About Evolution

[juantoo3]

2.0 Species Definitions

A discussion of speciation requires a definition of what constitutes a species. This is a topic of considerable debate within the biological community. Three recent reviews in the Journal of Phycology give some idea of the scope of the debate (Castenholz 1992, Manhart and McCourt 1992, Wood and Leatham 1992). There are a variety of different species concept currently in use by biologists. These include folk, biological, morphological, genetic, paleontological, evolutionary, phylogenetic and biosystematic definitions. In the interest of brevity, I'll only discuss four of these -- folk, biological, morphological and phylogenetic. A good review of species definitions is given in Stuessy 1990.

Which means the term “species” does not have a clearly defined definition. Even among researchers it often remains unclear precisely which definition is being used at a given time, and all too frequently in lay publications the term is used in a very mixed way. Whether deliberate or not, it clouds the issue and the message. The term “species” tends to be used in an arbitrary manner.

2.2.1 History of the Biological Species Concept

The BSC has undergone a number of changes over the years. The earliest precursor that I could find was in Du Rietz 1930. Du Rietz defined a species as

"... the smallest natural populations permanently separated from each other by a distinct discontinuity in the series of biotypes."

Barriers to interbreeding are implicit in this definition and explicit in Du Rietz's dicussion of it.

(emphasis mine)
This is the answer I am typically given when I pose the question, “Define ‘species’.”

However, as anyone who has spent any time studying the subject can attest, this is * not * the way the word is most often used, especially in the popular literature.

2.2.2 Criticisms of the Biological Species Concept

The application of the BSC to a number of groups, including land plants, is problematical because of interspecific hybridization between clearly delimited species (McCourt and Hoshaw 1990, Mishler 1985).

Which means that even when “related” species are not supposed to interbreed, they often do, successfully. Which negates the non-breeding criterion, or it negates the use of the term in these instances. Which is it, if one is to remain consistent? * Factual truth is nothing if it is not consistent. *

A more serious criticism is that the BSC is inapplicable in practice. This charge asserts that, in most cases, the BSC cannot be practically applied to delimit species. The BSC suggests breeding experiments as the test of species membership. But this is a test that is rarely made. The number of crosses needed to delimit membership in a species can be astronomical. The following example will illustrate the problem.

Here in Wisconsin we have about 16,000 lakes and ponds. A common (and tasty ;-)) inhabitant of many of these bodies of water is the bluegill sunfish. Let's ask a question -- do all these bluegill populations constitute one species or several morphologically similar species? Assume that only 1,000 of these lakes and ponds contain bluegills. Assuming that each lake constitutes a population, an investigator would have to perform 499,500 separate crosses to determine whether the populations could interbreed. But to do this right we should really do reciprocal crosses (i.e. cross a male from population A with a female from population B and a male from population B with a female from population A). This brings the total crosses we need to make up to 999,000. But don't we also need to make replicates? Having three replicates brings the total to 2,997,000 crosses. In addition, you just can't put a pair of bluegills into a bucket and expect them to mate. In nature, male bluegills excavate and defend nests in large mating colonies. After the nests are excavated the females come in to the colony to spawn. Here the females choose among potential mates. This means that we would need to simulate a colony in our test. Assume that 20 fish would be sufficient for a single test. We find that we would need about 60,000,000 fish to test whether all these populations are members of the same species! (We would also need a large number of large aquaria to run these crosses in). But bluegills are not restricted to Wisconsin...

Yet, how is this any different when applied to the human animal?

I smell apologetics…

This is enough for now, need I go on? This is just the beginning of the first “talkorigins” link.

 

[juantoo3]

The greatest problem I see stemming from "blind" acceptance of evolutionary theory, especially as it is construed at the lay level, is that it opens a door towards what became eugenics. We start thinking of humans as separate species when we look at other animals in the same way. Granted not everybody, many are content to let others think for them. But for those who hold the meme of evolution as their religion, eugenics is a natural end. And what we got from eugenics is World War II. Did our fathers and grandfathers fight and die to support such a ludicrous thing?

