How can scientists possibly know ... ?? An open exploration thread

[Mallon]

Back to OP. How do you know "we have undergone different selection pressures"?

Because if we hadn't, all species would converge on the same bodyplan.

Isn't it obvious to you that as terrestrial, bipedal omnivores, we undergo different selection pressures than, say, benthic, marine filter-feeders?

 

[holdon]

Because if we hadn't, all species would converge on the same bodyplan.

And why would that be?

Isn't it obvious to you that as terrestrial, bipedal omnivores, we undergo different selection pressures than, say, benthic, marine filter-feeders?

But how do you know that we are different because of different selection pressures?

 

[Mallon]

And why would that be?

Because if selection pressures were similar, we would all evolve to fill the same niche. We see this type of convergent evolution throughout the animal kingdom.

The fact that we do not all fill the same niche (thankfully) is thanks to differential natural selection.

But how do you know that we are different because of different selection pressures?

Because it has been shown empirically over and over again. Competition for resources leads to divergent phenotypes. This is the significance of Darwin's finch study.

Do you have a better explanation that can be tested empirically? What problem do you have with natural selection if most other creationists accept it, too?

 

[holdon]

Because if selection pressures were similar, we would all evolve to fill the same niche.

But how do you know that?? It's a big supposition, I think.

Because it has been shown empirically over and over again. Competition for resources leads to divergent phenotypes. This is the significance of Darwin's finch study.

But to what extent are divergent phenotypes different?

Do you have a better explanation that can be tested empirically? What problem do you have with natural selection if most other creationists accept it, too?

I think you're mistaken that this whole concept of natural selection can be tested empirically so as to explain all the different species, families, orders, etc..
I didn't say that I don't accept natural selection. Not at all. But it doesn't explain at all why all the differences exist.

 

[Mallon]

I didn't say that I don't accept natural selection. Not at all. But it doesn't explain at all why all the differences exist.

If you have a better explanation that can be tested, feel free to provide one. In the meantime, methinks you are disagreeing for the sole purpose of being argumentative.

 

[shernren]

Sorry, I am willing to learn, but if I can't make heads or tails out of your fancy story, it must be above my capabilities.....
Now, you said you came to conclusions. How did you?

Warg! I'm going to have to go through the entirety of post #183 again, slower this time. Let's start with the first two paragraphs:

Take a look, however, at life. Suppose I try to create a classification system in which I start by lumping cats and lizards together in a category, and everything else in a different category. How might I justify that? Absolutely no way. (Other than the trivial justification "I said so!") For in what morphological characteristics are cats and lizards more similar to each other than anything else? Are they both tetrapedal? But so are dogs and goannas and dinosaurs and rabbits and people. Do both have jaws? But so do all fish and all mammals. Do they have segmented bodies? (Yes, they do. Your fancy textbook should have something about that under embryonic development.)* So do all the other, uh, animals that have segmented bodies (can't remember the technical name offhand), all the way from whales to worms.

As a matter of fact, the smallest set of all living organisms that would contain both cats and lizards is the set Reptilia inclusive - namely the union of Reptilia, Aves, and Mammalia. Let's call this big set Felidasauri. (Heh heh.) [EDIT: The proper name for this taxonomic clade is Diapsida; nevertheless, I preserve the original "name" to show where it came from.]

Is this, or is this not, true? Is there any way to group cats and lizards together, under which you do not have to include the rest of all reptiles, birds and mammals because they look similar? Note that I am NOT saying that similarity, by itself, must show evolutionary development. Even a creationist like you should be able to acknowledge and agree that, say, dogs are far more similar to cats than lizards, without accepting that evolution has any part to do with it. (The logic of evolution comes not in the similarities but in the distribution of similarities.)

So is the smallest taxonomical set that can fit the cats and lizards together Reptilia inclusive - that is, does it have to include all reptiles, birds, and mammals? Or can you think of a smaller taxonomical set (based purely on taxonomical features) that incorporates them both?

 

[holdon]

If you have a better explanation that can be tested, feel free to provide one. In the meantime, methinks you are disagreeing for the sole purpose of being argumentative.

Keep thinking.

 

[Mallon]

Keep thinking.

Snnnnnap!

