Evolutionary apologetics thread

[shernren]

My question was simple. Take your illustration to explain it:

There are B', B'' ... etc. So, which one is used to define species B? And what is the population of each B derivation?

No matter which one you choose to define the B species, the population of other B derivations MUST be significantly more than that of B. So, if all Bs are subject to fossilization, why don't we see more B derivations, but only a bunch of B?

Notice that in the ring species, all Bs are coexisting at the same time. And the same argument applies to species C.

They are, to the best of my knowledge, all considered different subspecies. Again, fossilization is an extremely random process, especially when it comes to land vertebrates, and not all species that exist are fossilized.

The real point of this is that we have an interspecies boundary being erected right before our eyes. Ring species push the concept of speciation but they show us that the basic mechanics of it are sound and workable. Separate two populations, let them adapt to their different environments, and you ultimately get two different species - which stay different species even when they are brought together at the end of their separation.

You are right to note that ring species are spatially separated. And the boundaries over which ring species are found today are often not enough to guarantee "radical" phenotypical change. But we can safely extrapolate, based on the phenomena of ring species, the phylogenetic evidence, and the fossil evidence (which indeed does contain many transitionals, though not as many as we'd like), that evolution can indeed do much more.

 

[Mallon]

What's important is not that an event is repeatable, but rather that the measurements detailing the event(s) are capable of being duplicated and show statistical significance. In this regard, paleontology and geology pass with flying colors.

Exactly. What's important in science is that experimental results are repeatable, not necessarily history. This is what is meant by repeatability in science. Indeed, history is not repeatable and so does not factor into the definition of science.

 

[Jadis40]

pfft physicist, Heck my physicist friends used to call me a "physicist wannabe who couldn't hack the math",

Of course when they wanted a new sample of material to test, they'd come groveling into my lab singing a slightly different tune...but that's another story!

Now as to repeatability... It's nice in principle but sometimes the universe just won't comply. A stellar astrophysicists studying coronal mass ejection doesn't get a chance to call Aldrich and order up a dozen class G stars (like our sun) and bring them into the lab. He, like geologists and paleontologists, has to work with what the universe makes available. Try telling him that he's not doing science!!
Heck, it's a lot tougher than what a bench chemist or physicist has to go through, at least we sometimes get to control our environments but it is no less science than what happens in an Erlenmeyer flask. It's just tougher to separate the noise from the signal. Quite frankly, I'm in awe about how much information they (being geologists/paleontologist) can ferret out of this ancient planet.

What's important is not that an event is repeatable, but rather that the measurements detailing the event(s) are capable of being duplicated and show statistical significance. In this regard, paleontology and geology pass with flying colors.

I think this is why astronomy and the other sciences have become sort of my amateur hobby. Astronomy has been one of my continuing interests for most of my life, at least from the time I was in elementary school for sure, when I couldn't wait to get to the part of the class where we delved into our science books. It still is, and I have a subscription to both Sky and Telescope and Astronomy magazines.

I would have to say that if I had been gifted by God with a more mathematically inclined brain, I would have become an astronomer. Ah well. The greatest thing is, it doesn't take a PhD to be awed by the heavens.

 

[grimbly]

I think this is why astronomy and the other sciences have become sort of my amateur hobby. Astronomy has been one of my continuing interests for most of my life, at least from the time I was in elementary school for sure, when I couldn't wait to get to the part of the class where we delved into our science books. It still is, and I have a subscription to both Sky and Telescope and Astronomy magazines.

I would have to say that if I had been gifted by God with a more mathematically inclined brain, I would have become an astronomer. Ah well. The greatest thing is, it doesn't take a PhD to be awed by the heavens.

Check around your area and I'll bet that you will find a local amateur astronomy club. If you do have one nearby, I'm sure they would welcome a guest at their star parties. Bring a red flashlight, a lot of bug spray(DON"T spray when you're near a scope), and be prepared to be awed. People love to show off their scopes and the wonders of the universe to anybody who is interested. To bad, It's a little late to see the Virgo cluster, but there's still the wonders of the summer sky... Lots of nebula, globular clusters and still quite a few galaxies available. Go for it, your wallet will never be the same!!!!