I am no fan of political correctness, but in this much I am in firm agreement, all humans are related, all humans have the same inherent potential, we are one. Regardless of skin color, hair color or consistency, eye color, number of fingers or toes, type, kind or size of genetalia, language, culture, religion, meme or whatever seems to divide us, we are * in truth * ONE.

Now, if science wishes to take a different tack, and deny what it knows to be correct, then Santayana will again be correct. We will have to relearn the lessons of great and terrible war again. If skin color is all that it takes to denote a species, and so very many of the "speciation" examples trotted out for public view are no more than that, then what is there to stop some group of people from believing that their skin color is superior to another's?

This is not religion folks. It is not fantasy. It is the end of the road this logical inconsistency is taking us down. It already has once before.

 

[Bandit]

Great links...and they point out the artificial changes and genetic modifications by man and some isolated changes which have occurred which meet the argued criteria for speciation...

Obviously what we are looking for is the series of fishes that walked onto land...not the notion that has the big holes in the middle, or the formation of the eye, eyelid etc. And we know that the theory does not state man descended from apes but from a common ancestor which we cannot find.

that is because a T rex ate the evidence right after the fish gave birth to the monkey, but the monkey made it back to the water safely & swam away. then the T Rex grew wings & changed into a chicken.

Again I appreciate the links as they prove the weakness of the thesis. I would really hate to have to hang my hat on such conjecture. In court this evidence would be categorized as circumspect and circumstantial, you don't have the gun or the body...just lots of miising links...

i was not expecting a post like this from you Wil . it made me chuckle because i see it the same way. it is nice to be in a non-dom religion & at the same time be in a non-dom science class.

 

[Bandit]

The greatest problem I see stemming from "blind" acceptance of evolutionary theory, especially as it is construed at the lay level, is that it opens a door towards what became eugenics. We start thinking of humans as separate species when we look at other animals in the same way. Granted not everybody, many are content to let others think for them. But for those who hold the meme of evolution as their religion, eugenics is a natural end. And what we got from eugenics is World War II. Did our fathers and grandfathers fight and die to support such a ludicrous thing?

I am no fan of political correctness, but in this much I am in firm agreement, all humans are related, all humans have the same inherent potential, we are one. Regardless of skin color, hair color or consistency, eye color, number of fingers or toes, type, kind or size of genetalia, language, culture, religion, meme or whatever seems to divide us, we are * in truth * ONE.

Now, if science wishes to take a different tack, and deny what it knows to be correct, then Santayana will again be correct. We will have to relearn the lessons of great and terrible war again. If skin color is all that it takes to denote a species, and so very many of the "speciation" examples trotted out for public view are no more than that, then what is there to stop some group of people from believing that their skin color is superior to another's?

This is not religion folks. It is not fantasy. It is the end of the road this logical inconsistency is taking us down. It already has once before.

wow. i have never thought of it that way before & i do see that as a possibility. the blind leading the blind (so to speak). get everyone to believe it then get rid of the 'lesser' humans because evolution says they will die anyway & just keep the supreme race of 'evolved' humans.
or just call it the 'bottle neck theory' & cage them like animals, which like you say- we have seen before & that is not a good thing.
it seems a bit off the beaten path to claim something as science that can not be witnessed. maybe logical inconsistency is a good term for it.

what is that so many say? "when i see it i will believe it"
perhaps there is a bit of that in all of us somewhere.

thanks for the post Juan. it was good insight for me.

 

[bob x]

Great links...and they point out the artificial changes and genetic modifications by man and some isolated changes which have occurred which meet the argued criteria for speciation...

Some of the speciations which occurred were artificially induced. Others occurred in nature with no human intervention.
The assertion that speciations have never been observed is simply false. That will not stop creationists from continuing to assert it.

 

[bob x]

If skin color is all that it takes to denote a species

WHERE are you getting that from? There is no obstacle to interbreeding whatsoever between humans of any skin color, as has been experimentally verified time and again.

