When you start discussing evolution you have to begin by establishing your definitions and declaring what version of evolutionary theory you support. This is especially important if you are debating extensions of evolutionary theory and it's even more important if you are debating a creationist. Creationists need to understand that evolution is both a Fact and a Theory, for example. If they don't understand that then they don't understand anything about evolution.
Creationists aren't the only problem. Even non-creationists get confused about evolution. Most don't know the difference between evolution and natural selection and that makes it difficult to talk about molecular evolution and a host of other topics. It's hard to explain junk DNA to an adaptationist and it's hard to show you why Michael Behe is wrong in The Edge of Evolution if you've never heard of Neutral Theory and random genetic drift.
I thought I'd point my students to a few of the definitions on the web. It's shocking to see how many different definitions of evolution there are and it's shocking to see how often websites ignore any mechanisms other than natural selection. You will be surprised at how many supposedly reputable sources get it wrong. It's no wonder everyone is confused.
Which ones do you like?
- What is Evolution?
- What Is Evolution? Another curious aspect of the theory of evolution is that everybody thinks he understands it. I mean philosophers, social scientists, and so on. While in fact very few people understand it, actually, as it stands, even as it stood when Darwin expressed it, and even less as we now may be able to understand it in biology. Jacques Monod (1974)
- What is evolution? Darwin's brilliant idea
- WHAT IS EVOLUTION?
- What Is Evolution Anyway?
- Get Answers: Evolution
- Understanding Science & Evolution
- The Teaching of Evolution
- What is evolution?
- What is Evolution?
- What Evolution Is and What It Isn’t
- An introduction to evolution
- What is Evolution?
- Evolution Is Change in the Inherited Traits of a Population through Successive Generations
- What is evolution?
- What is Evolution?
- Introduction: Evolution
- What is evolution?
- WHAT IS EVOLUTION?
- What Is Evolution?
In my area, the last few holdouts who still want to formally recognize non-monophyletic taxa prefer the definition "descent with modification". Don't know where they have it from originally but they like it because they want to stress the latter part to imply that phylogenetic systematics "ignores" the modification.
ReplyDelete(See, a cladist says that birds are dinosaurs, so obviously the cladist ignores the evolutionary changes that happened between Jurassic theropods and modern birds. Which is complete nonsense because although birds are dinosaurs, they are also still a special subgroup of dinosaurs called birds, and the cladist recognizes those modifications as the synapomorphies of that subgroup.)
Point is, I was wondering what you would make of that definition.
In my own case, I use the changing allele frequencies one myself under certain circumstances but it all depends. When somebody says "evolution" one generally has to assume that they mean more. The creationists do not attack changing allele frequencies, they attack the idea that we had a common ancestor with monkeys, goats and red algae.
When discussing the concept of evolution in that context, withdrawing to a minimalist definition from the real of population genetics would be nothing but evasion because "evolution" is then to be understood to include the fact of the common ancestry of all life on earth and the various mechanisms that lead to the present diversity of life.
One could also add that Darwin would not have known about population genetics in the way we understand it now...
realm
Delete"Descent with modification" is what Darwin called it in the Origin of Species.
DeleteCharles Darwin died on April 19, 1882. That's more than 130 years ago. It's time to update the definition.
DeleteThe whole last chapter of Michael Lynch's book is on exactly the issue that quote from Monod addresses.
ReplyDeleteAnd you can just feel the pain with which those pages were written when you read them
Also, I obviously wasn't around in the 1970s so I have no direct observations but from what I read about the history of the field, it seems like in that period the mainstream discussion was a lot closer to reality than it is now. Neutral evolution was a relatively new idea and was debated. But in more recent times the adaptationists won the fight for the public portrayal of the theory while the appreciation of neutral mechanisms was relegated to the realm of the small group of experts in the field.
I personally was never thought those things and I passed through quite esteemed institutions. In which it wasn't thought because there is simply nobody to teach such a course. And I am still filling gaps in my education on the subject as a result.
