What exactly is natural selection and precisely where does it occur?

If evolution happens at all it must occur through some agency, like NS, for example. My OP question was about what NS is and where it occurs. And my position all along has been that individuals do not get naturally selected for or against in any microevolutionary or macroevolutionary event.Other posters seem to disagree: So, Percy, does that help to answer your initial question? I still don’t understand how "natural selection operates on individuals." Educate me, please.”HM

In your individual-centric view of ns, yes. However, in the gene centric view there are simply different strategies for survival. Working well with other genes towards reproductive sucess is one strategy for survival. Having little or no effect on the other genes' reproductive success, is another one. This strategy is parasitic, the neutral genes simply try and get their replication for free. The best way to stick around is by being shorter. So there is a selection pressure on shorter neutral genes just as there is a selection pressure producing better cooperating genes.If there are three alleles for each gene, and there are two genes, we can set up an interesting example of cooperation. The alleles for the first gene are A,B, and C and those of the second gene are 1,2 and 3.If an individual has the alleles C and 3, or C3, then its reproductive sucess is massively improved. However, if an individual has C1 or C2, then disaster - they die late into childhood!Having allele A, with either 1, 2, or 3 has bright prospects - decent reproductive success.B1 is mediocre, but B2 is a bit better than Ax. B3 is a little better yet.So, does an individual with C3 get selected for? In your view yes! However, for some reason, in this sexual species...C3 seems to be declining rapidly.How to explain that with the individualists view? Having C3 is reproductively helpful to the individual, but not to that individual's children necessarily. Suddenly we have to start considering some entity that lives beyond the individual to understand why C3 is in decilne.The genecentric view could explain it qutie easily - allele C does not play well with other many of the alleles it will come across in the gene pool. Each time it replicates it has a good chance of being replicated alongside the '3' allele - since that is a good allele regardless. However, everytime it comes into contact with '2' or a '1', major problems ensue.The genecentric view allows us to look even more in detail. What if most individuals also have a collection of genes that promotes sexual attraction to individuals who posess the '2' allele. That means the C3 organisms will try to mate with with individuals with the '2' allele, meaning its offspring are less successful than Axs that mate with y2s (where y is not C - since they never mate!). There is then an even stronger pressure against C.Of course, it all depends on the degree of success each allele actually gives, but thinking in terms of selection on the genes gives us a more exact understanding of the evolution of this population. I can see that thinking in terms of individuals has its uses, since it is simpler. Likewise we can think in terms of selection of tribes, races, species, genera etc etc etc. The bigger the group, the more broad our strokes. Most of the time, thinking in terms of individuals suffices, but I think a complete understanding of natural selection requires examining natural selection at the level of the gene - since that is where the action takes place. Genecentric selection leads to what you see as individual selection. However, the individual is somewhat arbitrary in my view. The true replicators are genes, they are what gets selected to replicate. Naturally, since genes go towards making individuals, it looks like individuals get selected to replicate as it also looks like species get selected to replicate, as other larger groupings of entities that share common genetic ancestry could be seen as being selected to replicate. The genepool is an abstraction in a sense. However, so is gene frequency, yet it is the gene frequency that changes that causes the very non-abstract evolution. There isn't just one allele of each gene - those alleles replicate using the vehicle that is the individual. Those alleles that are able to replicate the most frequently become more frequent. To replicate the most, the allele has to be able to work well in a significant number of the potential individuals that could exist. It has to be more cooperative with other genes and their alleles than its own alleles to increase its frequency.The genepool is an important concept - it is the frequencies (and their changes) that are contained within that are of interest to evolutionary biologists. I certainly could not tell them apart. Of course, they are not genetically identical. That genetic difference may affect the reproductive future of the its genes. Lets say there are only two positions. A and B. Let us also have 10 rowers available for each one, numbered 1-10. The number happens to coincide with the contribution that rower makes towards success. Thus 20 = maximum success and 2 = minimum sucess. A10 is Speedy McRow, and B1 is Draggy.We start with ten random teams. They get three races max, but there is a max population of twenty, so if you don't come in the top twenty, you're team is 'dead'.The average success of Speedy is 15.5 (he always gets his 10, and the average of all the other possible rowers is 5.5).The average success is 11. Speedy and Draggy together are average.However, Draggy's average is only 6.5, so there will be less teams that have Draggy selected for the next round (Draggy can be selected for multiple teams per round as can Speedy).Thus:- Speedy will tend to be on teams that do better than average. So he has more chance of being on the new teams that get selected and mutated. The average success of the next round is likely to be higher. Edited by Modulous, : No reason given.