 

[juantoo3]

WHERE are you getting that from? There is no obstacle to interbreeding whatsoever between humans of any skin color, as has been experimentally verified time and again.

May I remind?:

The origin of the goldfish is thoroughly documented: a Chinese fisher found a bright-red carp among his catch (Chinese carp are black) and saved it in a pail as a gift to the local lord (who rewarded him handsomely). The lord bred the fish in his carp pools, and segregated out all the colored ones which appeared. After a few generations, the colors started shifting unstably, settling on the golden color now seen. This is a classic example of speciation by "punctuated equilibrium." emphasis mine

This is in my experience quite typical, such as the "evidence" of pepper moths turning darker in post industrial England. Coloration is a very commonly presented example held out to demonstrate "speciation," regardless of ability to interbreed with the parent stock.

So actually, it is not an example of "punctuated equilibrium." I doubt Gould would agree either. I seem to recall Gould suggesting periods of time in which speciation took place in very rapid spates across the board among most if not all animals, evidenced by the fossil record, and it was this he called punctuated equilibrium.

 

[juantoo3]

WHERE are you getting that from? There is no obstacle to interbreeding whatsoever between humans of any skin color, as has been experimentally verified time and again.

So, I must ask again, is the human animal to be held to a different standard than the rest of nature? Is this not apologetics to attempt to overcome the logical inconsistencies surrounding the term "species?"

 

[Vajradhara]

so....


would you folks that deny that speciation has happen, accept a CreationISM source which asserts that it did?


why or why not?

metta,

~v

 

[juantoo3]

Kindest Regards, Vaj!

so....


would you folks that deny that speciation has happen, accept a CreationISM source which asserts that it did?


why or why not?

metta,

~v

I am not certain I follow if this is being asked of me? For one, I have at no time espoused creationism in its raw form.

What I have asked for, consistently, is consistency in use of the term "speciation." Otherwise, I am accepting without questioning, just because it is written, just because others say so, just because it is tradition, am I not? Especially when the logic is inconsistent with the use of the terminology.

It is difficult for me to logically accept illogic application.

 

[bob x]

So, I must ask again, is the human animal to be held to a different standard than the rest of nature? Is this not apologetics to attempt to overcome the logical inconsistencies surrounding the term "species?"

??????
In the rest of nature, we are concerned about barriers to interbreedability, not just about single isolated differences like skin color or whatever. There can be fuzziness about levels of difficulty in interbreeding, but when there is no difficulty whatsoever about interbreeding then there is no conceivable basis for drawing a species line.

 

[wil]

Darwin had written "If my theory be true, numberless intermediate
varieties… must assuredly have existed". However evolutionists, who have
been doing excavations all over the world, have been unable to uncover
even a single intermediate form.

hmmm

 

[Vajradhara]

Kindest Regards, Vaj!

I am not certain I follow if this is being asked of me? For one, I have at no time espoused creationism in its raw form.

What I have asked for, consistently, is consistency in use of the term "speciation." Otherwise, I am accepting without questioning, just because it is written, just because others say so, just because it is tradition, am I not? Especially when the logic is inconsistent with the use of the terminology.

It is difficult for me to logically accept illogic application.

what is it that you want to see, Juan?

it seems like you are simply quibbling over semantics... or perhaps i'm missing your point. it's like consistency in using the term "theory". yet, i note that you have no real issue using that term, even though there are several meanings of said term.

let me ask you...

which view of gravity do you accept, the Newtonian or Einsteinian view?

the follow on is why you accept one and not the other.

metta,

~v

 

[juantoo3]

Kindest Regards, bobx!

??????
In the rest of nature, we are concerned about barriers to interbreedability, not just about single isolated differences like skin color or whatever. There can be fuzziness about levels of difficulty in interbreeding, but when there is no difficulty whatsoever about interbreeding then there is no conceivable basis for drawing a species line.