The literature has become segregated too. I see the occasional molecular evolution paper in the genomics journals but I almost never see a paper from people specializing in genomics in the molecular evolution journals. Which makes me think that almost nobody in genomics reads those journals.
I think, though, that you might be a bit mistaken about lack of genomics papers in journals on evolution. The journal "Genome Biology and Evolution" is an offshoot of "Molecular Biology and Evolution" that resulted from the editors of the latter thinking that they had so many articles from genomicists, that the field might deserve its own journal.
DeleteGeorgi says,
DeleteAnd you can just feel the pain with which those pages were written when you read them
For example, Michael Lynch writes on page 370 ...
With interest in evolution now emerging among scientists working at all levels of biological organization, it is time to stop the trivialization of the field of evolutionary biology. A strong belief in cells does not make one a cell biologist, and a strong belief in Darwin's principle of natural selection is not a sufficient condition for understanding evolution. The standards for research in evolutionary biology should be set no lower than those in any other area of scientific inquiry.
I agree. If you don't understand evolution then don't write about it in your papers. I hope the ENCODE Consortium leaders are listening.
But it's even worse than that. If one doesn't understand evolution then one shouldn't debate creationists. It makes them look intelligent.
Larry says: "If one doesn't understand evolution then one shouldn't debate creationists. It makes them look intelligent."
DeleteI'll go you one better. If you don't understand creationism as well as evolution, don't debate creationists.
If you're a geneticist they'll throw at you all kinds of very specific, factually false assertions from outside your field-- from geology ("radiometric dating is based on assumptions that have been disproven") and paleontology ("no indisputable transitional fossils") etc.
If you're a paleontologist, then they'll throw at you all kinds of very specific, factually false assertions from outside that field too -- from genetics ("Darwinists said all non-coding DNA was junk") and molecular biology and probability ("tornado in a junkyard, probability of one protein is 1 over 1 followed by 200 zeroes") etc.
If you don't know the creationist arguments that claim to "debunk" radiometric dating etc., don't debate YECs. Their arguments are all dishonest but you must know the technical details. They'll throw stuff at you that sounds very "scientific" to church audiences, even though theyr'e false they sound good-- and you can't just stand there and say, "Duh, if we all just have faith in the scientific method..."
That's why I think Zack Kopplin, 19 years old, screwed the pooch by "debating" Casey Luskin on Medved's radio show.
It's also why Ken Ham challenges Bill Nye to a debate, but won't debate Aron Ra. Aron Ra knows creationist tricks and doesn't put up with BS.
@Diogenes,
DeleteI agree with you. I spend a lot of time trying to understand creationist arguments in those fields where I have some knowledge. I don't dare debate creationists on physics or astronomy or paleontology. It's not because they are right, it's because I don't have the expertise to refute them effectively.
That's a good point - it takes a team of scientists to properly deal with a single creationist. And even then it's an asymmetric warfare in which the creationist has all the advantage - because:
Delete1) he doesn't have to adhere to the same intellectual standards as his opponents
2) the audience usually doesn't even understand what those standards are
3) one can always say a lot more lies and falsehoods in a given unit of time than anyone can hope to properly debunk.
http://www.jesusandmo.net/2008/12/17/edge/
DeleteI dunno. I don't see this ignoring of neutral evolution by biologists that you're on about. Maybe it's just my particular corner (molecular phylogenetics), but every evolutionary model I ever encounter assumes neutrality.
ReplyDeleteAgain I will make the complaint that "change in allele frequencies in populations" doesn't cover selection or sorting above the within-population level, though I would still consider that to be evolution. How about you? And no, I don't have a better definition.
Well, yes, every evolutionary model in the field of molecular evolution assumes neutrality. But that's the field of molecular evolution. Outside of it, it's a very different situation. That's the point.
DeleteSame here. Neutrality is the null hypothesis, be it in evolutionary biology or population genetics, and phylogenetics uses a lot of spacer regions that are assumed not to be under selection.
DeleteBut the thing is, drift does not give you the illusion of design that is explained by the theory of evolution sens. lat. If we tried to explain succulent plants, the peacock tail or mimicry of stinging insects by harmless ones through random genetic drift then the creationists would be justified to dismiss evolutionary biology. In other words, the really interesting stories are all about adaptation. Can't be helped.
