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

I hope we can address this misunderstanding quickly and not spend much time on it.One oft-cited example of natural selection is the peppered moth of Great Britain during the industrial revolution. As tree trunks became darker due to industrial soot, the peppered moth population went from predominantly light to predominantly dark. The explanation for this change was natural selection. Light colored moths on dark tree trunks were easy targets for birds, so light coloration was selected against, and dark coloration was selected for.As Great Britain's industries became gradually more environmentally responsible, peppered moth coloration again changed with the light color returning to dominance. Because it is individual moth coloration that governs how visible it is to birds that prey upon it, selection occurs at the individual moth level according to coloration.I cite this example not to argue about the validity of Kettlewell's peppered moth experiments, but because this is a familiar topic in creation/evolution debates. In discussions of this topic creationists and evolutionists agree that selection occurs at the level of individuals. Where they disagree concerns whether Kettlewell's experiments uncovered actual natural selection occurring in the wild. They don't disagree on the definition of natural selection.In other words, your understanding of natural selection differs from both creationists and evolutionists. You might want to rethink things.--Percy

Hi Hoot Mon,I was only trying to explain that natural selection operates on individuals and that there's really no disagreement about this among creationists and evolutionists. Your reply mentions all kinds of other things, and sounds like you may have made the mistake of delving into the details of evolution before obtaining an overview.Darwin said it best. Evolution combines two things: descent with modification is one, and natural selection is the other. Descent with modification means that offspring are not exact copies of the parents. Natural selection means that individuals best suited for their environment have the best chance of surviving to produce offspring. Any organism that produces offspring in the wild has been naturally selected. It's as simple as that.Of course, as you've noted elsewhere, the real differentiator often isn't merely surviving to reproduce or not. A more accurate term is differential reproductive success. Some organisms are better at producing offspring than others, and this can happen in any number of ways. Some organisms live longer than others of their species, and so live through more reproductive seasons, thereby producing more offspring. Some organisms simply produce more offspring during each reproductive season. Some organisms mate more often, etc.Darwin drew an analogy between human breeders (artificial selection) and breeding in the wild (natural selection). A human breeder brings together two specific individuals to mate based upon what he judges to be favorable characteristics. In an analogous way, the environment brings individuals together to mate based upon their ability to survive to that point in time and upon their ability to persuade the other they are worth mating with (asexual species do not have this latter problem, of course).If it helps, Wikipedia has a good definition: Natural selection - Wikipedia. Pay particular attention to this sentence in the opening paragraph: Some of the detailed items you mentioned, genetic drift, gene flow, and random mutation, really have nothing to do conceptually with natural selection. A definition of natural selection doesn't require these concepts. Darwin certainly never knew anything about these things, and he had no trouble at all defining natural selection.But with your last two items, differential mating and differential reproductive success, the former is just one type of the latter.--Percy

The gene is the unit of heredity, not the unit of selection. Genes can only be selected in entire collective bunches because natural selection operates on individuals.--Percy

I think the viewpoint that "Natural selection operates upon gangs of mutually compatible genes" is an interesting perspective, but Darwin didn't need genes to define natural selection, I don't myself find it a helpful perspective, I don't think it's found much acceptance as a way of defining natural selection, I think it is a less accurate characterization of what is actually happening, I think it makes it more difficult to explain natural selection to Hoot Mon, and I don't think Dawkin's selfish gene concept has been as influential within scientific circles as you seem to believe.--Percy

As Quetzal makes clear in Message 82, we all understand both Darwin's and Dawkins' perspective, it's just that we happen to prefer Darwin's for defining natural selection while Modulous prefers Dawkins'. If you prefer Dawkins perspective then I think that's fine, but what you've written so far in this thread leads me to suspect that you don't understand either one. The Darwin and Dawkins perspectives are only minimally in opposition to one another. In many ways they're saying the same thing. After all, what is a "gang of mutually compatible genes" but an individual!Quetzal, Chrioptera, Crashfrog and myself are not saying that the selfish gene perspective is erroneous, not at all. We're only saying that it isn't the most helpful perspective for defining natural selection, it isn't the way natural selection was originally defined, it isn't defined that way in popularizations, it isn't defined that way in textbooks, and it isn't the way most scientists would define it today. As with memes, Dawkins has influenced a generation of laypeople to a point of view that holds little sway in scientific circles, much like Stephen Gould and punctuated equilibria, which has had a far greater influence in forums like this than in scientific research.I think even E. O. Wilson agrees that the selfish gene perspective is not an effective one for defining natural selection, which he explains like this in the introduction to his book of Darwin's collected works: As much as E. O. Wilson might accept the selfish gene perspective, he doesn't seem to think it a very effective approach to explaining natural selection. You can prefer the Dawkins' perspective if you wish, as does Modulous, but Modulous understands the Darwin perspective and realizes it isn't in significant opposition to Dawkins.--Percy

