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Member (Idle past 4871 days) Posts: 624 From: Pittsburgh, PA, USA Joined: |
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Author | Topic: Fitness: Hueristic or Fundamental to Biology? | |||||||||||||||||||
Allopatrik Member (Idle past 6214 days) Posts: 59 Joined: |
quote: Sorry to introduce even moré terms here, but when you are discussing the reproductive behavior of the social insects, you are talking about eusociality, a kind of cooperation called kin altruism. To discuss it in an evolutionary context requires bringing in Hamilton’s concept of inclusive fitness. In short, a gene (or genotype) can increase its own fitness by influencing behavior that benefits copies of that gene in other organisms. That is, by behaving altruistically toward kin (which share more copies of genes in common than non-kin) an organism can still increase the fitness of the genes it carries, even if it does so at its own risk, or if it forgoes reproduction. A Edited by Allopatrik, : No reason given. Natural Selection is not Evolution-- R.A. Fisher
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Modulous Member Posts: 7801 From: Manchester, UK Joined: |
Hi there, thanks for the input.
In short, a gene (or genotype) can increase its own fitness by influencing behavior that benefits copies of that gene in other organisms. That is, by behaving altruistically toward kin (which share more copies of genes in common than non-kin) an organism can still increase the fitness of the genes it carries, even if it does so at its own risk, or if it forgoes reproduction. I don't know if you followed the related thread at all - but this idea was bandied around there too, and it is worthy of discussion. I was asked to define fitness in a way could explain the positive selection of these insects - and it was Hamilton's views I put forward. They were also alluded to earlier in this thread. And there is a good reason for it to come up - I believe Hamilton et al were right on the money when they tackled this issue.
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Allopatrik Member (Idle past 6214 days) Posts: 59 Joined: |
quote: Which thread was that? A Natural Selection is not Evolution-- R.A. Fisher
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Modulous Member Posts: 7801 From: Manchester, UK Joined: |
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Allopatrik Member (Idle past 6214 days) Posts: 59 Joined: |
Thanks. I haven't read the whole thing, but I think I come closer to agreeing with you than some others, regarding the gene/individual controversy. Frankly, I've always been a bit confused about arguments for the "individual" side, mainly because individuals don't transcend generations; gene sequences do. So it only makes sense-- for an evolutionary perspective to be able to span more than one generation, that is-- to take a gene-centered POV.
A Natural Selection is not Evolution-- R.A. Fisher
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Quetzal Member (Idle past 5899 days) Posts: 3228 Joined: |
Look folks, it appears you all are getting wrapped around the axle on what is essentially a very trivial point. Fitness is simply a metric that was developed by scientists (probably pop geneticists, since they're the ones mostly concerned with this kind of thing) in an attempt to put a quantitative measurement on what is an inherently qualitative comparison - the relative adaptiveness of a particular genotype in its current environment. As such, it is no more recursive than any other metric - say using a meter-stick to measure the length of a wall. In addition, as anyone who's had to develop a performance monitoring plan for a project can atttest, this is probably one of the most difficult excercises to accomplish. The worst argument I've had with my current contractor developed over establishing performance measures for our project: how do you measure the impact of a nature center on local attitudes and actions? The metrics have to be both realistic (i.e., attainable), and measureable. Don't ask me why people demand numbers for this kind of thing, but there it is. Fitness calculations are no different.
You can argue until the next ice age over whether or not the currently accepted metric is valid. Those who find it useful (I don't particularly - I don't deal with those kinds of questions) will continue to use it and/or seek for a better one. Those who don't find it useful will continue to argue against it.
