It is roughly the same as the "Selfish Gene" account popularized by Dawkins.
No amount of genetic "selfishness" allowed large dinosaurs to survive the KT extinction event.
The problem I have is that genes don't get selected on their own, that they are necessarily {groups\sets\associations\clubs}.
The evolutionary result can be derived from a "profligate" {set of genes} that necessarily have numerous small genetic "errors in translation" in the process of making a {carrier\progeny} such that there are a number of near copies (of the whole {group\set\association\club}) made ... of which the best copies survive -- when tested.
But not every generation is tested by {competition\environmental} factors, and not every individual in a generation is tested by {genetic\developmental} factors (although very poor adaptations would be readily eliminated). Environmental factors can reverse over the course of a species lifetime.
This means that there is often quite a bit of mixing up of {carrier\progeny} bits and pieces by generations of reproduction before any selection testing takes place.
This can result in stasis because you are looking at the difference between a bell curve with 100 data points and a bell curve with 10,000 data points - the average is the same, and the only difference is in the extreme ends where the numbers are necessarily low in proportion to the population.
To me this also means there can be some 'backin-an-fillin' around a general "trendency" rather than a progression, whenever there are no extreme tests, but there are oscillating factors (like {environment\climate} or population {explosion\contraction}).
And this can result in "spandrels" that have no apparent purpose or function, variations on a theme (which perhaps can lead to 'accidental' speciation when potential mates do not recognize each other as mate-able -- a la ring species {termination\overlaps}). Curly hair versus straight. Blue eyes.
But they are not necessary, nor is the development of more complex structures when the existing ones are adequate.
In the absence of extreme events life kind of just muddles along, all the available niches are pretty well filled with species that are adequately adapted to them, and the relationship of species to environment, to others (competition, predation), whatever, is pretty constant.
When extreme events occur they may overwhelm the ability of adaptation to allow survival, so it may just be a case of life that existed outside the test area picks up the slack rather than any survivors.
Certainly this appears to have been the case following the major extinction events, where other species moved in to fill the voids in the available niches.
In my opinion, neodarwinism explain extinction rather well. But it doesn't do so well at accounting for novelty.
I don't quite see it that way. To my mind "neo-Darwinism" explains the gradual accumulation of genetic diversity within a population, so there is (all else being equal) more diversity the longer a species is around, and the more spread out it is, which can easily lead to {genetic novelty} changes occurring in pockets within the population as a whole.
But genetics doesn't explain the mechanism of selection beyond basic organism viability -- basically, if the organism is alive then the genes have done what they can for it. At this point they wait for the organism to do its job (of surviving to reproduce) while they prepare for the next generation. They are not involved in the action of selection, because the genes are the same whether the selection event(s) happen or not.
A selection event could go one way and select one subgroup of organisms, or it could go another way and select an entirely different subgroup. A drought selects finches with big beaks to eat tougher (dried) seeds, while lush weather selects finches with finer beaks. (Just a moment...).
You need to consider ecology (the relation of species to other species and to the {local} environment) to explain {eliminations of individuals (or groups of individuals)}. When conditions within an ecosystem (species can inhabit more than one) reach levels outside the experience of {past ecology} for a species (ancestors), conditions for which the individuals are, or are not, (genetically\physiologically) equipped, and those individuals that aren't sufficiently equipped are eliminated.
Such eliminations may result in only sub-groups with novelty features - selecting the novelty, but not making it - even if the novelty feature has nothing to do with the {group} survival.
What makes the feature "novel" is the elimination of the other groups - and the novelty is in the eye of the observer that sees one genetic variation stand out as more novel than any other.
In central Siberia, two distinct forms of greenish warbler coexist without interbreeding, and therefore these forms can be considered distinct species. The two forms are connected by a long chain of populations encircling the Tibetan Plateau to the south, and traits change gradually through this ring of populations. There is no place where there is an obvious species boundary along the southern side of the ring.
In Siberia one form is {novel} compared to the other, but around the ring there is no such {novel} distinction, although there are (gradual) changes around the ring.
To then create the species differentiating novelty, it takes the elimination of intermediate forms, which can happen by the elimination of habitat for some intermediate form - or just for a path of interbreeding.
(Ibid)
Map of Asia showing the six subspecies of the greenish warbler described by Ticehurst in 1938. The crosshatched blue and red area in central Siberia shows the contact zone between viridanus and plumbeitarsus, which do not interbreed. Colors grade together where Ticehurst described gradual morphological change. The gap in northern China is most likely the result of habitat destruction.
Thus habitat destruction in one area can cause speciation in another area by breaking a genetic link, but the novelty of differences between the groups existed genetically before this happened.
