Evolution: Science or Philosophy

[cheeseburger]

I just skimmed this and I couldn't resist.

He tried to figure out if he could make the arms of the frog grow on other parts of the body.

This has already been done on drosophila flies. In answer to "what makes your arms grow out of your shoulder," it's controlled by "Hox genes." So... not sure what the point is, but this has been studied in depth in several genetic model organisms. If you care...

And Rhabbi, your entropy argument is my favorite. The way that argument goes is, if you take some closed system and leave it alone, it gets more disordered. Therefore, the earth should get more disordered over time instead of evolving life. Makes sense, right?

The earth is not a closed system. It's getting energy thrown at it by the bucketfull in the form of light from the sun. In case you still don't get it, lets go back to the staple entropy analogy: your room.

A mess, right? Let's say you go and clean up your room. You're adding energy to your room, and decreasing the entropy of your room. You're also not violating any laws of physics, because the entropy of the 'universe' is increasing ever so slightly while the entropy of your room is decreasing.

The second law does NOT state that entropy always increases. You can add order to a system by adding energy to it; but, you are also increasing disorder somewhere else. The definition, according to wikipedia, is

"The total entropy of any isolated thermodynamic system tends to increase over time"

Wikipedia has a cute example:
"In general, according to the second law, the entropy of a system that is not isolated may decrease. An air conditioner, for example, cools the air in a room, thus reducing the entropy of the air. The heat, however, involved in operating the air conditioner always makes a bigger contribution to the entropy of the environment than the decrease of the entropy of the air. Thus the total entropy of the room and the environment increases, in agreement with the second law."

Just as a general statement, there is no debate. Evolution vs. 'intelligent design' is a moot point. If you really want to read up on evidence of evolution, take a trip to pubmed and browse some articles on evolution.

[Rhabbi]

The earth is not a closed system. It's getting energy thrown at it by the bucketfull in the form of light from the sun. In case you still don't get it, lets go back to the staple entropy analogy: your room.

A mess, right? Let's say you go and clean up your room. You're adding energy to your room, and decreasing the entropy of your room. You're also not violating any laws of physics, because the entropy of the 'universe' is increasing ever so slightly while the entropy of your room is decreasing.

Agreed, but the amount of energy that has apparently been added by the sun does not seem to account for the drastic decrease in entropy. It is almost the equivelant of adding a nuclear bomb to a normal bonfire. The Earth does not retain most of the energy that actually reaches it from the sun.

[cheeseburger]

Agreed, but the amount of energy that has apparently been added by the sun does not seem to account for the drastic decrease in entropy.

I'd like to see your source on this before I respond to it.

Mitochondrial DNA has been traced back to an "Eve" who apparently lived in Africa, but it has not been traced back to anything else.

It's mitochondrial DNA. (In case you don't know what a mitochondrion is, it's the organelle most human (and not so human) cells contain which functions in aerobic respiration; i.e. making ATP or energy).

Where did it come from? According to the secondary endosymbiotic theory, it was originally some single celled bacterium/prokrayote that made it's energy by aerobic respiration (citric acid cycle), and got engulfed by a bigger organism that couldn't digest it.

Point is, it has been traced back to something else.

Maybe Tom is more accurate than I thought in saying that scientists are diluting the definition of a secies. It makes me wonder why.

Scientists are not 'diluting' anything. Over the last decade or so, scientists have gone from a morphological approach to what constitutes a species, to a molecular approach. As a result, some species that 'looked' the same turned out to be unrelated, and some species that didn't look similar were actually related.

Very few different species can mate due to pre-zygotic mating barriers, i.e. you physically cannot mate a whale with a fly. But even if you tried to fertilize a whale egg with sperm from a fly in vitro, you would fail nearly 100% of the time. Mating barriers are generally the first to appear in any speciation event.

You are telling me that evolution is not random chance, yet that is exactly what I was taught in school and college.

This quote indicates you don't even know what evolution is.

Let's take a step back and consider why species even undergo sexual reproduction. It is far 'cheaper' (in terms of energy) to reproduce asexually.

Species reproduce sexually in order to increase variation within the species, because that increases the chances the species will survive. Mutations occur far too infrequently, and are too often detrimental, for it to replace sexual reproduction.

So if species didn't evolve, why bother with the variation within species? If there is no selection, or 'survival of the fittest,' why do practically all species have some mechanism for genetic recombination?

No one's even going to read this. Makes me wonder why I write it...

[Rhabbi]

I'd like to see your source on this before I respond to it.

Will try to find it, it is from a book I read so I do not heve it handy.

It's mitochondrial DNA. (In case you don't know what a mitochondrion is, it's the organelle most human (and not so human) cells contain which functions in aerobic respiration; i.e. making ATP or energy.

Where did it come from? According to the secondary endosymbiotic theory, it was originally some single celled bacterium/prokrayote that made it's energy by aerobic respiration (citric acid cycle), and got engulfed by a bigger organism that couldn't digest it.

Point is, it has been traced back to something else.

Not really, at least not in the sense I meant. Scientists have, at least theoretically, traced the mitchondrial DNA back to "Eve" through the testing the similarities of different women's mDNA and extrapolating it back to a woman in Africa.

