Other "evolution" theories outside of evolution, intelligent design and lamarckism

[CheeseDonkey]

Are there any other "evolution"/how animals came to be theories out there outside of evolution, intelligent design and Lamarckism? Just curious.

[Lemur866]

Lamarckism, the inheritance of acquired characteristics, is a theory of evolution that was disproven when we discovered how genes work and found that changes in somatic tissue don't alter the genes in your germ-line tissue. Intelligent design--what do you mean by that? You mean supernatural entities of known or unknown types (like, say, Prometheus?) creating life exactly as it exists today? Or aliens? Or something else?

This article might be helpful: http://en.wikipedia.org/wiki/History...ionary_thought

[Laggard]

Xenu http://en.wikipedia.org/wiki/Xenu

[GilaB]

Lysenkoism, at least kinda. It was, for a long time, the official theory of heritability and genetics in the Soviet Union. From my limited understanding of it, it's a variation on Lamarckism.

[thelabdude]

Does ''created with age count'', i.e. the world was indeed created in 144 hours 6000 year ago, but in such a way as to look of great age. This being GQ, all I will say about that idea is that I have heard it expressed.

[Revtim]

I just spent too much time at work searching for this - I know I read in a blog, almost certainly http://scienceblogs.com/pharyngula/, about a female scientist who denies evolution, but has a completely scientific non-supernatural alternative, unrelated to creationism/ID or Lamarckism. I can't find the goddamn thing now though.

[John Mace]

Originally Posted by Revtim

I just spent too much time at work searching for this - I know I read in a blog, almost certainly http://scienceblogs.com/pharyngula/, about a female scientist who denies evolution, but has a completely scientific non-supernatural alternative, unrelated to creationism/ID or Lamarckism. I can't find the goddamn thing now though.

Does she deny evolution by natural selection, proposing a different mechanism? If not, then it's hard to imagine how it could be scientific. We know that organisms change over time. That was known before Darwin. Darwin proposed the mechanism.

[Revtim]

Originally Posted by John Mace

Does she deny evolution by natural selection, proposing a different mechanism? If not, then it's hard to imagine how it could be scientific. We know that organisms change over time. That was known before Darwin. Darwin proposed the mechanism.

I don't recall the mechanism of her alternative, but it may have indeed been contrary to natural selection.

Just to be clear, I wasn't convinced by it at all, and I'm not saying it was a reasonable theory (and P.Z. Meyers, the author of the blog, ripped it to shreds). I really only recall clearly that she was clearly not proposing creationism (or even creationism in its flimsy ID disguise). That's what I meant by scientific.

[njtt]

Originally Posted by Revtim

I just spent too much time at work searching for this - I know I read in a blog, almost certainly http://scienceblogs.com/pharyngula/, about a female scientist who denies evolution, but has a completely scientific non-supernatural alternative, unrelated to creationism/ID or Lamarckism. I can't find the goddamn thing now though.

That would be Lynn Margulis. She is famous for having shown that eucaryotic cells originated from a symbiosis between what were originally independent organisms, that now form organelles (specialized structures) within the main cell, such as mitochondria. As I understand it, she does not exactly reject Darwinian evolution by natural selection, and certainly does not reject evolution in teh broad sense, but she thinks that the standard account of it puts much too much stress on competition, and not nearly enough on the role of cooperation and symbiosis between different organisms. It is generally recognized that she showed that this was true of the original evolution of the eukaryotic cell, but most other biologists seem to think she has since attempted to push the general idea much too far and apply it much too widely.

As for alternatives to Darwinism, aside from Lamark and creationism (of which “intelligent design” is a sort of stealth version), before Darwin and Wallace published their ideas about natural selection a number of authors, such as Erasmus Darwin, Robert Chambers, and Herbert Spencer had put forward more or less evolutionary ideas (usually seeing some sort of natural law of progress which they thought applied not just to biology, but to the universe as a whole, and to the development of human society too), but they were pretty vague about the mechanisms involved. Spencer, who was at a fairly early stage of his career when Darwin’s work appeared, became an enthusiastic supporter of Darwin (although, arguably, he misunderstood him in significant ways), and attempted to assimilate Darwin’s theory into his own, presenting it as lending support to, and being a special case of, his own progressivist theory of the evolution of the universe and society. (I believe it was Spencer, rather than Darwin, who coined the phrase “survival of the fittest” to attempt to capture the essence of Darwin’s key idea.)

