Ignorant evolution question

[Somthing Witty]

I was watching nerd TV today about the Earth's core and an interesting thought came to mind. I'm sure I'm not the first person who's raised this, but I really can't find a lot about this idea.

Please excuse the lack of knowledge; I'm learning, but still a layman.

Great changes to the Earth's magnetic poles bring a lessening of protection from the sun's radiation across certain regions during the shift in polarity. As DNA can be mutated by radiation, has there been much research into whether this might be a driving force behind evolution?

I've been reading about Gould's theory, but it seems he's dealing with the handedness of DNA being effected by the reversal of poles. However, I'm specifically curious about the effect of cosmic radiation.

[WhatRoughBeast]

Witty -

Well, yes, sort of, but not really. Transcription errors which normally occur in DNA replication do the job quite well. To the tune of (about) one in a billion base pairs in human DNA. Then there are larger scale errors involving whole sections of DNA which get transposed, and translocated, and all sorts of weird stuff. Radiation damage seems to play a pretty minor role.

DNA copying is a remarkably messy process, with more stuff going wrong on a regular basis than is good for your peace of mind if you think about it.

[MaxMurx]

Evolution being driven by nothing but spontaneous gene mutations is questionnable to me. If those lead to chromosome's breaking, after millions of generations all chromosomes ought to be pretty short.
I am convinced that we pass our memories (or at least some of them) to our following generations stored on our DNA. Those memories were misunderstood by Sigmund Freud and led to misinterpretations of "deja vu" experiences and the oedipal phase. Those are in fact memories of former generations. The magnetic field example is very feasible to explain the hypothesis.

First: Nature does not create anything which is useless and has only 3 general rules: Protect your existance, protect the existance of your species and mix your genetic material with copy from a place far away to avoid both DNAs having existed at the same place being exposed to identical stress and also far off from the own string of heredity to avoid copies of broken material. Freuds oedipal phase is characterised by the son's wish to remove (kill) the father based on his upcoming desire towards the mother.
The theory is absurd, unlogic and violates all laws of nature This theory for me is wrong. All observations also can be explained that the son remebers the father's desire towards the mother and has to find out which is his own and which is his ancestory's memory in his own material. The impression to exist twice (which occurs in shizophrenics) is in fact connected to the intention to kill the other one and happened to John Lennon, unfortunately he was not the one with shizophreny.

The magnetic field of the earth does not damage our genetic material, especially not the direction of the lines of force. We wouldn't be able to turn around if the theory would be correct. However changes of direction are frequent and I read recently that a complete change of north and south poles is expected every second at present.
My theory is possibly explained by the behaviour of European oscine birds (also oceanic mammals travelling long distances). Those birds were already present during the times of dinosaurs 45 million years ago. In late september they travel to the African continent to escape northern European winter temperatures. Their navigation is along the magnetic field lines. 45 million years ago according to the "continental drift" theory Europe, Africa and the US were one big land mass which moved excentrically by a few centimeters per year. That means each generation of birds misses its goal by a few centimeters. That error easily can be corrected by sight control and correction. However, after hundreds of thousands of years flying constantly along the magnetic field vector which once and for all times was engraved in the genetic code of the birds, the African landmass has moved out of visibility; those birds would die if not the slight re adjustment of the navigation path would have been passed from one generation to the next.
I think that the sum of a multitude of mechanisms is "evolution" and until nobody can prove the contrary I even do not rule out creation or some contribution to evolution by that activity. I only do not believe in it.

[DC]

Evolution being driven by nothing but spontaneous gene mutations is questionnable to me. If those lead to chromosome's breaking, after millions of generations all chromosomes ought to be pretty short.
I am convinced that we pass our memories (or at least some of them) to our following generations stored on our DNA. Those memories were misunderstood by Sigmund Freud and led to misinterpretations of "deja vu" experiences and the oedipal phase. Those are in fact memories of former generations. The magnetic field example is very feasible to explain the hypothesis.