There are many fascinating evolutionary stories that are all about drift.
DeleteExamples?
Delete(Of course, there might be some that are interesting to you and me, but ask yourself honestly: are they interesting to non-specialists on a "that is why the giraffe has such a long neck" level?)
The Origins of Genome Architecture is full of them.
DeleteAnd then, this is of course speculation, but it might well be true:
http://www.ncbi.nlm.nih.gov/pubmed/16511485
The Origins of Genome Architecture is full of them.
DeleteSee, this is where we will have to conclude that "interesting" lies in the eye of the beholder. This topic would not look so great in an Evolution for Dummies textbook or when trying to explain to my family how populations evolve.
More generally I am afraid the core of any drift story will always be "it happened purely by chance, could have been different and nothing of importance would have changed", because that is kind of the definition of drift. If something of importance (in other words, something interesting) turned on it then it would have been selected for, making it *not drift*. So by definition neutrality is the background noise behind the important events.
I am really puzzled about your link. If the story is true, then it means that something that we thought was an adaptation for X started out as an adaptation for Y. So it is still a story of adaptation. Where does the randomness even come in here?
More generally I am afraid the core of any drift story will always be "it happened purely by chance, could have been different and nothing of importance would have changed", because that is kind of the definition of drift. If something of importance (in other words, something interesting) turned on it then it would have been selected for, making it *not drift*. So by definition neutrality is the background noise behind the important events.
DeleteNot at all. What seems to have happened is that the low N_e of eukaryotes has allowed for all the complexification you see in them. Because most genomic changes that lead to higher complexity are slightly deleterious. In contrast, prokaryotes are kind of stuck in a highly adapted but simplified state of organization. There isn't a single prokaryote group that made the transition to multicellularity and you would think that if multicellularity was so beneficial, it would have evolved in them given how strong selection is in prokaryotes.
Basically the relative strength of selection and drift is what has opened or closed certain evolutionary directions for different groups.
That seems pretty important stuff to me
P.S. In that link I sent, low N_e and drift play a very important role in the initial establishment of introns.
Maybe I am obtuse, but now you seem to be saying that one needs random processes to produce the diversity that selection towards a certain evolutionary direction can ultimately work on. That does not sound like drift either but merely like the standard combination of mutation plus selection.
DeleteUnless I severely misunderstand, drift is when no selection happens. As in, you have three chloroplast lineages in one plant species, and 500K years later only one is left, not because it was better but purely because it got lucky.
That is a typical drift story, and it is boring precisely because it is about drift. The eukaryote story is different because the larger genome allowed them to reach a different peak in the fitness landscape, i.e. because of adaptation.
In response to a statement by Georgi that, "There are many fascinating evolutionary stories that are all about drift."
DeleteAlex SL responded with,
See, this is where we will have to conclude that "interesting" lies in the eye of the beholder. This topic would not look so great in an Evolution for Dummies textbook or when trying to explain to my family how populations evolve.
Is your family interested in knowing why so many people from Ireland have red hair or why some genetic diseases are more common in people from Quebec than in people from France? Are they interested in knowing why their children look like them but look different from other children? Are they curious about blood types and DNA fingerprints?
If so, how do you explain these things if you don't talk about random genetic drift?
John Hashman asks,
DeleteAgain I will make the complaint that "change in allele frequencies in populations" doesn't cover selection or sorting above the within-population level, though I would still consider that to be evolution. How about you?
I agree. The minimal definition doesn't even cover speciation and that's very important in evolution.
And no, I don't have a better definition.
But that's the problem, isn't it? You have to start somewhere, Why not start by setting out the minimum characteristics that count as evolution?
Larry,
DeleteLike Joe, I'm not sure what the point it. I don't consider the definition very important. It looks as if your main gripe is that some people try to define evolution as "mutation and natural selection", which leaves out all the stochastic processes you like so much. Now in this case, I think you're right. Leaving out drift is a serious distortion, much greater than what I complain about. But it's still not such a big deal; just definitions.