So far as biological evolution goes, Lamark’s theory is really the only one apart from Darwinian natural selection to offer any real mechanism of how the process might work. It is quite a nice theory, in a way, but it ultimately does not fit the facts. Not only is it inconsistent with what we now know (but neither Lamark nor Darwin knew) about the mechanisms of inheritance, it fails to explain the facts, such as the patterns of geographical distribution of species, that Darwin’s (and Wallace’s) theory was specifically designed to explain. Thus, although he did not reject the possibility that Lamarkin style inheritance of acquired characteristics might sometimes happen, even before heredity was understood, Darwin had very good reasons to think such a mechanism could not be the main engine of evolution.

[John Mace]

Originally Posted by njtt

That would be Lynn Margulis.

Of course. I think I had a mental block preventing me from thinking of her based on the "denies evolution" statement.

She is famous for having shown that eucaryotic cells originated from a symbiosis between what were originally independent organisms, that now form organelles (specialized structures) within the main cell, such as mitochondria. As I understand it, she does not exactly reject Darwinian evolution by natural selection, and certainly does not reject evolution in teh broad sense, but she thinks that the standard account of it puts much too much stress on competition, and not nearly enough on the role of cooperation and symbiosis between different organisms.

So, a dude pushes the "competition" side of things and a chick pushes the "cooperation" side of things. How stereotypical!

[Revtim]

That's almost certainly who I was thinking of, thanks njtt. It was likely this blog entry referenced by P.Z. Meyers that I was remembering:
http://scienceblogs.com/aetiology/20...s_it_again.php

[Napier]

There is a theory for a kind of evolution that runs parallel to Darwinian selection, based on epigenetics, as I understand. There is a means of carrying adaptive information downstream for maybe three or so generations, that responds to conditions, without relying on a differential survival advantage causing genes to proliferate. The example I read about was that if you starve an animal during its youth, and it later recovers and has descendants, their metabolic behavior is adapted somewhat to help cope with food shortages. The effect wears off in a few generations. Darwinian evolution should not accomplish anything in a hypothetical system where every animal creates the same number of progeny, whereas this mechanism is fully functional in such a system.

[njtt]

Incidentally, it is likely that modern conservatives hate evolution so much, and are thus driven towards creationism and fundamentalist Christianity as an alternative, not so much because of anything Darwin himself claimed, but because of the “social Darwinism” through which Spencer and others tried to link Dawinism (largely illegitimately, and certainly without Darwin’s support) to what then passed for progressivist politics. Of course, conservatives who are dumb enough to be creationists are also too dumb to know this.

Through the irony of history, from a modern perspective Spencer looks more like a hard right libertarian than a left-wing “progressive”. Nevertheless, he was very anti-conservative in the sense that he very much believed in change (and progress) through Darwinian/capitalist competition.

[njtt]

Originally Posted by Napier

There is a theory for a kind of evolution that runs parallel to Darwinian selection, based on epigenetics, as I understand. There is a means of carrying adaptive information downstream for maybe three or so generations, that responds to conditions, without relying on a differential survival advantage causing genes to proliferate. The example I read about was that if you starve an animal during its youth, and it later recovers and has descendants, their metabolic behavior is adapted somewhat to help cope with food shortages. The effect wears off in a few generations. Darwinian evolution should not accomplish anything in a hypothetical system where every animal creates the same number of progeny, whereas this mechanism is fully functional in such a system.

I think the Darwinian natural selection mechanism can accommodate epigenetic inheritance well enough. Epigenetics is a challenge to (or, more accurately, a modification of) the standard neo-Mendelian model of heredity, and, since the neo-Darwinian synthesis of the early 20th century, Darwinism and Mendelian inheritance have become strongly associated. However, that does not mean that if you modify your model of inheritance a bit to accommodate epigenetic mechanisms then Darwinian mechanisms are thereby challenged. Darwin himself, after all, had no clue how inheritance works, he just knew (as people had known for millennia) that it does.

