Tautology and Natural Selection

There are any number of ways to do it, that would be one of them, and it would let you measure all of the individuals of that generation that had survived to mating age, but exclude older individuals from previous generations.Alternatively, and most easily, as Mammuthus has pointed out you simply do what you can of the entire population. Obviously you have to tailor your approach to what you are studying, large sea mammals are going to be a very different problem than an insect species with a very limited breeding period and lifespan.Really you are choosing an arbitrary method which best fits your particular study, any reasonable sampling strategy shouldn't affect your results too much, especially if you can repeat them to even out any oddities.

But you could only do that for females since you won't
necessarily know which males have bred?Or would you look at all individuals that have come to
mating age?

As I pointed out what would be appropriate would vary, I don't see what advantage there is in trying to pinpoint where I personally would measure an indeterminate population of things. In my original suggestion I meant all the animals which had reached mating age.Given a population observed closely enough there is no reason why you couldn't tell which males had mated, and if you had enough information you could even tell which male was successfull out of several which mated with one female, obviously this would be an awful lot of analysis just for that though.

The reason I asked was to see whether or not I agree
with your definition of 'fitness'.The way you have suggested measuring it agrees with the way
I view fitness -- which is what I thought.By looking at which 'trait sets' have survived to maturity
you are assessing the reproductive fitness of those 'trait
sets' from the previous generation.If you were only looking at which first-timers have bred
you would be looking at reproductive output only.I think the former is a means of assessing fitness, and it
combines reproductive output and survival -- which makes
me happy.

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Hi Justin..sounds like a nasty injury...I busted up my hand about a year and a half ago and it was really miserable working on the computer.

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Yeah, it's pretty pathetic. I'm forced to type with my nose :-)....or my left hand.

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Natural selection is only a part of the theory of evolution..and the theory of evolution is not that survivors survive. However, it is not that survivors survive that is of interest to fitness primarly. It is that traits conferring benefits be it food gathering, more accurate transcription, etc. tend to increase in the population and some case become fixed in the population. This is much different than saying survivors survive.

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Yeah, I agree. I wasn't very coherent. I'm referring to the phrase "Survival of the Fittest". I forget, you may of answered this already. Do you think the phrase is (or can be with some interpolation)an accurate description of NS and if so how would you interpret it to make it more accurate.

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Lot's of organisms of different potential fitness are born in each generation..in each generation some will reproduce more than others and will have a higher representation in the next generation i.e. higher fitness.

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It doesn't seem like reproductive success should be the definition of fitness. Say an asteroid hits the earth and incinerates the surrounding animals, is it fair to say they were less fit? Shouldn't it be that on average if an animal is more adapted for reproductive success in a certain environment it will have reproductive success? I understand genetic drift has a major role in evolution, but for this I'm talking about a specific selection process...industrial melanism possibly.

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As this is genetically/epigenetically based, alleles will change in frequency over time (evolution) due to some alleles conferrring an advantage on their host. But you can't leave out drift either..some traits/alleles become fixed in populations without conferring a benefit i.e. they are not selected for...they become fixed due to genetic drift.

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Yeah, I agree. I'm referring specifically to NS though, not evolution is general.

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Why "designed"? As I have pointed out in other examples, there can be situations that are ultimately destructive to the host or its reproductive capacity but propagate anyway because of some other advantage....what is the "design" difference in a family that has 14 children versus a family that has 1 child. The family with 14 kids has a much higher fitness...what is "designed" for reproduction in that family that is not present in the family with 1?

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Was the differential reproductive success caused by inheritable traits? If not then I wouldn't say they are more fit, just they had more offspring in a generation than another.I just can't tear myself away from design. Why not design? Design doesn't imply 100% efficiency. In NS, it just has to be better at reproductive success than another design in an inheritable way. It can still have sub-optimal qualities about it as in your Apert syndrome example. It also depends on what level you are looking on. From the sperm cell's perspective, it is becoming better at reproductive success than other sperm cells, though this may be horribly disadvantagous to the organism as a whole.JustinC

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Yeah, it's pretty pathetic. I'm forced to type with my nose :-)....or my left hand.

