Explain this, creationists...a Liger!

[Hellbound]

In response to the OP title, and echoing Dr. A, what Ligers really do is provide actual evidence that evolutionists need to be more careful in identifying what constitutes a species.

Um, care to elaborate? Because I fail to see how this follows. This result doesn't contradict the major determinations of species, at least none that I know of.

 

[neutrino_cannon]

Um, care to elaborate? Because I fail to see how this follows. This result doesn't contradict the major determinations of species, at least none that I know of.

Species lines are often defined as being the barrier across which interbreeding is impossible. Obviously, there are problems. Look up "ring species" sometime if you want a real headache. There are also other examples of poor species definition, see the genus canis, in which all constituent species can interbreed (so you could have a dingo/poodle if you were so inclined).

The underlying problem with defining this or that as a species is that populations often overlap, obvious physical characteristics are often loosely related to genetics, similar looking animals could be very genetically different, and interbreeding can often produce strange results. In short, we should not expect Nature Infinite to confirm to our preconceptions about how it ought to organize. Evolution is an impersonal force, and therefore never had any intentions of making everything clean and easily organizable for a particularly curious primate sometime down the line. It is our system of organization that makes way for new discoveries, not the other way around.

 

[Dr Adequate]

In response to the OP title, and echoing Dr. A, what Ligers really do is provide actual evidence that evolutionists need to be more careful in identifying what constitutes a species.

Actually, I've been thinking about this lately, and I agree with Darwin. It is hard, maybe impossible, to draw a line between species and well-marked varieties. Consider the famous ciclid fish of East Africa

The Cichlid fish species flocks of East Africa compose the most species rich assemblage of vertebrates on earth... African Cichlids are widely known for their stunning diversity of trophic morphologies and behaviors.

And yet if you choose a different criterion of "species", such as being able to interfertilise producing fertile offspring, there is in fact only one species of fish in Lake Malawi (the different species don't interbreed, but they "could if they wanted to", except that not wanting to is part of their genetic make-up, which leads to other questions...) And then this criterion is not itself hard-and-fast. For example, mules are sometimes fertile. Obviously, this doesn't mean that horses and donkeys are sometimes the same species. So what should we say? Are horses and donkeys the same species? Or with the two types of European mice: the female offspring of crossing are fertile but the males aren't. Are we meant to say that the females are the same species and the males aren't? (I may have got that the wrong way round, but the point still stands.)

The more specific cases like this you look at, the more you realise that what is needed is not a "more careful" definition of species, but an explanation (as in Darwin or Jones) of just what's wrong with the concept, and of how varieties shade into species.

I've yet to see a creationist offer a definition of "species". They seem a little coy on the subject. And no wonder.

 

[hammegk]

... It is our system of organization that makes way for new discoveries, not the other way around.

Which new discoveries are uppermost in your mind, other the ongoing discovery that using "undefinable species" as a key part of your classifications seems to lack mathematical and predictive rigor expected in other scientific theories?

 

[Dr Adequate]

Which new discoveries are uppermost in your mind, other the ongoing discovery that using "undefinable species" as a key part of your classifications seems to lack mathematical and predictive rigor expected in other scientific theories?

Well, the knowledge that species are a sloppy, fuzzy concept is quiite an important one, as it confirms what Darwin wrote in the Origin of Species. That would be "predictive rigour" by the way. This is why modern biologists replace fuzzy concepts such as variety, genus, species with the precise concept of "clade" --- that would be "mathematical rigour", if you're interested.

Nice try though --- attempting to twist strong evidence for evolution into proof that biologists don't know what they're doing. That's some real classy distortion right there.

 

[Badly Shaved Monkey]

The mystery for me is that rapidly mutating species with short-generation time and huge populations don't just shoot off across the genetic landscape instead of managing to stay roughly the same species from day to day, never mind over geological time.

