Observable evolution

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Observable evolution

Postby Fuqin on February 17th, 2006, 5:20 am 

http://newsbreak.com.au/related/a494729

I was just wondering are there any other animal species that have exhibited observable evolutionary adaptations in nature
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Postby cheaky monkey on February 17th, 2006, 6:09 am 

The famous evolutionary example of the moths in England that changed from a light colour to a dark brown (I think) colour in response to the industrial revolution is a fantastic example. However, I think the Cain toad example is much cooler :P.
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Postby mabus on February 17th, 2006, 10:44 am 

Fuqin, fact is that evidence of evolution is everywhere, we even find it in humans. Look at the appendix which has become evolutionary useless for example or how we appear to be growing taller with each new generation. Creationists have skated around all this evidence by declaring it "adaptation".
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Postby BioWizard on February 17th, 2006, 10:53 am 

I think humans growing taller or more obsese over the course of a couple generations does not count as evolution, and is more likely related to changs in our dietary and exercise habits. Evolution needs to involve shifts in allelic frequency, and I am not sure that is the case in this example. The reason it is called an adaptive response is because it involves a biochemical metabolic response at the level of indidviduals, rather than allelic frequency changes at the level of the population. But yes I absolutely agree that examples of evolution occur all around us, and are especially evident in rapidly reproducing organisms, where allelic frequency variations can occur on much smaller time scale.
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Postby Forest_Dump on February 17th, 2006, 12:59 pm 

A certain amount of care is necessary here as the case of the peppered moth has been critiqued. A minimalist defintion of evolution holds that evolution is the change in ellele frequencies in a population from one generation to the next. This has certainly been observed in the case of the peppered moth. The variation was present before but changes in the environment, brought about by pollution, changed the pressures of natural selection on different coloured morphs. So a previously rare variant was favoured in the new environment and thus increased in frequency. This is considered a classic example of natural selection but is not and was not ever an example of macroevolution where an entirely new variant "appeared". Some have tried to interpret it this way, erroneously, and this has led to spurious critiques from the creationist crowd.
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Postby BioWizard on February 17th, 2006, 7:54 pm 

Agreed Forest. In evolution, adaptive variants dont "appear" in response to an environmental pressure. Variants appear independantly by drift and introduction of allele variants, which enriches the gene pool and generates allelic frequencies. Selective pressure follows to modify these frequencies (as opposed to random frequency distributions).
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Postby Hardstreet on February 18th, 2006, 2:09 am 

Fuqin: Check out "Beak of the Finch" that tells the story of Amy and Peter Grant's 20--year study of Darwin's finches on the Galapagos Islands. The birds evolved right before the eyes of the Grants. Important morphological changes leading to partial reproductive isolation were visible in as little as one year. There is also a fascinating story about real-time speciation in membracid leafhoppers, but I forget the details and so far I haven't been able to locate the literature on the web.
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Postby Fuqin on February 18th, 2006, 9:53 am 

cheers guys,
hardstreet so far I haven't been able to locate the literature on the web.

I think I found the literature you were after

http://www.eeb.princeton.edu/FACULTY/Gr ... Peter.html

http://www.eeb.princeton.edu/FACULTY/Gr ... n_2004.pdf

http://www.eeb.princeton.edu/FACULTY/Gr ... e_2004.pdf

but I have another question what are allelic frequencies?
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Postby cheaky monkey on February 18th, 2006, 3:55 pm 

allelic frequencies refer to the different ratios of alleles present in organisms within a specified population. For example, we might define our population as Perth, Australia, on the 22nd of January 1995 at 13:00 hours (human populations are highly mobile!). And within this population we could specify what alleles are in what frequency. For example, the allele for blue eyes. Out of the 2 million (or so) people, say 70% of brown eyes (and therefore 30% have green eyes). However, things get a little confusing because the allele for blue eyes is recessive to bown. I can not remember exactly how this is done, but i will find out.

Here is the equation.

p^2 refers to the domminate homozygote allele (in our case Brown eyes)
pq refers to the heterozygote
q^ refers to the recessive homozygote

The equation for this is
Fequency for q =
(2 x q )
-------------
2 x ( p + q)


frequency for p=
2 x p
---------
2 x (p +q)

p^2 = p x p

pq = 2 x p x q

q^2 = q x q

however, I think this is wrong :(

We could than compare this ratio to say Seattle, USA at the same time.