First: Nature does not create anything which is useless and has only 3 general rules: Protect your existance, protect the existance of your species and mix your genetic material with copy from a place far away to avoid both DNAs having existed at the same place being exposed to identical stress and also far off from the own string of heredity to avoid copies of broken material. Freuds oedipal phase is characterised by the son's wish to remove (kill) the father based on his upcoming desire towards the mother.
The theory is absurd, unlogic and violates all laws of nature This theory for me is wrong. All observations also can be explained that the son remebers the father's desire towards the mother and has to find out which is his own and which is his ancestory's memory in his own material. The impression to exist twice (which occurs in shizophrenics) is in fact connected to the intention to kill the other one and happened to John Lennon, unfortunately he was not the one with shizophreny.

The magnetic field of the earth does not damage our genetic material, especially not the direction of the lines of force. We wouldn't be able to turn around if the theory would be correct. However changes of direction are frequent and I read recently that a complete change of north and south poles is expected every second at present.
My theory is possibly explained by the behaviour of European oscine birds (also oceanic mammals travelling long distances). Those birds were already present during the times of dinosaurs 45 million years ago. In late september they travel to the African continent to escape northern European winter temperatures. Their navigation is along the magnetic field lines. 45 million years ago according to the "continental drift" theory Europe, Africa and the US were one big land mass which moved excentrically by a few centimeters per year. That means each generation of birds misses its goal by a few centimeters. That error easily can be corrected by sight control and correction. However, after hundreds of thousands of years flying constantly along the magnetic field vector which once and for all times was engraved in the genetic code of the birds, the African landmass has moved out of visibility; those birds would die if not the slight re adjustment of the navigation path would have been passed from one generation to the next.
I think that the sum of a multitude of mechanisms is "evolution" and until nobody can prove the contrary I even do not rule out creation or some contribution to evolution by that activity. I only do not believe in it.

woot?:boggled:

[steenkh]

Evolution being driven by nothing but spontaneous gene mutations is questionnable to me. If those lead to chromosome's breaking, after millions of generations all chromosomes ought to be pretty short.
If that was what the theory of evolution was all about, you would be right, however, you are wrong. There is a lot more to evolution than spontaneous gene mutations and chromosome breaking.

I am convinced that we pass our memories (or at least some of them) to our following generations stored on our DNA.
And you would be wrong again. There is not the slightest hint that any memories are stored in DNA (depending on what you would term a "memory").

First: Nature does not create anything which is useless and has only 3 general rules: Protect your existance, protect the existance of your species and mix your genetic material with copy from a place far away to avoid both DNAs having existed at the same place being exposed to identical stress and also far off from the own string of heredity to avoid copies of broken material.
So what about all those species that never move far at all? Or all those species that produce plenty of offspring precisely because the individual survival is not important, but that of the species is. I also doubt the "protect your species" rule. It is certainly not something that any individual cares much about, except some humans, and perhaps even a few animals. But you are right that if a species is not adapted to survive, it will become extinct.

The theory is absurd, unlogic and violates all laws of nature This theory for me is wrong.
Perhaps you could explain why you bring up Freud's theories in the first place? This thread was about evolution.

The magnetic field of the earth does not damage our genetic material, especially not the direction of the lines of force.
Not in any direction. The Earth has had magnetism as long as life has existed, so life has adapted well to magnetism.

We wouldn't be able to turn around if the theory would be correct.
If the theory was correct, there would be repair mechanisms in place, or we would not have life on Earth.

However changes of direction are frequent and I read recently that a complete change of north and south poles is expected every second at present.
Now you are suddenly talking about switching the magnetic poles, and not changing direction of humans. The pole switch is not something expected "every second", but is a slow process lasting hundreds of years. The problem for us is that possibly, the magnetic field will drop for a while, leaving us unprotected against cosmic rays.

My theory is possibly explained by the behaviour of European oscine birds (also oceanic mammals travelling long distances). Those birds were already present during the times of dinosaurs 45 million years ago.
They were?