[njtt]

To return to the OP's question, the Greek presocratic philosopher Anaximander (one of history's greatest minds, IMHO) held that "animals came to be" through spontaneous generation out the muck on the seashore. He observed that tiny bugs of various sorts often come out of this muck (their eggs, of course, are too small to see without a microscope) and reasoned that it was possible that larger animals might also emerge from it on rare occasions, so that, for instance the first horses or lions or whatever may have come out of it at some indefinite time in the past.

However, he held that human beings could not have emerged directly from the muck, because, unlike the newborns of most species, human newborns are too helpless to survive without a parent to take care of them. Thus he thought that humans must have developed from some other sort of creature probably, he thought, some sort of fish). Because of this, Anaximander has sometimes been held up as the very first evolutionary theorist.

The theory of spontaneous generation of living animals from non-living muck lasted for a very long time, and was not decisively refuted until the work of Louis Pasteur in the 19th century. In a way it has even been revived since then in modern theories of abiogenesis, the emergence of the first life forms from the “chemical soup” of the ancient Earth.

OK, I will shut up now.

[Der Trihs]

Originally Posted by thelabdude

Does ''created with age count'', i.e. the world was indeed created in 144 hours 6000 year ago, but in such a way as to look of great age.

That's the Omphalos hypothesis.

[SeldomSeen]

Originally Posted by Der Trihs

That's the Omphalos hypothesis.

Wikipedia on Omphalos hypothesis:

As everyone knows, it was predicted that the world would end last Wednesday at 10:00 PST. Since there appears to be a world in existance now, the entire universe must therefore have been recreated, complete with an apparent "history" last *Thursday*. QED.

So....This means Harold Camping was right!

[thelabdude]

The person that explained it to me didn't call it the Omphalos hypothesis.

[Colibri]

Originally Posted by njtt

Incidentally, it is likely that modern conservatives hate evolution so much, and are thus driven towards creationism and fundamentalist Christianity as an alternative, not so much because of anything Darwin himself claimed, but because of the “social Darwinism” through which Spencer and others tried to link Dawinism (largely illegitimately, and certainly without Darwin’s support) to what then passed for progressivist politics. Of course, conservatives who are dumb enough to be creationists are also too dumb to know this.

[Moderator Note]

Let's avoid political commentary of this kind in GQ. No warning issued.

Colibri
General Questions Moderator

[Hari Seldon]

Let's get some facts straight. First, the idea of evolution was in the air long before (Charles) Darwin. A most notable advocate was Erasmus Darwin, his grandfather. Darwin's (as well as Wallace's) new idea was natural selection (and I don't think he called survival of the fittest, which is misleading anyway, since it is reproductive success). Darwin actually called it descent with modification, which is quite descriptive, even if it lacks the zing of natural selection. Second, it is not incompatible with Lamarckianism. Darwin had no idea of what the mechanism was and he probably thought that variation was continuous rather than discrete. When a trait (such as skin or hair color) depends on many genes, it does appear to be continuous. It was Mendel who carried out the crucial experiments that suggested genes. It was not until the 1940s that it was even known that the chromosomes were where the genes were. I believe a man named Avery demonstrated that.

Then came Watson and Crick and the double helix. There was a now-discarded idea of one gene/one protein. Then "junk" (non-coding) DNA was discovered and thought to be...junk. It isn't. Then epigenetic factors, including genes that were active only if they came from the mother, others only from the father. The sometimes fierce battle in the womb fought by such genes that can result in complications--occasionally quite serious--such as pre-eclampsia and maternal diabetes. Wherever they look, it seems to get more complicated.

But it all fits comfortably within the Darwinian concepts. A good friend of mine observed once that Darwinism didn't make atheism necessary, but it did make it possible. Before that, no one could imagine any other answer than god(s) to the question how did we get here. It is easy to see why organized religions have problems with it.

[Napier]

Originally Posted by njtt

I think the Darwinian natural selection mechanism can accommodate epigenetic inheritance well enough. Epigenetics is a challenge to (or, more accurately, a modification of) the standard neo-Mendelian model of heredity, and, since the neo-Darwinian synthesis of the early 20th century, Darwinism and Mendelian inheritance have become strongly associated. However, that does not mean that if you modify your model of inheritance a bit to accommodate epigenetic mechanisms then Darwinian mechanisms are thereby challenged. Darwin himself, after all, had no clue how inheritance works, he just knew (as people had known for millennia) that it does.

