continuation of evolution thread

robindch

Continuing a thread in the christianity forum on evolutiuon/creationism (at http://www.boards.ie/vbulletin/showthread.php?t=316566).

> [Wibbs] I said more complex life would be expected to
> have more complex DNA. [...] a slug still has more
> chromosomes than a chimp.

So, how do you define complexity? It's not immediately obvious to me why something with a greater amount of DNA, assuming the chromosomes in both cases are equally sized, shouldn't be considered "more complex" than something with a lesser amount -- there's more 'source' information available, so doesn't that make the slug more complex, by any reasonable definition of the words?

> The ring species you describe are very
> arguably still sub-species.

Then we're quibbling about the definition of "species" -- the definition I'm happiest with is the one where a breeding pair can produce viable offspring with others of their, or their parents, kind. Given this definition, ring species are a nightmare to pin down, as the ends can't interbreed (making it a 'species'), but each individual group along the way can interbreed (making it not a species)! See:

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

Anyhow, regardless of what we call them, they do quite clearly show how genetic drift can produce non-interbreedable organisms from a common ancestor. Incidentally, I believe that Darwin's principal evidence for the existence of natural selection and the evolution of species came from the geographical distribution of species, and not at all from his case study on the finches.

> American wolves have been isolated from their European
> cousins for many 1000s of yrs, yet still will happily
> crossbreed in captivity with each other. You expect some
> drift in that time given environmental diffs between them.

Well, I've no idea how distinct the populations are, nor how long they've been separated from each other, but evolution doesn't say that organisms *must* become genetically distinct, or even evolve, over time -- take a look at the genetic stability of sharks, coelacanths, and the entertainingly ancient cyannobacteria (etc, etc) over millions of years. If something's perfectly suited to its environment, there's no selection pressure to 'force' any change.

> that there's more than meets the eye re the
> mechanism based on the current theories.

So, assuming (hopefully!), that you're happy with the above, where exactly do you believe that it's brushing over details?

Wibbs

robindch wrote:

Continuing a thread in the christianity forum on evolutiuon/creationism (at http://www.boards.ie/vbulletin/showthread.php?t=316566).

So, how do you define complexity? It's not immediately obvious to me why something with a greater amount of DNA, assuming the chromosomes in both cases are equally sized, shouldn't be considered "more complex" than something with a lesser amount -- there's more 'source' information available, so doesn't that make the slug more complex, by any reasonable definition of the words?

Right so...:D
Richard Dawkins explains that evolution "is a theory of gradual, incremental change over millions of years, which starts with something very simple and works up along slow, gradual gradients to greater complexity." Right there, something very simple that works up to greater complexity. On that basis alone when we compare the slug, a much less complex animal whose ancestors evolved 100's of millions of years ago, to a human, an animal that evolved much more recently, you would expect to find a less complex genetic instruction set needed to "build" a slug. A carp has an even more complex DNA structure than a primate. It makes little sense in the context of Dawkins gradual incremental change leading to greater complexity. Evolution can go in reverse as well. Look at the fossil history of the Ammonite. They start off simple enough in the Devonian go through ever increasing complexity(in their suture line balance chambers alone) then start to lose this complexity before their extinction which leaves us with the only survivor, the nautilus, which is a very boring example of the breed. A virus is another example. It's alive(barely), but requires the services of a more complex host cell to reproduce. Therefore it stands to reason that the virus evolved after the more complex cell. So much for the inexorable rise towards complexity.

Then we're quibbling about the definition of "species" -- the definition I'm happiest with is the one where a breeding pair can produce viable offspring with others of their, or their parents, kind. Given this definition, ring species are a nightmare to pin down, as the ends can't interbreed (making it a 'species'), but each individual group along the way can interbreed (making it not a species)

Well I agree the concept of species is a difficult one. Adding DNA profiles to the mix muddies the water further. Like the frogs I mentioned in the other thread. 3 odd thousand of the buggers with a bigger difference in DNA than between mice and whales, yet a frog looks pretty much like a frog worldwide.