Then please forgive my misunderstanding when one of the first examples you trotted out to someone you believed to be an illogical Christian fool was an example of skin coloration, goldfish, and not only holding it out as evidence of speciation, but claiming that it serves as an example of punctuated equilibrium. All this, when koi (grown goldfish) readily breed with their parent "species", carp. So please excuse my not understanding you here when you make this comment regarding humans. Please excuse my seeing ... an inconsistency in logic, and daring to point it out.

 

[juantoo3]

Kindest Regards, Vaj!

what is it that you want to see, Juan?

Truth.

it seems like you are simply quibbling over semantics... or perhaps i'm missing your point. it's like consistency in using the term "theory". yet, i note that you have no real issue using that term, even though there are several meanings of said term.

I am not against using the term "theory." However, I also do not use it frequently. I do believe the term is misused and abused.

However, I must ask "why the dodge?" I am certain you see, clearly, the issue I have raised. I have been slowly doing so almost since I started at CR. You of all people here, lacking perhaps only Brian, know exactly what I am at.

let me ask you...

which view of gravity do you accept, the Newtonian or Einsteinian view?

the follow on is why you accept one and not the other.

What possible bearing does this have on the subject at hand? Another dodge? Why the artful tactics of logic? Do you feel too weak to meet the challenge head on? Have I somehow struck a scientific nerve? Now you must parry and look for a weak spot to pounce upon, instead of facing the issue raised?

 

[bob x]

Then please forgive my misunderstanding when one of the first examples you trotted out to someone you believed to be an illogical Christian fool was an example of skin coloration, goldfish, and not only holding it out as evidence of speciation, but claiming that it serves as an example of punctuated equilibrium.

If nothing had changed but the skin color, Cyprinus aureata (goldfish) would not be reckoned a separate species from C. crassus (the "black" or "crucian" carp). There are many specialized breeds of C. aureata with different colors (including the jet-black which is a reversion to the C. crassus coloration), but none of these breeds are considered separate "species" anymore than poodles vs. chihuahuas.
When a small population is isolated, it may happen due to "founder effect" that some otherwise-rare alleles become fixed in the whole population, affecting the relative fitness of some otherwise-common genetic combinations, so that there is a rapid drift away from the old equilibrium to a new one. In this case, aside from the increased color-variability which was the original motive for segregating these fish from the others, there also followed: a change in head-shape, eliminating the barbels ("beard" fronds) found in C. crassus or C. carpio (the "common" carp); a substantial increase in the dorsal fin; and a shift in the pheromones, so that while C. crassus can interbreed with C. aureata, it doesn't like to. The barrier to interbreeding is low, which does make it ambiguous whether a "new species" should be recognized; but with time the reproductive isolation can be expected to increase, until it is the same as the barrier between either C. crassus or C. aureata on the one side and C. carpio on the other (the crassus/carpio split is likely to be rather recent).

 

[juantoo3]

Kindest Regards, bobx!

If nothing had changed but the skin color, Cyprinus aureata (goldfish) would not be reckoned a separate species from C. crassus (the "black" or "crucian" carp). There are many specialized breeds of C. aureata with different colors (including the jet-black which is a reversion to the C. crassus coloration), but none of these breeds are considered separate "species" anymore than poodles vs. chihuahuas.
When a small population is isolated, it may happen due to "founder effect" that some otherwise-rare alleles become fixed in the whole population, affecting the relative fitness of some otherwise-common genetic combinations, so that there is a rapid drift away from the old equilibrium to a new one. In this case, aside from the increased color-variability which was the original motive for segregating these fish from the others, there also followed: a change in head-shape, eliminating the barbels ("beard" fronds) found in C. crassus or C. carpio (the "common" carp); a substantial increase in the dorsal fin; and a shift in the pheromones, so that while C. crassus can interbreed with C. aureata, it doesn't like to. The barrier to interbreeding is low, which does make it ambiguous whether a "new species" should be recognized; but with time the reproductive isolation can be expected to increase, until it is the same as the barrier between either C. crassus or C. aureata on the one side and C. carpio on the other (the crassus/carpio split is likely to be rather recent).

Thank you. Thank you very much for the clarification.

