…the noyau, an animal society held together by mutual animosity rather than co-operation
Robert Ardrey, The Territorial Imperative.
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The Skeptical Zone
"I beseech you, in the bowels of Christ, think it possible that you may be mistaken."
To confuse phoodoo even more, there is also the phenomenon of linkage, and there’s hitchhiking.
So even if there was a genetic component to near-sightedness, the causes responsible for it rising in frequency could be that it is hitchiking with a very beneficial allele nearby.
I’m sure this will make his head explode. Omg how can anyone know anything when it’s complicated? There’s more than two factors in this equation HOW CAN ANYONE FIGURE IT OUT?
Yes, and there is epistasis, dominance, pleiotropy and gene-by-environment interactions as well. Didn’t think it wise to go there, before we established that alleles do affect the phenotype in predictable ways.
I don’t think there exists a definition that is appropriate to each and every situation that gets thrown around here. There is a good reason multiple definitions are in use.
Corneel,
I think that phoodoo’s main problem is his lack of understanding the difference between conceptual definitions of fitness, and their working definition counterparts. The theory versus practice issues.
Unable to understand that there’s a need for a lot of work before we can detect something that looks like the conceptual definitions, phoodoo holds to all kinds of excuses to dismiss the work altogether, mostly by focusing on one step in the working / practice problem, loaded with distractions about complex issues that might confound the process.
P.S. Maybe, it’s not that phoodoo doesn’t understand the difference between conceptual and working definitions, but still focuses on the working issues, still by imagining that all scientists do is assert that because some thing increased in a population, that is a fitness-related thing. Mixed with all those distractions, etc.
It has everything to do with fitness. Reproductive success depends on how fit, compared to other individuals, an organism is in a particular niche.
Entropy,
Risking your tendency to just spout parroted bullshit, and outright revulsion to thinking, I don’t really read what you write much anymore.
It amazing how in such a short amount of time, you have managed to post so much vacuous shit.
Blasphemy!
Nice of you to let me know this. I only suspected that you didn’t read. Now I know.
Given your confession above, compounded with your illiteracy, you cannot know.
I’ll go and chastise myself.
Entropy,
Well, you think models and equations are evidence, so don’t start tooting your horn just yet princess.
FWIW, I’m sympathetic to phoodoo’s complaint about shifting definitions. If you can’t put together one that works generally, and you need, say, seven (one for alleles, one for species, etc.), then you should provide all seven, A lot of what is done in philosophy (if you can actually call it doing anything) is concocting counterexamples–or trying to concoct definitions that are immune to them. It can be really frustrating to have people shift around, maybe hoping nobody will notice.
So, on that point, I’m totally with phoo. He says nobody can provide him with a good (i.e., universally applicable in evolutionary theory) definition of “fitness”). If that’s true, then admit it, say why you think that’s OK anyhow, and move on. If it’s not true, then give him one.
He should not be criticized for noticing this.
phoodoo,
Well, in agreement with your confession, it’s obvious that you didn’t read the whole thing, besides you’d be unable to understand it anyway.
You should not haste to judge. It only shows your incompetence.
walto,
The reason for different definitions is the different situations under analysis. It’s about bridging the gaps between a conceptual definition and a working ones. This has been clear in Corneel’s explanations.
For example, there’s several definitions of species because life forms don’t diverge and reproduce and do “their stuff” in the same way. Because some definitions require work that simply cannot be done (like mating all kinds of organisms with all kinds of organisms to see if they can reproduce and bring forth fertile offspring, of course there’s a point where trying to do that would be ridiculous, but how do you prove a universal negative such as “these populations cannot breed with each other”?). Other times reproduction is not sexual. Etc.
Situations make us think of working definitions that then can be very difficult to translate from one line and type of research to another. Sometimes in obvious ways, like trying to use the “breeding” definition of species on bacteria. However, definitions are molded and clarified for the sake of each situation. I see nothing wrong with that, as long as we make sure that the working definition works towards the conceptual one in biologically meaningful ways.
