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

I will disagree, Modulous. The individual is a specific and concrete idea. It is our human viewpoint that is arbitrary and malleable. Getting a human mind around the concept of what we choose to call a “colony,” and recognizing the reality that this is but one organism, one individual, is not easy.

There is an identifiable thread that runs through the survivors. All massed less than 5 kg on land, and 25 kg in water.

Are the individual ants, not offspring of the queen? Are they not genetically speaking, offspring? In some ants, there is a mother and a father, so the individual ants are genetically different from their brothers/sisters. I would consider these to be genetic and thus phenetic individuals. They are not arms or legs because their genomes are not identical in each of the 'cells' or 'organs' or 'limbs'.Think of it human terms. If a mother gave birth to children 90% of whom were infertile, and those infertile kids were genetically predisposed to be farmers. So they tolled away in the fields to feed the mother's enormous appetite for child birth...you would not regard them as individual organisms, simply because it becomes tricky to contemplate how a family filled with infertility could be evolutionarily succesful via natural selection?Incidentally, I 'get' the perspective of treating the colony as an individual, with the soldiers being one organ, and the workers another etc. This is merely metaphorical, and natural selection doesn't act on metaphorical constructs. Each of those ants is an individual entity, with its own interests to look out for, and its own phenotype/genotype. Just because the ants are infertile does not change this - their genes 'want' to replicate just as much as anyone else's. Since they are infertile, the best way to ensure the replication of the genes that are hosted in these individuals is to protect/serve the interests of the fertile and reproducing members of the family (since they are replicating many of the same genes).Thinking of the colony as an individual has its uses, but when trying to unveil natural selection - I think it can easily miss the interesting stuff going on underneath.

The issues I have with this approach, Modulous, are these:- Infertile members cannot be said to be individually subject to the rigors of Natural Selection since they are incapable of breeding. Regardless of what happens to them in life changes nothing in regards to reproductive success, except for the contribution of their work to the success of the reproduction of the whole.- I have a difficult time ascribing any concept of “altruism” to members of ant colonies since, with brains the size of pinpoints, controlled by the mind-bending chemicals of that fat drug-pushing bitch down at the bottom of the hole, there are no options but to act in accordance with her will just as surely as your right hand must (usually) obey the dictates of your brain, with no freedom of anything approaching “individual action” let alone any prospect of independent reproduction.- Their work for the success of the reproductive part of the organism is vital in that if the various non-reproductive members are inadequately configured (phenotype) for the task the reproductive capabilities of the “colony” are adversely affected in the same way a dysfunctional pituitary or pancreas adversely affects a human. Because of this any Natural Selective pressures are not felt by the non-reproductive members but on the organism (colony) as a whole.- There is not even the possibility of any “evolution” of worker generations from any specific queen. (Queen can last 5-7 years while worker lasts from 4-5 weeks.) Only the reproductive progeny can carry the mutation/allele re-combinations necessary for the species as a whole to evolve any/all the phenotypes expressed by the organism (various workers, queen, drone). A Queen cannot improve the phenotypes of her workers. Only her reproductive progeny can create better (or worse) workers. It is again the whole of the single organism, the colony, which is the focus of Natural Selection.In this view the worker is but an appendage, vital though it may be, to the organism and “individuality” (in a Natural Selection sense) is lost.Now, having said all this I will push back on myself. Some recent studies appear to show that in some species of ants the “nursery workers” (diploid female) can impact the sexual distribution of the reproductive offspring favoring queens (diploid female) over drones (haploid male). They do this by not feeding the drones resulting in a more tilted distribution. The queen may compensate for this by pushing out more haploid eggs.There are further studies that appear to show that in some older colonies on the verge of death some of the new larva are spawned not by the queen but by a worker.But these are exceptions that my argument so I’ll ignore them.

If you read Hoot Mon's last post, Message 120, he's still confused about natural selection. This concept is nearly always introduced in terms of the individual organism, and Hoot Mon's confusion is an illustration why. Whether or not viewing natural selection as operating on genes is the most accurate (and we could go round and round about it I'm sure), I think the confusion still evident shows that it shouldn't be the first rung on the ladder of understanding the concept.Rather than debating which view is best, I think our time might be better spent making sure Hoot Mon understands both.--Percy

