Kotatsu
Phthirapterist
I apologise in advance for any disorderliness in the following post. I seem to have eaten something that doesn't agree with me, and have been running back and forth to the little boys' room to throw up while writing it.
That is merely a repetition of your earlier point, without any attempt to actually explain it. I contend that you are wrong, and that it makes absolutely no difference for the theory of evolution whether or not we know that a gene is functional or not.
Evolutionary theory predicts changes in a given section of a DNA sequence over time regardless of if that section is used for coding a protein, is structural, or is actually just nonsense. Whether or not we know which of these (or any other categories) a given section falls into at the time they are being compared does not factor in at any point whatsoever (however, as I have stated before, if a certain gene region is known to be protein-coding and thus expected to evolve slower than a structural gene, it may not be chosen for comparison in the first place if the study undertaken requires evolution of a higher speed to test its hypotheses).
What you are claiming is that if a phylogeny is published based on what is believed to be a non-functional section of DNA, and this section is later found to have a function, the data and result of that phylogenetic study is no longer valid as evidence for the structuring within and common descent of the taxon studied. I will grant you that if the section in question is found to have a vastly different speed of evolution than previously thought, there may be problems with, e.g., long-branch attraction, however these will typically be picked up during the initial analysis, and will typically disappear in comparisons with other genes (I have this exact scenario in one of the data sets I am working on at the moment).
However, if this is the case -- and we discount long-branch attraction and similar for the sake of simplicity -- the only difference between the utility of the DNA section before and after its revelation as functional is the type of questions subsequent researchers would use this particular DNA section to try to answer. It does in no way whatsoever nullify its previous status as evidence for the obtained internal structures and hypotheses of descent. It remains the case that common ancestry and common descent is the only known robust theory for explaining the obtained pattern. It certainly does not in any way discredit or discount the initial findings.
Since we know that different groups of animals use different methods to solve the same problem on an organ level, there is no reason a priori to assume that the same does not hold true on a molecular level. Therefore, we have no reason to believe that similar function, understood as similar sequence, on a molecular level is evidence of anything other than common descent, unless other data makes this less likely.
So if I suggest a sample of randomly chosen phylogenies from the last 10 years or so covering a random sample of animals, you will be able to show me that it contains groupings of species that would not be predicted by the theory of evolution? If so, I could provide you with a list of phylogenies tomorrow and you would have as much time as you require to look them over and present your case.
This is true inasmuch as for the studied individuals, the process of evolution has ended, as they are typically dead. We have a few dozen fridges filled with biological samples from a range of vertebrate and invertebrate taxa here at my institute, and apart from the birds, of which only a few feathers are typically stored, it is true that for the individuals actually used in a phylogeny, evolution has ended. These individuals will never again contribute to evolution in any way.
It is also true to the extent that we can only use material that exists today. therefore, all phylogenies stretches only up until the date of collection for the oldest included specimen in any given clade. I collected my first clitellates in 2005, for instance, so when my latest paper on the group was published in 2009, I could only claim to have tracked the evolution of that particular group of clitellates until 2005 (well, I used some earlier material as well, so I think it is actually 2004). We cannot extrapolate into the future beyond the point of collection, and thus we are essentially looking at a process that has ended. This does not suggest, however, that the process has ended outside the laboratory.
This is necessarily true inasmuch as these ancestors typically are not available for DNA extraction and sequencing. It does not hold true for phylogenies based on morphology or ones that actually do include so-celled "ancient DNA", such as sequences from moas and the Great Auk.
However, the way a phylogeny is usually presented could easily give the uninitiated exactly the impression you outline. This suggests exactly one thing: that any observer needs to understand how to read a tree and what the various features of a tree represent before attempting to comment on it. For a beginner like yourself, it is often easier to start with trees that do character tracking, as these will often comment on likely traits of organisms at ancestral nodes, and therefore the process of visualising, e.g., morphological change throughout a tree is easier.
Naturally some aspects of the DNA of extant marsupials and mammals were present in the DNA of their common ancestors.
Could you elaborate? I cannot see how a phylogeny could look like anything but an unguided process.
We have most likely not found all phyla. At least three new extant phyla have been found within my lifetime; I have no idea if there have been any discoveries of phyla that are only known from the fossil record within this time.
