Defining Fitness

There is a pretty interesting discussion going on in Noyau regarding the many definitions of “fitness” in evolutionary biology. It would be a shame for it to be lost in that particular venue here at TSZ. At the risk of being censored by the admins for posting too many OPs in one month I thought I’d start this thread.

Here’s my take so far:

Allan Miller was charged by phoodoo with resorting to different definitions of fitness. Allan denied the charge and when asked for a definition of fitness Allan provided one. Allan later stated that his definition only properly applied to asexual species.

Others chimed in to say that the definition of fitness depends on the context, which hardly seems to contradict what phoodoo was saying.

My own position is that fitness has its definition within a particular mathematical framework. My position is also that fitness can be defined generically but that such a definition is tautological. Special definitions of fitness are required to make the concept testable.

Here’s hoping we can move the discussion about fitness out of Noyau.

239 thoughts on “Defining Fitness

  1. Allan Miller: If you see a difference between Joe and I, I’d recommend that your default position should be to side with him, but in this instance the difference is, I think, in your imagination.

    Of course! You are united in one goal…right or wrong; with contradictory views you call slight differences or not…

    I get it!

  2. phoodoo:
    Rumraket,
    Because you see, now we have a whole other issue.The question now becomes ARE THERE traits which universally give certain organisms a reproductive advantage?

    Universally? No, I don’t think there are traits that universally (which I take to mean always) give a reproductive advantage.

    Not fitness, remember, because fitness means a reproductive advantage, try to keep that in your steaming head.

    No phoodoo, it doesn’t. You’re going to have to learn to state this properly or you will keep being confused by your own words.

    It is not the case that “fitness means a reproductive advantage”. Fitness refers to a relative value of reproductive success. It is a quantity, like height, or weight.

    It would be meaningless to say that “reproductive success” always gives a reproductive advantage. Because it would be equivalent to saying “height always gives a tallness advantage”. Uhm, that depends on HOW MUCH height we are talking about.

    Fitness is the measure of reproductive success, as in how many offspring is made over some period of time. So it’s a quantity of some measurable characteristic.

    Ways to properly use the term “fitness” in questions and statements are, for example:
    1. What is the fitness of allele A?
    2. Is the allele associated with higher fitness?
    3. The allele has a negative effect on fitness.

    Which is like saying, respectively:
    1. What is the relative reproductive success of carriers of allele A?
    2. Is the allele associated with a higher relative reproductive success?
    3. The allele has a negative effect on relative reproductive success.

    Which, to really cut it out into small pieces, means:
    1. How many successful offspring on average, do organisms which carry allele A, have compared to organisms which do not carry allele A?
    2. Is the allele associated with an increase in average number of successful offspring by carriers?
    3. The allele has a negative effect on the average number of successful offspring of carriers.

    I hope I don’t have to cut this out any more for you. I presume you can still chew food.

    But that’s a problem, see.

    The only problem here is your confused use of terminology. You don’t even know how to properly use the word in a sentence or what it means when that is done.

    Think of the word ‘fitness’ like the word ‘height’. Having “height” doesn’t tell you anything. It is the actual height that is informative. The number. The quantity of the dimension from one point to another.

    What is your height? Is like asking “how tall are you?” A sensible answer would be to give a measure of that, in meters or yards or feet or some other unit of distance.

    What is your fitness? Is like asking “how many successful offspring do you have?” A sensible answer would be to count how many children you have, who also had children of their own.

    Because first off we have no frickin clue, because its an impossible study to do, to see what traits cause organisms to reproduce.

    If you can just sit there and brainlessly declare that it is impossible and nobody has a clue, then I can do the opposite. If it’s good enough for you, you can’t fault me for doing it too.

    No, it isn’t an impossible study to do. It has in fact been extensively studied.

    You can bullshit tall you want about bacteria in a dish, but that doesn’t tell us what traits, when, why how, or anything.