 

[holdon]

Warg! I'm going to have to go through the entirety of post #183 again, slower this time. Let's start with the first two paragraphs:

Take a look, however, at life. Suppose I try to create a classification system in which I start by lumping cats and lizards together in a category, and everything else in a different category. How might I justify that? Absolutely no way. (Other than the trivial justification "I said so!") For in what morphological characteristics are cats and lizards more similar to each other than anything else? Are they both tetrapedal? But so are dogs and goannas and dinosaurs and rabbits and people. Do both have jaws? But so do all fish and all mammals. Do they have segmented bodies? (Yes, they do. Your fancy textbook should have something about that under embryonic development.)* So do all the other, uh, animals that have segmented bodies (can't remember the technical name offhand), all the way from whales to worms.

As a matter of fact, the smallest set of all living organisms that would contain both cats and lizards is the set Reptilia inclusive - namely the union of Reptilia, Aves, and Mammalia. Let's call this big set Felidasauri. (Heh heh.) [EDIT: The proper name for this taxonomic clade is Diapsida; nevertheless, I preserve the original "name" to show where it came from.]

Is this, or is this not, true? Is there any way to group cats and lizards together, under which you do not have to include the rest of all reptiles, birds and mammals because they look similar? Note that I am NOT saying that similarity, by itself, must show evolutionary development. Even a creationist like you should be able to acknowledge and agree that, say, dogs are far more similar to cats than lizards, without accepting that evolution has any part to do with it. (The logic of evolution comes not in the similarities but in the distribution of similarities.)

So is the smallest taxonomical set that can fit the cats and lizards together Reptilia inclusive - that is, does it have to include all reptiles, birds, and mammals? Or can you think of a smaller taxonomical set (based purely on taxonomical features) that incorporates them both?

I still don't understand what the real issue is. Why would I care about wanting to include lizards and cats in one class?

 

[gluadys]

But when you use the word "previous" here, you certainly have to do with "advancement". Well you "know" then. Good for you. And why do you want to accuse me of conflation and what not? Why so defensive?

You mean you don't know what "must have come from" means? This is becoming quite silly.

Yes, I know what "must have come from" means and also "previous". But I would not consider these terms to be equivalent to "advancement".

"Advancement" to me implies something like a promotion, not just being the consequence of what has gone before.

If you are not using "advancement" as a value-laden term i.e. if by "advancement" you simply mean that "A came from/after B" and not "A is an improvement on B", I think we are just using different terminology for the same concept.

As Mallon said, what we are trying to get away from is some sort of value-judgment which grades some species as improvements on others or closer to some ideal of perfection.

So if all you mean is "species A is the ancestor of species B" fine. It just would have been a lot more clear if you had avoided terms that usually imply an evaluation of quality and not simply a sequence in time.

 

[gluadys]

No, I don't. But do you feel more biologically advanced then your ancestors the chimps, or even "more simple" life forms as Darwin put it?

No, I don't.

That's the point we are trying to make.

Evolution does not imply value judgments of the quality of different species.

As a human being I have capabilities (notably intellectual) which a chimp does not have. By the same token, chimps have capabilities which I do not have. As do many other species.

 

[gluadys]

My belief in God is not subject to "science". So the answer is no.

Good to hear. Too many people rest their faith on whether or not they are right about science. Nice to find someone who does not.

And it doesn't say anything about whether "primordial soup" is a good recipe for the origin of life.

Right. That will be something for science to explore. God can certainly use primordial soup as an intermediate step. Or something else.

What does "natural selection" mean then?

It means that in any set of natural circumstances, some members of a species will be more successful at surviving and reproducing than others. Since nature is a complex phenomenon, this can refer to a great many different particular items. One hunter may be quicker or stealthier or stronger than another and so be better able to nourish itself and its family. One potential prey may be quicker, quieter, better camouflaged, more alert, etc. and so better able to escape being dinner. One organism may be better able to fend off infection, tolerate light, cold, drought, (or in marine environments, pressure, saltiness) etc. One male may have more success attracting a mate. For myriads of different reasons, in different situations, not every organism in a species is equally successful in producing progeny, especially progeny which themselves survive into and through their own reproductive cycle.

Those who are the most successful reproducers pass on their genes to a larger proportion of the next generation than their peers, and it is their genes which eventually dominate in the species. The repetition of this pattern, generation after generation, changes the characteristics of the species.