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As a right hander..I rather type with my nose than left hand

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It doesn't seem like reproductive success should be the definition of fitness. Say an asteroid hits the earth and incinerates the surrounding animals, is it fair to say they were less fit? Shouldn't it be that on average if an animal is more adapted for reproductive success in a certain environment it will have reproductive success? I understand genetic drift has a major role in evolution, but for this I'm talking about a specific selection process...industrial melanism possibly.

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The incinerated animals were less fit..they contributed nothing to the next generation. However, in that case, you know exactly what the source of the reproductive differential was unlike the more subtle effects of competition.

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Was the differential reproductive success caused by inheritable traits? If not then I wouldn't say they are more fit, just they had more offspring in a generation than another.

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If they leave behind more offspring they are more fit i.e. they produced more offspring. If it is not heritable the trait will not be passed on and the next generation will not have this advantage and thus will not evolve....as a dumb example, I can't pass on a penile implant but it could potentially allow me to produce more offspring and thus increase my relative fitness.

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I just can't tear myself away from design. Why not design? Design doesn't imply 100% efficiency.

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...but design does imply purpose and pre-adapatation.

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In NS, it just has to be better at reproductive success than another design in an inheritable way. It can still have sub-optimal qualities about it as in your Apert syndrome example. It also depends on what level you are looking on. From the sperm cell's perspective, it is becoming better at reproductive success than other sperm cells, though this may be horribly disadvantagous to the organism as a whole.

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I think the problem here is that within a species or population even there will be no way to say what the design is. Some individuals may benefit from something while others from something else thus they are not coalescing on any one "design". Arctic char for example have morphotypes that are enormous and some that are small that live in the same population and occupy a slightly different niche...however, they interbreed as their genetics show no differentiation between types...what is the "design" of char? I prefer the concept of local optima or adaptive peaks. You have many possible solutions to a particular challenge and whichever works slightly better than the others becomes fixed or frequent. Mutations constantly occur that can move the group up or down the peak or even to a new and better one (or a worse one). The process is thus random i.e. mutation driven with each generation re-starting the competition to increase its representation in the next generation...this also allows for genetic drift and allows for catastrophic accidents which if not causing extinction can start the population at a completely different area in the fitness landscape.cheers,
M

Sorry for the lateness, I just got back from an Alaskan vacation.

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The incinerated animals were less fit..they contributed nothing to the next generation. However, in that case, you know exactly what the source of the reproductive differential was unlike the more subtle effects of competition.

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What is the point of having that definition of fitness if it is merely defined by post hoc analysis? Aren't you just saying that some animals survive and some don't? How does that factor into natural selection? Aren't we looking for why on average some animals survive due to traits they possess? (Sorry for all the questions)

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If they leave behind more offspring they are more fit i.e. they produced more offspring. If it is not heritable the trait will not be passed on and the next generation will not have this advantage and thus will not evolve....as a dumb example, I can't pass on a penile implant but it could potentially allow me to produce more offspring and thus increase my relative fitness.

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So if they leave behind more offspring they leave behind more offspring? In natural selection doesn't the trait have to be heritable(genetically or culturally) in order for an animal to be considered fit because of it?

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but design does imply purpose and pre-adapatation

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Maybe purpose or function, I don't know about pre-adaptation. Can you expound a bit?

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I think the problem here is that within a species or population even there will be no way to say what the design is. Some individuals may benefit from something while others from something else thus they are not coalescing on any one "design". Arctic char for example have morphotypes that are enormous and some that are small that live in the same population and occupy a slightly different niche...however, they interbreed as their genetics show no differentiation between types...what is the "design" of char? I prefer the concept of local optima or adaptive peaks. You have many possible solutions to a particular challenge and whichever works slightly better than the others becomes fixed or frequent. Mutations constantly occur that can move the group up or down the peak or even to a new and better one (or a worse one). The process is thus random i.e. mutation driven with each generation re-starting the competition to increase its representation in the next generation...this also allows for genetic drift and allows for catastrophic accidents which if not causing extinction can start the population at a completely different area in the fitness landscape

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I'm not sure you can generalize about the design of char, I do think you can theoretically look at the individual and determine its chances of reproductive success in a certain environment.Why would a certain trait be better? What standard do you use for 'better'....better designed for reproductive success perhaps ;-)[edit: non homosexual wink, not that there's anything wrong with that]Species may be able to move to a worse area on an adaptive landscape, but not in a selection event...right?JustinC[This message has been edited by JustinCy, 08-20-2003]

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Sorry for the lateness, I just got back from an Alaskan vacation.