Hope this helped.
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Postby Hardstreet on February 18th, 2006, 4:57 pm 

If the frequency of a phenotype determined by a recessive allele is 30% (=.3), the frequency of the allele in the population must be the square root of .3, or .55. I think. It's been a hundred years since I studied this, so I'm not sure of a lot of basic stuff anymore.
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Postby Fuqin on February 18th, 2006, 8:48 pm 

Thanks cheaky monkey yes that cleared things up for me all except the equations, :? but that’s only because I’m allergic to math’s :)
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Postby BioWizard on March 5th, 2006, 11:50 pm 

Forest,

I think your post on allelic frequencies is correct, but I doubt that variations, or even wiping out of a single allele from a population counts as macroevolution. I think genes need to be thought of as clusters of genes, not single genes, when considering evolution by allelic frequency variation. I think the relative frequencies of the overall genes is what determines a specie. These are still very blurry concepts, at least to me, and I cannot see the distinction between two species being reduced down to a mathematical equation that one can calculate and based on the result decide whether or not speciation has occured, but I do think that following a single allele, as in the case of the moth, is overly simplistic.
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Postby BioWizard on March 6th, 2006, 12:00 am 

As for the math, I think this is what everyone was trying to say:

Dominant allele p
recessive allele q

Dominent phenotype possible genotypes: qq, pq
Recessive phenotype genotype: qq

Now if we consider the presence of p and q alleles in the population as a pool of alleles:

let frequency of p = x
left frequency of q = y

Frequency of dominant phenotype = frequency of pp + frequency of pq = x^2 + 2xy
Frequency of recessive phenotype = freqyency of qq = y^2

Now it is difficult to derive numbers by looking at the frequency of the dominant phenotype, because we dont know which is pp and which is pq

So we first sample the recessive phenotype. That frequency will be equal to y^2. The frequency of q is y, and hence is the square root of the frequency of the recessive phenotype. From the frequency of the recessive homozygotes, frequencies of both alleles can be deduced (unless one of the biologists around corrects me).
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Postby Forest_Dump on March 6th, 2006, 4:49 am 

Bio

I agree. The example is a straight forward case of natural selection. nothing more but a great example of nothing less.
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Postby psionic11 on May 15th, 2006, 10:52 pm 

While I appreciate some kind of working model, are not the assumptions p = dominant, q = recessive, rather simplistic? The arbitrary assignment of a single variable to a single observable phenotype seems to ignore a multitude of possibly significant factors....
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Postby BioWizard on May 15th, 2006, 11:03 pm 

psionic11,

It is a simplistic model indeed. However it works fine for certain considerations, where some phenotypic discontinuity is observed between a dominant and a recessive trait that obeys mendalian genetics. With the advent of functional genomics, we know for sure that gene interactions are by far more complex than a (p,q) model. But biologists would tell you "hey, it works", and well, it does.
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Postby Antone on July 1st, 2006, 5:50 pm 

cheaky monkey wrote:The famous evolutionary example of the moths in England that changed from a light colour to a dark brown (I think) colour in response to the industrial revolution is a fantastic example. However, I think the Cain toad example is much cooler :P.

While others have mentioned this in passing, the peppered moth case is probably not a valid example of evolution.

There are a great many indicators as to why this is so, but I'll just give a very cursory rundown of a few--bit first a very brief rundown of the facts in the case.

In the early part of the nineteenth century (before th industrial revolution) most peppered moths were of the light-colored variety. As pollution increased, more than 90% of the moth population around Manchester, England became the dark-colored variety. This phenomenon was called "industrial melanism".

Bernard Kettlewell performed some experiments which seemed to suggest that predatory birds ate the lighter color moths in greater numbers when they became more conspicuous on the darker colored bark of the local trees.

One problem with the experiment is that it created artificial conditions that do not exist in the wild--for the experimental moths were released in the daytime instead of at night. Being night fliers, this caused the moths to land on more exposed places where they would not have normally landed, amplifying the camaflouging effects of the trees.

It should be noted that Industrial melanism also affected a great many other animals in the area, including other moths, beetle and even birds. And Heslop Harrison reported that moth species fed leaves contaminated with metalic salts produced industrial melanism--suggesting that (at least some cases of) industrial melanism might not be genetic at all, but caused by environmental factors.

Over all, there was observed an increase in dark-colored moths during the years of heaviest pollution--and when pollution laws were enacted there was a return in the percentage of light-colored moths. However, it was assumed that the reason for this was that darker moths were better hidden on the darker/polluted lichen on the trees. But the return of the light-colored moths does NOT coincide with the return of light colored litchen--suggesting that the moths being eaten was not the only contributing factor.

Even Kettlewell himself noted this discrepancy in the data. And there were other areas where the trend was actually the reverse of what would have been expected... dark moths increased when litchen became lighter--and vice versa.

However, even if we interpret the Kettlewell experiements in the best possible light... and assume that the changes in the populations of the moths really were
caused by an increase in predatory efficiency... there still isn't any significant proof of evolution.

