|
||||||||||||||||||||||||||||||||||||||
Evolution and the Origin of Life
Motivation: Do you believe in evolution? Is it REALLY scientific proven? Can we say it is a "theory"?
In Science when we have a theory we need to prove it. When two or more opposite models are used to explain a theory, there is no explanation at all.
When the first individual of a new species is created:
- it must be suddenly, by mutation; or
- it must be slow, with natural selection and adaptation.
Do you think these models are compatible? When LIFE started to exist in the Evolution theory?
In Science when we have a theory we need to prove it. When two or more opposite models are used to explain a theory, there is no explanation at all.
When the first individual of a new species is created:
- it must be suddenly, by mutation; or
- it must be slow, with natural selection and adaptation.
Do you think these models are compatible? When LIFE started to exist in the Evolution theory?
1) Why is there even an issue? Evolution allows that a new species may arise due to both mutation as well as adaptation; the two models need not be exclusive.
2) It's also possible to believe in evolution and a deity-based creation; they definitely don't need to be exclusive...
HM
2) It's also possible to believe in evolution and a deity-based creation; they definitely don't need to be exclusive...
HM
or the genetic engineering... I can go for that!
| volotao wrote: |
| Motivation: Do you believe in evolution? Is it REALLY scientific proven? Can we say it is a "theory"?
In Science when we have a theory we need to prove it. When two or more opposite models are used to explain a theory, there is no explanation at all. When the first individual of a new species is created: - it must be suddenly, by mutation; or - it must be slow, with natural selection and adaptation. Do you think these models are compatible? When LIFE started to exist in the Evolution theory? |
Evolution has been proven and it is a theory (read here) and there is no other module competing with it. Sudden mutation will not produce a new species.
Evolution is something that does exist, and is understood. We've observed mutation, know of adaptation - the precursors of evolution. We've seen fossils and DNA evidence of its occurence in both plants and animals. I am completely certain that it is in fact evolution that exists and certainly not intelligent design. It certainly fits into what we know better than any biblical text does. And yet people deny it.
Actually, I think intelligent design is what's right! After all, the Linux kernel couldn't have gotten to the state it is today be mere evolution. It must have been intelligently designed to be that way since its start!
Actually, I think intelligent design is what's right! After all, the Linux kernel couldn't have gotten to the state it is today be mere evolution. It must have been intelligently designed to be that way since its start!
| volotao wrote: |
| Motivation: Do you believe in evolution? Is it REALLY scientific proven? Can we say it is a "theory"?
In Science when we have a theory we need to prove it. When two or more opposite models are used to explain a theory, there is no explanation at all. When the first individual of a new species is created: - it must be suddenly, by mutation; or - it must be slow, with natural selection and adaptation. Do you think these models are compatible? When LIFE started to exist in the Evolution theory? |
Wow, that is quite a posting Volotao. It is completely wrong in most important respects and partly wrong in the rest. I'll just run through the corrections quickly....
- Line 1) Theory is what science has. Theories cannot be proven - they can only be disproved (refuted). Theory is the top of the tree in science - as good as it gets, the best available. Words like 'true', and 'proved' are NEVER used by scientists when talking about their models - only by those who do not understand how science works would use such terms.
- Line 1) With any standard scientific theory, like evolution, the title 'theory' means that it is what is currently believed to be the best and most accurate model or account we have and is the result of work by many scientists which is still ongoing.
- Line 3) No. You can never prove a theory is correct, all you can do is say it is correct up to now. It might be that tomorrow there is a new experiment which shows the theory breaks down in some circumstances. Scientists do NOT try to prove theories. They try to DISPROVE them - a process known as refutation. This is very important because if you don't realise this you cannot talk sensibly about science at all....
- Line 3) Two opposite models could never explain the same phenomenon so that is a bad example.
- Line 3) Theory is written in formal notation which explains exactly how it works, what the predictions or consequences will be and how you could show that the theory is wrong. In the case of evolution all you have to do is find a single fossil that is in the wrong geological layer - that's it. Just 1. Nobody has, of course, because the theory is solid.
- Line 5) There is never a sudden point when 1 species becomes another - it is a gradual change rather than a single generational change (otherwise, who would the new member of the new species be able to breed with)? A species can be technically defined as a group which are no longer able to breed with their previous ancestral group. That happens slowly and there is not 1 individual, therefore, who would be the first of a new species. Think of the word - EVOLUTION - it should suggest gradual and slow change. The alternative would be REVOLUTION which is sudden and normally violent change.
- Line 6) Yes, a significant genetic change will occur in a single individual, this is true. 1 genetic change, though, is seldom enough to create a completely new species. Again you need to think of a slow incremental process of many such changes over generations before a truly new species emerges....
- Line 7) The mutation itself is very fast normally and is caused by 1 of several possible mechanisms - the most important being cosmic rays - radiation, and chemical damage from chemicals known as mutagens for the obvious reason.