    Yes it does. The contributions of to fitness (average reproductive success) of individual mutations has been measured in for bacteria, and many other species.

    And if it comes down to it, and all we can do is count, then we have to count everything, and that means male pattern baldness, tongue rolling, one nostril bigger than the other, widows peaks, and every other thing you can think of.

    It can certainly be difficult, no doubt about it, and some times it is true we don’t know what the contribution to fitness some allele has.

    That’s why there’s this field of mathematics called statistics. And why we do science both by observation and by experiment. You do lots of field observations, and you try to do experiments to minimize the number of variables. Then you do statistics on the results and see what we get.

    Just because you can’t figure out how to do it doesn’t mean it can’t ever be done. You’re really just expression your own ignorance here.

    You will never know if its the shape of the fingernail, the speed which one can run, the backgammon prowess, or the love of mobile homes. You will, never ever ever be able to know.

    Or maybe I will be able to know, because I can do lots of observations and I can do experiments and statistics on the results?

    It maybe be easier to do experiments on it, than to think clearly about it, but its impossible to ever know because EVERY SINGLE genotype is different.

    Again, if YOU can just declare what the facts are, then I can just declare what the facts are.

    It’s NOT impossible, because everyone single genotype is NOT different.

    Every time you remix, and reboot the environment, you got a new answer.

    What are these remix-and-reboot-the-environment experiments again? I’d like to hear about them.

  3. Allan Miller: 1) Because NS can be expressed tautologously, it doesn’t happen.

    Natural selection is easily seen with an open mind as “the survival of the survivors”…

    You, Joe with Harshman perhaps can test it and prove it to be “the survival and the fittest’…

  4. J-Mac: Natural selection is easily seen with an open mind as“the survival of the survivors”…

    You, Joe with Harshman perhaps can test it and prove it to be “the survival and the fittest’…

    I’m beginning to think one of the reasons you creationists have such a hard time with this is your extremely poor grammar. You can barely write a coherent sentence, so when information from the scientific literature permeates down the ranks of creationist misinformers, it gets mangled into incoherence along the way.

    Imagine someone like Bill Cole having to make sense of the concept of fitness, by being taught about it by someone like J-mac.

    GIGO.

  5. Rumraket: No, I don’t think there are traits that universally (which I take to mean always) give a reproductive advantage.

    Wouldn’t leaving more offspring give a reproductive advantage?

    Rumraket: Fitness is the measure of reproductive success, as in how many offspring is made over some period of time. So it’s a quantity of some measurable characteristic.

    So the more offspring the greater the reproductive success and the higher the fitness? Like the taller someone is the greater their height? The fittest are those that leave the greatest number of offspring? Like the people with the greatest height are the tallest?

    Rumraket: Imagine someone like Bill Cole having to make sense of the concept of fitness, by being taught about it by someone like J-mac.

    No thanks. You’re doing a fine job.

  6. J-Mac: Fine. You have also conceded that not only the fittest survive, right? Just like in thecase of 120 000 of fertilized eggs of green frog when only 2 survive…

    I refer you again to statements just made, and my ‘gametes’ post addressing an equivalent scenario to the frogs. No one says that NS is all that happens. Disabuse yourself of that notion.

  7. Mung,

    Just to sum up Rumraket’s logic:
    They survived; therefore they were the fittest ones.
    Why were they the fittest? Because they survived.
    Obviously those which didn’t survive can’t reproduce can they? Why? The answer should take much to figure out, should it?

  8. J-Mac: Of course! You are united in one goal…right or wrong; with contradictory views you call slight differencesor not…

    I get it!

    I don’t think you do. Neither Joe nor I says that random deaths do not occur. Stop trying to manufacture disagreements when they don’t exist. That’s Mung’s job.

  9. J-Mac: Natural selection is easily seen with an open mind as“the survival of the survivors”…

    An even more open mind might recognise that a tautology is not the only way to express NS. Yours is not that mind.