I'm worried that our discussion is pushing us both to extremes, when really, it's probably true that the gene view and the organism view are both valid approaches that serve to illuminate different types of questions. I know that I, personally, am susceptible to creeping dogmatism, and I don't want to head in that direction.Mostly what concerns me is the possibility that Hoot Man will have so much of his nonsense validated by well-meaning people who use his clumsy, inaccurate references to scientific controversies he really doesn't understand as a springboard for interesting discussions, such as the one we've been having. Like Buz, he's got somewhat of a tendency to act as a flashpoint in that regard; also, like Buz, he incomprehensibly tries to take credit for it.

What is the problem with this quote then?

quote:

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[PDF] Stephen Jay Gould, The Structure of Evolutionary Theory , The ... File Format: PDF/Adobe Acrobat - View as HTML
“We define selection as occurring when plurifaction results from a causal. interaction between traits of an evolutionary individual (a unit of selection) ...
http://www.philipmcshane.ca/cantower15.pdf - Similar pages

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Do you simply want more information on the 'definition' or are you disagreeing with the use of the word "we"?We are not disagreeing here that natural selection occurrs as we may in another thread taking the lead from a creationist bias for instance.You see if you are going to object towards the notion of THE 'causal' etc then it really does matter if one starts from form or function or has a particular philosophy or is a creationist etc.Perhaps we need different threads for the possible or actual ontology of NS and one for the epistemology of artifical vs natural selection.If you insist on the gene-view I simply would like to know the biophysics vectors BETWEEN traits. As is apparent from the view at the level of the small the forces and the function come to a foreground but from the organism the shape of the traits viewed out-in may still overdetermine the adumbration. The word "trait" carries way to much logos for me from a purely redutionist position. Biology is depauperate for me in that case. The diveristy of life can not be linguistically sedimented to me when this is the "largest" level of organization available to discuss form-making and translation in space.

Frog, I think you may be right. Arguments are strong on either side. Dawkins vs. Gould brought out the best of many good evolutionary biologists, IMO. This matter remains unsettled, which is a good thing for evolutionary biology.”HM

Natural Selection is an agency of Evolution, agreed. Not just an agency but one of the major pillars.OK. Let us start with the gamete. Gametocytes are formed just like somatic cells via mitosis with the usual mixing of the genes that ensues. When a gametocyte undergoes meiosis half the genes end up in each gamete. Which gene ends up in which gamete is pretty much random. Is the formation of the gamete an event of Natural Selection?When 100 million sperm storm up the vestibule to court the ovum (a bit of Dave Berry there) only one can succeed (usually). Is this an event of Natural Selection?As has been discussed here and other threads, (if I recall correctly) somewhere around half of all conceptions are spontaneously aborted, usually due to mutation causing non-viable embryo. Is this an event of Natural Selection?Gestation is fraught with its own dangers dealing with mom’s plumbing, diet, environment, dangers from blood and serum antigens, infections etc. Is birth an event of Natural Selection?Now the individual is on their own in the world. We all know the dangers impinging on life. Is mere survival an event of Natural Selection?Boy meets girl. Girl likes boy. Sexual selection in all its glory. Is this an event of Natural Selection?Repeat all the above.

I hope you are not too troubled by my "nonsense validated by well-meaning people who use his clumsy, inaccurate references to scientific controversies he really doesn't understand as a springboard for interesting discussions." Gosh, thanks, I didn't think I was that good.”HM

I'll live, thanks for your concern. I'm not yet convinced that there's not hope for you - that is, if you can ever get rid of that big chip on your shoulder. How do you carry that thing around without getting tired?

AZPaul3, I like your post. I'm thinking it over. Selection usually means that some critical change in environmental circumstances ends up favoring one suite of genes, or allele frequencies, over another. But your phrasing of the "where" question is good. Still, NS must happen somewhere, don't you think?”HM

Strange that you should say this, frog, after posting this chippie tirade in Message 54: If I let my imagination run wild, frog, I’d say you have shoulder load of chips against me. Ah, but I'm flalltered”didn't know I was worth all that.BTW: Do you actually have an argument, or even a brain, under all those chips?”HM