I'm hot for understanding, so please teach me. I want to know how an individual organism undergoes natural selection, or evolution, for that matter.And while I'm stumbling around in my confusion, let me ask another stupid question: Why couldn't NS simply act on lineages? Maybe they present another context for consideration. I think it was Ringo who once refuted my definition of a gene as a digital code of nucleotides. I think he argued instead that genes are just "lineages of traits." While I still think a gene can be defined as a code, I also think Ringo's view has merit. Lineages are perhaps another useful way to describe genes for evolutionary purposes. The genetic codes are important in one context and lineages may be important in another.One thing useful about Ringo's concept is that lineages are awfully good candidates for locating where natural selection takes place. This idea is well rooted in homology. So maybe it's the lineages where NS does its work. This still seems a bit abstract to me, because I was hoping for more of a mechanism with a site. But if the genes themselves are not selected then at least their traits get some credit for the honor.Of course, this all takes individual organisms for those traits (genes) to be expressed. But, so far as NS is concerned, I don't think the individual organism is the biological thingy that is either selected of not selected. I agree that everything that goes on in life requires, first and foremost, the organism. But biological evolution is about something more than organisms; it's about homologies of organisms. Organisms don't evolve (I know that you agree); and whatever it is that evolves must be, precisely or abstractly, where natural selection takes place.”HM

Now biologists have an understanding of how Star Trek techo-babble sounds to physicists.

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Actually, if their god makes better pancakes, I'm totally switching sides. -- Charley the Australopithecine

Hi Hoot Mon,Here's a few brief excerpts from this thread just to indicate that natural selection has been explained several times, and that references to other sources have also been provided: So when you say in your most recent msg:

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Hoot Mon writes:

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I'm hot for understanding, so please teach me.

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I'm sort of at a loss. Teaching is a two way street. Perhaps you could questions about the explanations and examples already provided. The example of natural selection of the peppered moth during Britain's industrial revolution can't be any more clear. It's in practically every textbook in the section explaining natural selection. Why don't you start with questions about that?

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If I could be forgiven drifting briefly into disgruntlement, I think the digression into side discussions about selfish genes has hindered communicating a clear definition of natural selection. I think it's important to first have the concept clearly explained with simple examples, like bacteria experiments, white rabbits being selected for in snowy climates, and so forth.

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--Percy

Percy, I'll respond to this one specifically: Should I then adopt this definition of NS? Does this mean that humans have to go out into the wild to be naturally selected? Can't they get selected at home in the comfort and privacy of their own bedrooms? Does this mean that every reproducing organism is naturally selected? I have children. Does this mean that I have been naturally selected? And what about gay individuals who put their sperm into the mouths and rectums of other gay individuals? Does this mean they are being naturally selected against?I certainly do agree that unless individuals mate and have offspring there is no role for natural selection to play in the course of biological evolution. I'm just having trouble seeing how the individual gets naturally selected. By your definition, then, if the individual has offspring it has been "selected," in the Darwinian sense, to undergo biological evolution (since selection = evolution). This seems to concur with what AZPaul3 who wrote in Message 46: I do not agree that sexual selection is an "element" of natural selection, but I'll defer on that issue. I suppose, then, that everything that reproduces is evolving. Makes me wonder how there are any species at all.But wait, doesn't natural selection, in Darwinian terms, amount to evolution? And is there something other than individuals, per se, that get "selected for," rather than individuals being merely "selected" by nature to evolve? Maybe "selected for"”as in "selected for traits"”is a better perspective. JustinC wrote in Message 37: But of course we know that individuals die in relatively short order, so maybe we need to look at the extant genes, traits, or lineages as those biological thingies that get naturally selected and evolve, since they don't die with the ephemeral individuals. I suppose you could say they live on in their homologies, but that seems self-evident.”HM

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Should I then adopt this definition of NS?

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You should probably use the definition of natural selection that everyone else uses (which is pretty much how Percy describes it). The purpose of language is allow communication between people; one aspect of language is the use of words with meanings that people pretty much agree upon. When you start making up your own definitions as you go along, you defeat the whole purpose of communication.-

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Can't they get selected at home in the comfort and privacy of their own bedrooms? Does this mean that every reproducing organism is naturally selected?

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What the holy hell are you babbling about now?This isn't so hard, Hoot. Populations consist of a number of different individuals. These individuals are different in physical features, some of which are heritable. When some individuals leave more surviving offspring behind than others due to these heritable differences, we call that "natural selection".There are over six billion human beings on this planet. These humans beings are different, often in heritable features. Some human beings have more surviving offspring than others -- when this is due to those heritable differences, then we say that "natural selection" is occurring.You have children. I do not. If that is due to physical, heritable differences between you and I, then we can say that "natural selection" has occurred. There are probably people who have more children than you do. If that is due to physical, heritable differences between you and those other people, then we say that "natural selection" has occurred.This is the meaning of natural selection. This is how natural selection is used by any biologist who is using the term. Sure, you can use natural selection to mean any thing you want it to, but then you are not talking about the same thing everyone else is. Then communication is no longer occurring. By reading your own idiosyncratic meaning onto the phrase when everyone else is using it to mean the standard concept, you are putting yourself in a position where you will not understand what anyone else is saying. By using the phrase to mean your own idiosyncratic meaning, then you are putting yourself into a position where no one else is going to understand what you are saying.If you don't want to communicate with anyone, then you can do that more efficiently by not typing anything at all.