  10. Rumraket,

    Thank you!
    And your point is? You don’t have one…naturally…
    Well, we can all rightly assume that this, and many of your other pointless comments, are at least not related to your exceptional grammar…
    Pleasure talking to you!
    Ciao ciao!

  11. Greater minds than these have been pursuing this tautology line, without success, for years. Imagine them trying to do simple lab work with this rhetorical burden.

    Imagine one had two strains of bacterium. When mixed 50/50 in 10 replicate flasks, A outcompetes B in 8 of them. Which is the fitter? The one that outcompeted more often! Which one outcompeted more often? The fitter!

    So are we to conclude from the possibility of a tautologous statement of the relative performance that

    A) neither is fitter
    B) both are fitter
    C) one is fitter but we don’t know which.

    Or something else?

  12. J-Mac: Natural selection is easily seen with an open mind as “the survival of the survivors”…

    Hahahaha, come on you stubborn scientists! why can’t you have an “open mind” and accept some random YEC’s retarded misrepresentation of a concept that’s been useful for ages in it’s proper form? We’ve gone from “we’re still waiting for a definition of fitness” to “this YEC is gonna tell you what your definition of fitness must be. All you need is an open mind!!!11!1!1”

  13. Also Christmas is easily seen with an open mind as “the celebration of Santa’s birthday”. Just because I say so, you know. Do Xtians have an open mind or what?

  14. dazz: Hahahaha, come on you stubborn scientists! why can’t you have an “open mind” and accept some random YEC’s retarded misrepresentation of a concept that’s been useful for ages in it’s proper form? We’ve gone from “we’re still waiting for a definition of fitness” to “this YEC is gonna tell you what your definition of fitness must be. All you need is an open mind!!!11!1!1”

    Why should I even talk to you?

    You wanna take fitness?

    OK. Why don’t you tell us everything you know about the definition of fitness and the survival of the fitness in any size of the population of the same sex individuals…

    You can apply any version of your no doubt well trained perceptions and you can be as open minded as you wish…

    Please try not to run away from this challenge…

    If you need help, Allan Miller used to claim to be an expert on the theme…

    Don’t disappoint me with any evolutionary dead ends! 😉

  15. J-Mac: Why should I even talk to you?

    Participation here is utterly voluntary.

    You wanna take fitness?

    Can I just remind you about the niche. Fitness is an attribute that has a context. Swimming ability is not much use in the Sahara and the ability to survive drought is not much use in the Pacific.

    OK. Why don’t you tell us everything you know about the definition of fitness and survival of the fitness in any size of the population of the same sex individuals…

    *chuckles* Fitness is assessed as number of offspring. I’d agree that homosexuality (if lifelong) should not be a heritable trait. Though there’s nothing wrong with that. There are too many people on the planet as it is.

    You can apply any version of your no doubt well trained perceptions and you can be as open minded as you wish…

    Matthew 7: 3-5

    Please try not to run away from this challenge…If you need help, Allan Miller used to claim to be an expert on the theme…

    Don’t recall him claiming such – he’s far too modest. He has demonstrated his breadth of biological knowledge though.

    Don’t disappoint me with any evolutionary dead ends!

    They happen. It’s called extinction!

  16. J-Mac: Why don’t you tell us everything you know about the definition of fitness

    I already did that. Actually I essentially just parroted some of what Joe and others have been trying to explain to hopeless ignoramuses like you.

    Happy Santa’s birthday holidays!

  17. dazz: I already did that. Actually I essentially just parroted some of what Joe and others have been trying to explain to hopeless ignoramuses like you

    As predicted…;-)
    At least I have this problem out of my way…but not you…
    No! You have to live with your reliance of Joe Legend and he likes… for obvious reasons…
    Have a nice life !

  18. Alan Fox,

    You can’t be serious?!
    I was challenging dazz’s views by using an imaginary population…knowing that he is going to shrink back from it…

    Please don’t tell me you bought it? On the other hand…

  19. J-Mac: Why should I even talk to you?

    You wanna take fitness?