It MUST be kept in mind that both varieties of moth were around before the pollution changed their environment... and both varieties were around after the pollution. There is no evidence that had the pollution lasted for thousands of generations the lighter colored variety would have disappeared from the mix--If we are to assume that this would have happened, then we must assume that the darker-variety would have been on it's way to disappearing because of the pre-industrial environment. But is that is so then it would seem to imply that there was once a time when the darker variety was more common--but this doesn't make any sense.

Much more sensible is the obvious fact that the two varieties serve as a safegaurd mechanism--much as the light and dark colored daisies of daisy-world. When the environment favors one over the other, that variety becomes dominant--but the other varieity doesn't disappear. That would be extremely counter productive in evolutionary terms.

Assume for instance that all the light-colored moths did eventually disappear--and then when they were all gone the anti-pollution laws were inacted and the environment changed. Now there would be no way for the moths to counter the change in their environment--and the chances would be exponentially increased that they would all be killed off and become extinct.

The way I see it, the changes in the proportion of existing varieities of a given species is not an example of [inter-species, evolutionary change]. It is merely a demonstration of a given species defensive mechanism at work.
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Postby Antone on July 1st, 2006, 6:49 pm 

Hardstreet wrote:Fuqin: Check out "Beak of the Finch" that tells the story of Amy and Peter Grant's 20--year study of Darwin's finches on the Galapagos Islands. The birds evolved right before the eyes of the Grants. Important morphological changes leading to partial reproductive isolation were visible in as little as one year. There is also a fascinating story about real-time speciation in membracid leafhoppers, but I forget the details and so far I haven't been able to locate the literature on the web.

I think it is quite erroneous to suggest that any change that can occur [in as little as one year] qualifies as evolution.

I suspect that what you are referring to is the observation that in the year after a severe drought the average beak size of those birds who survive (only about 15%) increases by about 5%. Meaning, of course, that those birds with the largest beaks were the ones who survived.

Since beak size is directly inherited, this implies that the larger beak characteristic would be passed on to the next generation. If this characteristic were cumulatively inherited from one drought to the next--it is conceivable that a new species could evolve in as little as about 200 years, according to Grant. However, this does not happen, because the characteristic reverses during the wet seasons when smaller beak size is highly preferable. Thus, beak size is larglely a cyclical pattern.

To complicate things even more, it appears that (while un common) hybrid finches do occur naturally--and they actually tend to thrive to a greater extent than do their parents. This acts to merge the two species. And Grant states that this process of hybridization is enough to cause two different species to become the same species in as little as 200 years. Thus, while there is one potential force acting to make the Finch species diverge there is another effectively acting to make them merge--and the later force is at least the equal of the former.

Further, the main distinction between the some 13 species of Darwin's finches that live on the Galapagos Islands is that they have different mating behavior. They select their mates based on beak morphology and song pattern. The first is inherited and the second is learned from the bird's parents.

We might compare this to human populations, where different races are separated by minor inherited differences and a different language--and the different races rarely interbreed--yet these differences designate a separate race, not a separate species.

In conclusion, the finch data is primarily evidence of oscillating natural selection--it is not evidence for speciation (two species arising from one) since the evidence is just as strong that the species are merging as it is that they are separating. And in either case, there is no significant (i.e. non incidental) evidence to suggests that this tendancy can produce macro-evloutionary effects--i.e. those that could create a new species, which is infertile with the other.
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Postby BioWizard on July 2nd, 2006, 5:38 pm 

Antone wrote:The way I see it, the changes in the proportion of existing varieities of a given species is not an example of [inter-species, evolutionary change]. It is merely a demonstration of a given species defensive mechanism at work.


There is no doubt that genetic variation bears great advantage for the survival of any species in the kind of safety net mechanism which you described. However, there should also be no doubt that evolutionary segregation utilizes the same mechanisms of drift combined with sufficiently long reproductive isolation between diverging populations (otherwise they keep fluctuating and merging back).

A few changes in shape and color dont indicate a speciation event anyway, and probably only constitue a potential for speciation if they somehow prevent the new phenotypes from associating and mating with the original ones.
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Postby Antone on July 2nd, 2006, 9:55 pm 

BioWizard wrote: ...there should also be no doubt that evolutionary segregation utilizes the same mechanisms of drift combined with sufficiently long reproductive isolation between diverging populations (otherwise they keep fluctuating and merging back).

I'm not sure I agree. In any case where something can't be conclusively proven there should always be some doubt.

And while there is ample evidence to suggest that evolutionary change of an intra-species varitey does occur--what little evidence there is for inter-species transformation is highly suspect if we allow only for the gradual Darwinian mechanisms of natural selection, etc.