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MartinV  Suspended Member (Idle past 5856 days) Posts: 502 From: Slovakia, Bratislava Joined: |
(Fitness of a genotype)= (Average Fecundity)X(Fitness of offspring's genotypes)
Using fecundity as parameter of fitness is very misleading one. I suppose it to be another striking darwinistic "invention". According such an idea genotyope of Leonardo da Vinci was less fit as genotype of Giacomo Dindi who had 15 children 10 of which survived and each of them have another 15 children. Also lions having just two offsprings have their genotype less fit as rats with 14 offsprings. Yet the lions sleeps 16 hours a day. If lions were sleeping less they would feed more progeny. Consequently they would be more "fit" in eyes of a Darwinian. Such measuring of fitness is very curious one indeed. It did not take into consideration the fact that there are qualitative differences between species, their structures, their complexity, hierarchy. No one medieval king would have given rat into coat-of-arms even if he had heard that rats are more fit as lions or eagles. Survival of progeny is only one parameter of "fitness" and I am afraid one of the unimportant. It is also important what "freedom" a species have, if it is occupied with forage all day or if it has also time for singing like song-birds etc... quality of life... --- No wonder there are under "Papilio Dardanus" 20.000 Google registerd items and under "Biston betularia" 40.000. Darwinists like to study and discuss more black peppered moth as colorfull and polymorphyc Mocker swallowtail. They suppose to observe on this uninteresting moth "average fecundity".
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JustinC Member (Idle past 4871 days) Posts: 624 From: Pittsburgh, PA, USA Joined: |
quote:So can I mark you down for the "Fitness: Not Necessary for Understanding Natural Selection" column?
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Quetzal Member (Idle past 5899 days) Posts: 3228 Joined: |
So can I mark you down for the "Fitness: Not Necessary for Understanding Natural Selection" column? "Have you stopped beating your wife yet?" It is not "necessary", but it can be useful for understanding some questions under the rubric of natural selection. The current definition of fitness refers to a metric measuring the outcome of NS. The unit of time used is one generation. Any other questions?
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JustinC Member (Idle past 4871 days) Posts: 624 From: Pittsburgh, PA, USA Joined: |
quote:So is this purely a semantic quibble i'm starting? I understand that the tendency for an allele/trait to increase/decrease in frequency at a certain rate is an essential part of understanding NS, and if that is fitness then I see nothing wrong with using the term for convenience (as stating, "tendency for.." would get a bit tedioius). As I asked RAZD, are there two equivalent ways to describe natural selection. 1.)Alleles have different tendencies to increase or decrease in frequency per generation (or whatever time frame one uses) due to heritable traits and 2.) Alleles have different fitnesses That is fine with me. Though one problem I have with fitness is that it seems inextricably intertwined with "survival of the fittest" in most of the populace's mind, and I don't think that phrase is accurate at all wrt to explaining natural selection. This is a different concern, though, than my OP's.
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Chiroptera Inactive Member |
This thread really doesn't seem to be going any where. Why don't you go to your university's library and check out a book on population genetics? Read up on what professionals say about fitness, work out some of the homework problems, and see if that answers your questions.
Actually, if their god makes better pancakes, I'm totally switching sides. -- Charley the Australopithecine
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JustinC Member (Idle past 4871 days) Posts: 624 From: Pittsburgh, PA, USA Joined: |
quote:Come now, the question wasn't that loaded quote:'Can be useful but not necessary'- agreed quote:If fitness is just a defined metric then I'd say its just a hueristic device designed to measure something more fundamental, i.e., adaptiveness.
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Modulous Member Posts: 7801 From: Manchester, UK Joined: |
Also lions having just two offsprings have their genotype less fit as rats with 14 offsprings. Yet the lions sleeps 16 hours a day. If lions were sleeping less they would feed more progeny. Consequently they would be more "fit" in eyes of a Darwinian. Rats are small omnivorous scavengers that thrive alongside man, by eating his scraps. They can afford to have fourteen kids, because there is plenty of food to feed them. Lions are large carnivorous hunters, with scavenging on the side. If a lioness was carrying a litter of fourteen, she'd be much much much larger (she and her cubs are bigger than rats, so her surface area would go through the roof). Rats gestate for three weeks, and the rats become completely self sufficient after a very short period of time. Lions have pushed the limits of childbirth to their max. They only gestate for 108 days or so, their cubs are not full sighted and are reliant on their parents for up to two years (by which time, rat pups have possibly had a couple of litters of their own!). Any lioness that pushed the limits any more (increasing litter size, reducing gestation etc) would probably be less fit than other lionesses, less cubs would survive (or the lioness wouldn't survive past childbirth) and so the genes to push the limits would be lost (they'd be selected out). As such, given their evolutionary background, lions are as fit as they can be now in their environment. If you have any doubt over which is more successful, the lion or the rat - you need help!