Well, this betrays a fundamental lack of knowledge with what a taxon actually is. These limits between phyla and other taxonomic units are arbitrary distinctions, which correspond to certain basic bauplans found in nature, but which could theoretically be subdivided further. Nothing is stopping you from redefining the phylum concept so that all groups that diverged between 70-65 million years ago are separate phyla. The lack of descriptions on phylum level of taxa which diverged more recently than 500 million years ago or so has more to do with conservatism in the biological community than any feature of evolution or evolutionary theory.
Examples of families, genera and species which have evolved more recently than 500 million years ago are, I think you will find, plentiful. You're holding this discussion with one, for instance.
Why should they? There is nothing in evolutionary theory that obliges them to, so for a more serious answer to your question, you will have to ask someone who subscribes to a distinctly different theory in which they would be.
Please provide evidence for the claim that microevolution never adds up to macroevolution.
Do you have a reference for this claim?
The fact that predators, when moving on old leaves, produce sound? The fact that many prey species, when moving in similar terrain, also produce sounds? The fact that it is detrimental to the survival of the species if none of them can hear warning sounds? The need for heat regulation?
If you, by "pairs", are talking about gross morphology in comparison between placentals and mammals, then I can think of a range of environmental pressures that could modify a given common ancestor. Assuming that Australian and Eurasian soils are sufficiently similar, similar solutions and adaptation to living underneath it would likely evolve, such as strong front paws, partial or entire loss of sight, a heightened sense of smell and perhaps tactile and chemo-sensory senses, a diet of roots, tubers, seeds, insect larvae, worms, and other kinds of food available in a subterranean environment (with the necessary changes in tooth and jaw structure and intestinal morphology, if needed). This could -- and did -- result in similar groups of animals which meet the requirements of a subterranean life in similar ways.
It does change it completely. Evos claimed pseudogenes not being functional but appearing among certain groupings of species thought to have a common ancestor was "very strong evidence" for evolution. They had been told they were overstating their case. Their idea is that since the genes were not functional, similar function cannot explain similar design (similar genes) but that ONLY common ancestry could explain the appearance of homologous pseudogenes.
That is merely a repetition of your earlier point, without any attempt to actually explain it. I contend that you are wrong, and that it makes absolutely no difference for the theory of evolution whether or not we know that a gene is functional or not.
Evolutionary theory predicts changes in a given section of a DNA sequence over time regardless of if that section is used for coding a protein, is structural, or is actually just nonsense. Whether or not we know which of these (or any other categories) a given section falls into at the time they are being compared does not factor in at any point whatsoever (however, as I have stated before, if a certain gene region is known to be protein-coding and thus expected to evolve slower than a structural gene, it may not be chosen for comparison in the first place if the study undertaken requires evolution of a higher speed to test its hypotheses).
What you are claiming is that if a phylogeny is published based on what is believed to be a non-functional section of DNA, and this section is later found to have a function, the data and result of that phylogenetic study is no longer valid as evidence for the structuring within and common descent of the taxon studied. I will grant you that if the section in question is found to have a vastly different speed of evolution than previously thought, there may be problems with, e.g., long-branch attraction, however these will typically be picked up during the initial analysis, and will typically disappear in comparisons with other genes (I have this exact scenario in one of the data sets I am working on at the moment).
However, if this is the case -- and we discount long-branch attraction and similar for the sake of simplicity -- the only difference between the utility of the DNA section before and after its revelation as functional is the type of questions subsequent researchers would use this particular DNA section to try to answer. It does in no way whatsoever nullify its previous status as evidence for the obtained internal structures and hypotheses of descent. It remains the case that common ancestry and common descent is the only known robust theory for explaining the obtained pattern. It certainly does not in any way discredit or discount the initial findings.
Since we know that different groups of animals use different methods to solve the same problem on an organ level, there is no reason a priori to assume that the same does not hold true on a molecular level. Therefore, we have no reason to believe that similar function, understood as similar sequence, on a molecular level is evidence of anything other than common descent, unless other data makes this less likely.
On the phylogeny, I am talking about the overall pattern so we're talking all of them.
So if I suggest a sample of randomly chosen phylogenies from the last 10 years or so covering a random sample of animals, you will be able to show me that it contains groupings of species that would not be predicted by the theory of evolution? If so, I could provide you with a list of phylogenies tomorrow and you would have as much time as you require to look them over and present your case.
It's not a point original I have thought of. If you look at the pattern and assume common descent, it suggests a couple of things; first a process that has largely ended
This is true inasmuch as for the studied individuals, the process of evolution has ended, as they are typically dead. We have a few dozen fridges filled with biological samples from a range of vertebrate and invertebrate taxa here at my institute, and apart from the birds, of which only a few feathers are typically stored, it is true that for the individuals actually used in a phylogeny, evolution has ended. These individuals will never again contribute to evolution in any way.