Well it is not really measurable in my opinion.

Your opinion does not change the fact. As Galileo is reputed to have said after recanting his support for Copernicus' ideas "It [the earth] moves anyway."

Scientists can and have measured natural selection. I believe I have already referred to the work of the Grants in this respect.

But that "natural selection" was apparently not able to delete the particular variant from the population.

So what? Evolution is the change in the frequency in which a given trait appears. Whether the trait is eliminated or not is irrelevant. Even when it is, to all intents and purposes, eliminated as a phenotype, the genetic information usually still exists. And natural selection has no effect on genetic information which is not expressed. So, while an unfavorable trait may become quite rare, it is seldom completely eliminated.

No, it is the desired trend of progress observed by looking back. (if the word "origin" has any meaning at all). It is first and foremost about "the origin of species", possibly even from the origin of life to the origin of families and orders etc..

Sorry, if I am being dense here, but I don't get what you are driving at. You claim this "desired trend of progress" is not observed in any case, but if anyone is desiring to see such a trend, they must be looking for it. What is it you assume they are looking for and not finding?

I still think you are writing a script for evolution that is not known to science. That would constitute a straw man--an image of evolution that is not really evolution.

But you contradict yourself when you say: "Biologists don't evaluate any species as being better than others.", because that's what the notion of natural selection is all about! Didn't you say "better adapted"??

No, adaptation is quite a different thing than one species being better than another. A species may become more efficient, via evolution, at using the natural resources available to it. But since there are thousands upon thousands of different ecological niches in as many geographical regions, being "better adapted" is always a relative term. "Better adapted" to which set of environmental pressures? in which ecological niche? compared to what similar species?

I was just reading today about tiny wasps whose larvae feed parasitically on the larvae of other wasps that make their home inside the body of a certain kind of caterpiller which feeds on a certain plant that lives parasitically on another plant. Now that is a pretty specialized adaptation.

Does it make this species of wasp better than another species of wasp adapted to a different life-style? Does it make wasps in general better than moths in general? Or insects better than mollusks?

In reference to one specific set of ecological opportunities and constraints, one may judge species A better adapted than species B. But that is as far as it goes.

Natural selection does bring about better adaptation in this sense.

 

[holdon]

No, I don't.

That's the point we are trying to make.

Evolution does not imply value judgments of the quality of different species.

As a human being I have capabilities (notably intellectual) which a chimp does not have. By the same token, chimps have capabilities which I do not have. As do many other species.

Please note that "biological advancement" came from Mallon and that's why I responded that way. If you want to make a point, take it up with him.

 

[holdon]

It means that in any set of natural circumstances, some members of a species will be more successful at surviving and reproducing than others. Since nature is a complex phenomenon, this can refer to a great many different particular items. One hunter may be quicker or stealthier or stronger than another and so be better able to nourish itself and its family. One potential prey may be quicker, quieter, better camouflaged, more alert, etc. and so better able to escape being dinner. One organism may be better able to fend off infection, tolerate light, cold, drought, (or in marine environments, pressure, saltiness) etc. One male may have more success attracting a mate. For myriads of different reasons, in different situations, not every organism in a species is equally successful in producing progeny, especially progeny which themselves survive into and through their own reproductive cycle.

Those who are the most successful reproducers pass on their genes to a larger proportion of the next generation than their peers, and it is their genes which eventually dominate in the species.

Well, that's just micro evolution.

The repetition of this pattern, generation after generation, changes the characteristics of the species.

To what extend? That is not measurable.

Scientists can and have measured natural selection.

Have they measured to what extend n.s. contributes to changing (adding and deleting includes) genes?

So what? Evolution is the change in the frequency in which a given trait appears. Whether the trait is eliminated or not is irrelevant. Even when it is, to all intents and purposes, eliminated as a phenotype, the genetic information usually still exists. And natural selection has no effect on genetic information which is not expressed. So, while an unfavorable trait may become quite rare, it is seldom completely eliminated.

So, if the genetic info still exists, then we don't have much change do we?

Sorry, if I am being dense here, but I don't get what you are driving at. You claim this "desired trend of progress" is not observed in any case, but if anyone is desiring to see such a trend, they must be looking for it. What is it you assume they are looking for and not finding?