But accommodating the inheritance part of it isn't the issue, I think. Darwin would have said that the characteristics of species evolve through differences in reproductive success, and epigenetics provides for evolution without necessarily relying on reproductive success differences. That there be any reproduction at all is sufficient to change characteristics for a few generations.
Thus, it's a kind of evolution other than Darwin's. Which is not to say that Darwin's kind does not occur or even isn't the most important, but only to say that Darwin's kind isn't the only kind.
Or do I miss your point?

[TriPolar]

Originally Posted by Napier

But accommodating the inheritance part of it isn't the issue, I think. Darwin would have said that the characteristics of species evolve through differences in reproductive success, and epigenetics provides for evolution without necessarily relying on reproductive success differences. That there be any reproduction at all is sufficient to change characteristics for a few generations.
Thus, it's a kind of evolution other than Darwin's. Which is not to say that Darwin's kind does not occur or even isn't the most important, but only to say that Darwin's kind isn't the only kind.
Or do I miss your point?

Reproductive success determines who gets to have their heritable traits continue. Epigenetics works the same way. Darwin didn't know what the underlying mechanism of inheritance was. Epigenetics is no different. It does open up the broader realm of 'mutation' to more factors though. We still don't know how all the factors in inheritance work, but we do know it's not by magic, which is what Darwin was trying to prove.

[njtt]

Originally Posted by Napier

But accommodating the inheritance part of it isn't the issue, I think. Darwin would have said that the characteristics of species evolve through differences in reproductive success, and epigenetics provides for evolution without necessarily relying on reproductive success differences. That there be any reproduction at all is sufficient to change characteristics for a few generations.
Thus, it's a kind of evolution other than Darwin's. Which is not to say that Darwin's kind does not occur or even isn't the most important, but only to say that Darwin's kind isn't the only kind.
Or do I miss your point?

Well, I am not sure I understand your point. How do you think that epigenetic effects amount to evolution? Yes, it has been shown that environmental conditions can have epigenetic effects a generation or two down the line, but I do not think that that itself amounts to evolution.

I admit I am far from confident that I fully understand the issues here, but so far as I can see, when these epigenetic effects manifest themselves, the genome (or the frequency of certain genes in the population, or whatever) hasn’t really been changed, just the way that certain genes are expressed in subsequent generations, and later changes in environmental conditions may reverse the first set of epigenetic effects, or cause others, but all without necessarily changing the genome or gene frequencies. There are, presumably, genes behind the capacity to display particular epigenetic effects, and they have not (or not necessarily) changed. Epigenetic effects may complicate what we take to be the unit of selection (because it may be that in some cases what is selected for is only manifested over multiple generations), but long term evolution is still going to depend on selection of genes. That is to say, being susceptible to certain epigenetic effects may confer a survival (or reproductive) advantage upon a population, and if so, the genes underlying that susceptibility will be selected for. This is still evolution by natural selection.

ETA: TriPolar has probably made the point more clearly than I managed to.

[kanicbird]

Aliens?

[njtt]

Originally Posted by Hari Seldon

Let's get some facts straight. First, the idea of evolution was in the air long before (Charles) Darwin. A most notable advocate was Erasmus Darwin, his grandfather. Darwin's (as well as Wallace's) new idea was natural selection (and I don't think he called survival of the fittest, which is misleading anyway, since it is reproductive success).

Yes. As I said above, the phrase “survival of the fittest” came from Herbert Spenser’

Originally Posted by Hari Seldon

Darwin actually called it descent with modification, which is quite descriptive, even if it lacks the zing of natural selection.

Descent with modification and natural selection are different things. Darwin referred to both, and his mechanism for evolution depends on both processes working together in concert. However, unlike natural selection, descent with modification wasn’t a particularly revolutionary idea. It was more just a formulation of common sense. After all, people had always known that children resemble their parents, but not exactly.

Originally Posted by Hari Seldon

Second, it is not incompatible with Lamarckianism.

Well, that depends what you mean by Lamarkianism. It is not inconsistent with Lamark’s idea of inheritance of acquired characteristics, but the was more to Lamark’s actual theory than that, and other key aspects of Lamark’s theory are incompatible with Darwinian theory. For instance, Lamark thought that species (or, more accurately, lineages) never went extinct, but just evolved into different forms, so that, for instance, the direct descendants of T. Rex and of trilobites are still with us. Darwin’s theory, by contrast, depends on extinction as a mechanism. If unsuccessful forms did not die out, there would be no speciation.

