these, random genetic drift, may be as important as natural selection.
It recognizes that characteristics are inherited as discrete entities called genes. Variation within a population is due to the presence of multiple alleles of a gene.
It postulates that speciation is (usually) due to the gradual accumulation of small genetic changes. This is equivalent to saying that macroevolution is simply a lot of microevolution.]
The part I need to study is this: "Variation within a population is due to the presence of multiple alleles of a gene."
Reference:
http://www.talkorigins.org/faqs/modern-synthesis.html
Brandon, et al.
What this post is talking about is the mechanisms of evolution as far as I can see.
What I tend to think, hopefully judging from results, is that evolution may progress more like a "Bingo" game than a straight lottery.
Mechanically speaking :wink: I am trying to figure out how portions of a genome (alles) are incorporated into a species as a "sub assembly".
For instance, a eye without a brain to interpret would not be conducive to survival. Four stomachs without a "cud chewing reflex" in the brain wouldn't work too well either. The eye and dedicated portion of the brain have to be installed as an assembly or else it won't work.
The problem, as I see it is how to make, hold, and incorporate the various "sub assemblies" in our larger species. Need ideas.
We are going to try another thread along these lines soon. I hope y'all come
akaMechsmith wrote:Brandon, et al.
Mechanically speaking :wink: I am trying to figure out how portions of a genome (alles) are incorporated into a species as a "sub assembly".
I only have a vague idea of what you're asking. I hope that you will say more, either here or in your new thread.
rosborne-cocker spaniels breed more cocker spaniels if the are bred only with cocker spaniels. they are, howver the same genome as a chihuahua or a labrador retriever. Dimorphism is possible by the retention of genic expressions that , as time progresses, will either be clipped or reinforced.
True, genetic differences define evolution, but now youve moved about 60 degrees off your point and are no longer just relying upon accumulated mutations. So, I guess i can follow your trail here.
The expression of genes is controlled by other genes working in relationship. A genome can either preserve or clip batches of genes and thus preserve a feature or send it into "reserve status"
A lungfish has a genome 6 times bigger than a humans and a fruitfly has more coding DNA than does a human. The dNA is just a record of the evolutionary history of the species not something which requires "re-mutation" as the environment changes. thus , my pygmy elephant story can be compared to a variety within a species. had they survived by more room and a moderating climate , they could have returned"on" the sets of genes that describe the diversity and then wouldpossibly become, once again favored for full sized mammoths. Same thing with the tigers tooth.
MAny genes are responsible for the expression of a trait and many of these are senescent light switches that turn off and on in response to climate etc. So the tigers tooth or the elephants size can preserve the parents genome and, often , return to it as environments change .
Im a fan of Tlk origins, but not a 100% believer. remember, like all places on the web , there are spots that have little or no PEER REVIEW,
Also, I agree with dog that , the paleontological record does not show an increase in general complexity.Complexity has been tried in many forms before Because the evolutionary history of our planet has been dictated by a series of random, unconnected, episodic, cataclysms that have reshuffled and clipped entire germ lines and species. Consequently entire evolutionary experiments into more complex forms (multi brained, multi symmetry,complex morph structure,brain size) have been tried and rejected by subsequent environments.
BUT, the genomes that have tried the more complex forms still are preserved in existing extant forms, who knows, an opportunity for a multibrained lizard may once again present itself. (Im talking about stegosaurians which had a secondary brain gangion in their ass end, or trilobites, which exapted bizarre leg forms into the Devonian and then ent back to an almost bullet like form into the permian (then they went extinct by some environmental disaster)
Brandon
We are not quite ready yet so please be patient. Farmer man noticed that Rosborne is looking down a similar path. I think that what is going to happen is that we are going to graph out a genome and then apply the various laws of chance to it.
Everybody here can provide valuable input. Just as soon as I figure out how to ask the question.
Personally if it works as I think it should it may make a nice answer to the IDers and Creationists that Farmerman deals with occasionally.
.
Hope we don't lose anybody
Nothing wrong with the Creationists or the iDers, as long as , well.... you know my position here so... see you guys next day.
Hi Farmerman, your post has given me quite a bit to think about. I think I understand some subtleties now that I didn't before. I'm too tired right now to write much, but I'll try to paraphrase your post tomorrow to see if I'm getting it.
Thanks,