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Lucky lucky ...see any interesting animals?

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What is the point of having that definition of fitness if it is merely defined by post hoc analysis? Aren't you just saying that some animals survive and some don't? How does that factor into natural selection? Aren't we looking for why on average some animals survive due to traits they possess? (Sorry for all the questions)

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The observation is not that some animals survive and some do not...some variants be it morphological or genetic occur at higher frequency than others. The why is a different issue. You can make the observation without knowing what the underlying reason for the differential is...and it is one of the main subjects of evolutionary study to find out why. Such an observation is post hoc because you are observing an event that has occurred i.e. you see which traits in the current generation. However, you can track variants through generations in both lab and natural studies (though in the field it is a real pain in the butt depending on the animal you study). This can go a long way to helping find out what the source of the differential success might be.

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So if they leave behind more offspring they leave behind more offspring? In natural selection doesn't the trait have to be heritable(genetically or culturally) in order for an animal to be considered fit because of it?

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What you say in your second sentence is true to an extent...however, by definition since you asked if on your way to work you are hit by a car and never have kids your fitness is zero...a population that is incinerated by a meteor has a fitness of zero. That is the measure of that population at that specific time. Non heritable circumstances can contribute to your fitness though you cannot pass the advantage on to your offspring. For example, one of the chimp males Jane Goodall studied (forgot which one he was) was a smaller weaker and older male who would normally never have reached the dominant position in the group that he did..but dumb luck had it that he got hold of oil drums (I believe...read this ages ago) which made a hell of a lot of noise and scared the other males...he thus became the dominant male with greater access to the females and probably sired more young as a result..thus his fitness was increased though he cannot pass the advantage on to his young.

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Maybe purpose or function, I don't know about pre-adaptation. Can you expound a bit?

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It means that mutations do not anticipate what the environment will do and then Lamarkian like the organism magically fits...the environment applies pressure to the natural variation in a given population and as a consequence some variants will be more successful than others...how is this design where you go into a sitation, determine what the solution should be, and then design something to fit intentionally?

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I'm not sure you can generalize about the design of char, I do think you can theoretically look at the individual and determine its chances of reproductive success in a certain environment.
Why would a certain trait be better? What standard do you use for 'better'....better designed for reproductive success perhaps ;-)[edit: non homosexual wink, not that there's anything wrong with that]

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If you want some surreal debates on homosexuaity check out the Faith and Belief forum and the Free for All My standard for better is that the trait when put in competition with other variants is able to achieve a higher representation in the population...the individual does not matter to me in such a case. If I can determine that a trait provides a competitive advantage to the organism on average...I can make predictions about the potential fitness of organisms bearing that trait...in the lab, I could then refine the analysis by altering the environment to see more precisely why the trait is advantageous.

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Species may be able to move to a worse area on an adaptive landscape, but not in a selection event...right?

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It is possible but it is difficult to move from one adaptive peak to another incrementally since selection will work against individuals that are going down the peak eliminating them before they can go up another higher peak....you usually need the population to fragment and rare alleles to get fixed by drift such that the population can proceed along another trajectory.welcome back.cheers,
M

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For example, one of the chimp males Jane Goodall studied (forgot which one he was) was a smaller weaker and older male who would normally never have reached the dominant position in the group that he did..but dumb luck had it that he got hold of oil drums (I believe...read this ages ago) which made a hell of a lot of noise and scared the other males...he thus became the dominant male with greater access to the females and probably sired more young as a result..thus his fitness was increased though he cannot pass the advantage on to his young

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This sounds like a clue to the origin of human (so-called )
intelligence to me....

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but design does imply purpose and pre-adapatation.

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Not necessarily ... depends on exactly what you mean by
'design'.'Intelligently led design' implies purpose (otherwise why
would the intelligence enact design).Non-intelligent design (by natural selection) operates as a
kind of 'function fitting' process where the function to be
fitted is related to suitability to the environment.