Originally Posted by Hari Seldon

Darwin had no idea of what the mechanism was and he probably thought that variation was continuous rather than discrete. When a trait (such as skin or hair color) depends on many genes, it does appear to be continuous. It was Mendel who carried out the crucial experiments that suggested genes. It was not until the 1940s that it was even known that the chromosomes were where the genes were. I believe a man named Avery demonstrated that.

Actually, Avery is the person who first clearly demonstrated, in the 1940s, that it is the DNA in the chromosomes, rather than the protein, that carries the genetic information. (Although hardly anyone believed him at the time.) I think it was known that the genetic information is in the chromosomes well before that. However, I agree with the thrust of what you are saying (indeed, I already said it): Darwin did not know how inheritance works, but his theory does not depend upon that, it just depends on the fairly obvious fact that offspring do, somehow, inherit characteristics from their parents.

And yeah, it is all a lot more complicated than Mendel thought, too, but, as you say, none of these complications of the theory of inheritance are a threat to the basic Darwinian insight.

[Apollyon]

Originally Posted by kanicbird

Aliens?

I think that's covered by "Inteliigent design" in the OP. Aliens may not be what most ID proponents actually have in mind, but advanced non-mystical alien beings uplifting earthly organisms is ID... 'course that doesn't help all that much, just pushing the problem back a generation unless one is only interested in how life "on Earth" originated.

Exogenesis via panspermia is a variant of this with unintelligent aliens I guess.

[Chronos]

For instance, Lamark thought that species (or, more accurately, lineages) never went extinct, but just evolved into different forms, so that, for instance, the direct descendants of T. Rex and of trilobites are still with us.

Wasn't this after the extinction of the dodos? Surely Lamark would have realized that species (and their entire line) could go extinct. Maybe he just thought it didn't happen very often?

[Der Trihs]

Originally Posted by Apollyon

I think that's covered by "Inteliigent design" in the OP. Aliens may not be what most ID proponents actually have in mind, but advanced non-mystical alien beings uplifting earthly organisms is ID... 'course that doesn't help all that much, just pushing the problem back a generation unless one is only interested in how life "on Earth" originated.

Exogenesis via panspermia is a variant of this with unintelligent aliens I guess.

Directed Panspermia is a term used to refer to the idea that life is spread by technologically advanced aliens. While technically you could use intelligent design to mean "life was created by aliens", I've never heard of it being used that way. It always is used by and in reference to the religious crypto-creationists.

[njtt]

Originally Posted by Chronos

Wasn't this after the extinction of the dodos? Surely Lamark would have realized that species (and their entire line) could go extinct. Maybe he just thought it didn't happen very often?

Yes, good point. I am not sure what (if anything) Lamark had to say about the Dodo. He might, I think, (consistent with his principles) have dismissed it as an irrelevant, non-natural case of extinction, since humans were responsible, but I am not sure whether he ever actually said anything like that.

But, in any case, I should admit that I was oversimplifying by implying that it was axiomatic for Lamark that extinction does not occur. The point is, more that Lamark’s theory is designed to explain away apparent extinction as illusory, whereas, for Darwinian theory, it is very real and essential to his explanation of the origin of species (if there was no extinction there would be no distinct species, because all the intermediate forms would still be around).

Already, in the 18th century, and quite apart from any sort of Biblical literalism (which had little if any sway back then), paleontology was raising serious problems for Christianity. Fossil discoveries seemed to show that there had once been species on Earth that had now gone extinct. This appeared to be inconsistent with the doctrine (much more crucial to Christianity than a literal reading of Genesis) that God is omnipotent, omniscient and benevolent (or even just that He is just very powerful, very smart, and basically good). If God created species that He then allowed or caused to go extinct, this suggests that He is either incompetent or wantonly cruel. Lamark’s theory is designed to address this problem: fossil forms that we no longer find in living organisms have not really gone extinct, they have simply evolved into different forms that are still around today.