Can anyone give a concise explanation of why these species are stable, given that with every generational cycle of their vast populations their entire repertoire of one-step mutations is likely to be explored? I don't have a problem explaining evolution of species, I have a problem explaining the relatively static nature of speciation! (I've done the arithmetic for species like E. coli and I think I am right to say that given the error rate of DNA transcription, their small genome and the size of the population of them in one mammal all their one-step mutations should appear with each of their fission rounds in each of us)

 

[Hellbound]

Species lines are often defined as being the barrier across which interbreeding is impossible. Obviously, there are problems. Look up "ring species" sometime if you want a real headache. There are also other examples of poor species definition, see the genus canis, in which all constituent species can interbreed (so you could have a dingo/poodle if you were so inclined).

The underlying problem with defining this or that as a species is that populations often overlap, obvious physical characteristics are often loosely related to genetics, similar looking animals could be very genetically different, and interbreeding can often produce strange results. In short, we should not expect Nature Infinite to confirm to our preconceptions about how it ought to organize. Evolution is an impersonal force, and therefore never had any intentions of making everything clean and easily organizable for a particularly curious primate sometime down the line. It is our system of organization that makes way for new discoveries, not the other way around.

Hmm, that doesn't fit with what I've studied.

Althought he "a species can interbreed" is often used as shorthand, I'd always understood the biological test of species to be that they can "interbreed to produce viable offspring". Since ligers (and likewise, mules) produce primarily strile offspring, this excludes them from the definition.

However, I will also agree with others in stating that species is a fuzzy concept. There are at least four common definitions of species, each with areas of overlap. I don't believe any decision on whether an animal is a new species or a variety of an existing species is taken lightly.

 

[Dustin Kesselberg]

The only sure thing that would shut the theist's up is if somehow we had a population of fruit flies,Or some other extremly fast multiplying species...and then put them in an environment where evolving would be prefered to live.

Then we wait several years... And budabig buda boom we have another species and that proves evolution.

How many generations would it take in general for a species change to occur? maybe something like 5,000 generations? 10,000?

If humans changed in the past 4,000,000 years and lived on average 60 years it should only take about 6,000 generations.

Well....When you break it down,It would actually take a few hundred years even with fruit flies.

If there was a way to do it with a species that lived and died in a few days...it would probably take less than few years to see a change.


Is there any flaw in this?It seems like it would work.

 

[CFLarsen]

Is there any flaw in this?It seems like it would work.

Only one: If it doesn't correspond to what the Bible says, it will be deemed as false.

Nothing will persuade Creationists that they are wrong.

 

[athon]

The only sure thing that would shut the theist's up is if somehow we had a population of fruit flies,Or some other extremly fast multiplying species...and then put them in an environment where evolving would be prefered to live.

Then we wait several years... And budabig buda boom we have another species and that proves evolution.

How many generations would it take in general for a species change to occur? maybe something like 5,000 generations? 10,000?

If humans changed in the past 4,000,000 years and lived on average 60 years it should only take about 6,000 generations.

Well....When you break it down,It would actually take a few hundred years even with fruit flies.

If there was a way to do it with a species that lived and died in a few days...it would probably take less than few years to see a change.


Is there any flaw in this?It seems like it would work.

It works with bacteria. However, as it is asexual, the definition breaks down. Bacterial species are more determined on their biochemistry than anything (and the arguments still rage over where many belong).

Molecular genetics is offering some answers by suggesting that a % of genetic hybridity might be a good way of determining where the line could be drawn. What is a good figure, though...again, the arguments.

For sexual reproduction some short-lived species could work, and have done. Drosophila fruit flies have been changed so often that new phenotypes have been produced that cannot create fertile offspring with past family members.

However, the issue does not lie in the evidence, but in the creationist's interpretation of it. We have more than ample evidence to demonstrate speciation, both inside and outside the lab. It will never make any difference.

Athon

 

[Hellbound]

The only sure thing that would shut the theist's up is if somehow we had a population of fruit flies,Or some other extremly fast multiplying species...and then put them in an environment where evolving would be prefered to live.

Then we wait several years... And budabig buda boom we have another species and that proves evolution.

How many generations would it take in general for a species change to occur? maybe something like 5,000 generations? 10,000?