It is also true to the extent that we can only use material that exists today. therefore, all phylogenies stretches only up until the date of collection for the oldest included specimen in any given clade. I collected my first clitellates in 2005, for instance, so when my latest paper on the group was published in 2009, I could only claim to have tracked the evolution of that particular group of clitellates until 2005 (well, I used some earlier material as well, so I think it is actually 2004). We cannot extrapolate into the future beyond the point of collection, and thus we are essentially looking at a process that has ended. This does not suggest, however, that the process has ended outside the laboratory.
second, evolution seeming to occur via a pulse and burst of groupings of creatures that remain largely in stasis or go extinct but evolve around a range; the common ancestor that began each of these bursts is conspiciously absent;
This is necessarily true inasmuch as these ancestors typically are not available for DNA extraction and sequencing. It does not hold true for phylogenies based on morphology or ones that actually do include so-celled "ancient DNA", such as sequences from moas and the Great Auk.
However, the way a phylogeny is usually presented could easily give the uninitiated exactly the impression you outline. This suggests exactly one thing: that any observer needs to understand how to read a tree and what the various features of a tree represent before attempting to comment on it. For a beginner like yourself, it is often easier to start with trees that do character tracking, as these will often comment on likely traits of organisms at ancestral nodes, and therefore the process of visualising, e.g., morphological change throughout a tree is easier.
a repetition of forms such as with placentals and marsupials suggesting the pattern was in some sense preformed in DNA; etc,....
Naturally some aspects of the DNA of extant marsupials and mammals were present in the DNA of their common ancestors.
It doesn't look like an unguided process.
Could you elaborate? I cannot see how a phylogeny could look like anything but an unguided process.
We haven't seen a new phyla, for example, in what 500 million years or something like that?
We have most likely not found all phyla. At least three new extant phyla have been found within my lifetime; I have no idea if there have been any discoveries of phyla that are only known from the fossil record within this time.
How long for the other taxa? Say a new kingdom in what? even longer, right?
Well, this betrays a fundamental lack of knowledge with what a taxon actually is. These limits between phyla and other taxonomic units are arbitrary distinctions, which correspond to certain basic bauplans found in nature, but which could theoretically be subdivided further. Nothing is stopping you from redefining the phylum concept so that all groups that diverged between 70-65 million years ago are separate phyla. The lack of descriptions on phylum level of taxa which diverged more recently than 500 million years ago or so has more to do with conservatism in the biological community than any feature of evolution or evolutionary theory.
New family?New genus? New species?
Examples of families, genera and species which have evolved more recently than 500 million years ago are, I think you will find, plentiful. You're holding this discussion with one, for instance.
Hopefully you get the picture? Why have bacteria with such a remarkable adaptive and mutation rate not evolved something else in the past billion years?
Why should they? There is nothing in evolutionary theory that obliges them to, so for a more serious answer to your question, you will have to ask someone who subscribes to a distinctly different theory in which they would be.
They are one of the most stable forms around. Micrevolution happens all the time there but never adds up to macroevolution.
Please provide evidence for the claim that microevolution never adds up to macroevolution.
The mammalian ear is thought to have evolved independently among mammals, not that the common ancestor of mammals had a mammalian ear.
Do you have a reference for this claim?
Take some time to look at the different "pairs' between placentals and mammals. The Darwinian answer is that a random process still produced these pairs because of environmental pressures. That's ridiculous. What environmental pressures duplicated the mammalian ear, for example.
The fact that predators, when moving on old leaves, produce sound? The fact that many prey species, when moving in similar terrain, also produce sounds? The fact that it is detrimental to the survival of the species if none of them can hear warning sounds? The need for heat regulation?
If you, by "pairs", are talking about gross morphology in comparison between placentals and mammals, then I can think of a range of environmental pressures that could modify a given common ancestor. Assuming that Australian and Eurasian soils are sufficiently similar, similar solutions and adaptation to living underneath it would likely evolve, such as strong front paws, partial or entire loss of sight, a heightened sense of smell and perhaps tactile and chemo-sensory senses, a diet of roots, tubers, seeds, insect larvae, worms, and other kinds of food available in a subterranean environment (with the necessary changes in tooth and jaw structure and intestinal morphology, if needed). This could -- and did -- result in similar groups of animals which meet the requirements of a subterranean life in similar ways.