EricS... what Frank said is the issue :- ) I'm not sure how to parse all the options you provided, but you were trying to articulate something you were admittedly confused about, which is inherently a rough task. Luckily, Frank's comment simplified things.
Fitness = How well the organism fits the environment (or, it's niche within the larger environment). For example, a Macaw fit's well an environment in which rich nutrients are often stuck within nuts and seeds protected by hard shells, which themselves are dispersed over long distances in high canopies. They can readily fly from tree to tree, and crack open said nuts and berries with their extremely powerful beaks. One assesses fitness by the comparative method and by the engineering method. The comparative method takes the species in question and compares it to related species in different niches (e.g., the brown hooded parrot and the caique), as well as less-related species in similar niches (e.g., acorn woodpeckers, Clark's nutcrackers). The engineering method assesses fitness by creating models of a given function, and comparing the "ideal" model with the species in question (i.e., modeling the jaw/beak of a bird to apply nut-cracking pressure). Traditionally, of course, the comparative method has been dominant, but with the emergence of computers, there is now a lot of very fun work using the engineering method. It might not be immediately obvious, for further example, that the Geospiza magnirostris is a finch. But once that becomes obvious, a field biologist would be immediately tempted to compare it to other finches, and to other birds (such as the various parrots) that similarly eat nuts and seeds protected by hard shells. That species's adaptations to said environment are not nearly as exaggerated as the Macaw, but are on par with small parrots, and are quite distinct from mainland finches. They seem more specialized for nut-cracking than lovebirds, for example, which have a similar weight. We can observe all of that before we have spent any effort toward studying which individuals within the species are reproducing more or less successfully than other ones. Reproductive success is more straightforward, we can get at it by counting offspring. The *theory *of evolution by means of natural selection contained many components, but the most noteworthy component was the *hypothesis *that you could explain the phylogeny seen in the fossil record, as well as the dispersal of animals around the globe in present day, via a historic process by which those-organisms-better-designed-to-fit-their-niche had more offspring than their conspecifics, creating sustained change over time. We can quibble about the vocabulary in many ways, and the dislike for "design" is particularly understandable, given historic arguments over the term. But what we should not do, is allow that quibbling to erase crucial aspects of the theory. Much is lost if, for example, we reduce Darwin's theory to "the things that reproduced are the things that reproduced", which is something we risk doing when we mathematize the environment out of the picture. That is: We expect fitness to predict survival (to reproductive age) and reproductive success, but there is no guarantee that it does in any particular case, and we would not be at all surprised if occasional examples were found where it does not. However, if we follow a particular model of formalization in which we interdefine all of our terms (mathematically or otherwise), then we cannot go out in the field and discover that fit and reproductive success relate, and we cannot discover occasional exceptions, because we removed all potential empirical implication from the system of terms, and rendered all (well-constructed) claims in the system true by definition (ala the model of Euclidean Geometry), rather than allowing them to be true (or not true) based on the results of scientific investigation. <[email protected]> On Wed, Apr 1, 2026 at 11:51 AM Frank Wimberly <[email protected]> wrote: > I thought fitness was a measure of the likelihood of survival in a given > environment. Hence fitness together with the capacity and drive to > reproduce would determine the continuation of a species. But I'm no > biologist. > > Frank > --- > Frank C. Wimberly > 140 Calle Ojo Feliz, > Santa Fe, NM 87505 > > 505 670-9918 > Santa Fe, NM > > On Wed, Apr 1, 2026, 5:15 AM Santafe <[email protected]> wrote: > >> Can I ask one last question? after which I promise I really will shut up: >> >> The content of EricC’s note below (about the key in a lock), reflecting >> back on things Nick said in the early posts about selection’s being a >> tautology, which got me started digging a hole, have bothered me through >> the night, and made me wonder if I can understand how I have been missing >> both-of-y’all’s point. Was it something like the following:? >> >> — for me, “fitness” is a name given to (something like) the units (or >> dimension) in which reproductive success is measured, or quantified. Not >> sure “units” is quite the right term, but the point is that it’s about >> defining a quantification program for observed outcomes, or the model >> variables that we try to fit to them. I had taken the state of modern work >> to show that this is the only actual meaning the term was ever given. >> >> — are you two claiming otherwise; that my supposition is not at all the >> case? That there are biologists for whom