If humans changed in the past 4,000,000 years and lived on average 60 years it should only take about 6,000 generations.

Well....When you break it down,It would actually take a few hundred years even with fruit flies.

If there was a way to do it with a species that lived and died in a few days...it would probably take less than few years to see a change.


Is there any flaw in this?It seems like it would work.

It's been done, actually. New species and subspecies of fruit flies have been created in the lab. Creationists simply insist that they're not new, but the same kind, and thus it doesn't really count. Talk-origins has some info on this...look for their Speciation FAQ.

 

[Rolfe]

(I've done the arithmetic for species like E. coli and I think I am right to say that given the error rate of DNA transcription, their small genome and the size of the population of them in one mammal all their one-step mutations should appear with each of their fission rounds in each of us)

Slightly at a tangent, but antibiotic resistance genes seem to fit in here. If you expose the bacteria to an antibiotic it seems that as sure as God made little green apples that resistance gene will appear, and be selected for. So, this does imply that mutation is happening, regularly, and in fact regularly enough to throw up what's wanted in a particular situation. I can only presume that the undesirable mutations simply don't survive. What about the neutral ones though - is that what you're trying to say?

Now, we've got all these resistant bacteria. Is this likely to be a permanent state of affairs? I suspect not. I suspect that if the bacteria are not exposed to the antibiotic for a sufficient number of generations, they will lose the gene. I postulate that retaining the gene involves some cost, and if there is no benefit accruing (i.e. survival in the presence of antibiotic) the organism will cease to maintain the gene.

Am I anywhere near on target here?

Rolfe.

 

[Badly Shaved Monkey]

What about the neutral ones though - is that what you're trying to say?

Yes, the neutral and then the slightly advantageous ones that appear as two-step mutations at the next stage. Yes, I know that real speciation can arise by more radical gene swicthing and splicing than simple point mutation. My point is to wonder about what ties a species to its particular spot in the genetic landscape given that it did have to move at some time to get to that spot in the first place.

RNA viruses exist as something called quasi-species, so hard are they to define as species, but I can't really see why bacteria aren't subject to the same problem, though they seem not to be. I think this has the potential to be a quite interesting topic- studying why species don't change places calipers on the genetic landscape from the opposite direction compared with asking why they do change.

Now, we've got all these resistant bacteria. Is this likely to be a permanent state of affairs? I suspect not. I suspect that if the bacteria are not exposed to the antibiotic for a sufficient number of generations, they will lose the gene. I postulate that retaining the gene involves some cost, and if there is no benefit accruing (i.e. survival in the presence of antibiotic) the organism will cease to maintain the gene.


I've had part of this discussion previously and was told that the costs of keeping a gene were zero. I found that to defy common sense, so still assume that, over the long haul, if a gene is not needed for survival it will either break down because any failures to maintain its accuracy will not be selected against and/or the metabolic cost of maintaining and replicating a futile piece of genome will set an individual at a disadvantage.

 

[Dr Adequate]

The mystery for me is that rapidly mutating species with short-generation time and huge populations don't just shoot off across the genetic landscape instead of managing to stay roughly the same species from day to day, never mind over geological time.

Can anyone give a concise explanation of why these species are stable, given that with every generational cycle of their vast populations their entire repertoire of one-step mutations is likely to be explored?

In two words --- natural selection.

Unless their environment changes, they are already around the optimum, and any deviation from it is likely to be punished.

 

[Badly Shaved Monkey]

In two words --- natural selection.

Unless their environment changes, they are already around the optimum, and any deviation from it is likely to be punished.

Yes, I know that, the interesting point is that natural selection is being presented with all possible one-step point mutations all the time for many organisms. A species is only ever hovering around a local optimum. What this line of argument should lead to is quantification, at least in rough terms, of the distances between adjacent optima. It also needs to be borne in mind that "optimum" would be defined only in terms of fixed environmental conditions, but no real-world organisms occupy a completely uniform ecological niche so the true locations of that species' local optima vary across its habitat and with time.