Well, I've no idea how distinct the populations are, nor how long they've been separated from each other,

Quite distinct in both environment and phenotype. Regardless all of the canus lupus family can interbreed even after many 1000s of years separation.

but evolution doesn't say that organisms *must* become genetically distinct, or even evolve, over time -- take a look at the genetic stability of sharks, coelacanths, and the entertainingly ancient cyannobacteria (etc, etc) over millions of years. If something's perfectly suited to its environment, there's no selection pressure to 'force' any change.

There's a problem again. The environment has changed in all those cases. The earth that the cyanobacteria evolved in is radically different to the one they inhabit now. The same goes for sharks and the coelacanths. With regard to the shark family they have changed quite a bit in their history, They've lost many structures over the years and their DNA has changed quite radically if genetic clocks are anything to go by.

So, assuming (hopefully!), that you're happy with the above, where exactly do you believe that it's brushing over details?

Well other than the above, the sudden explosions of change in the fossil record are interesting. Sometimes they are preceeded by climactic change, sometimes not. They all have the commonality of speed. They seem so rapid when compared to the background speed of evolution. I suspect something else beyond survival of the fittest is involved(virusus gene swapping or something). Anyway it should be renamed survival of the most prolific as those who have the most progeny are supposed to be the ones that succeed.

DrIndy

Right so, I welcome this thread so long as it remains scientific in its contents.

Please continue!

robindch

> A carp has an even more complex DNA structure than a primate.

You still haven't explained why something with more complex genetic information can be considered "simpler" than something with less complex DNA.

> So much for the inexorable rise towards complexity.

You're picking holes in a 25-word summary of a theory of life which I suspect is taken out of context. Evolution is rather larger than 25 words, as Dawkins explains at considerable length elsewhere! There are plenty of well-known examples not only of vestigial functionality around the place (eg, five-finger flippers and all that), but also devolution (eg, blind, albino cave-crabs). Evolution has no problem whatsoever explaining these: if there's no reason to have some feature or other (eyes, in the cave-crab example), then over time, they will disappear from the population owing to the lack of any environmental force which selects in favour of keeping them.

> 3 odd thousand of the buggers with a bigger difference
> in DNA than between mice and whales

Firstly, can you provide a reference which demonstrates this bigger DNA difference? (haven't come across this before) Even still, I don't see how this invalidates evolution in any way. Guidance would be appreciated.

> I suspect something else beyond survival of the fittest is involved.
> Anyway it should be renamed survival of the most prolific as those
> who have the most progeny are supposed to be the ones that succeed.

Survival of the fittest was certainly discarded decades ago, if not actually in the 19th century and has been superceded by what's colloquially known as selfish gene theory (try Richard Dawkins excellent book "The Selfish Gene" for an absorbing explanation of this).

Wibbs

robindch wrote:

You still haven't explained why something with more complex genetic information can be considered "simpler" than something with less complex DNA.

That's the point. Is a slug not more ancient, primitive, less physically/structurally complex, less evolved biologically than a gorilla? Would you not expect to find a less complex instruction book to build a slug? It's like buying a TV and TV cabinet in pure kit form and finding that the cabinet has a much bigger instruction book. Makes no sense. Explaining it away as "junk" DNA doesn't cut it as an explanation either.* The virus example is also a good one.

You're picking holes in a 25-word summary of a theory of life which I suspect is taken out of context.

I've seen that explanation come from many biologists, not just Dawkins. I take your point however, but regardless of context the idea seems to favour greater complexity arising from lesser complexity(at least at the DNA level).

Evolution is rather larger than 25 words, as Dawkins explains at considerable length elsewhere!