Actually, Lamark’s theory is not even intended to explain the diversity of species, in the way that Darwin’s does. Darwin presents a picture in which one ancestral form differentiates, over geological time, into many diverse species. Lamark, however, retains the basic creationist idea (although not in its Biblical form) that each species around today has come into being separately. (I think he leaves it open whether this is by God’s fiat, or spontaneous generation from muck, or whatever.) In any case, as he sees it, each species (or lineage) originates as a fairly primitive organism, and gradually, over time, evolves into something much more complex and “advanced”. Simple, “primitive” organisms that are around today are, for Lamark, evidence that some species/lineages came into being relatively recently, and so have not yet got very far along with their process of evolution.

My underlying point, which I hope is now clear, was there was a lot more to the difference between Lamark and Darwin than the difference between natural selection and inheritance of acquired characteristics as mechanisms for evolution. Really, the two theories were designed to solve quite different sets of problems. This was the point I was trying to make when I said that Lamark held that species never go extinct, but in trying to be brief, I oversimplified.

[njtt]

Incidentally, it has never been clear to me what problem theories of panspermia (intelligently directed or otherwise) are meant to solve. Panspermia might explain life on Earth, but it leaves you with the problem of how the organisms that seeded the Earth originated. So far as I can see, the alternatives are the same as those we have if life originated on Earth: either the aliens arose from abiogenesis followed by evolution, or they were created/designed by a supernatural power (or by other aliens, whose own origins will then need explaining in their turn).

[BigT]

Originally Posted by njtt

Incidentally, it has never been clear to me what problem theories of panspermia (intelligently directed or otherwise) are meant to solve. Panspermia might explain life on Earth, but it leaves you with the problem of how the organisms that seeded the Earth originated. So far as I can see, the alternatives are the same as those we have if life originated on Earth: either the aliens arose from abiogenesis followed by evolution, or they were created/designed by a supernatural power (or by other aliens, whose own origins will then need explaining in their turn).

One (creationist) book I read claimed it was the problem of the prehistoric atmosphere not being conducive to the creation of life due to too much free oxygen. It claimed oxidation in the fossil record indicated an oxygenated atmosphere, and that all experiments required the removal of oxygen to work.

[glaeken]

Originally Posted by thelabdude

Does ''created with age count'', i.e. the world was indeed created in 144 hours 6000 year ago, but in such a way as to look of great age. This being GQ, all I will say about that idea is that I have heard it expressed.

You would have to question why would that have been done.

So that 144 hours 6000 years later when some humans came up with methods of determining the Earth was much older than 144 hours 6000 years that other humans could not believe them.

I am stuggling with the motivation for such a weird act.

[Der Trihs]

Originally Posted by njtt

Incidentally, it has never been clear to me what problem theories of panspermia (intelligently directed or otherwise) are meant to solve. Panspermia might explain life on Earth, but it leaves you with the problem of how the organisms that seeded the Earth originated. So far as I can see, the alternatives are the same as those we have if life originated on Earth: either the aliens arose from abiogenesis followed by evolution, or they were created/designed by a supernatural power (or by other aliens, whose own origins will then need explaining in their turn).

Well, for one thing it used to be thought that life was much less likely to appear than it is these days. Panspermia basically tried to solve that by saying "Well, even if it's really unlikely to have appeared on Earth by itself, the odds of life appearing somewhere in the larger universe are much higher, and once it appeared, it could spread."

[yoyodyne]

Originally Posted by njtt

Incidentally, it has never been clear to me what problem theories of panspermia (intelligently directed or otherwise) are meant to solve. Panspermia might explain life on Earth, but it leaves you with the problem of how the organisms that seeded the Earth originated. So far as I can see, the alternatives are the same as those we have if life originated on Earth: either the aliens arose from abiogenesis followed by evolution, or they were created/designed by a supernatural power (or by other aliens, whose own origins will then need explaining in their turn).

It's aliens all the way down.

[njtt]

Originally Posted by BigT

One (creationist) book I read claimed it was the problem of the prehistoric atmosphere not being conducive to the creation of life due to too much free oxygen. It claimed oxidation in the fossil record indicated an oxygenated atmosphere, and that all experiments required the removal of oxygen to work.

But that is just false according to everything I have ever heard. There was no significant free oxygen in the prebiotic atmosphere. Indeed, as oxygen is highly reactive with many of the other elements found in abundance on Earth, such as hydrogen and carbon, there would not be any any free oxygen in the atmosphere even today if it were not that plants continuously produce it.

