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Syamsu  Suspended Member (Idle past 5612 days) Posts: 1914 From: amsterdam Joined: |
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Author | Topic: Clear faults in Darwin's formulation of Natural Selection | |||||||||||||||||||||||
Peter Member (Idle past 1501 days) Posts: 2161 From: Cambridgeshire, UK. Joined: |
I have repsonded to the three 'faults' that you cited in your opening
post. You have then left them and carried on with a discussionthat we have been having for some months, but from a point somewhere back in time (months ago). The fundamental defintion of NS is not disputed anywhere. Some individuals have a survival advantage, and thereforetend to leave more offspring. If the advantage was a heritable one then there are moreindividuals in the population with this advantage than before. The above is how all evo's will understand NS. If you then wish to discuss how NS can drive evolutionyou will get some differences coming in as different people will have different ideas about how NS acts to promote evolution. They are two separate issues. NS happens. It is observed to happen. I really cannot seewhy you object so strongly to it.
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Syamsu  Suspended Member (Idle past 5612 days) Posts: 1914 From: amsterdam Joined: |
The fundamental definition of Natural Selection as you set out becomes disputed when variation is said to not be required for Natural Selection to apply. John, Quetzal, some people on sci.bio.evolution, and previously you, have said this is so, that Natural Selection can also for instance apply to a clone population.
Your assertive pronouncement that all evo's agree on the fundamentals of NS is simply wrong. regards,Mohammad Nor Syamsu
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Peter Member (Idle past 1501 days) Posts: 2161 From: Cambridgeshire, UK. Joined: |
Variation is not essential to NS ... but without it
the net result is either a slide into extinction or rises in population numbers to levels supportable by the environment. The definition in the glossary does not require variation,it says that:: '[NS] often act[s] on hereditary (genetic) variation'{my emphasis} Often means that it doesn't always. The glossary defintionhere is one with which evo's will agree. If there is no variation then there is no evolution ... butthere is still natural selection. I still do not understand the exact nature of your objection tothe observed phenomenon of natural selection.
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Syamsu  Suspended Member (Idle past 5612 days) Posts: 1914 From: amsterdam Joined: |
The faq is just distinguishing between heritable and non-heritable variation. In any case there are also several people on talk.origins and sci.bio.evolution insisting that Natural Selection requires variation.
How you can at once define Natural Selection to require variation, and then say Natural Selection doesn't require variation, is beyond me. Science should be judgemental this way, it's one or the other. You have included extinction of a population in non-variational selection. You seem to be wrongly dismissing population extinction as having no significant scientific interest. If you would admit extinction has much scientific interest, it logically follows you should exclude variation as a requirement for Natural Selection. Once again, you have no point. You have not thought this through, or even tried to. regards,Mohammad Nor Syamsu
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Peter Member (Idle past 1501 days) Posts: 2161 From: Cambridgeshire, UK. Joined: |
First, I do not count variation as a requirement for NS.
You pointed that out correctly from your interpretation of my previous posts. Second, I made no comment on whether or not the studyof extinction was useful/interesting. I merely stated that the consequence of NS without variation in the population would be to either select against (leading ultimately to extinction) or selection for (leading ultimately to a population size only limited by available resources). In terms of thinking things through, I would have to contend thatit is you who are lacking. You have a view which you are no longer attempting to support in the slightest. Every time I suggest a NS description or respond to one of your posts in a negative manner you simply start stamping your foot and saying 'tisn't!' as far as I can see. What is you objection to Natural Selection?
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Syamsu  Suspended Member (Idle past 5612 days) Posts: 1914 From: amsterdam Joined: |
I have no problem with the definition of Natural Selection that doesn't require variation to apply.