Well, I'd say his publisher wouldn't have been too happy if "the selfish gene" only ran to 25 words. "Now Rich, me old mucka, your editor was expecting... well more work frankly"

There are plenty of well-known examples not only of vestigial functionality around the place (eg, five-finger flippers and all that), but also devolution (eg, blind, albino cave-crabs). Evolution has no problem whatsoever explaining these: if there's no reason to have some feature or other (eyes, in the cave-crab example), then over time, they will disappear from the population owing to the lack of any environmental force which selects in favour of keeping them.

Yes but I'm saying that regardless of vestigials, less ornate/complex complete forms of various animals in the fossil record show up in more recent strata compared to more complex forms in earlier. A form of devolution as it were. This also ties in with my last paragraph a little. I think Dawkins(again:D ) said that one of the only things that would disprove evolution is if one found a hippo in cambrian rocks. He was joking, but those examples of devolution, while hardly hippos, do raise some questions.

> 3 odd thousand of the buggers with a bigger difference
> in DNA than between mice and whales

Firstly, can you provide a reference which demonstrates this bigger DNA difference? (haven't come across this before) Even still, I don't see how this invalidates evolution in any way. Guidance would be appreciated.

Have that in a zoology book around here someplace. I'll try and dig it up(and no it wasn't creationists for dummies either;) )It appears weird to me that animals that had a common ancestor, have common phenotypes and behaviour, have a greater DNA range than animals who don't share such similarities.

Survival of the fittest was certainly discarded decades ago, if not actually in the 19th century and has been superceded by what's colloquially known as selfish gene theory (try Richard Dawkins excellent book "The Selfish Gene" for an absorbing explanation of this).

True enough.

My response to your point about the cyanobacteria, sharks, coelacanths also has some merit too. You could also add stromatolites, gingkos and linguilla brachiopods and quite a few more to that lot too. The environment has changed, radically, yet they didn't. Why did pressures that forced others to evolve not effect them?

TBH one of the biggies for me is the very notion of evolving at all. If one thinks about it, bacteria can reproduce their selfish genes incredibly well and can and have adapted to pretty much any environment on the planet. In fact better than anything else, so why "evolve" a horse or anything else for that matter? It seems wasteful somehow. Why is there such a diversity of life, when the selfish gene/evolution seems coded for pure survival? A simpler DNA should be the one that "wins". Basically the race should favour the prolific, robust and simple, not the complex and delicate. Obviously it happened, but why?

PS. It's sometimes difficult to put these things without some of the language(build/wasteful etc) seeming like I'm advocating some sort of "design". For the record I'm not. I prefer to leave that stuff to the more spiritually minded types. I'm just interested in the subject really. Comes from collecting fossils when I was younger. No shop bought ones either(snob I was). Even found a couple of gastropods that I couldn't find in the lit. at the time. Brought them to the natural history museum, but nothing came of it sadly(my name in taxonomic lights didn't come to pass). Ah well, that's probably illegal as a hobby now.

*It's like the idea of dark matter in cosmology. Let's invent a concept because there's a hole in the theory. Junk DNA lately seems a catchall for difficulties in genetic studies. It smacks of here be dragons. Here come the flames from the cosmologists. I've no sense really.

John

Have that in a zoology book around here someplace. I'll try and dig it up(and no it wasn't creationists for dummies either;) )It appears weird to me that animals that had a common ancestor, have common phenotypes and behaviour, have a greater DNA range than animals who don't share such similarities.

I think greater DNA range is the wrong term to use. I don't know for a fact any of this but what I think you're saying is that the difference between the genome of certain frogs when compared to each other is greater than those of mice and whales. This would make sense to me considering frogs have been in existance in a huge myriad of environments for many millions of years more than mice and whales have been diverging.

There's a problem again. The environment has changed in all those cases. The earth that the cyanobacteria evolved in is radically different to the one they inhabit now. The same goes for sharks and the coelacanths. With regard to the shark family they have changed quite a bit in their history, They've lost many structures over the years and their DNA has changed quite radically if genetic clocks are anything to go by.

