Is there more than one definition of natural selection?

Hi Hoot Mon,I'm not going to take issue at this time with your definition of natural selection relative to differential reproductive success. I'm only going to note an internal inconsistency in your approach: When the differential reproductive success is 0, that is not the same thing as no differential reproductive success, no natural selection. The individuals happened to be equally fit and well adapted, but selection pressures were present just like they always are, and so the process of natural selection was still in force. It just didn't happen to have a measurable effect on that generation.Consider an analogy to your definition of natural selection. Just as natural selection is a measure of differential reproductive success, an automobile race is a measure of differential speed success. If all cars cross the finish line at the same time, that doesn't mean there was no race. It only means that all cars were equally fit and well adapted for that race.Or consider another analogy, this time to math. If at the end of your solution to a complex math problem you discover that the answer is 0, that doesn't mean that there is no answer. It means the answer is 0.--Percy

Good grief, Hoot Mon, are you as thick as a log? I gave you the argument, I added three analogies, and all you can do is restate your initial premise? How many ways do people have to explain things to you before they run off screaming in frustration, because that's going to happen long before you understand anyone's argument. You're like a Buzsaw-light - you have actual facts but there's still no comprehension.Hi Hoot Mon,It will difficult to give you a reply because you're just restating your initial position. I gave you the argument and added three analogies, it would be really helpful if you could try to pick up the thread of at least something I said and directly address it. I'll take a stab at this anyway.Think of Quetzal's marble analogy and consider the case where all the marbles are the same size. The marbles still fall through selection holes, but their size causes them to all fall through the same selection holes and end up in the same place. Selection still happened, it just had equal results because of equal size.Or consider an argument that assumes your premise is correct and follows it to its logical conclusions to see if it holds up. Your premise is that if the differential reproductive success was 0 that there was no selection. Consider the example of three creatures, A, B and C, who all mate and contribute progeny to the next generation. You compare A to B and discover that they both left an equal number of progeny, there was no differential reproductive success, so you conclude there was no selection. Now you compare A to C and discover that C left more progeny, and so now you conclude A was selected against because he had negative differential reproductive success as compared to C. Since it is contradictory that A wasn't subjected to selection pressures when compared to B but *was* subjected to selection pressures when compared to C, the only possible conclusion is that your initial premise that differential reproductive success of 0 means no selection was occurring was incorrect.--Percy

Hi Quetzal,I'm actually trying to accommodate myself to something closer to the way you and Modulous were looking at natural selection in the other thread. Though there were obvious differences in your preferred perspectives, there were also commonalities that I found I didn't share, and so I'm trying to adjust.My view of natural selection was very focused and individualistic. For example, when an organism dies during a period of environmental stress, to me that was natural selection. But looking carefully through several definitions on the web I found that that is more commonly just referred to as selection. When talking about natural selection these definitions tended to be addressing a higher level view of the process, a multigenerational view encompassing changes in allele frequency over time due to selection pressures and descent with modification (AbE: which appears to be the same as the definition as evolution, but I included everything that's going on in my description of the higher level perspective - natural selection still only refers to the selection aspects in this higher view).And so in my version of your marble example I referred only to selection, not natural selection, and it was intended to be analogous to only a single generation. Even though the marbles had identical phenotypes with respect to size, that is no guarantee that the next generation would all be the same size. The marble drop represents the selection part of the process, not the reproduction part. In the next generation some of the marbles may be of different sizes. Since selection pressures are operating in each generation, sometimes choosing more, sometimes less, sometimes all, sometimes none (extinction), the process of natural selection is going on. The fact that in one generation every marble survived doesn't mean natural selection suddenly stopped or was absent.I am trying to work toward a common definition, but as I've said before, the more finely the definition of a concept is sliced, the more different ways people will find to slice that concept into different definitions, giving the appearance of disagreement when everyone actually agrees on the specifics of what is happening in the real world that we're trying to describe.--PercyEdited by Percy, : Clarification.