Do it now, the eyes get old.....

 

[Deamiter]

What's important is not that an event is repeatable, but rather that the measurements detailing the event(s) are capable of being duplicated and show statistical significance. In this regard, paleontology and geology pass with flying colors.

This is exactly what I wanted to say (as one of those nasty fellows with a couple physics degrees). No experiment will ever be repeatable to the degree juvenissun seems to think is necessary. Even in physics, the universe itself will have expanded slightly and a butterfly in China will have slightly changed the gravitational center of the Earth etc... Just as in physics, in geology and palaeontology, predictions are made and observations are repeated -- not in exactly the same conditions but in conditions similar enough to warrant conclusions.

I certainly won't be stopped from poking fun at the chemists, geologists and palaeontologists (when I spell that last one right) and pointing out how my science is so much more pure, but unlike you I can't imagine honestly claiming that physics is somehow empirically 'better' than palaeontology because I repeat experiments whereas they repeat observations! I'm certainly not going to dismiss the entire field as you seem to want to do when their predictions of future finds are often spot-on!

 

[gluadys]

No. I can not. But that is the basic issue of evolution. Namely, given enough time, everything is possible. Statistically, it might be true. But for a reason unknown to me yet, I just do not believe in it.

No, everything is not possible. If it were we could not make accurate predictions relating to evolution, but we can and do. Your next question is an example.

Well, that is a good start on my next question. I wonder how fast, or what is the rate of the spiciation in this particular case. I am afraid you are going to tell me again that this question is not in the context of this study.

I don't know that we are given enough information on this site to answer the question, but in principle it can be answered. Toward the end of the exercise, the focus is on DNA analysis. Since rates of mutation are known, DNA analysis offers a way to date the existence of the last common ancestor of any two of the species. The site does offer a relative dating, identifying the order in which the species appeared, but I don't recall if it mentions actual dates. However, a thorough study (this is, after all, just a high school level exercise) would provide estimated dates of speciation.

Notice the webpage spent some paragraphs on the ages of the islands. Does that piece of data have anything to do with the spiciation? Does that imply that lizard "jumped (floated?)" to the new island AFTER the island was formed? If it does, then the age of the island would provide a minimum time needed for the spiciation.

Well, the most important aspect is the constraint placed on migration to the islands. Obviously, however the lizards arrived, the island(s) had to be there before their arrival. So yes, the age of the islands sets a maximum (not minimum) time needed for speciation. So this is an example of a situation in which not everything is possible given an evolutionary perspective.

IF, the age of the island is related to the spiciation, then would some of the suggested phylogenic trees become impossible? (lizard is there before the island was)

No. Because in itself a phylogeny only shows relative dating e.g. species A is older than species B which is older than species C. But without additional information, we have no idea whether that is a few decades, a few centuries or a few millennia older.

Additional information can come from various sources. As already noted, the age of the islands themselves sets a maximum time-frame. If there are fossils on the island, they can be dated. And DNA analysis can lead to probable dates of speciation.

With such additional information, the relative dating of the phylogeny can be assigned to probable historical dates.

 

[shernren]

Believe me, the ragging some people get is nothing compared to what I do to the engineering students in my tute group. ;D

 

[juvenissun]

They are, to the best of my knowledge, all considered different subspecies. Again, fossilization is an extremely random process, especially when it comes to land vertebrates, and not all species that exist are fossilized.

But we can safely extrapolate, based on the phenomena of ring species, the phylogenetic evidence, and the fossil evidence (which indeed does contain many transitionals, though not as many as we'd like), that evolution can indeed do much more.

The more you explain, the more obvious is the problem.
The ring species description (or discovery) DOES SUGGEST a much bigger population on transitional form or subspecies than that of distinctive species. Does it not?