Of course, I don't expect religious creationists to care much about facts or logic. They often just make shit up. But I thought the panspermists held themselves to slightly higher standards. (And I do not really understand why creationists should be interested in lending credence to panspermia.)

Originally Posted by Der Trihs

Well, for one thing it used to be thought that life was much less likely to appear than it is these days. Panspermia basically tried to solve that by saying "Well, even if it's really unlikely to have appeared on Earth by itself, the odds of life appearing somewhere in the larger universe are much higher, and once it appeared, it could spread."

I suppose that must be the reason, but why should anyone have thought that they had a good enough handle on the probabilities to make this a plausible argument? Indeed, why should anyone think that now? There are far too many imponderables about abiogenesis (and, come to that, about conditions on the early Earth, and elsewhere in the universe) for anyone to be able to give any decent estimate of its likelihood. It seems to me that all we can say is that it is probably a pretty chancy matter, but we know it happened at least once.

[thelabdude]

We only KNOW there is life here. Different ideas about how it started make more sense to some than others. This being GQ, I will continue to leave out my personal opinions.

[Gary "Wombat" Robson]

Originally Posted by njtt

Of course, I don't expect religious creationists to care much about facts or logic. They often just make shit up.

[mod note]
This is GQ, not Great Debates. Religious (and anti-religious) jabs do not belong here. Do not do this again.
[/mod note]

[Napier]

Originally Posted by TriPolar

Reproductive success determines who gets to have their heritable traits continue. Epigenetics works the same way.

This is what I understand isn't correct. Epigenetics does not depend on differences in reproductive success, while Darwin's evolution does.
The point of Darwin's evolution is not that traits get passed along through reproduction, it is that they become more or less common depending on whether they are associated with more or less reproductive success. Epigenetics does not depend on this.

[Napier]

Originally Posted by njtt

Well, I am not sure I understand your point. How do you think that epigenetic effects amount to evolution? Yes, it has been shown that environmental conditions can have epigenetic effects a generation or two down the line, but I do not think that that itself amounts to evolution.

I admit I am far from confident that I fully understand the issues here, but so far as I can see, when these epigenetic effects manifest themselves, the genome (or the frequency of certain genes in the population, or whatever) hasn’t really been changed, just the way that certain genes are expressed in subsequent generations

If by "evolution" we mean changing genomes, then epigenetics would not be a form of evolution, but if we mean how species change their characteristics, then it would. It's something that subgroups of a species are doing. I think it is interesting in that it is similar to Darwinian evolution but separate from it, parallel with it. And it is not in the individual, it is in subgroups of a species.
The classic explanation of Darwinian evolution often includes remarking that if you keep cutting the tails off of generations of mice, the next generation still has tails. Epigenetics comes a bit closer to changing this.

[TriPolar]

Originally Posted by Napier

This is what I understand isn't correct. Epigenetics does not depend on differences in reproductive success, while Darwin's evolution does.
The point of Darwin's evolution is not that traits get passed along through reproduction, it is that they become more or less common depending on whether they are associated with more or less reproductive success. Epigenetics does not depend on this.

Not sure I'm getting this. Mostly, epigenics are inherited factors, just not through DNA. I don't recall Darwin stating reproductive success as the only factor, as much as survivability of variations that were better suited to an environment would gradually change the common features of a species. Epigenics does present in some cases a manner of change that is not inherited. But then it operates as a mutation does, a non-inherited change. I don't think Darwin understood mutation, and considered variation to be limitless within his understanding of inheritance.

[EdwardLost]

Originally Posted by Napier

If by "evolution" we mean changing genomes, then epigenetics would not be a form of evolution, but if we mean how species change their characteristics, then it would. It's something that subgroups of a species are doing. I think it is interesting in that it is similar to Darwinian evolution but separate from it, parallel with it. And it is not in the individual, it is in subgroups of a species.
The classic explanation of Darwinian evolution often includes remarking that if you keep cutting the tails off of generations of mice, the next generation still has tails. Epigenetics comes a bit closer to changing this.

I think "evolution" should mean changing genomes - that is, traits that are reliably passed over multiple generations. Passing on traits epigenetically is not evolution, but the ability to pass traits epigenetically is evolved and evolvable.