There's nothing complicated here. If our unit of measure for differential reproductive success of two individuals were the difference in the number of progeny, what is the differential reproduction success of A with respect to C if C produced more progeny. If we call the number of progeny p, then: Since p_a < p_b, this will be a negative value. That's all it means. If you feel more comfortable with positive numbers then just reverse it and say you're measuring the differential reproductive success of C with respect to A, and then it's a positive number. No, of course not. I'm saying that any population can be divided into sub-populations. If you consider the sub-population consisting of A and B, then you conclude no natural selection, yet if you instead consider the sub-population consisting of A and C, then you conclude there was natural selection. How could whether A was subjected to natural selection or not vary simply by how you divide your population into sub-populations? It can't without being contradictory. Therefore it is incorrect to conclude that A was not subject to natural selection.--Percy

I'm actually saying something simpler. Simplicity is a theme that runs throughout my participation in the creation/evolution debate. If I really had to make clear subtle distinctions in order to successfully describe natural selection to someone just embarking on understanding the concept, then I'd feel I'd set myself an impossible task. I think it's important to take into account the level of understanding of the intended audience. So, no, I wasn't alluding to chance events or anything like that in my reply to Hoot Mon or to you.I had never watched Cosmos, so I'm gradually working my way through it. Today I completed episode 2 where Sagan talks about evolution. His presentation shadowed Darwin's, first explaining artificial selection, then using it to introduce natural selection. His presentation was something anyone could understand, and I think natural selection has to be understood at this level before launching into more detail. I still feel like we've skipped over the simple into the complex before the simple has been understood by everyone participating in this thread.I would never challenge a Futuyma definition, but I don't want to consider things at that level of detail. I was actually only trying to make a much simpler point. Plot differential reproductive success over time: Differential reproductive success is the y-axis and it doesn't matter what the units are, time is the x-axis. All I'm saying is that at the point in time where the line crosses the x-axis, natural selection is not suddenly absent. Differential reproductive success might be 0, the result of the selection pressures might all end up at the same equal outcomes, but the process of selection is still ongoing. The winter storms still happened, the summer drought still happened, the predators were still there, mates were still finicky, and the end result of it all for that generation was a differential reproductive success of 0, but the process of natural selection was still active. It doesn't suddenly cease at the crosspoints.For someone still trying to grasp the concept of natural selection, I think describing it as turning on and off as a function of whether differential reproductive success is zero contains a high potential for confusion. I think even mentioning differential reproductive success before getting the essence of the concept of natural selection across contains a high potential for confusion. Maybe it's just me, but this thread and the previous thread seem like prime evidence of this. I'm not blaming you or anyone else, I just wish we could all get on the same page. I know we're being pressured to discuss details because they're being introduced in other messages, but I don't see how repeating the approach of the previous thread could result in a different outcome.So for me it comes down to getting across this simple point, the same one that Darwin made: artificial selection is what breeders do, deciding which individuals get to contribute progeny to the next generation. Natural selection is what nature does, deciding through the effects of the environment which individuals get to contribute progeny to the next generation. Anyone who doesn't understand natural selection on this level is not going to understand it on a deeper level, no matter how many messages of explanation are posted.--Percy

I was heading off to bed when I saw this, so I'm just going to write a few sentences.Unless I'm reading your tone wrong, you seem somewhat peeved at me. As I stated in my first reply to you, I've been seeking a consilience. Much of what I've written in this thread is an attempt to incorporate my understanding of what you and Mod are saying into my own thinking. Not to hold myself up as God's gift to comprehension, I have no such conceit, but if I who enthusiastically accept evolution am so wildly off track in understanding what you and Mod are saying, you can just imagine what creationists are getting out of this.About me introducing the 0 differential reproductive success issue, I was responding to Hoot Mon's mention of it. In my message that your reply is addressed to I stated that I didn't think it was an appropriate level of detail, but that we're being pressured into it because others are bringing it up, so I'm puzzled that you think I'm introducing it.My own opinion is that we're doing a just making a terrible hash of describing natural selection. Hopefully none of us believe that we're the only one being perfectly clear.--Percy