- Line 7/
Once mutation has occurred (the *random* part) the individual then carries on living and may or may not survive and breed in time. The most adapted the individual is to their environment, the more likely this is and therefore the more genetic material with the new mutated gene will enter the population concerned. It's really very simple, logical and, I think, quite wonderful. - Line 8/9. Evolution has nothing to say about how life started - a common mistake. Evolution starts when life exists, it does NOT cause that life to exist in the first place...how could it?
POSTSCRIPT - ADDED LATER - SELF CORRECTION
I realised that I have made a claim above which I cannot support with evidence. It's not necessarily wrong but I can't say for sure that it's right always so I need to be clear about it. The sentence is question is
"There is never a sudden point when 1 species becomes another"
I was very definite and I still think it is probably correct, but I should not have been so definitive in my choice of words..the word NEVER is always asking for trouble...
I hope that makes it a bit clearer for you.. Here are some links to more reading which you could do with in order to get yourself at least literate in the theory of evolution and so that you will understand how science works as opposed to how you think it does at the moment....
Simple intro to scientific method for beginners.
Falsifiability and it's importance
Why you cannot prove something to be true - and why science does not try - the problem of INDUCTION
The solution to the problem of induction - turn the problem around.
Scientific method, hypothesis, theory and experiment
Tutorial on evolution
Another tutorial
A more historical look at evolution for context
Evidence supporting evolution
More reasons to think evolution is correct
That should give you enough to be able to talk a bit more sensibly and accurately on the issue.
Happy reading
Bickerman,
1) I understand your point of view and 2) you disagreed with me in the majority (or all) of what I wrote.
I am trying to write about some arguments I´ve heard and believe, until this moment. I like this subject, but I am not expert in this area at all. Maybe you want me to be more rigorous in my affirmations. For this reason, please forgive me (and, naturally, if you want, post the corrections) everytime you believe I am arguing wrong.
I will take a time to analyze your last message and then answer again.
I am satisfied with your reply.
Volotao.
1) I understand your point of view and 2) you disagreed with me in the majority (or all) of what I wrote.
I am trying to write about some arguments I´ve heard and believe, until this moment. I like this subject, but I am not expert in this area at all. Maybe you want me to be more rigorous in my affirmations. For this reason, please forgive me (and, naturally, if you want, post the corrections) everytime you believe I am arguing wrong.
I will take a time to analyze your last message and then answer again.
I am satisfied with your reply.
Volotao.
| Bikerman wrote: |
|
POSTSCRIPT - ADDED LATER - SELF CORRECTION I realised that I have made a claim above which I cannot support with evidence. It's not necessarily wrong but I can't say for sure that it's right always so I need to be clear about it. The sentence is question is "There is never a sudden point when 1 species becomes another" I was very definite and I still think it is probably correct, but I should not have been so definitive in my choice of words..the word NEVER is always asking for trouble... |
Bikerman,
Though selection occurs on the level of individual genes (so, slightly smaller than the single-organism level), speciation and evolution are population-level processes. Since the species concept is generally applied at the population level, it's not really valid to say that an individual can suddenly become a new species. The only exception being asexually-reproducing organisms (however, that most species definitions break down when applied to such organisms, anyways -- so speciation in this case may be a moot issue).
This all goes back to what I was arguing about in the previous topic. Evolution, and probably speciation, act on wholesale changes in allele frequencies throught an entire population, not the sudden emergence of novel genotypes (in sexually reproducing organisms). It actually begins to touch on a much hairier subject in biology: the species concept. Whether such a thing as a species actually exists is under heavy debate.
| Gagnar The Unruly wrote: |
|
Bikerman, Though selection occurs on the level of individual genes (so, slightly smaller than the single-organism level), speciation and evolution are population-level processes. Since the species concept is generally applied at the population level, it's not really valid to say that an individual can suddenly become a new species. The only exception being asexually-reproducing organisms (however, that most species definitions break down when applied to such organisms, anyways -- so speciation in this case may be a moot issue). This all goes back to what I was arguing about in the previous topic. Evolution, and probably speciation, act on wholesale changes in allele frequencies throught an entire population, not the sudden emergence of novel genotypes (in sexually reproducing organisms). It actually begins to touch on a much hairier subject in biology: the species concept. Whether such a thing as a species actually exists is under heavy debate. |
Yes, thanks for that. It fits what I thought and supports the point I was making but my language needed correcting and I think that was right to point it out up front, since if I have doubts about the appropriateness of what I read back and how it fits my strictly layman's picture of the reality, I certainly have no right or business in expressing a POV which is stronger or more certain in tone than my own feelings on the issue - that would be deception in my book....
I understand the species point you make - I got into a couple of papers on species and validity of current distinguishing criteria as good science and I know what you mean...the whole area felt a bit like it might be preparing for a rock-slide at least and might even be approaching a force 10 quake....