My response to your point about the cyanobacteria, sharks, coelacanths also has some merit too. You could also add stromatolites, gingkos and linguilla brachiopods and quite a few more to that lot too. The environment has changed, radically, yet they didn't. Why did pressures that forced others to evolve not effect them?

Firstly, the earth's environment may have changed but maybe these particular ecosystems are more stable or that even when the ecosystem changes the biochemistry and physiology (cellular and anatomic) are still suitable. Environment changes can have huge impacts but some organisms are just naturally more adaptive without the need for evolutionary changes. And there is no such thing as pressure to evolve. Animals evolve or go extinct. Nothing forces them in either direction really, it's all chance at the end of the day, i.e. do you have the means (and the genes) to survive or not?

TBH one of the biggies for me is the very notion of evolving at all. If one thinks about it, bacteria can reproduce their selfish genes incredibly well and can and have adapted to pretty much any environment on the planet. In fact better than anything else, so why "evolve" a horse or anything else for that matter? It seems wasteful somehow. Why is there such a diversity of life, when the selfish gene/evolution seems coded for pure survival? A simpler DNA should be the one that "wins". Basically the race should favour the prolific, robust and simple, not the complex and delicate. Obviously it happened, but why?

There is no why, there just is. With your logic about simpler being better has some basis (bacteria are relatively simple and are the most successful organisms on earth) but once something evolves with more refined biochemical machinery it will proliferate because it has more options open to it. That doesn't necessarily mean that all life will now be more complex but that there are more avenues now open for organisms to exist. Complex doesn't equal better, look at viruses. They may or may not be alive but they are very successful. However without a complex cell to act on they are nothing but a couple of molecules. Life is a balance.

Interesting discussion by the way.

Wibbs

John2 wrote:

I think greater DNA range is the wrong term to use.

Yea well I'm not too surprised I got that wrong.:)

This would make sense to me considering frogs have been in existance in a huge myriad of environments for many millions of years more than mice and whales have been diverging.

True, it's the only thing that makes some sort of sense, but the strange thing also referred to in the same book was that thebony fish which evolved earlier had less diversity and their environments were more varied. Most frogs have quite a narrow range of environments by comparison. I really wish I could find that bloody book now. The info I refer to, wasn't the thrust of the book. It was just something I noted in passing.

Firstly, the earth's environment may have changed but maybe these particular ecosystems are more stable or that even when the ecosystem changes the biochemistry and physiology (cellular and anatomic) are still suitable. Environment changes can have huge impacts but some organisms are just naturally more adaptive without the need for evolutionary changes. And there is no such thing as pressure to evolve. Animals evolve or go extinct. Nothing forces them in either direction really, it's all chance at the end of the day, i.e. do you have the means (and the genes) to survive or not?

Well the environments and ecosystems were anything but stable. If you consider the stromatolites alone, they have very very specific requirements. In fact IIRC there are very few places in the world today were they survive(shark bay in Australia is the only place I can think of). Same with the coelacanth. The gingko is a hardy bugger though. The nuclear blast directly above one in hiroshima failed to kill it. Stripped all the branches off, but a year later out came the leaves. Fantastic plant. Have 3 of them in the garden. The variety between individuals is amazing. Leaf size, speed of growth. They all seem so different and "individual". Maybe that's their secret of success(apologies for the gingko love in aside there ).

I would say that there are pressures to evolve. Environment being the main one. That's why these living fossils always fascinated me.

There is no why, there just is.

That's the problem. Obviously it happened, but it would be nice to have a theory why, rather than that's just the way it is.

With your logic about simpler being better has some basis (bacteria are relatively simple and are the most successful organisms on earth) but once something evolves with more refined biochemical machinery it will proliferate because it has more options open to it. That doesn't necessarily mean that all life will now be more complex but that there are more avenues now open for organisms to exist.