Scientists are not 'diluting' anything. Over the last decade or so, scientists have gone from a morphological approach to what constitutes a species, to a molecular approach. As a result, some species that 'looked' the same turned out to be unrelated, and some species that didn't look similar were actually related.

The definition of a species I learned says that they are unable to mate. As far as I know this would hold true on a molecular level. Species are being redefined because of early misconceptions. Yet you cite a study that shows two different 'species' of butterflies mating to produce a third. To me that means that the definition has been diluted. Artificial support to force a hybrid that is not viable in nature does not prove evolution, it proves an outside influence.

Very few different species can mate due to pre-zygotic mating barriers, i.e. you physically cannot mate a whale with a fly. But even if you tried to fertilize a whale egg with sperm from a fly in vitro, you would fail nearly 100% of the time. Mating barriers are generally the first to appear in any speciation event.

This quote indicates you don't even know what evolution is.

My language was not clear, I am referring to the genisis of life on Earth. Every model I have encountered tells me that the chemiacals in the pre-biotic soup came together and formed the organic molecules that support life, and then life spopntaneoulsy arose. Am I mistaken in this? (By the way, i am aware that this a goss oversimplification, but my point is that the original event seems to be random.)

Let's take a step back and consider why species even undergo sexual reproduction. It is far 'cheaper' (in terms of energy) to reproduce asexually.

Species reproduce sexually in order to increase variation within the species, because that increases the chances the species will survive. Mutations occur far too infrequently, and are too often detrimental, for it to replace sexual reproduction.

So if species didn't evolve, why bother with the variation within species? If there is no selection, or 'survival of the fittest,' why do practically all species have some mechanism for genetic recombination?

Adaptation to environment? I would have no idea, i am at a loss to explain how we went from asexual reproduction to binary reproduction anyway, another thing that has never been explained in any way other than, it happened, so it must have happened.

[cheeseburger]

Will try to find it, it is from a book I read so I do not heve it handy.

The only source I accept is an article from an accredited scientific journal. Sorry. Books fall under many genres, one of which is fiction.

Not really, at least not in the sense I meant. Scientists have, at least theoretically, traced the mitchondrial DNA back to "Eve" through the testing the similarities of different women's mDNA and extrapolating it back to a woman in Africa.

Ok. Everyone knows that the Y chromosome is passed down along the male lineage, since boys are XY and only the father can contribute the Y.

Mitochondrial DNA is passed along the female lineage, because a fertilized egg cell, or zygote, already has a mitochondrion. When it divides, just like any other cell, the mitochondrion divides first, and then the cell divides. Sperm has no play in this, and so mitochondrial DNA is passed down from mother to child.

The reason I'm saying this is to give you a better understanding of why people even want to 'trace' mitochondrial DNA. However, tracing it 'all the way back' is pointless. Humans are not the only species with mitochondria, so if you want to find out where the organelle originates, you turn to the secondary endosymbiotic theory, which is a fancy way of saying "what you engulf and can't digest you make friends with."

The definition of a species I learned says that they are unable to mate.

This is an extremely simplistic definition that does not hold true in many cases. Mules are one common example.

The way things are done now, they sequence the genome of a species and compare it to that of another. Good match means either same species or pretty close - but keep in mind, the difference is in the .01% or there abouts. I'm no expert on this, but what you stated is clearly wrong.

Species are being redefined because of early misconceptions.

Reorganized is a better word.

Yet you cite a study that shows two different 'species' of butterflies mating to produce a third. To me that means that the definition has been diluted. Artificial support to force a hybrid that is not viable in nature does not prove evolution, it proves an outside influence.

Wasn't me. And by the way, this means nothing. Another example of this is D. Melanogaster mating with D. Yakuba. Big deal; they're unlikely to create viable offspring due to post-zygotic mating barriers. Nothing is being 'diluted,' whatever you mean by that.

My language was not clear, I am referring to the genisis of life on Earth. Every model I have encountered tells me that the chemiacals in the pre-biotic soup came together and formed the organic molecules that support life, and then life spopntaneoulsy arose. Am I mistaken in this? (By the way, i am aware that this a goss oversimplification, but my point is that the original event seems to be random.)

You are diluting it, but not entirely. Let me add some detail but still keep it really simplistic.

Basically, under the right conditions (reducing atmosphere, lightning, whatever) you form organic (organic simply means containing carbon) molecules that are polar on one side and non-polar on the other side. In an aqueous solution, the non-polar sides get pushed together and you get a very rudimentary membrane, allowing some separation. This means you can do things inside your membrane that couldn't go on outside. Once you have something that reproduces itself, like some self replicating RNA enzymes ('ribozymes') the cat's out of the bag and whatever replicates the fastest sticks around.

Adaptation to environment? I would have no idea, i am at a loss to explain how we went from asexual reproduction to binary reproduction anyway, another thing that has never been explained in any way other than, it happened, so it must have happened.