    OK. Why don’t you tell us everything you know about the definition of fitness and the survival of the fitness in any size of the population of the same sex individuals…

    Such as bacteria?

    If you need help, Allan Miller used to claim to be an expert on the theme…

    Where? Not that it matters much, but I’m not an expert. Still, it seems unclear what you want, other than to get someone to write something, which seems quite trollish.

    What is your argument? State it clearly and calmly.

  20. Oh, excuse me for missing the reference to homosexual “populations”, I just can’t be bothered to pay too much attention to what Jerk-Mac writes.

    J-Mac: Why don’t you tell us everything you know about the definition of fitness and the survival of the fitness in any size of the population of the same sex individuals…

    It’s a well known fact that gays are usually much fitter! Just google “ripped gay” for documentation

  21. dazz: It’s a well known fact that gays are usually much fitter!

    You forgot the most important part of your comment:
    “…and that fitness certainly helps gay man to reproduce…” Isn’t it right dazz?

    There is one problem with their reproduction though… Can think of anything?

  22. J-Mac: You forgot the most important partof your comment:
    “…and that fitness certainly helps gay man to reproduce…” Isn’t it right dazz?

    There is one problem with their reproduction though… Canthink of anything?

    No, I don’t see a problem there. If homosexuality is a trait that makes them leave less offspring, it would contribute to make them biologically less fit, to the extent to which it’s a heritable trait. So?

  23. Mung: Mung
    December 26, 2017 at 6:38 pm
    Ignored

    But what is fitness and how can one tell when a trait enhances fitness, or more to the point, when one organism is fitter than another? Opponents of the theory of natural selection have long claimed that the theory is so treated by its proponents as to define fitness in terms of rates of reproduction, thus condemning the principle of the survival of the fittest to triviality: the claim that those organisms with higher rates of reproduction leave more offspring is an empty, unfalsifiable tautology bereft of explanatory power. In the century and a half since the publication of On the Origin of Species biologists have all too often reinforced this objection by actually so defining fitness. For example, C.H. Waddington writes, in Towards a Theoretical Biology (1968, 19), that the fittest individuals are those that are “most effective in leaving gametes to the next generation.” It appears therefore that evolutionary theory requires a definition of fitness that will protect it from the charges of tautology, triviality, unfalsifiabilty, and consequent explanatory infirmity. If no such definition is in fact forthcoming, then what is required by the theory’s adherents is an alternative account of its structure and content or its role in the research program of biology.

    https://plato.stanford.edu/entries/fitness/

    Whoa Mung! If you are going to destroy Rummy and Allan’s argument so forcefully, you should at least have to type a couple of words of your own. It makes it seem too easy. At least an emoji?

  24. Mung: Rumraket: Fitness is the measure of reproductive success,

    Fitness (reproductive success) is the measure of reproductive success.

  25. phoodoo:
    J-Mac,

    The trait of lucky never gets measured by evolutionists.So they pretend it doesn’t matter.

    … unless we count the work, from 1922 onwards, of Sewall Wright, R. A. Fisher, J.B.S. Haldane, Andrey Kolmogorov, Motoo Kimura, Richard Lewontin, Geoffrey Watterson, Warren Ewens, Sam Karlin, William Feller, and many others. By now, at least 1,000 papers, on genetic drift.

    But don’t worry, phoodoo dismisses these with the wave of a hand.

  26. Joe Felsenstein: … unless we count the work, from 1922 onwards, of Sewall Wright, R. A. Fisher, J.B.S. Haldane, Andrey Kolmogorov, Motoo Kimura, Richard Lewontin, Geoffrey Watterson, Warren Ewens, Sam Karlin, William Feller, and many others.By now, at least 1,000 papers, on genetic drift.

    But don’t worry, phoodoo dismisses these with the wave of a hand.