In late september they travel to the African continent to escape northern European winter temperatures. Their navigation is along the magnetic field lines. 45 million years ago according to the "continental drift" theory Europe, Africa and the US were one big land mass which moved excentrically by a few centimeters per year. That means each generation of birds misses its goal by a few centimeters. That error easily can be corrected by sight control and correction. However, after hundreds of thousands of years flying constantly along the magnetic field vector which once and for all times was engraved in the genetic code of the birds, the African landmass has moved out of visibility; those birds would die if not the slight re adjustment of the navigation path would have been passed from one generation to the next.
Obviously this information is passed on from generation to generation, but we do not need to call it memories. It could just as well be the case that there is always a certain spread in the ability to fly in certain directions, and if the birds who fly more in one direction than another tend not to survive, the trait to veer more to the other side will be favoured.

I think that the sum of a multitude of mechanisms is "evolution" and until nobody can prove the contrary I even do not rule out creation or some contribution to evolution by that activity. I only do not believe in it.
There are a multitude of mutation and selection mechanisms at play, but I really cannot see how "creation" would be one of them. I rather believe that the theory of evolution would be irrelevant if any supernatural act of magic was involved.

[yomero]

I was watching nerd TV today about the Earth's core and an interesting thought came to mind. I'm sure I'm not the first person who's raised this, but I really can't find a lot about this idea.

Please excuse the lack of knowledge; I'm learning, but still a layman.

Great changes to the Earth's magnetic poles bring a lessening of protection from the sun's radiation across certain regions during the shift in polarity. As DNA can be mutated by radiation, has there been much research into whether this might be a driving force behind evolution?

I've been reading about Gould's theory, but it seems he's dealing with the handedness of DNA being effected by the reversal of poles. However, I'm specifically curious about the effect of cosmic radiation.

I'm also a layman with as great a need to learn as you, perhaps greater. Other posters have already commented that mutations due to radiation are not the only the only driving force of evolution. No comment has been made on your last paragraph. As I understand it, you are saying a reversal of polarity at sometime early in the history of life, made the planet more vulnerable to cosmic radiation. This caused the ''handedness'' of DNA. I take it that you are talking about chirality, or optic isomerism. This is the faculty that some pairs of molecules that are identical structurally, have to bend polarized light. One of them to the right, the other to the left. This is a very confusing, arcane topic, very much over my head. But as I understand it, it is only short and simple molecules such as carbohydrates and aminoacids that present this behavior. I couldn't find any mention of DNA. Neither did I find that a reversal of polarity caused the fact that most natural aminoacids are L (left) and most sugars are D (right). Most scientist think it is a random result. Or that organic molecules originated in space, where radiation could indeed be a factor.

As I said, I'm also a layman. Perhaps I'm wrong. I hope someone who really knows would post here and correct any mistakes. Here is a paragraph from Wiki on Chirality.

In biology
Many biologically active molecules are chiral, including the naturally occurring amino acids (the building blocks of proteins) and sugars. In biological systems, most of these compounds are of the same chirality: most amino acids are L and sugars are D. Typical naturally occurring proteins, made of L amino acids, are known as left-handed proteins, whereas D amino acids produce right-handed proteins.

The origin of this homochirality in biology is the subject of much debate.[12] Most scientists believe that Earth life's "choice" of chirality was purely random, and that if carbon-based life forms exist elsewhere in the universe, their chemistry could theoretically have opposite chirality. However, there is some suggestion that early amino acids could have formed in comet dust. In this case, circularly polarised radiation (which makes up 17% of stellar radiation) could have caused the selective destruction of one chirality of amino acids, leading to a selection bias which ultimately resulted in all life on Earth being homochiral.[13]
http://en.wikipedia.org/wiki/Chirality_(chemistry)

ETA: It has just occurred to me that DNA has a ''backbone'' of sugar molecules, deoxyribose, which should be of the D variety. In RNA it is ribose. I was wrong on that. Again, from wiki:

Structure
Several isomers exist with the formula H-(C=O)-(CH2)-(CHOH)3-H, but in deoxyribose all the hydroxyl groups are on the same side in the Fischer projection. The term "2-deoxyribose" may refer to either of two enantiomers: the biologically important D-2-deoxyribose and to the rarely encountered mirror image L-2-deoxyribose.[2] D-2-Deoxyribose is a precursor to the nucleic acid DNA. 2-Deoxyribose is an aldopentose, that is, a monosaccharide with five carbon atoms and having an aldehyde functional group.]
http://en.wikipedia.org/wiki/Deoxyribose

[Dancing David]

First: Nature does not create anything which is useless and has only 3 general rules: Protect your existance, protect the existance of your species and mix your genetic material with copy from a place far away to avoid both DNAs having existed at the same place being exposed to identical stress and also far off from the own string of heredity to avoid copies of broken material.

Nature produces pleanty that is useless, you would be hard pressed to find a funtion for many reatutes of lifeforms.
Protect the existance of your species, um, no. There are plenty of examples of lfe forms that can not protect themselves, much less the species.
Plenty fo species do not move very far either.

[Mr. Purple]

My theory is possibly explained by the behaviour of European birds (also oceanic mammals travelling long distances). Those birds were already present during the times of dinosaurs 45 million years ago.

Perhaps you just mis-typed, but this isn't correct. The dinosaurs you are talking about weren't around until apprx. 15 million years after the Cretaceous Dinosaurs were gone.

I am not really sure if this matters or not, you kind of lost me in your post.

[Mr. Purple]

First: Nature does not create anything which is useless
Incorrect. Among any number of examples, Paris Hilton was in fact created by nature. :D
Joke, but seriously, nature creates plenty of "useless" stuff.


and has only 3 general rules:

Again, no. Don't forget that "nature" includes the laws of physics, chemistry, etc. Besides this, I don't even agree that evolution (if that is what you meant) has only 3 rules.

[WhatRoughBeast]

Sigh. I don't know why I can't resist this kind of bogosity. Character flaw, I guess.

MaxMurx, I'm afraid your thread title is wrong. These are not ignorant questions. They are delusional.

Evolution being driven by nothing but spontaneous gene mutations is questionnable to me. If those lead to chromosome's breaking, after millions of generations all chromosomes ought to be pretty short.


Mutations do not, in general, lead to chromosome breaking. Where in the world did you get that idea? Please provide a reference.

I am convinced that we pass our memories (or at least some of them) to our following generations stored on our DNA. Those memories were misunderstood by Sigmund Freud and led to misinterpretations of "deja vu" experiences and the oedipal phase. Those are in fact memories of former generations. The magnetic field example is very feasible to explain the hypothesis.

Huh? OK. That's so bizarre I have to ask. What, exactly is the magnetic field example? Why haven't you mentioned it? How is it possible, let alone feasible, let alone very feasible? Please provide references.

First: Nature does not create anything which is useless

I assume you're a guy. Have you checked the utility of your nipples lately? No, seriously. In the US a couple of hundred guys get breast cancer each year. What, exactly, do they get in return?

First: Nature does not create anything which is useless and has only 3 general rules: Protect your existance, protect the existance of your species and mix your genetic material with copy from a place far away to avoid both DNAs having existed at the same place being exposed to identical stress and also far off from the own string of heredity to avoid copies of broken material.

There are any number of species that practice incest as a normal part of their life cycle. Nature doesn't seem to mind. There is at least one species of bdelian rotifers which are parthenogenetic, and never mix their DNA with anybody, and have been doing this for millions of years. Nature doesn't seem to mind. And how do local conditions "stress" DNA? Don't tell me you're a Lamarckian, too?

The magnetic field of the earth does not damage our genetic material, especially not the direction of the lines of force.

As a matter of fact, standard theory says that the earth's magetic field protects our genetic material, and with no preference for the direction of lines of force. Do you truly not understand this?

We wouldn't be able to turn around if the theory would be correct. However changes of direction are frequent and I read recently that a complete change of north and south poles is expected every second at present.


So you're saying that evolutionary theory claims that all organisms are aligned to the earth's magnetic field, and cannot turn around?

Please give a reference for the "every second" claim. National Enquirer, perhaps?