It's just that this is not the common definition as it is in the glossary, or much of anywhere else, and several selfrespecting Darwinists I talked to, argue that the definition without variation is wrong. Even you have defined Natural Selection requiring variation. Yes you say it can also apply without variation, but this is not how you have defined it in a few posts previous, where you said that every evo accepts the definition requiring variation. That is ridiculous, that you define it one way, but use it in another. I supposed you do this because you don't find selection without variation to provide meaningful knowledge. I was just guessing here, since you gave no reason at all why you do this. regards,Mohammad Nor Syamsu
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Quetzal Member (Idle past 5894 days) Posts: 3228 Joined: |
Hi Syamasu,
I'm just jumping in here 'cause you mentioned my name earlier in the thread... Peter is absolutely correct in his post #18 where he says: quote:This is what I've been saying to you all along. In fact, it is a fairly trivial observation. NS can occur without variation, because NS is (essentially) the action of environmental factors on an organism. EVOLUTION, on the other hand, cannot occur without variation. EVOLUTION is the end result of natural selection operating on variation within a population. No variation = no evolution. Heritable variation + NS = evolution (ceteris paribus). I think one of the problems in this discussion is that you are continually attempting to decouple the two concepts, and I'm not sure that's a valid way of looking at the question.
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Peter Member (Idle past 1501 days) Posts: 2161 From: Cambridgeshire, UK. Joined: |
quote: Then we agree, and we can leave it at that. quote: I already pointed out in post #18 that the glossary defintionon this site does not state variation as a requirement for natural selection, but that when it acts on variation evolution results. The following links provide explanations or defintions forNS, none of them state that variation is a requirement. http://www.counterbalance.org/biogloss/natsel-body.htmlhttp://www.gate.net/~rwms/EvoDefinition.html#natural selection FishBase Glossary quote: I suspect you are misreading me, or that I have been unclear. Natural selection is not evolution. NS drives evolution, if and only if there is heritablevariation within a population. I think a part of the problem is that NS is not really consideredworth thinking about apart from in connection with evolution. The concepts are so fundamentally entwined that separating them becomes very difficult. Any illustrative description, or recorded observation of NS will focuss on cases where evolution has ocurred because that's when you see the 'power' of NS. No fundamental defintion of NS requires variation. Many defintions found are of 'evolution by natural selection'.
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Syamsu  Suspended Member (Idle past 5612 days) Posts: 1914 From: amsterdam Joined: |
Peter required variation in a post previous by talking about "advantage" which he previously defined as being a heritable difference=variation.
If you define Natural Selection with variation as is common, then you would tend to ignore the action of environmental factors on an organism. There is no description in the literature of Natural Selection like: Light (environment) falls on the photosynthetic cells of a plant (organism) which contributes to it's reproduction (is selected in). Tend to ignore. Actual arguments that have been offered to me why Natural Selection should require variation: - variation is required to distinguish adaptive evolution from random evolution- it is impossible to measure nonvariation selection To Peter: the references you gave require variation (at least the first one does, I just assumed the rest do also), as does the glossary definition require variation as I explained before. regards,Mohammad Nor Syamsu
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Quetzal Member (Idle past 5894 days) Posts: 3228 Joined: |
I think we may be talking past each other again.
quote:Since natural selection IS the action of environmental factors on an organism, it would be hard to ignore. I agree with you that there is no description of natural selection as you posted, because what you posted isn't natural selection. When light falls on the chloroplasts of a plant, it's simply light falling on the chloroplasts of a plant - not natural selection, because there's no "selection" occurring. Where NS comes in is when, for instance, you have a plant that is adapted for a certain light level (level being an environmental factor), and the average light level changes. IF the change in light level effects the survival (or reproductive chance if you prefer) of the plant, that effect is "natural selection". If the effect is adverse, the plant might die. In this case, we say the individual plant - or better said the suite of traits that make up the phenotype of that individual plant - was "selected against". With me so far? Note that up to now we haven't even mentioned variation. If ALL of the plants in a particular population are exactly like (no variation) our hypothetical plant above and the average light level changes with adverse effect, what do you think will happen to the population? Since the population is made up of identical individuals, what effects one will effect them all. Hence in this case, the entire population may go extinct. So let's introduce a simple variance - one "type" of this species is as described above (call it type A), another has a slight mutation in its chloroplasts that allows it to more efficiently process available light (call this one type B). Since they're all the same species living in the exact same spot, there's been no real advantage for one type or the other and up to now they've all been living quite happily side by side. Just that A and B are different varieties of the same plant. Some individuals are type A, some individuals are type B. Now let's change the environment (light level). We already know that type A doesn't do well in (say) low-light conditions. Just like our single type above, type A gets selected against and dies out, leaving type B all by itself. This is the most simplistic form of evolution - the change in the average frequency of alleles (types) in a population. A is gone, B is still there, evolution has occurred (in a very simple form). The mechanism that wiped out A is termed natural selection, the result of the mechanism is termed evolution. Hope this helps rather than confusing things further.