The problem there is that bacteria have populated far more environments than any other form of life. Their options and adaptablity are far higher than more complex creatures. It would seem strange for life to select for a less efficient way to colonise more environments which appears to be the case.

Complex doesn't equal better, look at viruses. They may or may not be alive but they are very successful. However without a complex cell to act on they are nothing but a couple of molecules. Life is a balance.

As you say complex doesn't equal better, which is my point. Why evolve from a form that works and works incredibly well to one that is less advantageous?

Interesting discussion by the way.

It is an' all.

robindch

> there are pressures to evolve. Environment being the main
> one. That's why these living fossils always fascinated me.

Likewise, but if the environment is stable -- as it is deep in the sea where the coelocanth lives -- then there's not really much selection pressure from the non-living environment to evolve. Which means that if you're an efficiently reproducing life-form, then you're likely to stay that way.

> Obviously it happened, but it would be nice to have a theory
> why, rather than that's just the way it is.

Until the arrival of selfish-genetic theory, nobody really had an answer to "why" life was -- it just happened to be and that was where the question lay for quite some time. Dawkins, together with the researchers whose ideas he collated, have provided an explanation which is as simple as it is convincing, namely, that things which are good at reproducing, tend to reproduce. Or alternatively, you're the (current) end-result of an unimaginably long series of creatures who reproduced, so it's quite likely that you'll be able to as well.

btw, it's only our comrades in the religious industries who insist, upon no basis whatsoever, that there *must* be more to it than that (and they'll be the folks who know what it is!). This teleological fallacy is disappointingly widespread

> As you say complex doesn't equal better, which is my
> point. Why evolve from a form that works and works
> incredibly well to one that is less advantageous?

A bacterium might evolve into something which is an arguably less efficient replicator, but that doesn't matter -- as long as the evolved form is able to reproduce itself, it's biologically successful and can continue, perhaps to evolve further, perhaps not. The key is the ability to replicate onself in an environmental niche, or to mutate over time into something which doesn't compete with the same environmental constraints which confine the replication of the earlier species (which can go on happily, as long as there's 'space' for it to do so).

Make sense?

Wibbs

robindch wrote:

Likewise, but if the environment is stable -- as it is deep in the sea where the coelocanth lives -- then there's not really much selection pressure from the non-living environment to evolve. Which means that if you're an efficiently reproducing life-form, then you're likely to stay that way.

Well for a start, the level of the ocean where the coelocanth abides is not what you would call stable. In any case their ancestors were found in more shallow water. Both their living habits and the environment itself have changed radically in the time they've been around with seemingly little change in the organism itself.

btw, it's only our comrades in the religious industries who insist, upon no basis whatsoever, that there *must* be more to it than that (and they'll be the folks who know what it is!). This teleological fallacy is disappointingly widespread

Maybe there is more to it than that, maybe there's not. I figure whatever greases your wheel. Hey, I don't believe it myself, but I don't have any objection to believing what you may, so long as it doesn't affect others unduly. I can agree to disagree while still respecting the other position. Objective "truth" is a hard one to pin down anyway. The sceptic brigade can be accused of being just as smug, dismissive and "evangelical" in their attitude. Both sides think they're the be all and end all and their path is the right one and both can be just as intransigent and arrogant with it. Many scientific theories have been equally dismissed by both the sceptical and religious in the past. Darwinism itself being one example. Look at how physics has progressed in the last 100yrs. Too many scientific "truths" have been overturned in favour of newer theories far to often, for me at least to be so sure of the current vogue. BTW, I only reply in response to your point as I certainly don't want to be dragging the religion V science debate over here. I've enough to contend with putting the rationalist approach across over in the Christianity forum. I'm stretching myself a bit thin here

Until the arrival of selfish-genetic theory, nobody really had an answer to "why" life was -- it just happened to be and that was where the question lay for quite some time. Dawkins, together with the researchers whose ideas he collated, have provided an explanation which is as simple as it is convincing, namely, that things which are good at reproducing, tend to reproduce. Or alternatively, you're the (current) end-result of an unimaginably long series of creatures who reproduced, so it's quite likely that you'll be able to as well.