The stongest argument seems to be that "if it looks a little like evolution...then it must be evolution." Whch, as I see it, is not a significant improvement on the argument "if it looks a little like the handiwork of god... then it must be the handiwork of god."
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Postby BioWizard on July 2nd, 2006, 10:52 pm 

The stongest argument seems to be that "if it looks a little like evolution...then it must be evolution." Whch, as I see it, is not a significant improvement on the argument "if it looks a little like the handiwork of god... then it must be the handiwork of god."


With the slight difference that what you are refering to as "looks like evolution" are the mechanisms of evolution. What "looks like the handiwork of God" is hardly equated with something you can study in a lab or observe first hand in nature. Arguing the exact route evolution took is one thing, arguing the mechanisms of evolution is another.

And while there is ample evidence to suggest that evolutionary change of an intra-species varitey does occur--what little evidence there is for inter-species transformation is highly suspect if we allow only for the gradual Darwinian mechanisms of natural selection, etc.


What other mechanisms do you suggest we examine?
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Postby Antone on July 3rd, 2006, 2:50 am 

BioWizard wrote:What other mechanisms do you suggest we examine?
First, just because there aren't any good explainations isn't a good reason to adopt a bad explaination. And I'm of the mind that there are a number of serious problems with all gradualism-based evolutionary theories.

Second, if I had to venture a guess as to what mechanism drove evolution, I would have to say that it was reoccuring catastrophic events of a global nature. These caused radical genetic changes to occur within an extremely short geological time span--possibly as little as a single generation.

Thus, the extinction of species and the development of new occured simultaneously--and from the same cause. This rapid and radical change is in marked contrast to the general condition of stasis that occured in between these events that repeatedly threated to anihilate all life on earth.

That would be my vote--if I had to guess.
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Postby Forest_Dump on July 3rd, 2006, 7:53 am 

Antone, you seem to be a little confused as to what, exactly, evolution is. A basic, most simple, definition would be something along the lines of changes in the genome of a population from one generation to the next. To address why there are changes from one generation to the next, you need to look at two things: 1) where genetic variation comes from in the first place; and 2) why some genetic variations, as expressed in the phenotype (i.e. the observable physical expression of the genotype), do not do as well as others. These are entirely seperate processes.

1) Changes in the genotype (i.e. increases in variation) come about in a number of ways. The most common is recombination during meiosis. Mutations are less common. I think Bio can fill you in best here.

2) Not all physical variants do equally well in any given environment. Those that are not as well adapted to their specific environments experience decreased reproductive success, increased loss due to predation, etc. While the differences in adaptation are due to the genome, things that happen here do not increase genetic diversity, it is reduced by removing the less well-adapted variants. The experiment with the moths works simply to illustrate that there are animals that rely on camoflage to avoid predation. Those that blend in well with their environment avoid predation better than those that "stick out" in a predator's field of vision. This could be illustrated equally well with black or brown rabbits in the arctic - which ones would a fox or hunter be more likely to see? There is no suggestion that this kind of process leads to new genetic variation except that the genetic "stock" of the population of the next generation will be determined on the basis of what survives to reproduce and the relative frequencies of the variants of those that do. If "black" variants of any species are selected against or for any reason have less reproductive success, then the next generation will have relatively more "lighter" variants, etc.

Yes, there is some evidence that the "catastrophism" first employed by Cuvier may have been a factor at times. Meteor impacts, tidal waves, volcanoes, etc. would have played a part in evolution. But a few things must be kept in mind: 1) specific cases must be examined in detail to determine whether they happened and what the impact was on affected populations; 2) where these things happened, the impact would, in most cases, have been huge with numerous individuals wiped out. A tidal wave obliterating an island would not have allowed many or any genetic variants survive. It would not matter whether you were a black bunny or a white bunny if there was a wall of lava coming and you had no place to run to. Events like this are considered "chance" or "stochastic" because the impact on the population or portions of it, are entirely independant of genetic variation, etc. and what survived, survived independantly of genome, etc.; 3) unless the event or process somehow released a lot of mutagens into the environment, these did not create new genetic diversity. Other processes like the "founder effect" certainly did occur but this is not the same as the diversity from recombination, etc. Catastrophies do not create new species although they may create the conditions for new species to emerge by permanently blocking gene flow between segments of populations and allowing genetic drift, etc. to take place.
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Postby Antone on July 3rd, 2006, 7:11 pm 

Forest_Dump wrote:Antone, you seem to be a little confused as to what, exactly, evolution is. A basic, most simple, definition would be something along the lines of changes in the genome of a population from one generation to the next.
No, I am not confuse...