No matter how random is the fossilization process, it should still reflect this fact. But the fossil record shows the opposite.

 

[shernren]

The more you explain, the more obvious is the problem.
The ring species description (or discovery) DOES SUGGEST a much bigger population on transitional form or subspecies than that of distinctive species. Does it not?

No matter how random is the fossilization process, it should still reflect this fact. But the fossil record shows the opposite.

But what makes a "transitional species" different from a "distinctive species"? How are you defining those terms? And what convinces you that we don't actually have enough transitional species in the fossil record?

 

[juvenissun]

The ring species shernren referred to are a good place to start.

You might like to follow that with this execise (for high school students) in tracing the evolution of a group of lizard species in the Canary Islands.

http://www.ucmp.berkeley.edu/fosrec/Filson.html

A question of different thread: IF, it is possible to have the original species “drifted” from Africa, then why not expand this assumption a little bit to assume all three species came from Africa? The consequence would be that there was no speciation at all on these islands? The phylogeny discovered on island is simply transferred over from the continent.

 

[juvenissun]

Quite frankly, I'm in awe about how much information they (being geologists/paleontologist) can ferret out of this ancient planet.

What's important is not that an event is repeatable, but rather that the measurements detailing the event(s) are capable of being duplicated and show statistical significance. In this regard, paleontology and geology pass with flying colors.

All classic geological knowledge (include paleontology) is nothing but logic guess. Not until physics and chemistry came in to help, geology has no precision and no repeatability to talk about.

I admit your elaboration to my definition on science is very good. However, even today, if the repeatability (in statistical meaning) on physics and chemistry knowledge is on scale 10, then geology is only at 5 to its best. Of course, we have to consider that there are more precise branches of geology such as geochemistry, geophysics etc. But they only fostered a precision appearance on a basically speculated foundation. When the foundation is modified, everything built on top will have to be modified all together. It is an unstable top-down structure and I will not call knowledge obtained in such a system solid science.

Exactly because of this reason, I am not convinced at all by all the oppositional ideas to an actual Noah's Flood. I think we do not understand the fundamental principle of this Flood yet. All logically sound arguments made against it are only built upon a poorly-known base.

Please understand that I do agree that the methodology we used today in the study of geological science is solid. Because it comes directly to us from God, and is used to discover everything in the physical world.

 

[juvenissun]

But what makes a "transitional species" different from a "distinctive species"? How are you defining those terms? And what convinces you that we don't actually have enough transitional species in the fossil record?

That was my question to you. I am not in the position to pick up one and define it as a flagged "species".

The current fossil record would be very very pale in number, and in detail of variation, when compared with that in the ring species example. Is it not?

 

[shernren]

That was my question to you. I am not in the position to pick up one and define it as a flagged "species".

The current fossil record would be very very pale in number, and in detail of variation, when compared with that in the ring species example. Is it not?

Well, the fossil record is very pale, fullstop. It simply can't possibly be as detailed as we'd like it to be.

Nevertheless, the point of the ring species example is again to demonstrate how speciation occurs: The real point of this is that we have an interspecies boundary being erected right before our eyes. Ring species push the concept of speciation but they show us that the basic mechanics of it are sound and workable. Separate two populations, let them adapt to their different environments, and you ultimately get two different species - which stay different species even when they are brought together at the end of their separation.

Perhaps a third diagram will make the picture clear to you:

AAA
B||C
D||E
F||G
H||I
JJKK

There is nothing particularly different about the species along the ring. It just happens that D is closer to B and F than to A and H, that E is closer to C and G than to A and I, etc. etc. They are all organisms in their own right, and if a million years from now we had complete fossilization along the ring, we would probably classify them all either as different species or as a single large species. We probably wouldn't be able to distinguish them as transitionals because the transitions are rather small - but just large enough to make J and K reproductively separate populations.

If you are concerned in turn by the "lack" of transitional fossils, we could pick it up. It really doesn't have much to do with ring species, particularly considering how many transitionals we have, and how many hominid transitionals we have in particular.