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Syamsu  Suspended Member (Idle past 5612 days) Posts: 1914 From: amsterdam Joined: |
That can't be right. There are many both positive and negative factors which need not change for them to be called selective factors. That is the meaningful knowledge arrived at here, to view an organism's relation to the environment in regards to the event of it's reproduction.
That is also the meaningful knowledge in your example of adaptive evolution. To know that the one plant is selected for at a certain lightlevel, and the other at another lightlevel, or that if they are together that one is a negative selective factor to the other by outcompeting it. regards,Mohammad Nor Syamsu
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Syamsu  Suspended Member (Idle past 5612 days) Posts: 1914 From: amsterdam Joined: |
As before all the references you gave require variation for natural selection to apply.
http://www.counterbalance.org/biogloss/natsel-body.html ", giving those with *greater "fitness"* " http://www.gate.net/~rwms/EvoDefinition.html#natural "Here are a list of the conditions Darwin thought were required for evolution by natural selection: ......2. Organisms *vary* in many ways,..." FishBase Glossary "Natural selection is the differential contribution of offspring to the next generation by *various* genetic types.." regards,Mohammad Nor Syamsu
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Quetzal Member (Idle past 5894 days) Posts: 3228 Joined: |
quote:Well, it IS correct, at least in the simplified example I used. However, the selection pressures on a REAL organism are - as you noted - incredibly complex. A population of organisms without variation that is adapted to its environment (the sum of all selection pressures involved - whether living things or abiotic factors), will be fine unless something changes. Whether that change is introduction of a new pathogen, climate change, a new predator, an invasive species, a new parasite, habitat fragmentation, ecosystem decay, etc, without variation that population is in trouble. WITH variation, there may be individuals within that population that are more likely to survive/reproduce than other members of the population given the change. Sooner or later, by sheer mathematics, the variant alleles that allowed the "better chance" will come to dominate in the population and a new equilibrium will be reached. The variation could even be simply related to our slightly-more-capable plant B slowly supplanting the slightly-less-capable plant A, simply because it's marginally more efficient at processing light at all levels (remember that "environment" includes all the other members of the same population competing for the same resources).
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Peter Member (Idle past 1501 days) Posts: 2161 From: Cambridgeshire, UK. Joined: |
1. The process by which individuals’ inherited needs and abilities are more or less closely matched to resources available in their environment, giving those with greater "fitness" a better chance of survival and reproduction.
Above, the part up to the italics is a definition of NS, thepart in italics is a consequence when variation is present. The definition does not require variation, it simply includes the consequence of natural selection. 2."Here are a list of the conditions Darwin thought were required for evolution by natural selection:......2. Organisms *vary* in many ways,..." This is under a list started by the phrase 'requirements forevolution by natural selection'. It is not part of the definition of natural selection. The last one I'll give you does include variation as part ofitsm defintion ... so maybe you are right that there is some disparity in views. On the otherhand the definition is targetted at evolution again. However, natural selection as described by Darwin IS theeffect of the environment on the individual. Variation is only required once we use NS to explain evolution. [This message has been edited by Peter, 02-27-2003]
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Peter Member (Idle past 1501 days) Posts: 2161 From: Cambridgeshire, UK. Joined: |
The main problem you are having is that you have
redefine natural selection for yourself. You seem to say:NS is whether or not a individual reproduces. Standard form is:NS is how environmental factors affect which individuals live to produce offspring (or more offspring). They are not the same. I do see that there are definitions stated as being of NS thatare so deeply entwined with 'evolution by ns' and that is not made clear. To re-iterate:: Evolution requires variation. Natural selection doesn't require variation. When considered as a mechanism for evolutionary changeconsidering NS without variation is not useful.
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