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Actually, if their god makes better pancakes, I'm totally switching sides. -- Charley the Australopithecine

to add to Chiroptera's comments If natural selection only applies to relative survival ability then you could have a condition where some individuals survive better than other individuals, but don't reproduce. As such their genes are not passed on to the next generation and there is no effective difference due to their improved survival. Reproduction is necessary to complete the process of natural selection, and that means that sexual selection must be included. Consider that this is why ignorant brutish "cool" people continue to reproduce. {Mutation = variations on a theme} + {natural selection = choosing which variations are best fit to survive & reproduce} = evolution.Enjoy.

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And I thought I was the literalist on this board. You really take things to the extremes, Hoot. Precisely. Your phenotype was adequately composed for this environment conducive to reproduction. You survived and reproduced. You were successful. We call this being "Naturally Selected for." The jury is out on Gays. Is homosexuality in humans a lifestyle choice or a phenotypic imperative? That would be an interesting topic on its own. Natural Selection, though we have a tendency to personify these things in discussion, is not a "thing" but a description.If your phenotype is not able to fend off typhus and you succumb and die, there is no "Natural Selection" causing this to occur as some kind of test in the literal sense. We describe this as having been "selected against" while your neighbor, who has survived the disease is said to have been "selected for."On a grander scale then, surviving typhus, surviving predation and surviving everything the environment can muster while finding a suitable mate and making babies is defined as "being selected for." You have passed through the filter of Natural Selection, figuratively speaking, and were successful. Do not confuse Natural Selection with Evolution. Natural Selection is a pillar, one of many elements, of the overarching concept of Evolution. Something passing through the Natural Selection filter is NOT Evolving. Many individuals of a species passing through these selective pressures over generations building genetic diversity and changing, over the long stretch of hundreds of generations, the phenotype of the species IS Evolution.

Hi Hoot Mon,One of Darwin's special insights was that breeders do in the small what nature does in the large. A breeder controls a great deal of the environment of his animal charges. In particular he exercises extremely tight control over which animals get to breed and which do not, and which specific animal pairs are bred together. This is called artificial selection.What Darwin realized is that an animal's natural environment is exercising control over which animals get to breed and which do not. Historical evidence suggests that it was Malthus's essay on population that powered this particular one of Darwin's inspirations, helping him realize that competition among members of a population both with each other for food and mates and with other species for food and sheer survival meant that many more animals are born than survive to the point of adulthood where they can mate. This struggle for existence meant that only the most fit of a population succeeded in contributing to the next generation.When Thomas Huxley first learned of Darwin's theory of evolution (it wasn't called that at the time, the word evolution had not yet been co-opted by biology) he is rumored to have said, "How stupid of me not to have thought of that." I like to think that it is the idea of natural selection he was reacting to, not descent with modification which was already obvious from the common observation that offspring of sexual organisms are rarely identical to either parent. If you want to use the same definition of NS that everyone else is using then you sort of have no choice. I don't happen to think the version you chose to quote is all that good, but it's adequate. I think one of the problems in this thread is that different people will inevitably explain the same exact thing in different ways, and sometimes it takes some effort to recognize this. This question is sufficiently interesting to be worth a digression. We normally think of creatures living in their natural environment as being subject to natural selection, while creatures living under the control of human beings are more often subject to artificial selection. Creatures in the wild often exercise some degree of control over their environment. Gophers create burrows, birds build nests, bears and wolves create dens, and these constructions are a legitimate part of their natural environment.Human beings are just like many animals in having the ability to exercise some control over our environment, but we've done so to a remarkable extent. Depending upon which people and which part of the world we're talking about, people's normal living environment can be anything from a cardboard box to a crude hut to a warm and comfortable home to a multi-room mansion with scores of servants to a penthouse suite with room service hundreds of feet above the streets of Manhattan.In many parts of the world people live in much more comfortable surroundings than what we would think of as natural. Imagine spending a single night in the woods in the winter with no tent, no fire and no clothes and you get a sense for the kind of selection pressures that we now protect ourselves from and so are no longer subject to.One of the possibilities we must consider is that by protecting ourselves from the natural environment that we are becoming a weaker species. It's not just comfortable homes but also that we care for one another through illnesses, and most of all modern medical technology. For example, how is the appendix ever going to disappear completely if practically everyone who gets appendicitis survives to reproduce?Another factor possibly weakening our species is that we are constantly sending the best and brightest of our species off to fight in wars. Some wars are important to survival. For an ancient city-state losing a war might mean the slaughter and enslavement of all civilians, and so sending the best and brightest to the front lines is the only chance for saving everyone, and in that case it makes sense, but what about the mostly meaningless wars and genocides of today? Do wars have a long-term negative effect on our evolution? Interesting question, I don't think there are any answers.Even beliefs can have an influence over whether a person is selected to produce offspring. The best example of this effect occurred a couple decades ago when a Massachusetts couple's young son came down with a bowel obstruction. The Twitchells decided to treat Chad with prayer only and Chad died a few days later, and so while the Twitchells did reproduce, in the end they had no progeny since they'd rendered their successful reproductive act moot by murdering the resulting child (actually, they may have had other children, but you get the point). Individuals do not evolve, so an individual can never be selected to undergo biological evolution. What actually happens is that individuals are selected by their success in their natural environment to engage in the reproductive act that produces offspring who are not the same as their parents. The reproductive act is where evolutionary change actually takes place, and it affects the progeny, not the parents. I'm extremely perplexed that you're still saying this. Pardon my loss of patience, but how many times and how many people are going to have to tell you that selection is not evolution before it sinks in? That's because you still don't understand what natural selection is. When you finally figure it out you're going to make like Homer Simpson in a major way! I'm not going to address the rest of your post as it descends into nonsensical ramblings.--Percy