Enough muddled rambling for now ...
Enjoy.
This message has been edited by RAZD, 03*26*2006 08:11 PM
...in order to account for the amount of novelty that we see.
BUT
Fitness selection is only part of the equation. The challenge (mr phelps, should you choose to take it) is not only to survive but to reproduce.
Sexual selection is responsible for {some? most? all?} of the really remarkable features seen in species. Sexual selection can be caught in a feedback loop that emphasises certain characteristics that may have little or no (or negative) survival value - the peacock tail.
Personally I think normal sexual selection tends to select for stasis - picking most average individuals for most reproduction interactions - but the average values only apply to immediate population boundaries. Thus each of the main niches with the greenish warbler populations tend to be fairly hoomogeneous and thus make up the 6 varieties (subspecies) with the final two populations not recognizing the other as potential mates - sexually deselected.
Sexual selection is not dependent on ecology or periodic survival challenges to change a species over time.
(there's an image to give sexually selected human males a bit of a rise)
nwr is just saying that evolution to match a changing environment is one option, death is another and
Your proposal seems to be that the deer are moving over the actual landscape in such a way as to maintain the same position in the fitness environment as they currently hold.
is another.
If global warming is slow enough then wouldn't the environment "migrate" north so the deer could just follow it? Certainly we can see this occurring.
The basic issue of nwr's post to me was that evolution was not always the response to stimulii. If other options are available some populations will take advantage of them, and this is particularly true if the species has diversified into a number of environments where one is impacted and another isn't.
I have never found these "sexual selection" accounts to be persuasive.
Natural selection is supposed to be non-intentional. Once you introduce sexual selection, you introduce intentions.
I think you have a bit of a strawman there. It comes down to the level at which intention is applied. In a survival selection situation the organisms will intend to survive to the best of their ability, what you don't have is the intentional cultivation of survival specific features before a survival event. It does not rule out intentional behavior of individuals, whether that behavior is intended for day-to-day survival or for sex.
Let me expand on why I think sexual selection is (a) more important than survival selection, (2) tends to create species stasis in a fixed environment and (III) can make features that are unnecessary for survival.
First off, sexual selection occurs with every (sexual) mating -- no waiting around for some survival stress test or other to show up -- and any organism that fails to reproduce has ended it's (individual) genetic career no matter how good a survival specialist it is.
At it's simplest {form\level\degree} it means not wasting mating {time\behavior\energy} on non-viable mates -- mates of other species where offspring would be sterile at best.
We also see that "species recognition" can define a (new) "species" before genetic isolation occurs -- as we see with the Asian greenish warbler ring end varieties -- and this indicates an active sexual choice that does not have a (strict) genetic nor a survival basis.
Second, sexual selection is a way of finding the healthiest mates rather than just having indiscriminate sex with anyone. The healthiest mates are also those that are best fit to the specific environment at hand, especially if it is fairly fixed in characteristics, so sexual selection picks the fittest mates for the most mating -- even in total absence of any survival stress selection testing.
This 'fine-tuning' of the species for the environment at hand means that it is selected to fit the environment even as it changes on a large (geological?) time scale -- even though such changes are not to the level of survival stresses. With this mechanism, when the environment is (relatively) fixed, the active sexual selection is for species stasis (because those are still the healthy mates).
Of course, for sexual selection to work there needs to be some means of distinguishing {healthy} from {non-healthy} individuals. While this can be fairly obvious for very {sick\weak\malnourished} individuals, there is a threshold of {well\strength\nourished} that most individuals in a (relatively) fixed environment would be capable of meeting, and to distinguish the {healthiest} between them could take extensive testing (courtship rituals).
Thus you see herd animals having male competitions to determine who is the healthiest, best fit specimen in the neighborhood, and who passes the sexual selection test. Essentially "Alpha" individuals are the individuals (pre-)selected for sexual mating by their individual health.
Such mating behavior is unnecessary for species reproduction, and the reason it exists is because it works to 'fine-tune' the species population in a way that indiscriminate sexual mating would not.
For comparison, look at Bonobos: they practice indiscriminate sex at the drop of a hat, and compared to Chimpanzees they are less well adapted to their environment (smaller populations, more marginal areas, probably headed for extinction even without the hunting by humans).
A less exhaustive method of determining individual health than head-butting, is to have signal features. These can be fairly simple: the gloss of the fur and the fullness of the hair, the glow on the cheeks (whichever ones you prefer).
These can also involve distinctive features that advertise their signal qualities: the bright yellow of American goldfinches -- all mating plumage -- signals good health and readiness to mate.