Fair enough. I have already admitted in a previous post that I don’t think such a definition exists. Moreover, Allan already provided an excellent source that should clear up a lot of confusion.
I will repeat that all definitions agree on the same general idea: that there is variation in the ability to transmit heritable information to the next generation. This variation is the substrate of natural selection. So far, phoodoo has resisted this very obvious fact. If he simply admits that, that would cause a great sigh of relief from several of the TSZ residents and we could move on to more interesting discussions.
Thanks. I appreciated Allan’s link, but it’s a bit mathy for laymen like me.
I see that a definition of fitness would rely on that, but couldn’t heritability obtain without there being any such thing as fitness or natural selection? I really don’t know where phoodoo’s objections begin or end, myself. To me, natural selection seems highly intuitive, and that more people can roll their tongues than are like me doesn’t seem like a legitimate counterexample to the notion at all. So, I’d expect a good definition for fitness to be at hand, but I’m pretty ignorant of the details.
From the paper:
But what do you take to be conveyed by “fitness” in that quote?
walto,
Reproductive success.
I’m not.
“Fitness” should be thought of as a theoretical term, to be used in mathematical models (as in population genetics). As far as I know, there isn’t any serious attempt to come up with actual empirical measurements of fitness. It is defined by its role in the mathematical models.
The models themselves are evaluated by their predictions, as tested by measuring things that can more easily be measured.
Let’s not abolish theory on the basis that it can be hard to give empirical definitions of theoretical terms.
Have you seen videos of the “Giant Petri dish” experiment, where the environment has increasingly higher levels of antibiotic? A graphic illustration of fitness as differential reproductive success in bacteria.
ETA previously discussed at TSZ here.
OK, so let me see if I can replicate some phoodoo-style objections. Is it traits that have reproductive success or organisms or both? Suppose it is something that organisms can have. We note that some traits that one would expect to be harmful are on the rise. (He gives nearsightedness as an example.) So, it would be wrong to infer that traits that are on the rise are fitness enhancing.
It seems to me one could just respond to this with “Yes, that’s true. It actually doesn’t follow from the fact that incidences of some trait are increasing that that trait is fitness-enhancing. All we can infer is that the trait itself is more fit than others it is competing with for space.” So the definition for “fitness” is univocal, but the inference phoodoo is taking from it is fallacious.
Is that wrong?
Yeah, that was awesome.
Neil Rickert,
That’s a very good way to put it.
Who has required an “empirical defitinion” (whatever that may be)? All that has been asked for is an unchanging one. As a math guy you should insist on that.
No, it’s completely confused, actually.
walto,
In my view, it’s phenotypes (individual organisms) that vary in fitness depending on the mix of beneficial, neutral and deleterious alleles that contribute to that individual’s genotype.
OK, but if it’s ONLY phenotypes that can exhibit fitness, the definition Allan suggested we use is MUCH too broad. That’s the point.
walto,
There seems to be the need to clarify whether one is doing or discussing population genetics or making field observations of real populations.
Do you think the term “fitness” is used equivocally then?
My own sense is that it can be given a nice def that will work everywhere. (But I’m obviously not the guy to do it.)
Possibly. It seems the only practical assessment of fitness is reproductive success of whole organisms. Maybe we should speak of alleles contributing to fitness rather than having fitness. But I don’t think there’s real equivocation, just shorthand.
That’s not all has been asked for. What’s been “asked for” is a single definition that would apply in practice in all situations (empirically), which comes to show the tremendous ignorance of the way things can be explored in different situations. Phoodoo has been jumping around his own issues understanding that in practice (empirically), it might be hard to use a single definition, while others have explained, time and again, that here’s a gap to bridge between the conceptual (the theoretical term in the math), and the empirical (the “in practice” definitions), and that the difficulties in the empirical don’t mean that the theoretical should be dismissed. (Let alone the whole of evolutionary theory.)
The theory-to-practice problems are here to stay. They’re part of the process. We conceptualize hoping to understand something. We run the math, we use the models to make predictions, but then we have to find ways to measuring things in our tests, and then we have to conform to the limits of the system we’re studying and use a practical definition hoping that it will still bring the conceptual to life. This necessarily will change from system to system and from technological power to technological power.