While we're on the subject of definitions, I don't know what you mean by "minimal". I would have taken it to mean the simplest definition that covers everything. But you favor a definition that you agree doesn't cover everything. What makes that minimal instead of something with even less coverage? What, in other words, does "minimal" mean to you?
LAM,
DeleteYou are correct, I had not given enough thought to the fact that people will find such stories interesting when they revolve around, well, people. Unless we are plant or animal breeders we observe the intraspecific variation of humans with much more interest than those in other species.
Still, I am a botanist. I am not sure if any lay person would read a press release about genetic drift in some species of plants with the same curiosity as they would read a press release about the adaptation of that plant's flower to the needs of its pollinator, or about its adaptation to erratic rain fall regimes of the arid Australian interior.
Alex SL says,
DeleteStill, I am a botanist. I am not sure if any lay person would read a press release about genetic drift in some species of plants with the same curiosity as they would read a press release about the adaptation ...
Really? Don't you think people might be curious about why different species of maple trees have leaves that are slightly different shapes and different colors? (e.g. red maple, silver maple, sugar maple)
What about the different species of dandelion that they encounter? Might they wonder why the species differ only slightly in appearance so that it's difficult to tell them apart? How do you explain these things to the general public without mentioning the possibility that the differences might be due to chance rather than adaptation?
John Harshman says,
DeleteBut it's still not such a big deal; just definitions.
Actually, I think that defining your terms IS a big deal. We'll have to agree to disagree on this one.
While we're on the subject of definitions, I don't know what you mean by "minimal". I would have taken it to mean the simplest definition that covers everything. But you favor a definition that you agree doesn't cover everything. What makes that minimal instead of something with even less coverage? What, in other words, does "minimal" mean to you?
It means the minimum criteria that are required in order to declare that something counts as evolution. It covers the idea that it's populations that evolve and not individuals, that the characteristics that change are genetic (alleles), and that any change in the frequency of those characteristics in the gene pool counts as evolution.
All of the higher levels of evolution encompass this minimal concept or they wouldn't be examples of evolution. The only exception is extinction, which is a special case.
All of the higher levels of evolution encompass this minimal concept or they wouldn't be examples of evolution. The only exception is extinction, which is a special case.
DeleteThat isn't true, and even your second sentence acknowledges it. Higher levels of evolution do not involve change in allele frequencies in populations. They involve differential speciation and extinction with no particular expectation of change within populations. If you want to say those aren't evolution, that's fine. But don't simultaneously claim they are evolution and that your definition encompasses them.
Evolution is not a fact or a theory in explaining changes in populations beyond reproducing types at any one point in history.
ReplyDeleteShow where a population changed so that it could no longer reproduce with its parent population??
Mincro evolution is very rare and minor itself in nature. In fact probably only at bacteria levels.
Of coarse extrapolating from these is not scientific evidence for a history of biology. Even if true history.
Creationists understand evolution in small or great is the idea of biology changing without a thinking being making the change. So from natural causes.
We can live with some, if oproven, but not with the big stuff.
We need evidence before its a fact.
I need evidence evolution is a theory. I think its just a hypothesis supported, claimed, by non biological evidences.
Robert, You say "I need evidence evolution is a theory. I think its just a hypothesis supported, claimed, by non biological evidences."
DeleteThis is not the place for you to be, we can't teach understanding science here. To point out the obvious: We have been doing archaeology for a very long time. A lot of evidence of human activity has been found. Now tell me, are stone or flint tools, arrowheads or axes evidence of past humans existence and activity? If you want evidence, look for and study the evidence!
Do you claim that fossilized bones are not evidence of past life? Are not insects captured in several million years old amber biological evidence?
Please don't come back before you have learned anything.
I wonder how useful it is to try to have an exact definition of evolution. It is the same with definitions of "life". Frequently in discussions online, someone comes along and says that "there is no point in having this discussion unless we define Life first." At that point I disappear from the discussion. I've been able to do work, perhaps even useful work, for 50+ years in life sciences, without ever having my own precise definition of Life. The same is true for many other people in many other fields. What is the definition of "human society"? What is the definition of "engineering"? For that matter what is the precise definition of "biochemistry"?