Nothing to argue with there, and I might reconsider my approach if someone said, "Define natural selection, but you have to use soldier ants as your example and you have to tie it in to altruism," but it's not an approach I would associate with simplicity and clarity. We're having difficulty just getting across the point that sexual selection is a type of natural selection, so framing the definition in terms of genes would only seem to add more opportunities for potential confusion.I think the Dawkins' perspective is widely recognized as not the best way for introducing the concept, and this is backed up if you go and look up a dozen definitions of natural selection around the web. As Quetzal said, it might be a better perspective for population geneticists, but discussing evolution from a population perspective is not one with which I've had much success with creationists, perhaps because it isn't very intuitive for many people.But defining natural selection as the environment placing pressure on an individual's survival through its characteristics, its phenotype, is something grade school kids understand, and before going too far with any discussion about natural selection I'd want to make sure it is understood at that level, the level that E. O. Wilson used in the excerpt I provided in Message 88 using birds' eye color.I hope I've been clear that I'm not saying you're wrong or that Dawkins' is wrong. I think we just disagree about the best way to introduce the concept of natural selection.--Percy

I'm not trying to accuse anyone of anything, I'm just trying to help you understand the Darwinian definition of natural selection.No one is saying that individuals evolve, so you can just relax your concerns along these lines. But this isn't the first time in this thread that you've concluded that someone was claiming individuals evolve, so if you could point to what it was I said that led you to think this it might enable me to help clarify things. You're confusing natural selection with genetic change. Perhaps it would help to talk a little about where evolutionary change actually takes place. Unlike natural selection, identifying the precise origin of evolutionary change is probably easier to talk about at the level of genes. For asexual unicellular organisms, evolution occurs during cell division. The copying of the original DNA is not a perfect process, and some number of errors almost always result. Neither of the resulting organisms can be considered the parent, and it is possible that both can differ genetically from the original organism.For most sexual multicellular organisms, evolution occurs during the combination of sperm and egg with each providing half the DNA. Not only does allele mixing take place, but once again copying errors play a role, and so it is very common that neither sperm nor egg is a perfect copy of the half-strand of the parents DNA.This precise point where evolutionary change occurs is not where selection occurs (we're not talking about selection of sperm, of course, which only applies in the sexual case, anyway). By the time cell division or combination of sperm and egg is taking place, selection has already occurred. The asexual cell was selected because it is still alive and in a position to take in enough nutients in a sufficiently favorable environment to divide. The sexual multicellular organisms were already selected before the evolutionary event took place, because they were still alive and in good enough health and location to engage in sexual relations with each other. Those that died in a drought or a storm or that didn't have enough strength to make it to the mating island (in time or perhaps at all) and any number of other possible events, these organisms were selected against and so did not have the opportunity to engage in sexual relations in order to produce offspring.The criticism isn't that you don't accept this perspective. As I said to Modulous, though I feel the Dawkins' view has little to recommend it in terms of explication, I do think that it generally boils down to the same thing as the Darwinian perspective. The actual criticism is that you don't understand the Darwinian perspective yet. Your continuance of replies like "No, you're wrong because individuals don't evolve" make the fact, though not the precise nature, of your misunderstanding very clear.If it's just a case of us just not writing clearly enough, then see the Wikipedia definition (Natural selection - Wikipedia) or the glossary here at EvC Forum (http:///WebPages/Glossary.html#N). This is all we're trying to say.--Percy

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

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

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

As I said in the very message you're replying to, everyone is just explaining the same thing to you, but in different words and from different perspectives. There are not "three schools of thought" about natural selection. It's a simple concept with only a single school of thought. I hope Modulous sees this, because it makes clear that you understand natural selection neither in terms of genes nor of individuals. Darwin didn't know about genes. He described natural selection in terms of selection of individuals.What was it about the analogy of natural selection to artificial selection that you didn't understand? People keep explaining natural selection to you, and you keep asking what it is. I see no evidence that yet another of my explanations is finally going to do the trick, maybe someone else will finally find the right words.--Percy