I suspect that it is largely that there are many practical definitions of evolution depending on what your goal is when you formulate the definition.

No one--except possibly the the most brain-dead creationists would insist that no evolution of any kind occurs. Particularly not if the only thing necessary to demonstrate evolution is some change in the genome from one generation to the next. Under such a definition, a mongaloid child would qualify as an example of evolution. But a mongaloid child is essentially a genetic dead end, because they would be hard pressed to care for themselves effectively in the big-bad-comptetive world.

Thus, I suspect a much better definition might be sustainable changes in the genome. This change, however, contains a lot of subtle implications. Under this definition, a fly that mutates isn't evolution if it can't find a mate becasue the changes in its genome won't get passed down to the next generation. Similarly, the changes that man have created in dogs is not indicative of evolution (by this definition) because if you release a pure breed dog into the wild its ofspring will alsmost invariably loose those pure breed characteristics within the first generation. And subsequent generations that start with two distinctly different purebreeds will quickly begin to look more and more alike over time.

Most species of animals have mating rituals that tend to exclude any animals that have unusual features. Thus, there is a tremendous force working against evolution. It is presumed that isolation in the necessary mechanism that allows two species to evolve in different locations--but I've seen no evidence that isn't entirely circumstance which suggest that this divergence is even possible under normal conditions--even if you allow for issolation.

We've been selectively breeding cats and dogs for thousands of years. It seems plausible to me that the pressures to form a new species is greatly amplified when we go from natural selection to selective breeding, for we don't have to worry about the natural tendency to reject uniques--not to mention that the desired animals are hand selected, etc, etc. Yet no new dog species have appeared due to such activity.

There are dogs that are so large and others so small that the two cannot breed together--but few would dare to claim these varieites are different species, under any definition of the word.

As far as I know, there is absolutely no evidence to suggest that such a species separating event can occur naturally--and far, far less that enough of these species separating events could have occurred to produce the millions upon millions of different species-both current and extinct that have populated the earth over the relatively short time frame that evolution has to work with.

There are, however, a number of observations, studies and experiments that seem to support the notion that the rate of evolution change can be radically increased at times of extreme environmental stress. For instance, plants not indiginous to the local have been found in the craters of bomb blasts. Under the right conditions, bacteria placed in a solution that isn't their food source, can mutate so that it can use the solution as a food source. And the apparent high rate of evolutionary change that occurs in the rain forests, etc., etc.

Forest_Dump wrote: unless the event or process somehow released a lot of mutagens into the environment, these did not create new genetic diversity. Other processes like the "founder effect" certainly did occur but this is not the same as the diversity from recombination, etc. Catastrophies do not create new species although they may create the conditions for new species to emerge by permanently blocking gene flow between segments of populations and allowing genetic drift, etc. to take place.

The catastrophic events I envision involve thousands of massive lightning strikes and other radical changes in the electrical environment of the earth--increase in radiation, heat, alien chemicals, loss of food source, changes in environment and climate etc.

In the potential scenario that I envision, all of these factors (and others) contributed to create a massive pool of genetic mutation. Millions and millions of animals were born with mutations--and many of them died out without ever becoming a viable species. But the shere numbers of them meant that animals with essentially the same mutations could find one another and mate. In this way, the tendency to avoid unique individuals was side-stepped.

The animals in the mix were radically different before and after these catastrophes--and the way I see it, it is plausible that these catastrophes might have given rise to many of the world wide myths such as the Garden of Eden story and the Flood stories which are nearly universal, they cut across so many different cultures.

But that's a discussion for a different thread, I suspect.
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Postby Fuqin on July 4th, 2006, 9:20 am 

Most species of animals have mating rituals that tend to exclude any animals that have unusual features, Thus, there is a tremendous force working against evolution.

is This sexual selection or a part of it ?, I had always assumed it worked for evolution ,doesn’t the ritual and appearance relate to the selection of the fittest mate!
But it would go something like this .
As environmental change occurs’ so what determines the ‘fittest’ changes!
Therefore the appearance changes and therefore the ritual .I may be wrong I’m no expert.
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Postby Fuqin on July 4th, 2006, 9:53 am 

But that's a discussion for a different thread, I suspect

Ok catasrophy and mythology, may I bulleti ... 5929#15929
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Postby Antone on July 4th, 2006, 1:36 pm 

Fuqin wrote:is This sexual selection or a part of it ?, I had always assumed it worked for evolution,

Yes this is a type of sexual selection. But no, it does not always work in favor of evolutionary change. The vast majority of the time, in fact, I suspect it functions as a stabilizing evolutionary force.