ReplyDeleteThe online discussion that intended to come up with a Definition Of Life gets mired in details and exceptions, disputes about the essentialness of this and that, and attempts to build into the definition the answers to controversies in biology. It never comes to a consensus and discussion of it finally dies out. I glance at it once and awhile and am glad I did not participate. This has happened repeatably in different forums.
Good luck with this discussion, folks.
I understand what you're saying about the definition of "life" but the definition of evolution is another matter altogether. We may not be able to agree on a definition of evolution but we should at least, declare our definition before entering into a debate or discussion about evolution.
DeleteIf you want to define evolution as "descent with modification," for example, then the fact that Europeans have grown taller in the past five hundred years counts as evolution. I think it's important to know that this is what people have in mind when they use certain definitions because that doesn't count as evolution in my book.
Similarly, when I say that the fixation of O type blood alleles in native American populations is an example of evolution, it's important that strict adaptationists realize that this could be purely by accident according to my definition of evolution.
It's important that I understand YOUR definition of evolution of we ever have a serious disagreement about some issue in evolutionary biology. Don't you agree?
If you want to define evolution as "descent with modification," for example, then the fact that Europeans have grown taller in the past five hundred years counts as evolution.
DeleteI may be helping to make Joe's point, but I don't think that environmentally-conditioned variation counts as 'modification'. I doubt anyone would attempt to argue that a series of pea seeds had undergone 'descent with modification' simply because some were bigger than others. The obvious clarification can be provided by inserting 'genetic', but it is not strictly necessary provided one's definition of 'modification' encompasses heritability.
Larry: It's important that I understand YOUR definition of evolution of we ever have a serious disagreement about some issue in evolutionary biology. Don't you agree?
DeleteNot at all. In order to discuss whether type O blood group has reached fixation in natirve South American populations by genetic drift or by natural selection, why do we need to first agree on What Is Evolution ? We don't need to, as far as I can see,
Allan, what, at a minimum, would you count as modification? Will you state some example please?
DeleteLarry, on the page you linked to that talks about your favorite definition of evolution it says:
Delete"Evolution is a process that results in heritable changes in a population spread over many generations."
How many generations? And what number would the rest of you put on "many"? And what is the minimum change that would satisfy the definition of "change"?
Joe asks,
DeleteNot at all. In order to discuss whether type O blood group has reached fixation in natirve South American populations by genetic drift or by natural selection, why do we need to first agree on What Is Evolution ? We don't need to, as far as I can see,
I guess you've never discussed that topic with Richard Dawkins! He has argued in the past that changes in allele frequencies due to random genetic drift don't really count as evolution. So has Ernst Mayr.
However, in most cases the problem isn't that people have considered drift and rejected it. It's that they don't even know about it so they assume that the only kind of change allowed is that due to natural selection. If that's the definition they start with then you're going to have a lot of trouble using random genetic drift as an explanation.
You're probably also going to encounter resistance if you allude to the fact that deleterious mutations can be fixed in a population or that beneficial alleles might not fix.
It's much better if everyone is on the same page at the beginning of the discussion.
twt - At a minimum, it could be any bit or bit series in the genome of an individual that differs from the same position in the parent(s). Too small to be worth accounting for, but following fixation of one such, all descendants would see the 'moment the genome changed' as that minor, inconsequential blip. Promoting the generality of such blips as 'minimal evolution' might not be to everyone's taste, perhaps. But the insertion of 'over many generations' seems arvbitrary.
DeleteGnnnnhhh! *arbitrary!
DeleteLarry I guess you've never discussed that topic with Richard Dawkins! He has argued in the past that changes in allele frequencies due to random genetic drift don't really count as evolution. So has Ernst Mayr.
DeleteDo you have a reference?
@Allan Miller,
DeleteTo see Dawkin's view, check out: Richard Dawkins' View of Random Genetic Drift
Ernst Mayr's take is summarized in: What Is Darwinism?