In some cases the signal feature may become selected for beyond the level needed to advertise health, even to the point of jeopardizing it. The peacock tail is just one of these feedback signal features: the healthiest males have the biggest and most colorful tails to the point where it endangers their individual survival.
I think you would do better to say that the peacock tail is a spandrel.
But the key point is that without a full tail the male peacock doesn't get any. It's become necessary for the male to have tail to get tail.
That's not a spandrel, that's a key feature, essential for passing on the individual's genes to the next generation.
In such a case you have a fitness explanation. So why bring in sexual selection?
Because plain vanilla fitness doesn't explain why the two ring varieties in the overlap zone do not mate.
Sexual selection on the other hand explains the mating choices in the overlap area, where both are otherwise viable choices: both are fit for the ecological niche and both are healthy specimens.
And it gives a mechanism for how "fitness" is judged by the participants without wasting energy in trial and error. This leads to more {energy\resources} left for raising young, and so is more beneficial to species with longer gestation times and lower reproductivity rates, resulting in positive selection for such behavior.
On the other hand "fitness selection" has always seemed to me to be more of an after the fact catch-all mechanism -- it gives me the image of (the males anyway) going around mating with everything that moves without regard for the results and only the fit matings producing viable offspring ... if there are viable offspring then the parents must have been fit?
This is fine for 'mindless' species like plants, and others that broadcast eggs and sperm (or whatever), wholesale, but it does not explain the lack of mating behavior in closely related species or the reduced mating behavior between varieties within a species population.
Again, that seems to be a fitness explanation.
Many of your other examples seem to be fitness explanations.
But how does "fitness" work? It seems to me that sexual selection is one of the mechanisms by which individual fitness is judged by potential mates.
It's more than just health and vigor, but some species specific signal that says: "hey sailor, new in town?"
That seems like a weak argument. You can find other species probably headed for extinction, where sex is not so indiscriminate.
Of course it is just an anecdotal correlation at best (with the information available), but my reason for using it is that these are two very closely related species living in similar habitats, with very little to distinguish them other than sexual behavior and a slight difference in size.
One could argue that both are headed for extinction at the hands of their major predator (man), but one is clearly closer than the other, and the other has also diversified into 3 varieties ... by the mechanism of sexual selection?
But the point is not that one is (or both are) headed for extinction, the point is the difference in adaptation to the environment, where the one that is less discriminating sexually is less {diversified\fit} to the ecology, matching my thesis that sexual selection helps fine tune a species to its environment in an on-going feed back.
The question of sexual selection is probably a side issue, and perhaps should have a separate thread ...
Plain vanilla "fitness" selection doesn't have the cajones to explain either these choices or these features, while sexual selection not only explains their existence but the extremes that some (novel) signal features get to in their expression, and it explains why they are effective mechanisms for fine tuning a species to it's ecology.
Re: "That no (new) mammalian order arose ...etc" (standard MartinV Canard)
No it doesn't, it just means that you still don't understand how taxonomic classification works. Can you present any reason why we should expect a steady rate of new order production? Or give any instance where it has been claimed that we should?
Evolution if anything would predict that IF we kept the classical taxonomic classification system intact (rather than switching to the more appropriate cladistics system), that the general increase in diversity over time would mean NOT new "orders" but more subclassifications between family and what we call species. THAT is where evolution is occurring: it is occurring today and CANNOT - by definition - occur today within past classifications. The only other options for dealing with diversity is to (a) just keep increasing the number of species within each family or (b) invoke a total reclassification of all species into a NEW taxonomy.
Cladistics avoids this "problem" of dealing with increased new diversity by avoiding classifications into multiple levels. This is WHY cladistics is overtaking classical taxonomy as the system of choice.
MartinV is looking for whole new and complete limbs to grow on old trees - something he will never see. This is also why Davidson is wrong - it is just a reformulation of the old canard about species appearing suddenly fully formed, just in different sack-cloth.
Re: "That no (new) mammalian order arose ...etc" (standard MartinV Canard)
And has never been observed to happen in time past.
If you think of life on earth as a {tree\bush}, with the leaves at the ends of the twigs being all the individual organisms, you will perceive a structure to the whole when you trace the common ancestry of each leaf back to the trunk.
If you think of time as the layer of earth around the trunk, and the passage of time adds layers that bury old trunks, limbs, etc. You can still trace the common ancestry below ground, but all you have above ground are the existing organisms and their recent common ancestors.
You won't see a new leaf grow underground, and that is how all new limbs are started.
You won't see a new branch grow underground = in the past today that was not there yesterday.
Several problems with your post, the biggest is that it uses a website to make your case rather than your own words, which is a violation of forum rules. It is also a PRATT (point refuted a thousand times). Third it relies on a redefinition of the word faith, and we like to use common definitions so we are talking about the same things in the same ways: it's called communication.