Well, take Darwin's assumption that life went from simple to more complex forms: he observed that trend of progress. Since then mulitudes of scientist have sought to confirm this: desired to show the trend of progress: evolution. Therefore Darwin gave his book this title: Origin of species.

No, adaptation is quite a different thing than one species being better than another. A species may become more efficient, via evolution, at using the natural resources available to it. But since there are thousands upon thousands of different ecological niches in as many geographical regions, being "better adapted" is always a relative term. "Better adapted" to which set of environmental pressures? in which ecological niche? compared to what similar species?
I was just reading today about tiny wasps whose larvae feed parasitically on the larvae of other wasps that make their home inside the body of a certain kind of caterpiller which feeds on a certain plant that lives parasitically on another plant. Now that is a pretty specialized adaptation.

Does it make this species of wasp better than another species of wasp adapted to a different life-style? Does it make wasps in general better than moths in general? Or insects better than mollusks?

In reference to one specific set of ecological opportunities and constraints, one may judge species A better adapted than species B. But that is as far as it goes.

Natural selection does bring about better adaptation in this sense.

Do you believe that species originated out of previous existing different species or not?

 

[Mallon]

Please note that "biological advancement" came from Mallon and that's why I responded that way. If you want to make a point, take it up with him.

For what it's worth, you're the one who equated evolution with 'advancement' in your post here (to which I replied in kind with a rhetorical question):

And you saying "Current species have come from previous species in their same genus, family, etc." involves exactly what you're contesting "advancement".

 

[USincognito]

If you could just tell me what that "quote function" is, then please spill the beans.

Nevermind...

Yes, you're just a little different from the chimps (your ancestors?), I presume. (unless you are a chimp, which I have no way of knowing of course)

No, I can state with confidence both that I am human and that I am just a little different from chimps - which are my cousins, not my ancestors. I, and you, do share a common ancestor with chimps about 6-7 million years ago.

Who was talking about "value judgment"??? But when you use the word "previous" here, you certainly have to do with "advancement".

You were. You cited the definition and tried to conflate biological evolution with the colloquial definition. "Previous" is not synonymous with "advancement" by the way. One is a chronological evaluation while the other is a value judgement.

Well you "know" then. Good for you. And why do you want to accuse me of conflation and what not? Why so defensive?

How am I being defensive pointing out your attempts to conflate definitions of a word? Transferance much?

 

[USincognito]

I still don't understand what the real issue is. Why would I care about wanting to include lizards and cats in one class?

I really have to question one's familiarity with a topic one is spending so much time discussing when one doesn't seem to even know the most basic issue in that topic.

Have you never heard of Linneaus?

 

[gluadys]

Well, that's just micro evolution.

That is the process of evolution. There are two ways in which this produces new species:

1. Chronospecies A->a1->a2->a3->etc, etc, etc, where each a# is a variant of its predecessor. Carry this on long enough and aN may be different enough from A to be considered a different species. Note that in this scenario, we always have one species. It changes over time, with each variant replacing its predecessor.

2. Cladistics or sister species: Population A subdivides into two groups. Both evolve as above, but because they are separated from each other, they evolve in different directions. After a time the two populations do not, or even cannot, interbreed even when given opportunity to do so. In this case one species is ancestor to two species so the number of species is increased. We can also check that the new species do not interbreed with each other, and sometimes we can also check that they no longer interbreed with the parent species either.

In either case, you have a new species. This, by definition, is macro-evolution. It did not require any change in the process of evolution.

The process of evolution gives us both micro-evolution (change within the species) and macro-evolution (new species).

To what extend? That is not measurable.

Why do you assume it is not measurable? What is there about the frequency at which alleles or character traits appear that is not measurable? What is there about a change in the size or placement of a bone (think about reptilian jaw bones becoming mammalian ear bones) that is not measurable? What is there about a DNA sequence or the amino acid sequence of a protein that is not measurable?

Have they measured to what extend n.s. contributes to changing (adding and deleting includes) genes?

Natural selection has nothing to do with changing the genes themselves. What natural selection does is change the frequency with which certain versions of a gene (alleles) appear in a population.

Natural selection does not create a gene for melanism. It does, however, determine whether moths that carry the gene will be rare or plentiful.

So, if the genetic info still exists, then we don't have much change do we?