I think we’re rarely taught philosophy of science any more, and, when done, it doesn’t seem to include the important aspects related to scientific inquiry very well. This mess is something of an epistemological misunderstanding.
phoodoo,
I know what you think you saw there, but you also know that ‘skeptics’ never disagree about anything. Except when they do.
Yes, absolutely. I’ve cited 3-5 sources by various evolutionists to make my case:
Richard Lewontin
Andreas Wagner
Allen Orr
Stanley Salthe
Sharon Moalem
The most poignant example is Sickle Cell anemia. Evolutionary biologists will call it a fit trait in Africa, most medical doctors consider it an illness therefore an unfit trait. But this shows the precarious nature of it. Outside of Africa where there is less of a malaria threat, it is an unfit trait mathematically, whereas in Africa it is a fit trait mathematically.
But on a philosophical note comparing the medical notion of fit and unfit, most would regard the sickle cell trait as unfit.
Of course, one could invoke the technical issue of heterozygosity vs. homozygosity, but those are technical details, the essential problem of defining fit is there.
stcordova,
Are you seriously suggesting that the definitions of fitness should ignore the environment?
Do you really think that the term “natural selection” should refer to your preferences, rather than to environments where a trait might be helpful, neutral, or detrimental?
There’s no equivocation except in your conceptual framework Sal.
Yes. That’s what medical doctors essentially do for patients. The sickle cell is something to be concerned for as a medical condition whether you’re in Africa or North America. Same could be said for other “advantageous” traits leading to illnesses like Tay-Sach, diabetes, obesity and high cholesterol, etc.
I wouldn’t imagine treating someone with the Sickle Cell trait in the USA by sending him to Africa where the evolutionary biologists say it will become “beneficial” because of the Malaria environment there. That’s the absurdity of the definition of fitness that is so sensitive to environmental changes.
In contrast, the notion of length and inertial rest mass is so stable in physics. A meter long stick is a meter long all over the globe. Even the weight is about the same (adjusting for the equatorial centrifugal force correction) wherever you go on the planet.
For those reasons, I find physics a more satisfying discipline of study than evolutionary biology which is built on equivocal quantities like fitness.
walto,
The point is, the definition I offered is a math-y one, and it isn’t actually all that broad. It just allows for different ‘entities’ to be plugged into the same framework, if they have the fundamental characteristic of a capacity to increase or decrease their representation in a population of similar … thingies. Absolute and relative fitness are nothing more than averaged individual fitnesses, in two different scenarios; they aren’t wildly different things. All 3 concepts are linked by the same thread: a change in frequency of a particular variant is effected through average number of copies produced in whole individuals possessed of that variant. This is interchangeable with a rate of increase, as per my ‘soundbite’.
The purpose of fitness in population genetics is to provide some quantification or analytic tool that represents natural selection, which boils down to differential reproductive success. It has a ‘survival’ component, but ultimately it is survival to reproduction that ensures continuation of a copy lineage, so they are compounded into one measure. Its components are (probabilty of surviving to produce a zygote) times (number of zygotes produced). If either term is zero, there’s no reproductive success, so ultimately that’s what counts.
The only way an individual’s genes can spread through a population is by being passed on to offspring, and each extra offspring is an extra copy of half an individual’s genes. But of course each individual has a huge number of genes. You certainly can’t derive much from one individual’s output. But you can still have a sensible theoretical term – the mean offspring numbers of all individuals possessing a characteristic of interest, whatever it may be. For the maths, it doesn’t really matter what it is. But it’s important to note that this is a mean, an average. That indicates it is subject to a probability distribution, with a variance, and so the fittest allele is not always the winner. It’s probabilistic, so one cannot simply count the existent organisms and declare all their alleles ‘fittest’.