I think of it like tanning. If you migrate south and your skin can darken in response to the increased sunlight, that ability gives you a survival advantage. The tanning ability is a trait your ancestors acquired through evolution and passed on to you. However your darkened skin is not an evolved trait; you will not pass it on to your children. Your children will be born light skinned and must do their own tanning. But suppose your ancestors had evolved the ability not only to tan but to epigenetically pass on their current skin tone. Then your children would be be born with dark skin - but they would not have evolved dark skin. Their genetic makeup in that trait remains the same as yours. If they move north, their skins will lighten, their children will be born lighter, and eventually the darkened skin you acquired will have evaporated. It was not truly heritable. Your ability to pass on your darkened skin was evolved but the epigenetically darkened you passed to your children was not evolution.

[EdwardLost]

Originally Posted by Napier

If by "evolution" we mean changing genomes, then epigenetics would not be a form of evolution, ....

Here's another example: Say a bird eats food containing a foul-tasting chemical, and thus becomes foul-tasting itself. She passes the chemical from her own tissues into her egg, and thus her chick epigenetically acquires the foul taste. Did her line "evolve" a foul taste? I'd say not: the genome has not changed and the foul-taste trait will disappear without continued consumption of the chemical.

[thelabdude]

I am a bit disappointed in this thread. I try to keep an open mind on this stuff and was hoping for some new ideas. We are doing a fine job of finding intermediate species. I don't worry about the remaining holes I still struggle with how a new species develops that can no longer interbreed with the old. Yes selective breeding works. An isolated population will have more individuals with traits favored in its environment. But how does the first one to no longer be able to breed ever pass on its genes? I don't see how to cross the chasm in a series of small steps no matter how long you have.

As for the separate question of the origin of life,.we are still stuck with however unlikely, it did happen at least once.

[Cleophus]

Originally Posted by thelabdude

An isolated population will have more individuals with traits favored in its environment. But how does the first one to no longer be able to breed ever pass on its genes? I don't see how to cross the chasm in a series of small steps no matter how long you have.

I assume you are referring to the development of new species. It seems to be a popular, but nonetheless wildly incorrect belief that evolution expects speciation to occur over a single generation from an existing population. Obviously, such an occurrence would be exceedingly unlikely for a sexually reproducing organism for the reason you state.

However, that is not how species form. Populations evolve, not individuals. For speciation to occur a population must become reproductively isolated from its main group. Once isolated, mutations that arise in the new population cannot propagate back to the original population and the new population can change independently of the original.

The Wikipedia article on speciation gives a good introduction on the different ways the populations become isolated in the first place.

[Francis Vaughan]

Passing on traits epigenetically is not evolution, but the ability to pass traits epigenetically is evolved and evolvable.

Exactly. It isn't a lot different to a form of nurture meme. Epigenics is a species survival mechanism. It improves the ability of the offspring to survive, and to hence procreate. Species that have evolved the ability to pass on useful epigenic traits will do better. Thus it fits perfectly within the standard model of evolution.

It is possible to imagine that it might be possible for something to evolve a mechanism that allows permanent modification of the genome, and that this might eventually evolve into a mechanism that allows Larmarkian evolution in some manner. However the barrier to do so within the usual mutation mechanisms is likely so high that the universe will be cold before such a thing comes about.


In the end it might be possible to simply set the theories into categories of how the information in the genome came about.

• divine creation/ intelligent design - the information is created fully formed and does not change.
• divine guidance - the information is mutated under the control of a divine/intelligent outside force.
• Lamarkian - the information contains mechanisms for self directed modification that will advantage the species.
• Darwin - the information is mutable, but mutates in an unguided manner, natural selection winnows out most mutations.

It isn't clear what other category there might be. One has the spread from fully controlled information in the genome to randomly varying information. You can't get any less controlled than random change, nor any more controlled than divine creation. In between is where you might find traction for another theory. But evidence is likely pretty thin.

Some small scale wiggle room might exist. I heard the idea years ago (with no recollection of where sadly) that stress might be used as a mutation trigger, and species that include this mechanism will begin to produce more variation in times of high stress on the species, with the result that there is a greater chance that some sub-population might survive. This could be considered a hybrid Larmarkian Darwinian mechanism. External factors cause the mutation, but it is undirected and natural selection picks of the winner. Like epigenics, one would probably regard this as simply another evolved species survival trait, and again consistent with Darwin.