I lack the tools to pick this ball up and run with it, I'm just wondering whether any one else has thought this through better than me.

 

[hammegk]

.... That would be "predictive rigour" by the way.

Please advise the fools who compile dictionaries ...

rig·or ( P ) Pronunciation Key (rgr)
n.
Strictness or severity, as in temperament, action, or judgment.

Other than that, thanks.

This is why modern biologists replace fuzzy concepts such as variety, genus, species with the precise concept of "clade" --- that would be "mathematical rigour", if you're interested.

http://www.staffs.ac.uk/schools/sciences/biology/Handbooks/evolseqphylo.htm

Good stuff alright. If you don't know what your doing, complicate it so no one knows what anyone is doing. Is that stuff just another data-mining exercise, or do people actually "predict something" using it? If no predictions can be made, is it better than butterfly collecting?

Nice try though --- attempting to twist strong evidence for evolution into proof that biologists don't know what they're doing. That's some real classy distortion right there.

You think a Liger is strong evidence for evolution? A cat mates with a cat and you come unglued?

And I don't recall mentioning biologists, since some as scientists actually accomplish things -- and without 'macro-evolution' in play.

 

[Dr Adequate]

Other than that, thanks.

Any time you have a misconception, just come to me.

Good stuff alright. If you don't know what your doing, complicate it so no one knows what anyone is doing.

I can understand what they're doing. If you can't, that isn't necessarily because it's been made deliberately obscure. I can think of at least one other reason, ie the natural revulsion for knowledge which all science deniers have in common.

Is that stuff just another data-mining exercise, or do people actually "predict something" using it? If no predictions can be made, is it better than butterfly collecting?

Cladistics is what is predicted. Look, if you don'ty understand what you're talking about here, and unless your air of bafflement is mendacious, you don't, then maybe you should find out. There are these wonderful things called books...

You think a Liger is strong evidence for evolution? A cat mates with a cat and you come unglued?

No. Dear me, are you deliberately twisting everything I say, or do you just have very poor comprehension skills?

The fact that Darwin turned out to be right when he said that species can't well be distinguished from well-marked varieties is good evidence that his theory was correct. When he wrote that, he was just right in theory. The existence of intermediate forms in geographical distribution --- e.g. that of "the" European shrew, for example, shows that the whole concept of species is incredibly fuzzy, since "is the same species as" turns out not to be an equivalence relation, not being transitive, as Darwinism demands. Hence we find that Darwin predicted precisely a class of phenomenon he had never observed. Now that's a rigorous test of a theory.

And I don't recall mentioning biologists, since some as scientists actually accomplish things -- and without 'macro-evolution' in play.

Scientists who study life are called biologists. All of them have to achieve something, or they get sacked.

I've always wondered, when you people talk about "macro-evolution" what do you mean? Do you mean the same thing as "speciation"? If not, what do you mean? I find it in nearly all creationist spam, but without a definition. Is it a secret? Like the definition of "species" I propmted you for? The crickets have been deafening ever since.

 

[fishbob]

BSM:

A species is only ever hovering around a local optimum. What this line of argument should lead to is quantification, at least in rough terms, of the distances between adjacent optima. It also needs to be borne in mind that "optimum" would be defined only in terms of fixed environmental conditions, but no real-world organisms occupy a completely uniform ecological niche so the true locations of that species' local optima vary across its habitat and with time.

The 'local optimum' is a moving target. Environmental conditions often vary in cycles; winter-summer, dry-rainy, glacial-interglacial, predator-prey ratios. The life-span of most bacterial sized organisms is much less than the duration of these environmental cycles. Survival of species is probably dependent on genetic variation.

 

[fishbob]

Dr Adequate:

Do you mean the same thing as "speciation"? If not, what do you mean? I find it in nearly all creationist spam, but without a definition.

This has come up a number of times over in the Nat Geo forum on Darwin. The usual distinction is micro vs macro evolution. The creationists usually accept 'microevolution'.

Non-creationist usage of these terms are roughly;
microevolution = adaptation
macroevolution = speciation

The creationists deny speciation.