Now, to confuse further, an ‘allele’ is itself rather a slippery thing. It doesn’t have to be a DNA sequence, it can be a phenotype, a trait – what is termed a ‘character state’, which can include both morphological characters and raw DNA sequences. What increases in the population are DNA copies, but it is not wrong to say that the trait increases too. It is through selection on the trait that frequencies change, but the frequencies of both DNA and trait change together. So, one can cut the crap and just treat the trait as an allele, and ignore the ya-boos who argue pedantically that the trait isn’t replicating.
stcordova,
Are you going to tell Sanford fitness is a meaningless concept, or shall I?
I’ve told him. But the point of generously using the Darwinian notion of fitness the simulations is that even according to evolutionary definitions, the human genome is decaying. The alternative is that if simplicity is favored, then increasing fitness of simplicity will favor the less intelligent, hence we may be headed for an Idiocracy since smart people have less kids than less-smart people. That’s not a creationist idea, but something the Eugenecists have been keen to note.
http://www.sciencedirect.com/science/article/pii/S016028961000005X
But regarding John Sanford, when I related to him the evolutionary solution to Genetic Entropy by redefining fitness as Sharon Moelem did with his “Survival of the Sickest”, Dr. Sanford couldn’t help laughing.
Sickle cell disease happens when you have two copies of the sickle cell allele. If you only have one copy it is asymptomatic. What heterozygous carriers get is some protection from malaria. So if the environment had no prevalence of malaria, the sickle cell allele in heterzygous form is neutral and would probably disappear through drift. But in areas where malaria was rife, heterzygous carriers benefited from the resistance to malaria, the allele was positively selected, which is why the sickle cell allele is present at higher levels in populations exposed to malaria. The environment is the crucial selecting factor.
stcordova,
It’s not really the definition of fitness that’s sensitive, but your chosen example. Fitness is context dependent, of course it is. That doesn’t make it worthless as a concept or without power to effect any change of frequency.
Well, I think I have to disagree here. Selection operates on the whole phenotype. The genotype makes it into the next generation only if the phenotype reproduces.
Alan Fox,
?
The phenotype of the trait only makes it into the next generation if its genotype is reproduced.
stcordova,
But we’re talking about evolution Sal, not about what medical doctors do.
Taking a concept out of its context doesn’t mean that the concept is wrong. It just means that you’re equivocating. Textbook example Sal.
I guess I think of a phenotype as the composite of the traits.
Allan Miller,
Thanks. As I said above, I do have the general sense that it’s possible (and even reasonable) to use ‘fitness’ univocally in these various settings. It’s not clear to me that the one-line attempt using ‘entitles’ above quite nails it, but I think it’s close and that it’s not a hopeless project.
Alan Fox,
Well, there’s a phenotype of the entire genome, but also potentially a phenotype of any part of it. The term ‘genotype’ can sometime cause similar confusion, being a part or a whole.
The definition of fitness in evolutionary theory is not equivocal. It’s you who equivocates by taking the definition of a word from a different context, and then pretending to use that definition back into the context where it doesn’t apply. The problem is you. Not biology. Not evolution. Just you.
“Fitness” is only equivocal to you, because you cannot put yourself into the context where the word is being defined. You want it to be about whatever you want it to be, not about what it stands for. That’s more of a personal problem accepting that words can mean different things under different contexts, than about evolutionary theory.
In certain cases, that’s easy to see, as in the glutamic-acid-to-valine mutation in sickle cell anaemia. But that’s not yet often the case. Pleiotropy, linkage, etc previously mentioned above.
Phoodoo, among others, has been complaining about empirical definitions.
The idea of fitness works perfectly well in mathematical models of population genetics. If you want the empirical version, then you can come close by counting the offspring if you are talking about mammals. But if you are talking about bees, it’s pretty hard to say what it is empirically. What’s the fitness of a sterile worker bee? It can’t be the number of offspring, unless the fitness is zero. But the fitness cannot be zero, because without worker bees the whole hive collapses. Perhaps we should be talking about fitness of a hive rather than of a particular bee. But it doesn’t matter. The mathematical model still works.
So just be an anti-realist about fitness. Do the math, and don’t think about what the definition is.