If we have changed from having 95% of the population with the gene to having it appear in only 5% of the population, that is a considerable change for that particular trait. If we also have other character traits changing as well, (for natural selection acts on the whole organism at once, not just one character at a time) there can be considerable change over a few generations. And, of course, the more generations, the more change there may be.

Well, take Darwin's assumption that life went from simple to more complex forms: he observed that trend of progress.

Did he assume it or did he observe it? One does not call what has been observed an assumption.

Actually, as far as I know, Darwin did not observe any simple forms. Micro-organisms had only recently been discovered and Darwin did not study them much if at all. All the examples he gives in his writings are of complex organisms. He was certainly totally unaware of micro-fossils.

So, he apparently did not observe a progression from simple to complex forms. Did he assume any such thing? Well, I have read Origin of Species, and I don't recall any passage in which he makes that assumption. Can you cite such a passage?

Now, since Darwin's time, we have explored the fossil record much more thoroughly and developed much more exhaustive studies of micro-organisms generally. It would be idiotic today to deny that simple organisms existed for a long time before any complex organisms appeared. The simpler prokaryotic cell is the only sort of fossil found in the first 2 billion years of the fossil record. And there is still another 700 million years before the eukaryotic cells developed complex multi-cellular forms. But all this is observation, not assumption.

Do you believe that species originated out of previous existing different species or not?

Of course they did.

 

[shernren]

I still don't understand what the real issue is. Why would I care about wanting to include lizards and cats in one class?

Well, that's exactly why you don't get what I'm saying. Why would I care what happens if I try to cut a loaf or brick in half infinite times? (You get atoms.) Why would I care what happens if I try to travel near the speed of light? (Relativity.) Why would I care about what makes the Moon go around the Earth? (Gravity.)

Why would I care about wanting to include lizards and cats in one class? Because trying to do so, and failing miserably without including a whole lot of other animals, demonstrates on the macroscopic level a unique cladistic system which lends itself powerfully to an evolutionary explanation.

Suppose I wanted to taxonomically classify motorcycles, bicycles, tricycles and cars. I could note, for example, that motorcycles and bicycles have two wheels, while tricycles have three and cars have four. I could then invent three clades: Bicyclidae, Tricyclidae, and Quadricyclae. I could also note that motorcycles and cars have internal combustion engines, while bicycles and tricycles don't. I could then invent two clades: Pyrodynamiae, and Pedodynamiae (Pig Latin for "moves with fire" and "moves with legs"). I could note that bicycles, tricycles and motorbikes are steered with handlebars, while cars employ a steering wheel. There's another possible taxonomy.

This demonstrates the general principle that no unique hierarchical principle needs to exist for groups of designed objects. It's not unique to transportation. When a computer has an AMD CPU, for example, that doesn't automatically guarantee that it will have a Samsung hard drive, a Sony LCD monitor, or Windows Vista.

Take a look, however, at life. Suppose I try to create a classification system in which I start by lumping cats and lizards together in a category, and everything else in a different category. How might I justify that? Absolutely no way. (Other than the trivial justification "I said so!") For in what morphological characteristics are cats and lizards more similar to each other than anything else? Are they both tetrapedal? But so are dogs and goannas and dinosaurs and rabbits and people. Do both have jaws? But so do all fish and all mammals. Do they have segmented bodies? (Yes, they do. Your fancy textbook should have something about that under embryonic development.)* So do all the other, uh, animals that have segmented bodies (can't remember the technical name offhand), all the way from whales to worms.

As a matter of fact, the smallest set of all living organisms that would contain both cats and lizards is the set Reptilia inclusive - namely the union of Reptilia, Aves, and Mammalia. Let's call this big set Felidasauri. (Heh heh.) [EDIT: The proper name for this taxonomic clade is Diapsida; nevertheless, I preserve the original "name" to show where it came from.]

Would the existence of a unique clade Diapsida be logically necessary within an evolutionary framework? Almost certainly. And what do we observe in the real world?

 

[holdon]

You were. You cited the definition and tried to conflate biological evolution with the colloquial definition. "Previous" is not synonymous with "advancement" by the way. One is a chronological evaluation while the other is a value judgement.

I guess we have to accept that on your authority? Not! I really have to wonder why several of you evolutionists are taking this to such absurdities. "Value judgment"???