    How did they decide when it was luck and when it wasn’t? What’s the crtiteria for luck?

  27. phoodoo: How did they decide when it was luck and when it wasn’t?What’s the crtiteria for luck?

    They modeled the deaths of individuals between birth and reaching reproductive age, assuming that survival was proportional to the genotype’s viability (part of its fitness) but that other than that, death fell on most individuals at random, with just enough surviving to replace the parent generation. That’s roughly what Wolf-Ekkehard Lönnig and the authors he quoted did.

    Of course all sorts of odd things could cause the deaths (predation, running out of food, being run over by charging rhinos, lightning bolts, etc.) but they didn’t have to specify what caused each death as long as those deaths were not dependent on the genotypes. Just that enough of them occurred to get us to the right number of surviving adults.

    This is a model (from 1930 and 1932) called the Wright-Fisher model, and it is central to the large body of work that has been done on genetic drift.

  28. Joe Felsenstein: They modeled the deaths of individuals between birth and reaching reproductive age, assuming that survival was proportional to the genotype’s viability (part of its fitness) but that other than that, death fell on most individuals at random, with just enough surviving to replace the parent generation.That’s roughly what Wolf-Ekkehard Lönnig and the authors he quoted did.

    Of course all sorts of odd things could cause the deaths (predation, running out of food, being run over by charging rhinos, lightning bolts, etc.) but they didn’t have to specify what caused each death as long as those deaths were not dependent on the genotypes.Just that enough of them occurred to get us to the right number of surviving adults.

    This is a model (from 1930 and 1932) called the Wright-Fisher model, and it is central to the large body of work that has been done on genetic drift.

    I can’t quite understand what you are trying to say.

    First, they modeled or they observed? It was reality or they imagined it?

    They modeled the deaths of individuals between birth and reaching reproductive age, assuming that survival was proportional to the genotype’s viability

    What does this mean? How do we know the genotypes viability?

    Furthermore, why should simply reaching reproductive age matter, if they never actually reproduce? Lots of people make it to reproductive age, but either can’t or don’t reproduce. Is this luck?

  29. phoodoo: I can’t quite understand what you are trying to say.

    First, they modeled or they observed? It was reality or they imagined it?

    They modeled the deaths of individuals between birth and reaching reproductive age, assuming that survival was proportional to the genotype’s viability

    What does this mean? How do we know the genotypes viability?

    Furthermore, why should simply reaching reproductive age matter, if they never actually reproduce? Lots of people make it to reproductive age, but either can’t or don’t reproduce. Is this luck?

    It’s a theoretical model, one on which you can do mathematics (and later it turned out to be one on which one could do computer simulation).

    The model was developed by R.A. Fisher in 1922, by J.B.S. Haldane in 1927, and by Sewall Wright in 1931. It is called the Wright-Fisher (or Fisher-Wright) model, and is one of the central models of theoretical population genetics.

    Later on, Sewall Wright and Warwick Kerr (in 1954) actually followed generation-by-generation changes of gene frequency in a laboratory population of fruit flies — and the changes were very close to those expected from the model.

    Modeling is important in all sorts of areas of science. For example, Brownian Motion was modeled by Albert Einstein in 1905 to show that atoms were real. Norbert Wiener did further mathematical description of that process. Or consider the cases of Galileo and of Newton in the 1600s. They were always considering what would happen to a perfectly spherical, uniform body, even though we know that no such perfect spheres exist in nature. Nevertheless the theory that they developed works pretty well. Similarly, in chemistry they imagine perfect gases.

    As to how they knew the viabilities and fertilities, they assumed values for them, and then used the mathematics (or computer simulation) to work out what the consequences would be.

    Does phoodoo think that we should not do this?

  30. Mung: Rumraket: No, I don’t think there are traits that universally (which I take to mean always) give a reproductive advantage.

    Wouldn’t leaving more offspring give a reproductive advantage?