If you're at a loss, let me explain. Something that reproduces asexually can very quickly 'fill up' a niche that it is well suited to. Any change in that niche that makes it unfavorable for one of these creatures makes it unfavorable for all of the creatures since they're basically clones, and they all die.

And clearly environments change over time. Life is basically adapted to survive stressors. So, some mechanism that enhances variation among a species was highly selected for - since everything else died out once the environment changed.

Or, some creature multiplied so fast mutations became significant and added to the variation. Viruses and bacteria are like this; mutations add a lot of variation to a culture of bacteria because they reproduce something like once every couple hours.

Although bacteria can also reproduce sexually, at a greater cost. If you stress them, by say adding antibiotics, then the 'cost' of reproducing sexually outweighs the 'cost' of dying to the antibiotics, and they all suddenly start reproducing sexually and passinga round resistance genes.

I typed this a little rushed so I apologize for any spelling/nonsense errors.

[Rhabbi]

The only source I accept is an article from an accredited scientific journal. Sorry. Books fall under many genres, one of which is fiction.

That is too bad because I was about to recommend a book that raises some of the issues I think are pertinant to this discussion. It is The Language of God by Francis Collins. Dr Collins has a PhD in Medical Genetics, is an MD, and was head of the human genome project. His book is as unbiased a book as I have ever read, and raises some serious questions about the current levle of understanding of genetics and evolution. He also raises questions about theistic evolution, which is the model he seems to prefer.

Ok. Everyone knows that the Y chromosome is passed down along the male lineage, since boys are XY and only the father can contribute the Y.

Mitochondrial DNA is passed along the female lineage, because a fertilized egg cell, or zygote, already has a mitochondrion. When it divides, just like any other cell, the mitochondrion divides first, and then the cell divides. Sperm has no play in this, and so mitochondrial DNA is passed down from mother to child.

The reason I'm saying this is to give you a better understanding of why people even want to 'trace' mitochondrial DNA. However, tracing it 'all the way back' is pointless. Humans are not the only species with mitochondria, so if you want to find out where the organelle originates, you turn to the secondary endosymbiotic theory, which is a fancy way of saying "what you engulf and can't digest you make friends with."

Humans are genetically unique because we are the only species on Earth that has mitochondrial DNA? Interesting, isn't it? But coming up with a theory to explain that with no way of actually testing it seems pointless to me. I have tried to read up on this, but molecular biology is not my fielad and i will need some time to study the subject before I can reply in a manner that would make any sense to me. I do enjoy learning about these things though, so I hope that you will continue to educate me. I especially enjoyed the definition you gave about making friends with something if you cannot digest it. This is essentially waht we do everytime our digestive tract gets upset, our 'friendly' bacteria battle with the invading bacteria, and we adapt or die.

This is an extremely simplistic definition that does not hold true in many cases. Mules are one common example.

The way things are done now, they sequence the genome of a species and compare it to that of another. Good match means either same species or pretty close - but keep in mind, the difference is in the .01% or there abouts. I'm no expert on this, but what you stated is clearly wrong.

I can see that now, and am able to admit that I am wrong. But I am now faced with the problem that I have no definition of species, nor does anyone else. How are we supposed to debate a topic with no objective definition?

Reorganized is a better word.

Wasn't me. And by the way, this means nothing. Another example of this is D. Melanogaster mating with D. Yakuba. Big deal; they're unlikely to create viable offspring due to post-zygotic mating barriers. Nothing is being 'diluted,' whatever you mean by that.

You are diluting it, but not entirely. Let me add some detail but still keep it really simplistic.

Basically, under the right conditions (reducing atmosphere, lightning, whatever) you form organic (organic simply means containing carbon) molecules that are polar on one side and non-polar on the other side. In an aqueous solution, the non-polar sides get pushed together and you get a very rudimentary membrane, allowing some separation. This means you can do things inside your membrane that couldn't go on outside. Once you have something that reproduces itself, like some self replicating RNA enzymes ('ribozymes') the cat's out of the bag and whatever replicates the fastest sticks around.

If you're at a loss, let me explain. Something that reproduces asexually can very quickly 'fill up' a niche that it is well suited to. Any change in that niche that makes it unfavorable for one of these creatures makes it unfavorable for all of the creatures since they're basically clones, and they all die.

And clearly environments change over time. Life is basically adapted to survive stressors. So, some mechanism that enhances variation among a species was highly selected for - since everything else died out once the environment changed.

Or, some creature multiplied so fast mutations became significant and added to the variation. Viruses and bacteria are like this; mutations add a lot of variation to a culture of bacteria because they reproduce something like once every couple hours.

Although bacteria can also reproduce sexually, at a greater cost. If you stress them, by say adding antibiotics, then the 'cost' of reproducing sexually outweighs the 'cost' of dying to the antibiotics, and they all suddenly start reproducing sexually and passinga round resistance genes.

I typed this a little rushed so I apologize for any spelling/nonsense errors.

I certainly will not complain aboiut spelling and nonsense errors as I make more than my share of those. I have a question for you though, are you saying that bacteria have been observed to reproduse sexually? I thought that the mutations that you spoke of where selected for when all the competing bacteria died out from the antibiotics.