Modulous: Percy: I’ll take this challenge.I lived in the Denver area for a few years and we used to go out in the fall into the foothills to see the Aspens turning. Among the brilliant golds, reds, yellows and rusts it was difficult to remember that this entire hillside of Aspen trees was all one organism . one individual. In fact the largest single organism on the planet is Pando living somewhere in Utah. Pando is a 6 million ton monster of an Aspen forest that is in fact one tree (Populus tremuloides). It has some 40,000 trunks all connected by an extensive continuous root system. This one organism has adopted a distributed physical form as an individual over the usual concept of what we think as a “tree.” It is instead a forest.If Modulous will excuse me I know nothing of soldier ants. What I do know are Solenopsis geminate . fire ants. If you have ever stepped on a Fire Ant mound and had them boil and roil over your Nikes chewing through to spit their acidic poison into your toes then you know why the name. They are also known as the National Pest of Texas. I know them only too well.The members of the colony come in different shapes and sizes. The forager is the one we usually see above ground out looking for food. Then there are Guards and Tenders and (usually) one queen. Colony is an artificial human distinction. This colony is in fact one organism . one individual. Like the Aspen they have adopted a distributed physical form. But they have taken it further. They have also adopted a distributed physical function and a distributed intelligence. They have also done away with the usual physical connection of blood, bone, skin or root in favor of a complex web of chemistry. A successful body plan, indeed.Your disembodied brain lies comfortably on the bed pillow while in the living room one of your ears and an eyeball rock gently in the Lazy-Boy slowing flipping through Discovery, History, SciFi and ESPN. A kitchen hand (literal) hobbles into the bedroom to announce, “Hey, brain, we’re out of bread.” No problem. Dispatch a shopping hand down the road to the nearest Safeway to pick up a loaf of Split-top Wheat.The success of the Solenopsis geminate body plan is that it can lose a few hundred legs, feet, arms, eyes and just grow them back. The colony as a single individual organism stands to the cauldron of Natural Selection.

My point exactly. The individual is an arbitrary grouping - maleable in definition. An individual ant is not an individual, its family is the individual entity to be considered.

I do, yes. It was all that material that you excised to misrepresent what I was posting in that thread. Is there some reason you weren't able to reply to it?Edited by crashfrog, : No reason given.

OK, so I’m prone to understatement. The fact is that at least one small furry mouse-thing survived where the Dinos and lots of others did not. And as for Dino, that is why I used “exacerbated” instead of “caused.” Let me try this approach.The mechanism, the nuts-and-bolts, of Natural Selection operates on the level of the individual organism. I define Natural Selection as any event, I emphasize, any event, that impacts, for well or ill, an organisms reproductive success.Chicxulub did more than make some largish waves, throw some dirt into the air and clobber a whole big bunch of poor slobs standing out in the open. It changed the environment for the ensuing millennia. Environment change has always been (unless I missed the memo) a major Natural Selection event. This “field of bullets” was an event of Natural Selection just as surely as an ice age, the rise of a better predator or the spread of an invasive microbe.Further, let me define “environment.” Environment is the availability of resources be they animal, vegetable or mineral that impact reproductive success. From heat to food, predator to competitor, water to oxygen, the orbit of the planet with its periodic seasons, ice ages and million year droughts, forest fire to flood, all impact the availability of resources. Environment, in its totality, is the major sieve of Natural Selection.Even on a gene’s-eye-view basis, the environment is the availability of resources, like the available pool of alleles. Changes to this environment are events of Natural Selection. Johnny’s football accident, the drunk driver, the pure bum luck of getting hit in the head with a comet, changes the environment in that it, first from the individual perspective, lessens the resources for reproductive success by taking out the individual itself, and from the gene’s-eye-view, lessens the available pool of alleles for reproduction. Like in my Bob and Hox example, Bob’s superior talents are no longer available in the environment. The environment has changed. The unlucky event, your “field of bullets,” was an event of Natural Selection and the effect of adapting to this changed environment is Evolution.Quetzel, I love your “field of bullets” analogy. The visual is striking and certainly appropriate. This is one of the best analogies I have seen in many a month. Realize that it is now firmly ensconced within my repertoire to be used as the occasions warrant. Thank you for the gift.

I agree with what you say about the individual. You probably know that good arguments have been made for kin selection (Hamilton, Wilson), which may be a kind of group selection but with a fous on the genes."Selection" has several faces and complexions, according to one's use of the term. Maybe we should sort them out and discuss their different meanings. We have this inventory of terms relating to selection:-natural selection
-sexual sedlection
-group selection
-interdemic selection (demes)
-gene selection
-kin selection
-migrant selection
-reinforcing selection
-stabilizing selection
-K selection
-r selection
-selection pressureEach term has a separate meaning”a different view of this crystal we call "selection." We should examine them, I think, to add clarity to the meaning of NS”but maybe on another thread (Adimin?).”HM