Fuqin wrote: ...doesn’t the ritual and appearance relate to the selection of the fittest mate!
This depends on the specific case--and on how you define the fittest mate.

Female peacocks, for instance, are attracted to males with the largest tails. Having a larger tail does not make the male more capable of surviving--instead it makes that male much more visible to predators, and less capable of escaping them. However, it does make that male a better decoy. The male's purpose in life is to reduce the danger on the female. Thus, in this instance, fitness is determined by the male's level of expendability. The better the male is at making himself expendable the fitter the male is.

This is not at all an unusual situation in the animal kingdom. A great many species have practices that make the male expendable. In fact, humans have a tendency to exhibit this same pattern of behavior. For example, it is men who historically have engaged in virtually all of the most dangerous activities.

It is the men who engage in war.
And the men who take all the most dangerous jobs. (Even in today's society, despite the stringent push for supposed equality, men are still employed at a much, much higher rate in those jobs that are the most dangerous.)
You can see this also in many of the traditional customs... Men walking closer to the street (so they'll be the one hit if a car jumps the curb) men walking first going downstairs and last going upstairs. (so they can catch a falling partner, but no one is there to catch them). The "women and children first" attitude exhibited during emergencies and catastrophes. A man giving a woman his jacket when it's chilly. Offering her his seat on a bus, (so she doesn't have to wear herself out by standing--and isn't as likely to be injured if there is a wreck) etc. etc.

This can all be interpreted in terms of the [fittest mate]. For historically, the main job of the men has been to protect and provide for the community. While the women's main job has been to make the community larger and stronger by birthing children and raising them properly. A single fertile man could (if necessary) impregnate well in excess of 365 women in any given year. But it takes a single fertile women 9 months (plus child rearing time) to birth a single child. Thus, if increasing the size of your community is of major concern, then so is protecting your women from danger--whether they want to be protected or not. I'd suggest that historically most gender-related social customs can be effectively interpreted in light of this basic division of labor--and the need for one society to protect itself from others.

And those who have failed to [fit in] to the standards of the communities have often been punished in various ways. It isn't mentioned very often, but I've read that during the witch trials many of those who were burned were actually gay men--which is where the term [fagot] comes from: because a fagot is the bundle of wood that is piles up around the stake for the burning. Also, the reason that many of the women who were burned were chosen is because of the isolated life-styles that they chose. And many of them were supposedly Lesbian women who chose to live together instead of fitting themselves into the community by marrying.
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Postby Antone on July 4th, 2006, 1:47 pm 

Fuqin wrote: As environmental change occurs’ so what determines the ‘fittest’ changes!
Therefore the appearance changes and therefore the ritual.

This would be pretty close to the traditional evolutionary interpretation. However, I don't think there is any significant evidence that such changes are highly likely to occur--particularly not in animals with lower levels of intelligence.

Bees (and other insects) for example, do not seem to have the ability to generalize in this way. They operate strictly from instinct.

Consider the case of a particular, solitary wasp... when it is time for this wasp to lay eggs she builds a burrow, then seeks out a cricket, paralyzes it by stinging it, then she drags the cricket back to her burrow. Instead of taking the cricket straight inside, however, the wasp enters alone first--does a once around to make sure the burrow is ready before dragging the cricket inside laying her eggs, sealing the burrow and flying away forever.

If the cricket is moved while the wasp is inside the burrow, however, the wasp will drag the cricket back to the threshold, and enter again to check out the inside. It doesn't seem to matter how many times the cricket is moved. The wasp never decides for herself, "You know, I've checked out the burrow enough times that it's probably okay to take the cricket straight inside this time."

Instinct totally dictates the wasp's behavior--it cannot change it just because it wants to, or even because it would make much more sense to do so.

I believe a good deal of evidence exists which seems to indicate that the mating rituals of many of the more advanced animals (including mammals) are also dictated to a very large extent by instinct. Thus, it is unrealistic to suppose that a change in environment would be sufficient to change the animals behavior all by itself.

We can add mutation to the mix, but--even if we ignore the fact that under normal conditions the vast majority of mutations (I'd guess more than 99.99%) are detrimental instead of beneficial--there simply aren't enough mutations.

--If a single animal results from a mutation, it's mutation is extremely likely to be lost because of failure to find a mate.
--If it does find a mate, the mutation might become part of the normal species genome (like light and dark variations of the Kettlewell moths). This may possibly enhance overall species survival, but it seems unlikely to lead to a significant (directed) change in the species as a whole.