A bacterium might evolve into something which is an arguably less efficient replicator, but that doesn't matter -- as long as the evolved form is able to reproduce itself, it's biologically successful and can continue, perhaps to evolve further, perhaps not. The key is the ability to replicate onself in an environmental niche, or to mutate over time into something which doesn't compete with the same environmental constraints which confine the replication of the earlier species (which can go on happily, as long as there's 'space' for it to do so).

Make sense?

At first glance yes, but it still very much open to debate. It doesn't answer the why evolve in the first place question at all. It's only slightly ahead of the "it just is" idea. Why evolve into any niche when the simpler lifeform is there already? From the subatomic scale upwards, nature abhors "wasted" energy, so why organise greater complexity when entropy is the order of the day?

We're still making the observation after the fact. It just happened that way because it happened that way does not a scientific theory make. For a start one can't predict future outcomes, or repeat the hypothesis in the lab. Surely that would be required of any scientific theory?

Directed computer simulations such as those conducted by Dawkins and others are not applicable either, as they are directing the process of both the start point and the selection itself. They "create" the life, they create the instructions and they create the evolutionary pressures. Of course they'll get a result that backs them up, but it does not explain the origin of the life, the origin of the complexity or the instructions themselves.

For me it's too dangerously close to the ID position they're trying to avoid. There is a scientific answer, but I for one think this is too simplistic an answer to a complicated problem.

robindch

> It doesn't answer the "why evolve in the first place" question at all.

In that case, you don't really understand (yet!) what selfish genetic theory is really all about.

An organism will evolve, not because it wants to or because it has to, but simply because mutations of one kind or another inevitably arise. Some mutations are beneficial in some way (and may be maintained in subsequent generations) and some are not beneficial (and may not be maintained in subsequent generations). Over time, and in some given environment, these mutations will inevitably give rise to organisms which are more successful replicators than other organisms. The more successful replicators are the ones which will tend to expand to fill their ecological niche which may, or may not, be the same as the niche occupied by their ancestors. If it's the same niche, then the descendants of its ancestors will probably die out; while if it's a different niche, then the old and new populations will continue to diverge until they're mutually non-viable separate species (cf, the ring species above).

All that the Selfish Genetic proposition really says is that things which are good at reproducing, will tend to reproduce more than things which aren't good at it. And the slow mutation of DNA is the mechism by which such better replicators arise. There isn't really any "why" about it at all -- it simply happens as a by-product of the physical process taking place.

> For a start one can't predict future outcomes, or repeat
> the hypothesis in the lab.

You are able to produce future outcomes, though not any more specific than "well, an organism is going to act in its DNA's best interest" -- this has been observed time and time again in the past. And, based upon this formulation, Dawkins did make predictions in the Selfish Gene which were subsequently found out to be accurate, for example, concerning kinship between a mother's offspring, and the mother's own siblings. See the chapter "Genesmanship" in the Selfish Gene, summary here:

http://www.simonyi.ox.ac.uk/dawkins/WorldOfDawkins-archive/Dawkins/Work/Books/selfish.shtml

In short, the Selfish Genetic Proposition, like any proposition in science, isn't something which can be "proved" true, because, in science, you can never "prove" anything true, you can only prove falsity. However SGP is a very simple, even obvious in retrospect, notion which explains a hefty series of observed facts, and is simply a refinement of natural selection.

Alf_Wiggum

John2 wrote:

I think greater DNA range is the wrong term to use. I don't know for a fact any of this but what I think you're saying is that the difference between the genome of certain frogs when compared to each other is greater than those of mice and whales.