I have more time for a reply now. I was originally responding to Hoot Mon's statement that when differential reproductive success equals 0 it means there was no natural selection. I wasn't talking about fitness equalling 0, by which I think you must mean differential fitness equals 0, i.e., that they're equally fit. If so, while it might be interesting to consider things from that point of view, they don't seem like synonyms to me. Not sure why you say this, since you're responding to a message where I say that I'm not saying anything about chance. It's not a derivation of data, it's just an illustration of a simple point. It doesn't really matter to the point I'm making, and this interpretation is fine, except for the cyclic part. The only reason my graph is cyclic is because of the difficulty of creating graphs with characters. So I went up and down once, then copied several times. If I'd been drawing freehand it wouldn't have been so regular, and its cyclic nature has nothing to do with my point. The shape of the graph is unimportant, the periodicity is unimportant. The only thing of significance is that the line crosses the 0-point, i.e., passes through the x-axis. It wasn't intended as capturing an actual situation. It was just an illustration of the fact that differential reproductive success is a time-dependent variable, and given that fact it is inevitable that it will cross the 0-point, the x-axis. The crossings of the x-axis are not points in time where natural selection has ceased to operate. As I said before, there were still winter storms and summer droughts, dangerous predators and finicky mates. The fact that during some seasons two sub-populations have equal success reproductively does not mean there was no natural selection during those seasons. Perhaps it would help if I reintroduced the original claim from Hoot Mon that I replied to and that started this discussion. This is from his Message 10: Does that help? I can elaborate about the discussion that ensued if you like, but it would just be a recapitulation of the messages that led eventually to your first reply to me. If you agree with Hoot Mon's statement then please help me understand why, while if you disagree please help me formulate a proper rebuttal. I'm not sure why you say this. If you take the example of a population of a species that reproduces once a year, then measuring the allele frequency across the gene pool every spring would show changes on an annual basis, which equates to measurable changes due to natural selection after a single generation. I grant the practical difficulties of making such measurements, but that's a separate issue. It's a concession to Modulous, actually. He said more than once and in different ways that natural selection is much more than just selection that is natural. And if you go to Wikipedia and look up selection and natural selection, they do not appear to be synonyms. Any clarity you can bring to this would be welcome.To repeat something I seem to find myself saying a lot, when people understand what is actually going on in the real world, they don't need precisely defined terminology to get their points across. You'll often hear people in technical discussions say things like, "Well, I wouldn't put it in those terms, but I understand what you're saying."But here we have a different problem. We're trying to explain what is going on in the real world by cutting our terminological definitions extremely fine, and when you get to that level of detail you simply won't find agreement. Until natural selection is understood at its simplest level, more detailed levels of understanding are simply not possible. But though we both say we believe this, we still seem helpless to escape these endless digressions involving the detailed definitions of specialized terms. I quoted Hoot Mon saying this just above. Is that why we're doing this, because you think I'm rebutting a point no one ever made? I can't figure out what the problem is, because you go on to say: Which, of course, I agree with. I was just trying to be thorough in describing where I was coming from and what definition I think is appropriate for the introductory level. I wasn't trying to tell you something I thought you didn't know. I naturally regret any contribution I've made to the confusion, but please don't mistake a venture in the wrong direction as reflecting insufficient concern, because a misstep is a possibility we're all vulnerable to.--Percy

I agree with all your definitions. It's the same way I would define those terms.In this thread I've been trying to express things in such a way that when I say something like, "When during a harsh winter one rabbit survives and another dies, that is natural selection," that Modulous doesn't object and say that it isn't, that natural selection is much more than just selection that is natural, because that led us to a big digression. And so I changed the way I expressed things in order to keep the focus on Hoot Mon's questions and not get into digressions, but that still caused digressions, this time with you. Is there a way for me to express things that both you and Modulous can agree with?Addressing specifics, about the graph, the y-axis isn't fitness, it's differential reproductive success. Whenever you calculate a difference, no matter how conceptual and difficult to measure something might be in reality, unless one quantity is always constrained to be greater than another, negative values are possible. Like you I don't know what negative fitness is, but the y-axis isn't fitness.I'm having trouble parsing this: You say that Hoot Mon thinks of NS as an outcome of differential reproductive success, then follow by saying that Hoot Mon isn't wrong to think that differential reproductive success is an outcome of NS, which is the exact opposite. Perhaps you can rephrase.Maybe I'll change my mind when I finally understand what you're saying, but I cannot at this time see how a differential reproductive success of 0 is always the equivalent of no natural selection taking place. For example, imagine two subpopulations which produce equal numbers of offspring, but that during that particular reproductive season leading up to the equal numbers of offspring that many eggs in both subpopulations were eaten by predators. That's natural selection, even though the differential reproductive success was 0.Futuyma's definition is I think trying to lay the foundation for a rigorous mathematical approach where specific traits are considered. Thus it makes sense to say that with respect to trait X there was no natural selection of X because there was a differential reproductive success of 0 with respect to X. That is indeed a possibility when considering single traits or small collections of traits. The requirements of a quantifiable approach require this. But we can't ignore the reality that during this period when there were supposedly no natural selection pressures with respect to X that many organisms possessing the trait were living and dying, mating and failing to mate. That's selection at work. And this is where I think you introduce the idea that chance selection with respect to X is not natural selection, which seems like a terminology preference that while perhaps widespread in the industry is not dominant? I don't know for sure, but it feels that way given all the reading and debating I've done about evolution without ever encountering this confusion before.--Percy