We do have evidence, evidence from several lines of investigation that do actually prove that common descent occurs: you are a product of common descent from your parents, your grandparents, your great-grandparents, etcetera; this is a fact. We also have evidence of non-arbitrary speciation events where the result is two populations that cannot or don't interbreed (the definition of species) that have both evolved from their common ancestor population: this too is a fact. We also have evidence from genetic studies that show again and again that common ancestry occurs, and HAS occurred in the past.
When you get down to the theory of common descent extending back to a primal common ancestor population, then yes, there is a degree of "faith" to believe it, because it is a prediction of the theory and has not been validated (nor invalidated) to date. However, this degree of "faith" is very different from your implication that it is like religion where things are believed without ANY evidence and without question. The later point is critical: science does not believe any theory without question.
quote:The first Church of Evolution, Author: pastor-bill
Funneling man’s focus on the sacred imaginary doctrine of the Prophet Charles Darwin. It is our calling and outreach to comfort, direct and guide those who believe they have ascended from lower animals. Only through imagination can change above species be seen . As we evolve together in the knowledge of those sacred writings dilivered to the Prophet Charles Darwin, it is our hope that Natural Selection will shine on you.
Nuff said: someone with no clue to what evolution is, who has no training in biology and who is so myopic they can only see the world through the hazy lenses of religion. A card carrying member of the Cult of Ignorance. Someone who will lie to you to sell you a book.
I wanted to know why he thought his faith was different to mine as I had just agreed with all the evidence he had put forth.
I believe God created everything and is in control. I believe that the hypothesis will be substantiated by fact in the future.
Because in science, theories are based on evidence and the predictions of those theories are not accepted without question: rather they are severely questioned.
Your belief is without evidence and is unquestioned. You admit this with the last sentence quoted.
No I cannot see the difference you are questioning my theory now.
But you aren't, that makes your faith different from mine.
Your evidence is hoped for in the future, my evidence is in the past and what the hypothesis is built on.
I am not, strictly speaking, "hoping that the facts will prove my hypothesis in the future" but that new evidence will not invalidate it OR that a better theory comes along. It may be possible that there was no universal common ancestor population, but a group of similar derived life forms, as some evidence points in that direction. Several of these pre-biotic systems may have come together to form the first life (as we define -- badly -- it).
Nor is science waiting for the answer, but they are looking for it. Religions are NOT looking. A fairly good overview of the current search is at:
Note the number of theories involved, each one given is possible, so there is no ONE theory that hopes are based on. Notice that they also discuss the problems with the different models.
Yes I said faith, but I also drew a distinction between the kind of faith needed and religious faith: that is the split hair of the issue, not that faith is not involved but that it is NOT religious faith.
(A) religious faith: absolute, not evidence based, not questioned (B) non-religious faith: tentative, evidence based, questioned
If there were more words perhaps the semantics would be clearer.
2. belief that is not based on proof: He had faith that the hypothesis would be substantiated by fact.
BUT the reality is that one is different from the other by the degree of faith and by the kind of faith involved. Equating them is equivocating on those differences.
For the scientific faith the hypothesis, based on evaluation of the available evidence, is tentative, subject to change (falsification), and until invalidating evidence is encountered OR a better theory comes along, it is tentatively taken as the best reasonable answer. It is NOT taken as the absolute must be true answer, and often the problems with the hypothesis, the reasons it could be invalid are also documented (this is where falsification tests come in to play). It is possible, in fact, to hold that two or more theories could be valid even though they are contradictory. The scientist could have equal faith in contradictory theories.
Whereas for the religious faith the hypothesis, based on no evidence, that God (A) exists, is taken on absolute faith as being absolutely true and not subject to change. Often this faith leads to denial of evidence that contradicts the beliefs involve, such as the age of the earth and whether the sun orbits the earth or the other way around. It is also not possible to believe in two contradictory religions, and thus there IS a fundamental difference in the degree and kind of faith.
To reach the level of faith that is used in science, religious faith has to give up certainty in dogma and documents and belief, and base it's hypothesis on the level of evidence that forms the basis for the original hypothesis. It has to accept that other religions are equally valid and possible.
The only religious faith that I am aware of that comes anywhere close to this level is deism. IMH(ysa)O. No dogma, no certainty other than non-falsifiable belief in {some god - or gods - somewhere: a relatively tentative concept}. Thus there is still a leap of faith even with deism that is missing in science. If you cannot show that science faith matches that of Deism then you have no case to assert that it matches any more formalized, ritualized, dogmatized religion.
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