I understand that you define it that way. However, perhaps you could identify the "selection" element in a bloody great rock falling out of the sky? How does a particular adaptation in a given population of individual organisms - whether optimal for their current environment or merely "good enough" - allow those individuals to survive such an event? Catastrophic extinction, which is inherently a random process (the opposite of selection), should not be subsumed under the accepted rubric of natural selection - because, in essence, there is no "selection". You die, or you don't, on the luck of the draw. As PaulK mentioned, luck isn't a part of natural selection.I will say that ecologists and conservation biologists have long sought a solid, theoretical construct that answers the "why" question in extinction. Just like with bioinvasion, all of the theories proposed to date are weak, unfortunately. We very often understand "what", and can in many local cases figure out post facto why, but a general theory of extinction has proven elusive. I disagree. The bloody great rock was certainly a "natural" event. But was it "selective"? One possible source of confusion (although I don't know if that's the case here), is that we often bandy about the phrase "selectivity of a mass extinction". The problem stems from the use of selectivity in this context. We are NOT talking about Darwinian selection - e.g., an environmental filter. Rather, we are using an anthropomorphic analogy (for lack of a better term), to describe how it appears that a mass extinction randomly "selects" certain taxa for destruction while leaving others untouched. This one but not that one. Kind of like a mad god's finger. If we ever come up with a General Theory of Extinction, I think this confusion will disappear. Right, as far as it goes. However, remember that in a mass extinction event we are not talking about individual death based on an individual's lack of a particular set of characteristics. We're talking about entire taxa being obliterated. As we both (I think) agree that natural selection operates at the individual level, how can an event that affects entire lineages be subsumed under this? Individual adaptations have absolutely no bearing on survival here (which is what natural selection is all about, n'est-ce pas?). Those individual members of surviving taxa which are capable of survival/reproduction in the new environment will - as per Darwinian evolution based on differential reproductive success (e.g., natural selection) - "inherit the earth" (but see, for example, the "Dead Clade Walking" hypothesis). You're welcome. I only wish I could take credit for it. It's one of the standard models used in ecology to describe extinction patterns. Along with this model, we have the "fair game" model where natural selection works to eliminate the less fit (the standard Darwinian model); the "wanton" model where individuals survive based on purely random factors - and may in fact be less fit than those who DIDN'T survive (mostly used on local scale); and the "gambler's ruin" model (where taxa with fewer sub-elements are more likely to go extinct); and the "mass extinction" model where everything in a particular area gets obliterated. This latter is an unfortunate choice of terminology because both field of bullets and wanton models can also be used to describe the extinction pattern of what we normally call mass extinction. I prefer the term "first strike" for this one, just to avoid confusion. Unfortunately, I haven't been promoted to the terminology police squad.

Sorry, O' tentacled one. I nearly missed this reply. This is indeed the popular characterization of the result of the K-T event, at least in North America. And as a first approximation to get across the idea of the devastation caused by the K-T, or P-T events or any other of the "big five" events, it's really very good. It is also, like many scientific "sound bites", not entirely accurate when you look at the details. Just to name two taxa that "give the lie" to this hyperbole that are being sort-of discussed on another thread, look up the crocodillians (terrrestrial) and sharks (marine).