I didn't say anything about fitness, except to clarify that that wasn't what I was talking about. I didn't mention negative selection, either.--Percy

Differential reproductive success is a function of fitness relative to the environment, but I wasn't graphing fitness, I was graphing differential reproductive success. No.I'm don't know why you're asking all these questions about fitness. You did not say words to the effect that, "When there's no fitness there's no natural selection." You said words to the effect that, "When there's no differential reproductive success there's no natural selection," and that's what I responded to. I have never, not in this thread or the other, raised or discussed the issue of fitness. I think it might make more sense to begin from the simplest and broadest definition of natural selection, reach agreement on that, then move forward from there.--Percy

No.How can you ask this when I just said, and you quoted it, that fitness is a factor in differential reproductive success?To Quetzal and Modulous,I have great respect for you both, and I'm trying as hard as I can to see merit in Hoot Mon's postings because you both give him credit for understanding many things. But I am growing weary of Hoot Mon making interpretations that are opposite to what is said, and I think WK and Crash feel the same way. I'm not asking for everyone to pile on to Hoot Mon, but I am lobbying for taking this thread to a level where Hoot Mon can understand and respond meaningfully to what is being posted.--Percy

If you can stay focused on the issue I actually raised and that prompted you to reply (namely your statement that no differential reproductive success is equivalent to no natural selection) then we can have a discussion. It makes no sense to introduce other issues before building a baseline of common understanding, unless you can make clear how they relate to my original point. Intimidated? No, of course not. It was addressed to Quetzal and Modulous. I suppose I could hope that it would spur you on to work harder to make sense, but you already know that some of us feel you have problems in that area, so that wasn't why I wrote it. I'm trying to get a handle on why Quetzal and Modulous believe you understand what you're talking about. The goal of EvC Forum is to provide a venue where an open dialogue is possible between evolutionists and creationists, but there are a few prerequisites. For one, one must be capable of reading and writing with comprehension in the English language. Those who have been here a while know that I object strongly to threads that descend into nonsense.--Percy

Hey, jump on in, the water's fine. All threads are open to all members. Right, I agree with this. I wonder if this is what Quetzal was saying, but I just couldn't tell?I'm finding this discussion defining natural selection to be an unexpectedly tough slog. We can't seem to get out of our own way. The approach I'm lobbying for is to start with a simple definition from which we elaborate. I proposed that we start with Darwin's definition, but I'm flexible as long as we start simply. I do feel that we're at far too detailed a level since there isn't even agreement that sexual selection is a type of natural selection.--Percy

Hi Hoot Mon,Concerning sexual selection, this diagram represents the mainstream view, and also the view shared by everyone else in this thread:Concerning the definition of natural selection, it can be used in two different ways, and which definition is in play is usually clear from context. It can refer to the mechanisms of selection, or it can refer to the process by which favorable heritable variation becomes more prevalent in a population. Many discussions of natural selection slip back and forth seamlessly between the two definitions while still retaining clarity.--Percy

Is the distinction between sexual selection and non-random mating really just based on whether or not the trait is heritable? Been poking around on the Internet and not finding a definitive answer.--Percy