It has been some time since first we met here. Allow me to share a little about myself. I am merely a God fearing clerk with a mostly self-directed education.

Of course, we all know a God fearing clerk with a mostly self-directed education cannot possibly make a contribution that shakes the foundations of a "known" science. Right? (where's a tongue-in-cheek smiley when you need one?)

 

[Vajradhara]

Salaam Juan,

thank you for the post.

Kindest Regards, Vaj!

Truth.

and how do you propose to determine this without an established intersubjective methodology? more to the point, how is "true speciation" related to the concept of "truth", with a capitol T? this seems to belie an understanding of the scientific process and how theories work and so forth.

I am not against using the term "theory." However, I also do not use it frequently. I do believe the term is misused and abused.

you, my friend, are the one that used the term "true speciation". until such time as you manage to define it, which i likened to a True Christian or a True Scotsman, then i cannot provide anything to satisfy your request.

once you do so, then i will have a chance, not saying that i can, but a chance, to provide the information which you seek.

However, I must ask "why the dodge?" I am certain you see, clearly, the issue I have raised. I have been slowly doing so almost since I started at CR. You of all people here, lacking perhaps only Brian, know exactly what I am at.

it's a moving target, Juan. define "true speciation" and i'll see what i can find to satisfy your query. however, there seems to be little value in that if you can simply say "that's not what i meant" whenever anything is presented. so, please define "true speciation" ( and i would be extra thankful if you can contrast "true" speciation from "speciation") and we can go forward.

What possible bearing does this have on the subject at hand?

it would allow me an insight into your decision making process. by which methodology have you determined which theory is correct? ipso facto, i can know what sort of information you are likely to consider as "valid".

Another dodge? Why the artful tactics of logic? Do you feel too weak to meet the challenge head on?

i do feel under the weather, if that is what your little ad hom is going for here. please, Juan, try your utmost to remain civil.

Have I somehow struck a scientific nerve? Now you must parry and look for a weak spot to pounce upon, instead of facing the issue raised?

the issue raised isn't clear, hence the asking of clarifying questions. no need to respond with such hostility, Juan. your mind reading skills do need some work, fyi.

metta,

~v

 

[juantoo3]

Kindest Regards, Vaj!

Thank you for the response. I am sorry to hear you are not feeling well.

define "true speciation" and i'll see what i can find to satisfy your query.

With all due respect old friend, you already have defined speciation, twice. #1) The proof of the pudding is that species cannot breed outside of their species (-my paraphrase, but pretty darn close to the original). #2) fallacy (if true speciation is like a true Christian, and a true Christian is a fallacy, then I must consider that in your mind true speciation is a fallacy.)

All along I have insistently held to the first definition. With the second, I don't know what to do...I do think it severely handicaps discussion though. If the goal posts are moving, it is not by my hand.

I hope you get better soon. In the meantime, I need to limit my time spent here, I have more pressing matters to attend to.

 

[I am free]

With all due respect old friend, you already have defined speciation, twice. #1) The proof of the pudding is that species cannot breed outside of their species (-my paraphrase, but pretty darn close to the original).

Hi juantoo,

IMHO, a species cannot be defined as above. Even biologists would not strictly hold to such a definition.

Horses and donkeys can interbreed, so can horses and zebras. Dogs, coyotes and wolves can interbreed. Tigers and lions can too. Are these not seperate species then?

I would say a more apt definition would be that "there are barriers to interbreeding such that there is no more gene flow between the populations". The barriers could be chemical such as different pheromones, behavioural such as different mating rituals. Even mechanical. Normally an animal would recognize another animal as its own species. When it stops doing so....it could be said speciation has occurred.

I also dont think there would be an "abrupt" speciation. Wolves and dogs I believe do sometimes mate naturally (i.e. without human intervention). But over a period of time, the changes would be great enough that there would be total incapability to interbreed.

Also there would be various other things to consider such as phenotype changes, anatomical changes, changes in diet preferences, changes in behaviour, etc. before declaring that speciation has occurred.

My 2 cents.

regards.