It's certainly an area in which I know that I am going to be very careful and very conservative when expressing any opinion or interpretations of theory
Systematics is a highly theoretical and relatively isolated branch of biology. There has been a raging debate among systematists for decades (between the cladists and phylogeneticists) as to whether or not a species is a real, absolute, distinct, evolutionary entity (obviously, other levels of the cladistic heirarchy are totally arbitrary). Another big argument is whether a single, biologically meaningful, species concept can be used and that is applicable to all systems.
Imagine that each organism in the world is defined according to coordinates on two axes: 1) space and 2) phenotype. A population is a group of organisms that are close enough on both axes that they are able to exchange genes. The tempting thing to say is that each population represents a single species. However, two discrete populations may be spatially separated but phenotypically similar enough to reproduce, in the event that they rejoined. It would then be tempting to say that a species definition is inclusive of spatial isolation but exclusive of phenotypic isolation. However, this could cause two sympatric (i.e. - sharing a portion of their spatial distribution), but phenotypically isolated organisms to be lumped into the same species, via a third, phenotypically intermediate but spatially isolated population.
One then might argue that we should draw a network among organisms capable of exchanging genes, and any solitary, unbroken network represents a species. Of course, this has it's own problems, as two individuals in a network may be so phenotypically and temporally isolated that our intuition tells us they should be of different species. Also, any event that caused spatial isolation would result in the formation of a new species -- but then what to do if the species fully or partially rejoined spatially?
Also, time is an important axis to consider. How do species hold up in three dimensions? The transition from one to two species may or may not be temporally abrupt, depending on the concept used and the assumptions given.
Finally, where do hybrids fit into the mix? Hybrids may be variably stable within an ecosystem, and in some cases enjoy selective advantages that belie the low frequency of their occurrence.
All of the elevated philosophising can become far-removed from actual biological practice, however, and non-systematists tend not to care too much about what species concept is being used. As long as they can agree on some form of nomenclature and communicate their findings, they are happy.
Imagine that each organism in the world is defined according to coordinates on two axes: 1) space and 2) phenotype. A population is a group of organisms that are close enough on both axes that they are able to exchange genes. The tempting thing to say is that each population represents a single species. However, two discrete populations may be spatially separated but phenotypically similar enough to reproduce, in the event that they rejoined. It would then be tempting to say that a species definition is inclusive of spatial isolation but exclusive of phenotypic isolation. However, this could cause two sympatric (i.e. - sharing a portion of their spatial distribution), but phenotypically isolated organisms to be lumped into the same species, via a third, phenotypically intermediate but spatially isolated population.
One then might argue that we should draw a network among organisms capable of exchanging genes, and any solitary, unbroken network represents a species. Of course, this has it's own problems, as two individuals in a network may be so phenotypically and temporally isolated that our intuition tells us they should be of different species. Also, any event that caused spatial isolation would result in the formation of a new species -- but then what to do if the species fully or partially rejoined spatially?
Also, time is an important axis to consider. How do species hold up in three dimensions? The transition from one to two species may or may not be temporally abrupt, depending on the concept used and the assumptions given.
Finally, where do hybrids fit into the mix? Hybrids may be variably stable within an ecosystem, and in some cases enjoy selective advantages that belie the low frequency of their occurrence.
All of the elevated philosophising can become far-removed from actual biological practice, however, and non-systematists tend not to care too much about what species concept is being used. As long as they can agree on some form of nomenclature and communicate their findings, they are happy.
Interesting posting. I raises a couple of issues I hadn't considered - the implications of spatial separation for example.
As far as the subject under consideration here is concerned I think the consensus is clear and unambiguous and, if I might be a little presumptuous, I will attempt a summary.
1) The question creates a false dichotomy between 'theory' and 'proof' which should be understood before considering the answer. The sticky in the science forum may be helpful in this regard.
2) Insofar as the question is asking whether the theory of Evolution is accepted by scientists as the best current model for speciation and the way in which life has developed on Earth, then the answer is a definite yes. Such dissent that does exist is almost exclusively based on religious objections, and is not supported by a coherent body of scientific work or published scientific papers. The only alternatives offered to the theory by such dissenters require much of current scientific thought to be assumed invalid and contradict scientific understanding and accepted scientific theory in many disciplines including :
Geology, cosmology, biology, palaeontology, physics and chemistry.
As far as the subject under consideration here is concerned I think the consensus is clear and unambiguous and, if I might be a little presumptuous, I will attempt a summary.
1) The question creates a false dichotomy between 'theory' and 'proof' which should be understood before considering the answer. The sticky in the science forum may be helpful in this regard.
2) Insofar as the question is asking whether the theory of Evolution is accepted by scientists as the best current model for speciation and the way in which life has developed on Earth, then the answer is a definite yes. Such dissent that does exist is almost exclusively based on religious objections, and is not supported by a coherent body of scientific work or published scientific papers. The only alternatives offered to the theory by such dissenters require much of current scientific thought to be assumed invalid and contradict scientific understanding and accepted scientific theory in many disciplines including :
Geology, cosmology, biology, palaeontology, physics and chemistry.
 |