Those birds were already present during the times of dinosaurs 45 million years ago.

No they weren't. 45 million years ago the dinosaurs were extinct, and had been extinct for 20 million years.

[Wowbagger]

First: Nature does not create anything which is uselessWell, it does. Though, it often doesn't last terribly long.

and has only 3 general rules: Protect your existance, protect the existance of your speciesProtection of the species is not really a fundamental "rule of nature" (if there could be said to be any). Protection of oneself, and one's own offspring is more of the priority. Protection of the species as a whole is, at best, a secondary consideration.

Though, it could be worse than that: Natural selection ultimately works at the gene level. Protection of the species is only considered important where it would impact the protection of one's own genes.
The good news is that, in a highly social species, such as ours, protection of the species becomes a more important consideration than otherwise.

and mix your genetic material with copy from a place far away to avoid both DNAs having existed at the same place being exposed to identical stress and also far off from the own string of heredity to avoid copies of broken material.I don't think "far away" is as important as spread and variability. There is some strategy involved in preventing problems caused by incest. But, that is hardly the principle drive of evolution.

Freuds oedipal phase is characterised by the son's wish to remove (kill) the father based on his upcoming desire towards the mother. I don't think any evolutionary scientists take most of what Freud said seriously, any more.

[godless dave]

Re: the OP. Yes, people have thought of this before. IIRC, people have looked for correlations between mass extinctions and the known times of geomagnetic pole reversal, and they didn't find any.

[Dinwar]

godless dave is correct--polar reversals are not correlated with mass extinctions, mass turn-overs, or radiation events. Simply put they're too common--we're getting all excited because one is probable right now, but in reality they're frequent enough to be used for fairly fine-scale dating of rocks and fossils (magnetostratigraphy). On a human scale it's a major event; on an evolutionary/geological scale it's background noise.

Evolution being driven by nothing but spontaneous gene mutations is questionnable to me. If those lead to chromosome's breaking, after millions of generations all chromosomes ought to be pretty short.
You're obviously unfamiliar with DNA, including the start/stop codons.

I am convinced that we pass our memories (or at least some of them) to our following generations stored on our DNA.
Evidence?

First: Nature does not create anything which is useless Utility presupposes intent, which presupposes a conciousness, and the only conciousnesses (coniousni?) we know of are organic--meaning that 99.99999....% of all of nature is incapable of being useful, as it can't be used. So, no.

and has only 3 general rules: Protect your existance, protect the existance of your species and mix your genetic material with copy from a place far away to avoid both DNAs having existed at the same place being exposed to identical stress and also far off from the own string of heredity to avoid copies of broken material.LIFE has those rules, if you squint hard and it's dark at the time. However, none are universal even in life. Your third rule applies only to exclusively sexually reproducing organisms, which is a minority. Your second rule is a consequence, not a rule--and it's also not universal. Plenty of organisms engage in canablism, and most do not rear offspring in any sense of the word. A lot of animals die after reproduction, and plants are incapable of rearing offspring (other then some chemical assistance). As for the first, again, it's a consequence: that which doesn't protect itself doesn't survive to reproduce. And considering there's humans who don't do this (those who cannot feel pain, for example), it's hardly a rule either.

No they weren't. 45 million years ago the dinosaurs were extinct, and had been extinct for 20 million years. Just a nit to pick: NONAVIAN dinosaurs were extinct. Dinosaurs as a whole never have gone exitnct, however. While I didn't eat any for lunch, many of my co-workers ate dino chilli for lunch. (A bit pedantic, perhaps, but important none the less in my opinion--the K/Pg event DID NOT cause the extinction of the dinosaurs, any more than the transition into the Holocene killed off mammals.)

My lunch is over, so I need to cut this post short. But as far as the OP goes, it's a parenial question in paleontology, and each time the answer is "Polar reversals really aren't correlated with anything of biological significance". It's a very good question, and we're still trying to figure out the follow-up. :)

[Dinwar]

The theory is absurd, unlogic and violates all laws of nature This theory for me is wrong. If you're referring to the theory of evolution here, I'd love to see what laws of nature it violates.