I didn't find anything in your quotations from Dawkins to suggest that drift doesn't count as evolution. What was I missing?
DeleteJohn, you are really being picky. Why?
DeleteIt should be clear from my post that Richard Dawkins goes out of his way to avoid using the term "genetic drift." Instead, he refers to "Neutral Theory." What he's talking about is the fixation of neutral alleles and the fact that he doesn't specifically mention genetic drift should not lull you into a false sense of "gotchaism."
When Dawkins says, "In this sense, the substitution of a neutral allele would not constitute evolution ...." do you really think I'm doing him a disservice by saying that Dawkins, "has argued in the past that changes in allele frequencies due to random genetic drift don't really count as evolution"?
Do you really want to insist that the only correct way to describe Dawkins' view is to say something like, "In the past Dawkins has said that the fixation of neutral alleles (by an unspecified mechanism) doesn't really count as evolution"?
Oops. I forgot to point out that it was Maynard Smith who said "In this sense, the substitution of a neutral allele would not constitute evolution ...." and Dawkins was just agreeing with him.
DeletePicky? No, just noticing that your claim was wrong. Dawkins wasn't agreeing with Maynard Smith, if that's even what Maynard Smith meant. He was just making a claim that neutral evolution doesn't affect phenotype. We could argue about whether that's true (I agree that it almost certainly isn't), but it hardly has anything to do with Dawkins' definition of evolution. I truly do not understand why you're so exercised about this.
DeleteThe issue of whether or not genetic drift "constitutes evolution" is irrelevant to my point.
DeleteI asked: when we try to figure out whether the fixation of type O alleles in native South American populations is due to selection or to drift, why do we need a formal definition of evolution?
The fact that many people do not understand genetic drift, or that Richard Dawkins doesn't consider it to be evolution, does not solve the South American type O problem.
I am still waiting to hear why making a definition of evolution has any bearing on what happened to the type O alleles. And that question is just a place-holder for many others that also do not depend on what gets defined as evolution.
PS John Maynard Smith was quite keenly aware of genetic drift and neutral mutation, and did not at all advocate ignoring them.
Joe asks,
DeleteI asked: when we try to figure out whether the fixation of type O alleles in native South American populations is due to selection or to drift, why do we need a formal definition of evolution?
In order to answer your question all you need to do is establish proper definitions of selection and drift.
On the other hand, if you ask whether the fixation of O alleles is an example of EVOLUTION you need to agree on a definition of evolution.
PS John Maynard Smith was quite keenly aware of genetic drift and neutral mutation, and did not at all advocate ignoring them.
I do not claim the he was unaware of drift. I claim that he considered it to be trivial and not really important in evolution.
John Maynard Smith managed to write an entire book (with Szathmary) on "The Major Transitions in Evolution" (1995). He never mentioned drift, even once, as far as I can tell. Could you do that, Joe? Could you write an entire book without mentioning the possibility that something might have arisen by drift?
Furthermore, Maynard Smtih explains his perspective in the opening chapter where he says, "The transitions must be explained in terms of immediate selective advantage to individual replicators: we are committed to the gene-centered approach outlined by Williams (1966), and made more explicit by Dawkins (1976)."
Michael Lynch could never write that and neither could I. How about you Joe (or anyone else reading this)? Could you commit to the idea that major transitions "MUST be explained in terms of immediate selective advantage"?
I was noting that the question of what accounts for the fixation of type O alleles in South America can be addressed without any need for a precise definition of evolution. That fact that people like Dawkins or Maynard Smith don't (or in JMS's case didn't) consider genetic drift to be an important part of evolution is irrelevant.
DeleteWe can ask, and maybe even answer, the Type O question without the definition of evolution. The point is that many, and I would even say most, questions in evolutionary biology do not require a precise definition of "evolution".
I suspect the same holds for "biochemistry".
I posted this quote from Michael Lynch on another thread but it's very relevant here.
ReplyDeleteSean Carroll is keen on storytelling as a way of teaching science. I disagreed with him when we talked about this last week but I didn't press the issue because there were other things we needed to discuss.