No one medieval king would have given rat into coat-of-arms even if he had heard that rats are more fit as lions or eagles. Lions are stronger and more ferocious than rats. Medieval kings had no concept of evolutionary fitness. Evolutionary fitness is irrelevant to medieval symbology/heraldry. Symbolic meaning is more relevant to heraldry. A springbok is fit for running away from lions. A lion is fit for killing springboks. It should be obvious which one a medieval autocrat (not just kinds, but any nobles) would want to be associated with. Eagles are fit for finding hard to find prey and swooping on them and destroying them. Rabbits are fit for running and hiding in dark holes.
Survival of progeny is only one parameter of "fitness" and I am afraid one of the unimportant. You seem to think that 'fitness' means 'healthiness' combined with 'strength' combined with 'freetime'. That is certainly one definition of fitness but the key to evolution is hereditary, and things only get inherited through progeny. The more progeny you have, the more you pass on. The more you pass on compared with other members of your population, the more evolutionary fit you are. Fit as in 'fit to task', as in 'gets the job done'.
It is also important what "freedom" a species have, if it is occupied with forage all day or if it has also time for singing like song-birds etc... quality of life... Once again, irrelevent to evolutionary fitness. How does 'free time' have an affect on natural selection? Sure - more efficient feeding can be selected for, because those that spend less time feeding spend more time replicating the genes for efficient feeding. But how quality of life and freedom come into it you don't explain.
No wonder there are under "Papilio Dardanus" 20.000 Google registerd items and under "Biston betularia" 40.000. Darwinists like to study and discuss more black peppered moth as colorfull and polymorphyc Mocker swallowtail. They suppose to observe on this uninteresting moth "average fecundity". The reason why the peppered moth has more discussion than a swallowtail should be readily apparent. The peppered moth is the easiest example of natural selection to describe to anyone - so it comes up a lot. It has absolutely nothing to do with the fecundity of peppered moths vs swallowtails.
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Modulous Member Posts: 7801 From: Manchester, UK Joined: |
Quetzal - you brought up fitness as some kind of acid test for genecentrism, now you are saying that it is a essentially an arbitrary metric. I'm sure I'm missing something here, what is it?
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Quetzal Member (Idle past 5899 days) Posts: 3228 Joined: |
Quetzal - you brought up fitness as some kind of acid test for genecentrism, now you are saying that it is a essentially an arbitrary metric. I'm sure I'm missing something here, what is it? I have no intention of re-hashing the gene/individual debate here. So two points only: 1. I never said - nor do I believe - that the fitness measure outlined here and in the previous thread is in any way "arbitrary". Or, at least, it is no more arbitrary than any other metric. Is a meter arbitrary? I suppose in a very trivial sense it might be so considered. After all, it is simply a standardized unit of distance whose length has been developed and adopted by concensus among those who need to measure such things. There have been other metrics of distance in the past - some of which are still in use today. I don't see "fitness" as being any different, although it is a bit fuzzier around the edges, and is still in the process of evolving. For those who need to measure such things, the concept is a practical one - just like a meter. 2. The use of fitness in the previous thread was not intended as some kind of "acid test" of genecentrism. It was, even if I didn't perhaps express myself as well as I could have, intended as an example of a type of question genecentrism doesn't appear to address well. Although you attempted to address the issue by postulating a different metric - number of times an allele replicates in a particular time frame (which is probably sufficient if what you're trying to measure is simply the relative fitness of a given allele, which undoubtedly has utility in some contexts) - I would still contend that this doesn't help us to understand higher-level outcomes such as genotype/phenotype contribution, etc, which is what fitness as defined is trying to do. Feel free to continue misrepresenting my position on this. Some day perhaps you'll explain why you've taken this approach to me on this subject.
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