Yeah, the first frog like amphibian, Traidobatrachus is found in Triassic rocks in Madagascar (about 200 million years ago). There are currently about 4300 different species of frog/toad (Order Anura) although this goes up and down, as does the definition of species. However, the first whales, came about in the Eocene epoch about 50 million years ago (about 80 different species in the order cetacea). However, this difference in millions of years doesn't directly account for the difference in diversity

John2 wrote:

This would make sense to me considering frogs have been in existance in a huge myriad of environments for many millions of years more than mice and whales have been diverging.

I'd slightly disagree, the reason I beleive that frogs have more genetic flexibility then whales is because, in my opinion, Fish -> Tetrapods -> Amphibians -> Reptiles -> Mammals. Therefore mammals are already quite specialised.

Frogs for example, as they've moved along the geological time scale has lost a lot of disparity and gained a lot of diversity. Like, most frogs look very very similar, but there is incredible amount of diversity (~numbers of species).

I don't know how the above can be used to prove/disprove the theory of evolution.

John

Alf_Wiggum wrote:

Yeah, the first frog like amphibian, Traidobatrachus is found in Triassic rocks in Madagascar (about 200 million years ago). There are currently about 4300 different species of frog/toad (Order Anura) although this goes up and down, as does the definition of species.

Wow, I though there were far more frog species than that. That's about the same amount as known mammals.

However, this difference in millions of years doesn't directly account for the difference in diversity

I know the time difference wouldn't be the sole cause but the extra time does allow more time for evolution to occur.

I'd slightly disagree, the reason I beleive that frogs have more genetic flexibility then whales is because, in my opinion, Fish -> Tetrapods -> Amphibians -> Reptiles -> Mammals. Therefore mammals are already quite specialised.

My main reasoning for the lower amount of genetic variation in mammals would be that frogs also lay eggs which are for the most part fairly open to genetic insults like UV light, viruses and whatnot. Mammals are bit more insulated. Also the complex life cycle of frogs means that there are more stages for changes to occur.

samb

Very interesting discussion above, I just read threw bits of it. I would like to make a few comments on what I have read and am sorry if I am not up to date on who is saying what and what you are now discussing. You all seem well informed, so well done to you;) lol.

With regard to the fact that some 'simple' organisms have larger genome's I think this is related to Epi-genetics. The way in which genes are turned on and off (methylation etc). Genetics is much more complex than was realised only some years ago. their is good evidence now for imprinting of genes,, genes somehow having a memory of what parent they came from... This makes evolution more complex and possibly slightly Lamarkian. However neo-darwinian evolution is undoubtedly the overwhelmingly important driving force in expaining how we evolve. It is more than adequate to do this the only question is how important if at all these other mechanisms may be.

biologist generally define a species as a population in which its members can reproduce with eachother (male with female obvoiusly). The ring speices demonstrate the falicy in this definition however. A species should now be defined as any population in which genes can flow through a gene pool. Infact species and gene-pool are the same really. before you mention it, I know viruses and humans can transplant genes from different species but these are rare anomallies.

I think that darwinian evolution easily explains how life was started from simple replicators. better replicators become more frequent than not so good ones. It is a simple exeption to entropy. Evolution does not go backwards or fowards it simply goes with the environment. If the environment doesn't change then after a certain amount of time the organism will cease to evolve. This is theoretical of course because the environments is always variable slightly at least. with regard the Ceolcanth, it has certainly changed slightly sinse ancient times and is probably variable today. The sensitivity of its oxygen absorbing cells may have changed, this and many subtle cellular and genetic changes are sure to have taken place that are not observable in the fossil record.

Keep up the good work

Wibbs

^Evolution at work. samb posts one and already it's reproducing.:D It's interesting you mention a possible Lamarckian twist in evolution. You would have raised some eyebrows not so long ago for that comment.

samb

what did I post that is reproducing

Wibbs

Nah it's just that when it was first posted it showed up twice. Some sort of glitch that's cleared itself methinks.