My definitions for creationist usage of the terminology:

microevolution - changes within species that are too obvious to deny.

macroevolution - changes that require evaluation of evidence and application of reason to figure out.

 

[hammegk]

Any time you have a misconception, just come to me.

Why? You can't even spele.

I can understand what they're doing. If you can't, that isn't necessarily because it's been made deliberately obscure. I can think of at least one other reason, ie the natural revulsion for knowledge which all science deniers have in common.

Goodo for you. You figure me for a 'science denier"? I figure you're mis-informed.

Cladistics is what is predicted. Look, if you don'ty understand what you're talking about here, and unless your air of bafflement is mendacious, you don't, then maybe you should find out. There are these wonderful things called books...

There's the net, too.

http://www.ucmp.berkeley.edu/clad/clad5.html

Cladistics predicts the properties of organisms.
As with any other system in science, a model is most useful when it not only describes what has been observed, but when it predicts that which has not yet been observed. Cladistics produces hypotheses about the relationships of organisms in a way that, unlike other systems, predicts properties of the organisms. This can be especially important in cases when particular genes or biological compounds are being sought. Such genes and compounds are being sought all the time by companies interested in improving crop yield or disease resistance, and in the search for medicines. Only an hypothesis based on evolutionary theory, such as cladistic hypotheses, can be used for these endeavours.

Sounds darn neat for micro-evolutionary effects at internal dna level. As some say "wheat" is "wheat".

Cladistics helps to elucidate mechanisms of evolution.
Unlike previous systems of analyzing relationships, cladistics is explicitly evolutionary. Because of this it is possible to examine the way in which characters change within groups over time -- the direction in which characters change, and the relative frequency with which they change. It is also possible to compare the descendants of a single ancestor to look at patterns of origin and extinction in these groups, or to look at relative size and diversity of the groups. Perhaps the most important feature of cladistic is its use in testing long-standing hypotheses about adaptation. For many years, since even before Darwin, it has been popular to tell "stories" about how certain traits of organisms came to be. With cladistics, it is possible to determine whether these stories have merit, or whether they should be abandoned in favor of a competing hypothesis. For instance, it was long said that the orb-weaving spiders, with their intricate and orderly webs, had evolved from spiders with cobweb-like webs. The cladistic analysis of these spiders showed that, in fact, orb-weaving was the primitive state, and that cobweb-weaving had evolved from spiders with more orderly webs. This situation has been repeated in many groups with many traits, including studies of parasitism, geographic distribution, and pollination.

And, gosh, spiders are spiders. Give me a hint; do any of these "groups" involve things that are obviously not just a bit more mutation resulting in (dare I say it, intraspecies) microevolution?

No. Dear me, are you deliberately twisting everything I say, or do you just have very poor comprehension skills?

I call it testing for understanding ....

The fact that Darwin turned out to be right when he said that species can't well be distinguished from well-marked varieties is good evidence that his theory was correct. When he wrote that, he was just right in theory. The existence of intermediate forms in geographical distribution --- e.g. that of "the" European shrew, for example, shows that the whole concept of species is incredibly fuzzy, since "is the same species as" turns out not to be an equivalence relation, not being transitive, as Darwinism demands. Hence we find that Darwin predicted precisely a class of phenomenon he had never observed. Now that's a rigorous test of a theory.

Well, we do continue to agree that "species" is tough to come to grips with.

Scientists who study life are called biologists. All of them have to achieve something, or they get sacked.

Nah. Some of them "teach".

I've always wondered, when you people talk about "macro-evolution" what do you mean? Do you mean the same thing as "speciation"? If not, what do you mean? I find it in nearly all creationist spam, but without a definition. Is it a secret? Like the definition of "species" I propmted you for? The crickets have been deafening ever since.

Fishbob's discussion is a fair one (Hmm, I'm not sure he's one of your "you people" group.) The continuing problem is that all mutations to date that that we can actually study (rather than theorize about -- using of course "evaluation of evidence and application of reason") are micro not macro.

May I finish with a horse is a horse, of course, of course?