 

[gluadys]

A question of different thread: IF, it is possible to have the original species “drifted” from Africa, then why not expand this assumption a little bit to assume all three species came from Africa? The consequence would be that there was no speciation at all on these islands? The phylogeny discovered on island is simply transferred over from the continent.

Cute. First you question the likelihood that they could get to the islands at all; then you want this improbable event to happen three times.

This is ad hockery at its best.

Could there have been more than one migration? Hypothetically yes. But the evidence does not support that.

Remember that the oldest island is likely to be colonized first, and also the island closest to the mainland. A multiple migration would require two out of the three colonizations to occur on a more recently formed island which is further from the mainland. So the geography is against a multiple migration.

Second, it is difficult to get the lizards from the mainland to the islands. So it is even more improbable that it would happen three times. The most parsimonious explanation is a single migration.

Third, the phylogeny based on the DNA analysis would be very different if there were separate migrations. The degrees of relatedness would be haphazard, unconnected to geographic distribution and not have the characteristic branches of a "family tree".

You suggest that the phylogeny of the mainland species could be "transferred" to the islands, but that is asking that quite by coincidence the phylogeny based on DNA match the phylogeny based on geographical distribution. There is no causal basis for that with separate migrations. It would be sheer luck if it happened.

It would be sheer luck that separate migrations would all land on different islands in the first place. You could get all three species on the same island.

Finally you are assuming that three species exist on the mainland to make the migration. But none of these species are found on the mainland---only on the islands. We must conclude that these species originated on the islands, not on the mainland.

 

[juvenissun]

Well, the fossil record is very pale, fullstop. It simply can't possibly be as detailed as we'd like it to be.

Nevertheless, the point of the ring species example is again to demonstrate how speciation occurs: The real point of this is that we have an interspecies boundary being erected right before our eyes.

OK, it is clear now to say: If the ring species theory (is it still a theory or is it a fact?) is right (because we SEE it), then the content of curreny taphonomy MUST be wrong (all wild guesses). Vice versa. You could not have both of them right.

 

[shernren]

OK, it is clear now to say: If the ring species theory (is it still a theory or is it a fact?) is right (because we SEE it), then the content of curreny taphonomy MUST be wrong (all wild guesses). Vice versa. You could not have both of them right.

Well, we observe ring species. How about I ask you two questions for a change. Suppose we had well-representative fossilization in every single area for, say, the Ensatina salamanders (was that one of the ring species models you looked at?). A million years from now, when paleontologists dig around, what do you expect that they will find? How would you describe it?

Suppose instead that we have very sketchy fossilization: one patch on the west of the mountains and two patches on the east. A million years from now, when paleontologists dig around, what do you expect that they will find? How would you describe it?

 

[juvenissun]

You are hitting on two of the reasons there is so much confusion about evolution.

First "gradual change of form" vs. "changing from one species to another".

Yes, evolution includes both. But note that it is not limited to "changing from one species to another". It also includes "gradual change of form".

I am not sure about the so-called “rate of mutation”. It is suggested in the order of 175 mutations per diploid genome per generation for human. I do not know what does this unit mean on the speed of mutation. I also found that for some insects, the rate is about 1e-6 per gene per generation. I also do not know how many genes need to be mutated in order to make a new species. How would the animal look like if half of the needed gene mutation has been made? How many mutations are needed to make a person look or feel different? Human has 2-4 millions of years history. Would it be enough to make a different human species? Does human have different “species” today? Why not?

If you could not answer these questions, that is fine. As long as you admit you do not quite understand it yet. This could be the bottom line question of the lizard case study, as well as any discussion of speciation. If this question is not answered, all the “higher level” questions are simply “discussions”. Nobody should say that evolution among species is a truth.

 

[juvenissun]

This is called "cladistic" (branching) speciation, and is the most common type of speciation, though there are others as well.