The magnetic field of the earth does not damage our genetic material, especially not the direction of the lines of force. The magnetic field doesn't damage us for two reasons. First, it's too low to really have any affect on us--the magnetic affects of metal we encounter are higher than the affects of the Earth's magnetosphere. Second, we evolved in this environment, which means that anything which couldn't handle the magnetosphere would have died out, or at least would be on its way out. It's like oxygen--so ubiquitous that we forget it's really an environmental factor, at least until something goes wrong.

We wouldn't be able to turn around if the theory would be correct. However changes of direction are frequent and I read recently that a complete change of north and south poles is expected every second at present.
I think you're talking about polar reversals here? If you are, you're correct that such reversals don't affect life much. I believe (but, due to your writing style, can't be sure) you have the wrong reasoning, however.

My theory is possibly explained by the behaviour of European oscine birds (also oceanic mammals travelling long distances). Those birds were already present during the times of dinosaurs 45 million years ago.There are many problems with this. First off, any organisms that's been around for more than a few million years has been through multiple polar reversals, so EVERY migratory species would potentially be affected by this. Second, the Mesozoic was roughly 250 to 65.4 million years ago, meaning you've got the time of the Age of Dinosaurs about 20 million years too late (probably a typo, but it's worth pointing out). Third, a theory needs to explain the behavior of ALL migratory animals (or at least all of them which use megnetic materials to migrate--not all do), not just one. If it's just one species it's probably a fluke (no pun intended).

45 million years ago according to the "continental drift" theory Europe, Africa and the US were one big land mass which moved excentrically by a few centimeters per year. No. Europe and Africa were split a long time ago, and still haven't really come together (though subduction is bringing them together). There are reefs in Austria, Spain, and Italy that date back to the Dannian/Thenetian transion, and you don't get reefs on dry land. And Africa and Europe were both separated by the Atlantic Ocean (it just wasn't as big as it is today). In the Triassic, yeah, Pangea connected all the continents, but by 65 ga they were well apart.

That means each generation of birds misses its goal by a few centimeters. That error easily can be corrected by sight control and correction. However, after hundreds of thousands of years flying constantly along the magnetic field vector which once and for all times was engraved in the genetic code of the birds, the African landmass has moved out of visibility; those birds would die if not the slight re adjustment of the navigation path would have been passed from one generation to the next.
I'll give you points for consistency--you tied the whole "memory stored in DNA" stuff back in to your idea. However, this doesn't make any sense. Each generation would make NEW memories. The continents are moving at a rate similar to that of the growth of your fingernails, at maximum--there'd be no sudden event that brought Africa out of sight of Europe (and in fact it's moving in the other direction--it's coliding with Europe....Well, actually it's rotating clockwise, so the eastern edge is, but the western edge is also movinig generally north, mostly....it's complicated). So this fails in multiple respects.

I think that the sum of a multitude of mechanisms is "evolution" and until nobody can prove the contrary I even do not rule out creation or some contribution to evolution by that activity. I only do not believe in it.
Nope. Evolution is heritable change through time. The magnetosphere does not play a significant role in this.

I assume you're a guy. Have you checked the utility of your nipples lately? No, seriously. Bad example. Nipples are very useful--gotta have something to put the clamps on. ;)

[Jeff Corey]

How did Freud get into that load of crap? That is akin to godwinning a political forum.

[WhatRoughBeast]

Bad example. Nipples are very useful--gotta have something to put the clamps on. ;)

Oh, yesssss! I stand corrected.

[WhatRoughBeast]

Just a nit to pick: NONAVIAN dinosaurs were extinct. Dinosaurs as a whole never have gone exitnct, however. While I didn't eat any for lunch, many of my co-workers ate dino chilli for lunch. (A bit pedantic, perhaps, but important none the less in my opinion--the K/Pg event DID NOT cause the extinction of the dinosaurs, any more than the transition into the Holocene killed off mammals.)



Dinwar - You are, of course, correct. I can only plead that, given the quality of the rest of MaxMurx's post, I presumed that "the time of the dinosaurs" referred to pre-65 Ma, and I was responding to what he meant.