    That’s like asking me “wouldn’t leaving more offspring give a reproductive advantage”? Yes. But that is not itself a trait, that is the effect of a trait. The question is what traits cause a reproductive advantage.

    Rumraket: Fitness is the measure of reproductive success, as in how many offspring is made over some period of time. So it’s a quantity of some measurable characteristic.

    Mung: So the more offspring the greater the reproductive success and the higher the fitness?

    Yes.

    Mung:Like the taller someone is the greater their height?

    Yes.

    Mung:The fittest are those that leave the greatest number of offspring?

    Yes.

    Mung:Like the people with the greatest height are the tallest?

    Yes.

    See, Mung is getting it. Now we just need phoodoo to catch up.

  31. Rumraket: The question is what traits cause a reproductive advantage.

    Every trait that exists.

    The ones that cause a reproductive disadvantage are the ones that don’t exist.

    That’s the problem with fitness.

  32. phoodoo: Things with the greatest reproductive success have the greatest reproductive success.

    In the context of the immediate environment. Remember the Niche! The niche is not random.

  33. phoodoo: Every trait that exists.

    The ones that cause a reproductive disadvantage are the ones that don’t exist.

    That’s the problem with fitness.

    You understand that multiple phenotypes with different levels of contribution to reproductive success can coexist in a population?

    To pick an example, Elephants are in danger of being hunted to extinction for their ivory tusks. There is a very direct correlation between the size of the tusks and the chance of being killed by poachers. So in elephant populations, there are quite dramatic differences in reproductive succcess between individuals with small and large tusks.

    So it is simply not correct that “the ones that cause a reproductive disadvantage are the ones that don’t exist”. Eventually less fit genotypes go extinct, but it’s not like it happens instantaneously. And new alleles are constantly arising which have better fitness, rendering the already existing allele the less fit one on a long-term trajectory to extinction.

  34. phoodoo:
    Rumraket,

    Things with the greatest reproductive success have the greatest reproductive success.

    I am pretty sure Mung always got that.

    I’m sure he did, but in this case he seems to have got more than that. It looks like Mung, unlike you, now understands that fitness refers to a real measurable quantity, in the same way that height does.

  35. Alan Fox: In the context of the immediate environment. Remember the Niche! The niche is not random.

    Things that have the greatest reproductive success, have the greatest reproductive success- and Sausage!

    Satisfied?

  36. phoodoo: Things that have the greatest reproductive success, have the greatest reproductive success- and Sausage!

    Satisfied?

    That’s funny. Just a bit ago phoodoo was acknowledging that fitness was like the playing skill of a poker player. That while it was circular to say that players of the highest skill won the most games, it was potentially a useful concept when investigating whether, say, height of the player was correlated with playing skill.

    But now phoodoo seems to be back to dismissing playing skill (and fitness) as a vacuous concept.

  37. Joe Felsenstein: Just a bit ago phoodoo was acknowledging that fitness was like the playing skill of a poker player.

    Wrong. I acknowledged that fitness was equivalent to calling the winning poker player the best player. I said nothing about playing skill.

  38. phoodoo: Wrong. I acknowledged that fitness was equivalent to calling the winning poker player the best player.

    Which would be entirely fine, since it doesn’t render the concept of a winning player incoherent.

    What contributes to winning or losing poker games can be analyzed, and so can it be what contributes to higher and lower reproductive success.

  39. Rumraket: What contributes to winning or losing poker games can be analyzed,

    Do you think the ability to curl one’s tongue is a positive or a negative factor for who will win at poker? Can we measure it and draw a conclusion?

    Like we just count the total number of poker winners and losers in a large tournament, and then count how many can roll their tongue, then we can know if its a beneficial or detrimental factor.

  40. Mung: Ignored
    Creationists finally disprove evolution?

    Speaking as a creationist yourself, do you actually think that or are you “just asking the question”?

  41. phoodoo: I said nothing about playing skill.

    Do poker players with higher skill levels win more or less often then those with lower skill levels?

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