This sounds more like the differential reproductive success that results from natural selection. Wikipedia: "Natural selection acts on individuals..."I write the above with strong reservations as I've been trying to avoid getting into quibbles with others while keeping my focus on explaining natural selection to Hoot Mon, but I can only see further and more profound confusion resulting from telling Hoot Mon that natural selection doesn't operate on individuals. He's going to be quoting that back to us for pages and pages.--Percy

Not that the discussion about how best to think of natural selection isn't important and useful, but I see this thread as focused on explaining natural selection to Hoot Mon, who posed this question in the thread's title: "What exactly is natural selection and precisely where does it occur?"If someone had explained natural selection to Hoot Mon from the selfish gene perspective and Hoot Mon had replied, "Oh, I get it," then no worries from me. But Hoot Mon is saying he accepts the gene level view and not the individual level view, views that are merely different perspectives on the same facts, which tells us he doesn't understand natural selection at all. He still thinks natural selection involves genetic change.I see the digression onto the relative merits of creature-level versus gene-level perspectives as inherently confusing to someone like Hoot Mon who is just embarking upon trying to understand the concept of natural selection, but I wasn't going to quibble about it until I saw the comment about it not making sense to think of natural selection operating on individuals. With the exception of Hoot Mon I think we all understood perfectly well the very valid point Chiroptera was making, but the comment was made in the context of a digression not related to the main purpose of this thread, and when interpreted in the main context it appeared to directly contradict Darwin's original definition of natural selection, so I felt I had to point that out. I regret that Chiroptera interpreted it as a comment that he was being confusing. He wasn't. It was the presence of the side-discussion that was confusing. Language is infinitely flexible and nuanced. There are countless ways to define the same thing. You'll often hear the comment, "Well, I wouldn't have described it that way myself, but I guess that's correct," or "Yes, I get what you're saying," and what people mean when they say things like this is that they don't think the person has expressed himself accurately or correctly or with sufficient precision, but they grasp his meaning anyway.It is virtually impossible to come up with definitions that everyone agrees upon, including natural selection. The best we can do is get people to say, "Yeah, close enough." That's why the side-discussion about the best way to think of natural selection was taking place, because people don't even agree on whether the views possess equal validity.If you've ever been in a meeting whose goal is to develop a clear mission statement or an unambiguous statement of a project's purpose, you know that several hours can be wasted just arguing about accurate and unambiguous expression. The meeting only ends as people gradually realize that they've set themselves an impossible goal. The ways in which language can be interpreted and misinterpreted are probably infinite.So I'm not going to set myself the impossible goal of coming up with a clear and unambiguous definition of natural selection. It isn't possible. I think all one can reasonable expect is to start with an explanation of natural selection, and then respond to questions as they arise, and hopefully the discussion will gradually improve the understanding of natural selection in the other person's mind.So if you already understand natural selection but don't like that definition from me that you quoted (probably only one of at least four or five different ways I've described natural selection in this thread), but you get my meaning, then that's fine. Or if you're uncertain of the definition of natural selection, then I think your definition is fine, too, and actually reflects a rather nuanced understanding of the term. We could even combine our two definitions and arrive at, "Natural selection operates on individuals, and their different fitnesses result in differential reproductive success."--Percy

This is crass and pretty rude. Chiroptera made clear he was ceasing participation because I told him he was being confusing (not what I was trying to say, but that's how he heard it).Chiroptera is not abandoning any positions. He was attempting to make the process of natural selection clear to you by enumerating a number of possibilities. I think your time would be well spent trying to find an understanding of natural selection within your own mind that is consistent with everything Chiroptera said. Trying to find fault with the individual examples he provided is preventing you from seeing the overall picture. You don't have to accept Chiroptera's viewpoint on natural selection, but unlike most others in this thread, you don't understand it, and that is preventing you from discussing it in any meaningful way.--Percy

I would explain this differently than Chiroptera, but please realize it is only the approach to explanation that is different, not the underlying concept being explained.Say you have two first-year brown rabbits that have never reproduced that have wandered a bit too far north and find themselves in a snow covered landscape in the spring. While seeking food they are both eaten by foxes. They have both been deselected by natural selection. The difference in their reproductive success is zero, but natural selection has occurred. Whatever it was in their phenotype that caused them to place themselves in a vulnerable position will not be passed on to the next generation.--Percy