Since he has not corrected my statement, I presume that I was correct.

[Kumar]

[QUOTE=Wowbagger;7135673]Protection of the species is not really a fundamental "rule of nature" (if there could be said to be any). Protection of oneself, and one's own offspring is more of the priority. Protection of the species as a whole is, at best, a secondary consideration.

Though, it could be worse than that: Natural selection ultimately works at the gene level. Protection of the species is only considered important where it would impact the protection of one's own genes.
The good news is that, in a highly social species, such as ours, protection of the species becomes a more important consideration than otherwise.

[QUOTE]

Good thought. "Rule of nature" can be to keep it in balance. Btw, whether "highly social species, like ours" are able to protect our genes--due to opting living in society?

[Beerina]

Insofar as you share most of your DNA with the rest of your species, your activities can support that DNA in others as well as yourself. Ant colonies where the hordes of workers have identical DNA demonstrate this, but it is not limited to identical clones.

That it's all about the tiny fraction that differs from your neighbor, or your brother, is so chauvinistic. "The problem of altruism" thus evaporates as a non-issue.

That it's all about DNA when we have this additional data encoding sequence that controls behaviors, external to DNA, is itself chauvinistic. It mutates, evolves, reproduces successfully, and all at a much greater rate than DNA. You're helping them spread right now.

[Dinwar]

"Rule of nature" can be to keep it in balance. Wrong. There is no ballance in nature. For one thing, the paleontological evidence suggests that what we consider a healthy ecosystem is actually HIGHLY lacking in predators (well, terrestrail ones anyway). Second, there's a background level of extinction. We tend to think of extinction as some dramatic event, but in truth extinction is the norm. Species live, on average, about 5 million years. Then they die out. In a ballanced system, this wouldn't happen--the domanent trend would be stasis. But in the fossil record faunal turnover is so common, even in times of "ballanced" ecology, that biostratigraphy is frequently more accurate than radiometric dating.

In truth, "nature' is a dynamic equilibrium; it's constantly changing, and either too much or too little leads to the destruction of an ecosystem.

Dinwar - You are, of course, correct. Actually, I'm not so sure now that I think about it more....Nonavian dinosaurs are a paraphyletic group, which normally is considered not to be a valid group. However, paleontologists use paraphyletic groups CONSTANTLY. We have to--any time a species speciates the old species name represents a paraphyletic grouping. So really the term "nonavian dinosaur" is just as valid as, say, "Articulata". Really, the reason I think it's important to use the true grouping is that it facilitates K/Pg research--some dinosaurs died and some didn't, which raises the question of "Why?" That said, for any other purpose splitting dinosaurs into avian and non-avian is, from a paleontological perspective, perfectly valid.

Ah, the joys of taxonomy. :D

[WhatRoughBeast]

Actually, I'm not so sure now that I think about it more....

Ok. You're not correct. There, that was easy.

[Dinwar]

Ok. You're not correct. There, that was easy. Eh, not quite. See, the problem is both the viewpoint that Dinosauria includes birds and that Dinosauria does not include birds are valid stances within paleontology. And considering my interest in the K/Pg event, it's an issue that I really struggle with, and one which I really should resolve one of these days. It's one of those nagging questions that's always at the back of my mind. And the two views have some serious implications. If birds are considered part of Dinosauria that means that The Age of The Dinosaurs came to an end at different times in different parts of the world--DRASTICALLY different times. Giant ground birds were top predators in the Gondwana continents well into the Cenozoic (and by "well into" I mean "humans may have encountered them"), and birds have a profound influence on most ecosystems today. If birds are NOT dinosaurs (or, rather, if we accept the commonly held definition of "dinosaur", which is paraphyletic) we can more easily deal with the fact that Ornithiscians died out at the K/Pg boundary, and many Sauricians as well--birds are different, and operate differently under selective pressures than "dinosaurs".

Like I said, it's fundamentally a taxonomical issue, but gets into some pretty serious paleoecological issues as well.