For instance, as I understand it, albino animals, have a great difficulty finding mates in the wild. If they could find other albino mates, then eventually albinos might become their own breed apart. Unfortunately, albinism is rare enough that it isn't very often that two albinos can mate. When they do mate they have offspring that are not all albinos. And their offspring are right back in the same problem as their parents. (Not to mention that even albino animals seem to prefer non-albino animals to mate with, when they can find them--but the only ones that generally will are those that are also on the fringe of society: the small, the weak and the infirm. which further lessens the albino's chances for survival as a separate species.)

--If the animal does find a mate, and all of their offspring exhibit the same characteristic features--there is still the extinction factor. A new species community has to reach a certain critical mass before they are considered self sustainable. For more solitary animals, this critical mass arises in part because it's not easy to find a mate in the wide open world when there are only a handful to be found. Thus, even if there are 100 animals on the continent, they might never find one another.

If they are more social animals the critical mass arises in part because there are social catastrophes that could wipe out all or most of the group at once. In both cases, a harsh season might decimate as much as 80% of their population. If there are only 50 animals, a reduction of 80% would leave only 10--making it more likely that those that remain might be killed by predators--and will have increased difficulty finding mates again. etc.

If, on the other hand, massive mutations are occurring--then there may be a fairly large selection of mates to choose from right from the git-go. And why shouldn't part of the mutation be the animals instinctual mating behavior--so instantly you do away with one of the more difficult barriers to gradual evolutionary change. Also, there seems to be evidence that suggest that during such times of environmental stress, the kinds of mutations that occur are much more likely to be beneficial, problem solving mutations--instead of defective ones.

It also avoids the problems that arise when you have multiple species evolving in the same area... You no longer have to wonder how they were once isolated (to avoid the devolution force of species merging) and then how they were reintroduced to the same environment enough years later. etc. Or any of the other multiplicity of difficulties that otherwise plague the notion of gradual evolution.
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Postby BioWizard on July 4th, 2006, 5:08 pm 

Antone wrote:We can add mutation to the mix, but--even if we ignore the fact that under normal conditions the vast majority of mutations (I'd guess more than 99.99%) are detrimental instead of beneficial--there simply aren't enough mutations.


I see your problem with gradual evolution now. Actually the majority of mutations are silent. Most of the time, only mutations that occur in coding DNA can be detrimental, and the majority of the mutations go unnoticed, either due to codon redudancy, synonymous aminoacid replacement, or simply because they dont affect the folding and function of the protein. Hence variation is introduced slowly and incrementally and can build up with time over a long period. The sum of biochemical processes within the cell are anything but tight, and there is always a buffer region for genes to play with, whereby variation is introduced without detriment. So any population is not a fixed assortment of genes, but more of a fluctuating set about a fittest average. When conditions change, the fittest configuration shifts, and the whole range shifts with it. So if you start with two population occupying a specific range, and allow them to evolve in distinct environments, their gene pools will shift slowly until they lose overlap (which is probably represented by inability to mate and produce viable offspring, and hence a speciation event).

--If a single animal results from a mutation, it's mutation is extremely likely to be lost because of failure to find a mate.


Correct, that is why this is almost never the case.

--If it does find a mate, the mutation might become part of the normal species genome (like light and dark variations of the Kettlewell moths). This may possibly enhance overall species survival, but it seems unlikely to lead to a significant (directed) change in the species as a whole.


The mutation shouldnt be drastic enough to prevent it from mating. That is the exact opposite of evolution.

For instance, as I understand it, albino animals, have a great difficulty finding mates in the wild. If they could find other albino mates, then eventually albinos might become their own breed apart.


No, that is a misconception. Albinos cannot become an independent species unless the are prevented from backcrossing with normal individuals and confined to a group which will have to evolve separately for thousands or maybe millions of years before they become a separate species from humans. But then again, if you take any two humans and subject them to the same conditions, you'll probably end up with a new species as well. This is called the founder effect.

Unfortunately, albinism is rare enough that it isn't very often that two albinos can mate. When they do mate they have offspring that are not all albinos. And their offspring are right back in the same problem as their parents. (Not to mention that even albino animals seem to prefer non-albino animals to mate with, when they can find them--but the only ones that generally will are those that are also on the fringe of society: the small, the weak and the infirm. which further lessens the albino's chances for survival as a separate species.)


Exactly, which is why albinism or any single phenotypic difference is not by itself sufficient to mark a speciation event.

If, on the other hand, massive mutations are occurring--then there may be a fairly large selection of mates to choose from right from the git-go. And why shouldn't part of the mutation be the animals instinctual mating behavior--so instantly you do away with one of the more difficult barriers to gradual evolutionary change. Also, there seems to be evidence that suggest that during such times of environmental stress, the kinds of mutations that occur are much more likely to be beneficial, problem solving mutations--instead of defective ones.