One question I am wondering about: Since the DNA data is available for lizard species, is there a difference of DNA sequence within ONE species of lizard? If yes, could the path of evolution be established on the mutation of that particular species, and “predict” when would the next new species emerge? If no, then the problem is obvious and is bigger.

 

[gluadys]

I am not sure about the so-called “rate of mutation”. It is suggested in the order of 175 mutations per diploid genome per generation for human. I do not know what does this unit mean on the speed of mutation. I also found that for some insects, the rate is about 1e-6 per gene per generation.

Well there are several different rates depending on exactly what is being measured. There is the rate at which mutations occur, which can be expressed as the number of mutations per gene, or per base nucleotide or per genome per generation.

There is also the rate at which mutations are accepted into the genome and spread through the species (become "fixed") as one of the identifying characteristics of the species. As this applies to only a very few of the thousands of mutations that occur, it is a much slower rate.

Since the point of DNA comparative analysis is to see the species differences (rather than the more common individual differences) this is the rate alluded to here. I'll try to find a link dealing with these rates, but I am too busy at the moment to do that research.

I also do not know how many genes need to be mutated in order to make a new species.

There is no particular number. It is the effect of the mutations on the reproductive compatibility of the different populations that defines a new species. You can get a new species with just one mutation or you may get millions of mutations without getting reproductive isolation.

The emergence of reproductive isolation depends on several factors, not on mutations alone. Usually one of those factors is geographic isolation, but sometimes speciation occurs without geographic isolation and sometimes it does not occur even with geographic isolation.

How would the animal look like if half of the needed gene mutation has been made?

Since there is no specific number of mutations needed, a newly emerging species looks like any other species--very ordinary.

Human has 2-4 millions of years history. Would it be enough to make a different human species? Does human have different “species” today? Why not?

Technically, the genus Homo has 2-4 millions years of history. Our species Homo sapiens has only about 200,000 years of history. I don't know if there is agreement on calling all species of the genus "human" or if that is reserved for our species.

There have been several species in the genus Homo, some of them living contemporaneously with each other. Some lived in the same time frame as early populations of our own species. But currently we are the only living species in the genus.

(Although there has been a suggestion that chimpanzees should be reassigned to the genus Homo. If this suggestion is carried through, there would be three species in the genus, but the additions would be due to reclassification, not to chimps becoming "human". )

This could be the bottom line question of the lizard case study, as well as any discussion of speciation.

I am sorry, but that sounds like an excuse to avoid the evidence.

Nobody should say that evolution among species is a truth.

We most certainly should say that, for it has been observed that speciation occurs. In the case of the lizards we are relying on inference from the evidence, not direct observation. But since we know from observation that speciation does happen, there is no reason not to infer that it did happen when the evidence makes that inference probable.

The question is "does this evidence make it probable that these lizard populations evolved from a common ancestor that migrated to the islands?"

To answer that question you have to engage with the evidence. You have to know what evidence would be implied by evolution and see if that evidence exists or if the evidence is contrary to expectations.

However, as is usual with creationists, you find myriad excuses to avoid this engagement. You use irrelevant questions to justify not even considering the evidence.

 

[gluadys]

One question I am wondering about: Since the DNA data is available for lizard species, is there a difference of DNA sequence within ONE species of lizard? If yes, could the path of evolution be established on the mutation of that particular species, and “predict” when would the next new species emerge? If no, then the problem is obvious and is bigger.

Since speciation usually depends on several independant factors, not mutation alone, it is not possible to predict accurately the occurrence of a new species. Speciation, like evolution in general, can occur at different rates in different circumstances.

But it does seem historically that species have a typical range of chronologicial existence in stable ecologies.

It is true that "enough" mutation would, over time, so change a species that it is appropriate to consider it a different species than its ancestor. (This would be speciation by phyletic gradualism rather than cladism). But lacking a means to test out whether the descendant species could or would interbreed with its ancestor, it would be a judgment call as to when the population would be considered a new species.

With cladistic speciation, you have both populations still available and can detect reproductive isolation. The lizard example is one of cladistic speciation, since all the species are still extant.