Here's what Michael Lynch says in his book (page 371).
... numerous biologists, particularly in the area of development, have expressed reservations about the entire population genetic enterprise. Consider this quote from Carroll [in "Endless Forms Most Beautiful"]: "Since the Modern Synthesis, most expositions of the evolutionary process have focused on microevolutionary mechanisms. Millions of biology students have been taught the view (from population genetics) that 'evolution is the change in gene frequencies.' Isn't that an inspiring theme? This view forces the explanation toward mathematics and abstract description of genes, and away from butterflies and zebras. ... The evolution of form is the main drama of life's story, both as found in the fossil record and in the diversity of living species. So, let's teach that story. Instead of 'change in gene frequencies' let's try 'evolution of form is change in development.'" Many similar statements could be quoted from other authors.
Even ignoring the fact that the vast majority of species are unicellular, differentiated by metabolic rather than developmental features, this type of statement paints an inaccurate portrait of the current field of evolutionary biology. Evolution is much more than a storytelling exercise, and the goal of population genetics is not to be inspiring, but to be explanatory.
I agree. Good teaching is more that just making students happy by telling them stories that cater to their misconceptions. Good teaching means getting students interested in things that they now think are boring. And good teaching involves hard work for both teachers and students. Most important concepts in biology are difficult. You don't avoid them just because they are difficult or because the appear at first glance to be boring.
It's your job as a good teacher to make population genetics as interesting as possible and to explain why it's fundamentally important in order to understand evolution. If the students don't get it then they don't pass the course. You're not doing them any favors by skipping the hard parts of evolution.
On the basis of some paleontological readings, the main macro evolutionary changes take place only in the period of ecological crisis. Since the organic progress is a complication of the internal organization of live systems, it may lead to a logical inference that the indispensable condition complexity of the internal organization is an alteration of homeostasis. But, a stable disturbance of homeostasis is called “disease”. Consequently, disease is prerequisite for the organic progress.
ReplyDeleteDisease is a breakage of self-controlling and regulation, including genetic processes. How reads, interprets a damaged cell the hereditary information? In the case of a non-classical transfer of genetic information, the above-stated question deserves a specific treatment. There is reason to assume, that the “erroneously” or “alternatively” realized genetic information in the damaged cells may become one of the major factor-provider of the evolutionary material.
The micro-changes of the genetic activity in the damaged cells are not ignored by the “magnifying lens of natural selection”. Better adapted organisms survive and multiply successfully.
The complication of the inner structure - an organic progress is an answerable reaction for the influence of pathological factors, which takes place on the historical periods (for example while global ecological catastrophes). The aim of it is a restoration of damaged homeostasis – recovering of filum, by creating the new evolution forms. Typical pathologic processes are the tools for the creation of new forms during the process of organic development (progress).
The excess of pathologic substrate detected at the onset of an individual development, both at the tissue, cellular and molecular levels, confirms that disease played an important role in the evolutionary transformations. Complex genetic, metabolic, morphologic changes that take place in embryogenesis are the reflection, in a tiny model, of those pathologic processes, to which adult ancestor embryos had been exposed on the corresponding stages of phylogenetic development, while ontogenesis itself presents a short history of disease of filum. By those characteristic nuances of the pathologic changes which take place in the developing organs, we may surmise, which pathology might have been the cause of those changes in the process of the organic progress. Disease itself is a developing style of living matter. Pathology, as a process of struggle for survival, is the only way, an essential condition of the progressive evolution. The progressive evolutionary objects were diseased organisms, “hopeful patients”. Pathology is a lack circle of evolution theory, some kind of Terra incognita, where there is hidden the answers of many actual questions of Evolution theory.
You do realize, don't you, that multicellular animals represent only a tiny percentage of all life on Earth?
DeleteIs that the only thing he got wrong, Larry? ;)
DeleteNo, but it really pisses me off when people make grandiose claims about evolution based entirely on what happens in some subset of species that they happen to know about. It's even worse when that subset happens to be humans and their close cousins.
Delete