Not really no. Mutations occur randomly with no bias what so ever at the biological level. However, under periods of stress, the beneficial variation introduced by mutation is experienced more strongly, and hence variants are selected for. In lesser stress, variants disperse and stabilize at low frequencies. No proactive problem solving mutations there.

It also avoids the problems that arise when you have multiple species evolving in the same area... You no longer have to wonder how they were once isolated (to avoid the devolution force of species merging) and then how they were reintroduced to the same environment enough years later. etc. Or any of the other multiplicity of difficulties that otherwise plague the notion of gradual evolution.


Tigers and lions have overlapping territories, and can still mate to produce viable fertile offspring, and yet it is clear that their populations are pulling apart rather than merging back. This scenario isnt as impossible as you seem to think.
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Postby Antone on July 4th, 2006, 6:32 pm 

BioWizard wrote:Hence variation is introduced slowly and incrementally and can build up with time over a long period.

Obviously, this is the traditional understand. I'm just saying that I don't think there is sufficient evidence to assume that this sort of evolutionary force can account for every species. It's perhaps even debatable whether it can account for any--although depending on how you define [species] I think it almost certainly can account for some.

BioWizard wrote: So any population is not a fixed assortment of genes, but more of a fluctuating set about a fittest average. When conditions change, the fittest configuration shifts, and the whole range shifts with it. So if you start with two population occupying a specific range, and allow them to evolve in distinct environments, their gene pools will shift slowly until they lose overlap (which is probably represented by inability to mate and produce viable offspring, and hence a speciation event).

This is all good. I have no problem with it--in as far as it goes.

Lets go back to my comments about the selective breeding of dogs. All breeds of dogs are still essentially dog-like. Some are quite large--I, however, seriously doubt that one could ever be able to create a dog that was as large as an elephant or as small as a mouse. The way I see it, the dog species has certain built-in parameters. It's kind of like a rubber band (or rather a shpere, perhaps) we can we can pull the rubber sphere to make it larger (analogous to creating larger dogs) or compress it to make the sphere smaller (analogous to creating smaller dogs)... But no matter how hard we compress the sphere, we can never make it smaller (or larger) than it's built-in limits. And if we reduce the pressures (letting pure-bred dogs loose to breed naturally)--the sphere reverts to it's relaxed state--just as pure bred dogs revert back to a more moderate average mut form when released into nature. Or if we reverse the pressures (changes in environmental conditions) then the
sphere may go from being compressed to being expanded--just as the Kettlewell moths went from predominantly light to predominantly melanomic varieties and back again, as a result of environmental conditions.

But none of that suggest that the changes can be cumulative to such an extent that an animal can become a new species, (at least not when defined as being incapable of being interbred--and notice that I said interbred, not mating totgether in the wild. Big dog and little dog can't mate effectively
together, but we can artificially mix their seed to breed them.)

--If it does find a mate, the mutation might become part of the normal species genome (like light and dark variations of the Kettlewell moths). This may possibly enhance overall species survival, but it seems unlikely to lead to a significant (directed) change in the species as a whole.


The mutation shouldnt be drastic enough to prevent it from mating. That is the exact opposite of evolution.

No, that is a misconception. Albinos cannot become an independent species unless the are prevented from backcrossing with normal individuals and confined to a group which will have to evolve separately for thousands or maybe millions of years

Isn't that exactly what I said? (except, of course, for your introducing the notion of albinism in humans). Yes, I think it was.

No proactive problem solving mutations there.

I recall reading about a study where bacteria raised in a hostile environment mutated so that the environment was no longer as hostile. (i.e. generations learned to eat the solution they were swimming in, so to speak) The rate of this kind of beneficial mutation was significant higher under these circumstances than it was for bacteria living in a non-hostile environment. (I'm not sure if it was greater than if the bacteria had been living in another hostile environment for which this mutation would not have been an effecient cure) ... but does it really mater? I don't see how it would change my argument either way. Not in the least. In both cases, new (and specifically beneficial, or problem solving) mutations would occur.

Similar scenarios are stated for higher animals--including the claim that there are HIV resistant mutations in humans which have been observed. This is from a little more crackpottish source--but then again, my whole POV is somewhat crackpottish--so I'm not as inclined to hold that against someone, if it's the only criticism I can find. :D

Tigers and lions have overlapping territories, and can still mate to produce viable fertile offspring, and yet it is clear that their populations are pulling apart rather than merging back. This scenario isnt as impossible as you seem to think.
Why would you expect anything different, given what I've said? The uniqueness factor would clearly cause them to remains separate--as I said. The question is (1) how did they diverge in the first place? and (2) will they ever separate enough to become incapable of mating together--biologically? These are questions that are much more uncertain.
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