there is some other meaning, >> instead of or in addition to the one I gave above, about being a >> measurement unit? Something like: “fitness” is a name for “the cause of >> reproductive success”. As if to say: Well, there’s this thing with the >> form of a name, so there must be something it names, that is a kind of >> causal force responsible for generating what we witness as reproductive >> success. And since there is one name, there must be some one kind of >> causal force it names. >> >> — to me, an interpretation like that is so bizarre, it would never have >> occurred to me to that there is anyone making it. It seems very similar to >> taking an expression like “elan vital”, and saying that, since it has the >> shape of a name, there must be something it names. To me, those are >> strings of words that satisfy rules of syntax and that don’t have any >> semantic referents at all. They may as well be Chomsky’s “colorless green >> dreams” or something. I would not have imagined that there was anything >> anyone expected, beyond the working out of the mechanics of lots of cases >> of how-lifecycles-play-out-in-contexts, which can fill out some vast >> taxonomy that has no singular “essence” underneath it. That could well be >> my lack of empathy for how many other people think, like my lack of empathy >> for their thoughts about God (along with my ignorance about who is in the >> world). >> >> — I guess, since there are people who continue to talk about Strong >> Emergence, and Philosophical Zombies, and who sound to me much like people >> who talk about God today, and maybe like people who would have talked about >> Elan Vital some generations ago, I should have right away imagined this >> reading of what you were writing. >> >> If the above is what you were claiming, it would explain why my long >> Emily Litella-like replies seemed like a tiresome recital of what >> population geneticists already do (Nick’s point that “all that would be >> left is EricS’s 2a and 2b”), which everybody already knows anyway, and >> which isn’t interesting and wasn’t to your point. >> >> So, were you claiming that there are biologists operating that way? >> >> And are there really biologists operating that way? >> >> As always, I appreciate whatever patience or indulgence, >> >> Eric >> >> >> >> >> On Mar 31, 2026, at 15:47, Eric Charles <[email protected]> >> wrote: >> >> I'm a bit confused here... >> The initial dog pile on Nick seemed (to me) to have as one of its main >> points something like "Look, old man, once you formalize something >> mathematically we don't need to care what any of the words might mean or >> imply in any other context, it is just math, stop thinking that the words >> matter!" >> >> And now there have been several posts by EricS, at least one by Glen, and >> I think Marcus and Frank are in there somewhere as well, claiming that the >> words are crucially important and we need to take them much more seriously. >> >> So.... where does that leave us? Is everyone now onboard with >> the metaphors mattering quite a bit? >> >> I'll also note that "function" can't do the work on its own to explain >> evolution. We still need to know why some functions are favored by >> selection and others are not. EricS seemed to indicate that we assess "fit" >> by determining if animals are "happy".... but the metaphor of "fit" is like >> a key in a lock. To explain evolution you need the matching of >> form-and-function-to-a-particular-environment. That matching *sometimes* >> increases reproductive success, and *sometimes* the traits in question are >> hereditary. >> >> Population genetics combined with field research can be very powerful >> along those lines, but the math of population genetics on its own, floating >> out in the ether, can't do it at all. >> >> Best, >> Eric >> >> >> <[email protected]> >> >> >> On Tue, Mar 31, 2026 at 6:10 AM Santafe <[email protected]> wrote: >> >>> Hi Nick, >>> >>> Two smaller replies to what have become two sub-threads: >>> >>> > On Mar 30, 2026, at 15:42, Nicholas Thompson <[email protected]> >>> wrote: >>> > >>> > DES, EPC, FW >>> > >>> > So far as I understand, the argument flowing from Fisher makes no >>> claims about the kind of trait that produces reproductive success other >>> than that it is the kind that produces reproductive success. FW, if that's >>> not a tautology, it's a pretty tight circle. >>> >>> As usual, let’s decamp to more neutral ground in the hope of having an >>> ordinary negotiation. >>> >>> Suppose that, in your overweening pursuit of the study of metaphor, you >>> never noticed that there is a once/4-year gathering called The Olympics. >>> Also never learned what any of its so-called “events” are, what they are >>> about, how they work, and how one differs from another. My hypothetical >>> here is meant to define a condition of having “very little prior >>> information” about some phenomenon that we can, nonetheless, still >>> reasonably unambiguously circumscribe. >>> >>> But a quick inspection shows that a subset of the participants (who all >>> together seem to be called “athletes”) are given metal disks and stand on >>> some kind of 3-tiered podium, while other athletes do not. Being a >>> statistician — a skill so helpful in the study of metaphor that it was >>> worth taking the time out to learn — you immediately recognize that this is >>> a kind of marking that can be used to partition the athletes. Taking >>> notice, for the first time, of some of the conversation in the society >>> around you, who seem not nearly so devoted to metaphor and thus have time >>> to do other things, you gather that these marked people seem to be called >>> “winners” (or better, “medalists”, this “winning” thing is a finer >>> sub-partition; I’ll mis-use “winner” to label the most salient marking for >>> this little parable). It’s handy to have such a term, for use in later >>> sentences, so they become less tedious than the ones I have been typing so >>> far. >>> >>> You also note that while there is only one 3-tiered podium and >>> metal-disk set per one “event”, there seem to be many such distinct >>> “events”, so some kind of event name gives you a second kind of marking you >>> can put on the athletes. Moreover, interestingly, the “event” label is >>> again a proper partition (or at least seems to be; this one is less >>> cut-and-dried than the observation that everyone carrying a metal disk is >>> not someone not-carrying a metal disk, so we are wary; the event label >>> seems to be a bit more abstract): every athlete is in some “event” set, and >>> it appears that no athlete is in more than one of them. As with the >>> “winners” label, you learn that there are conventionalized names for the >>> events, and you can find a look-up table if you need one or another of >>> them. >>> >>> Now, I can make a list of statements that seem to be of two different >>> kinds (scare quotes here indicate my statisticians’ attribute labels; in my >>> condition of very little prior knowledge, I don’t claim I have any more >>> semantics for them than I listed above): >>> >>> 1. Every “winner" is someone marked as having won something. >>> >>> 2a. Every winner in the “gymnastics” event is shorter than the average >>> over all the participants; >>> >>> 2b. Every winner in the “high jump” event is taller than the average >>> over all the participants; >>> >>> … (we could presumably look for other such summary statistics that seem >>> to be unusually regular and to carry different values in different >>> “events”). >>> >>> I would say sentence 1 is “a tautology”, or close enough to it for the >>> purpose of this negotiation. Maybe I should use EricC’s good, and slighly >>> more flexible term, “truism”. >>> >>> Now you may write a protest email: But the sentences 2a, 2b, have not >>> told me what constitutes “competition” in these “events”: “gymnastics” and >>> “high jump”, and given me the rule book for scoring them. Okay. And they >>> didn’t cook your dinner and do the dishes afterward either. Life is hard. >>> And more a propos (breaking my little 4th wall here), the path to a >>> fully-adequate “causal” theory through statistical inference is like the >>> Road to Heaven: narrow, tortuous, and inadequate to many things one can >>> rightly want to know. That’s what other sciences are then for. >>> >>> But if you claim: The sentences 2a and 2b didn’t give me _any >>> information_ about these “events”, and couldn’t have, because they are >>> tautologies, I would say you made an error. Of course, the real Nick would >>> not say that, so we are all safe. >>> >>> The above parable is, of course, about selection. I didn’t say anything >>> about heredity. But if I had happened to note that height is a fairly >>> heritable trait, I could have spun out a much longer story, and defined >>> some Bayesian-posterior conditional probabilities, which would be shown to >>> have properties such as: the posterior probability, under various ceteris >>> paribus conditions, for a child of a high-jump winner to turn out another >>> high-jump winner is higher than for that child to turn out a gymnastics >>> winner, and so forth. The amalgamation of both of those stories would go >>> in the direction of Fisher’s fundamental theorem. It would leave out all >>> the stuff that Fisher left out of emphasis in his mad pursuit of his >>> covariance term as an analog to the thermodynamic 2nd law (a non-valid >>> analogy, as it turns out to be easy to show), and that Price included >>> didactically (and here, to EricC’s answer): that I didn’t even mention >>> that the tall people might get drafted into wars and put into an infantry >>> to fire rifles over tall dijks, while the short people might be drafted >>> into Special Forces and sent on missions to attack through underground >>> tunnels, and so the number of survivors could depend on many factors about >>> which war their country had started, in what theater, and against what >>> opposition, etc. These are the world of everything-else that Fisher lumped >>> together into “deterioration of the environment”, as Steve Frank (and I >>> think also Price) lays out. They are probably not well-analogized to >>> “mutation”, but in genetics, mutation also goes into the same bin in the >>> Price equation — _outside_ the term of Fisher’s fundamental theorem — as >>> the “deterioration” effects. The accounting identity is flexible enough >>> that we don’t need analogies to use it; we can formulate a version for >>> whatever statistics our phenomenon-of-interest supplies. >>> >>> Anyway; at issue: Seriously, do we have a problem in scientific work, >>> of people being unable to gain partial knowledge about phenomena through >>> sentences of the kinds 2a, 2b, because they can’t tell the difference >>> between those and sentence 1? 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