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    Biological Costs
    By Gerhard Adam | June 13th 2013 08:15 PM | 24 comments | Print | E-mail | Track Comments
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    In several posts the question of biological costs is invariably mentioned in discussing evolution.  These costs are normally of the metabolic or fitness type.  Metabolic costs are associated with the existence of a particular trait and the energy necessary for the trait's existence, while fitness costs are those that have an impact on the organism's ability to survive and reproduce (1).

    In most instances, these concepts are taken from economic analogies, yet, like economics, the concept of cost is meaningless without a context.  The two defining elements that must be considered are value and affordability.

    In general economic terms we recognize that many items may have costs, but without assessing their value it is impossible to determine how to evaluate the cost of something.  Similarly, while something may have a high basic cost, this may be irrelevant if the item is readily affordable.  Therefore, it is quite difficult to arrive at any meaningful interpretation with which to assess something as vague as "efficiency".

    So it is in biology.  We must understand that the entire basis of life is that everything "costs" something.  The simplest organism "costs" more to exist than not to exist.  

    Therefore to assess these two main cost areas, let's consider that metabolic costs are incurred as a byproduct of having to acquire the energy to maintain a particular trait.  That a particular trait "costs" something is not in dispute, but the first question is whether such a trait has value and to what degree.  If a trait provides a useful quality, then it may have value, but this must be measured against the affordability aspect.  If it takes a tremendous amount of effort [energy] to sustain, then it becomes a delicately balanced objective which can quickly become a liability if conditions change.  Correspondingly if the energy requirements are readily met, then the value of such a trait becomes relatively easy to attain and maintain.

    Fitness costs also fall into this category, but they have an additional interpretative difficulty which includes assessing what the maximum fitness for a particular organism is.  Furthermore this presumes that the trait in question is highly heritable.  Since heritability represents the amount of variation in a population due to genetic influences, then the fundamental requirement to assess fitness costs requires that there be some variation in a population to begin with.  More importantly, this variation must be directly linked to genetics.  It isn't enough to simply argue that one animal may be more efficient operating on a reduced calorie diet, since even if it results in a fitness advantage to that animal, unless it is capable of being inherited by offspring and persists for future generations, such variations are simply minor oscillations in a species' existence.

    Using the common example of the peacock's tail, we invariably hear about the biological cost of such a structure, however, this is meaningless without establishing the actual difficulty presented to the peacock in maintaining it.  If resources are plentiful, then it isn't likely to be much of a "cost" factor, regardless of how much metabolic energy it takes.

    Similarly when considering fitness costs, the general assumption is that the tail presents a liability in dealing with predators, but again, for this to be a valid consideration one must be able to demonstrate that there is a distinct difference in survival rates between peacocks that possess such a tail versus those that don't.  

    Even further, if there is no demonstrable difference in the tails [or their implied liability] in a population of peacocks, then it cannot be argued that there is a heritability factor that is selectable.  In such creatures, should the tail prove to be a liability, then it may be that the species goes extinct, long before individuals can be selected for the absence of a tail.

    Therefore, fitness costs can only be considered when there are two traits offering different fitness criteria that may be selected for within a population.  As a result, one will tend to dominate as the conditions favoring its existence take hold.  If there is no variation, then the trait is not heritable, therefore it is not selectable, and there is nothing meaningful to be said about fitness costs.

    Similarly when considering metabolic "costs" it becomes convenient to think that efficiency is a significant factor, but we already have enough evidence that such efficiency is also a liability.  The simple reality is that too much resource translates into fat animals.  One point which is rarely considered is that some traits may serve as a regulatory mechanism to ensure proper caloric balance.  In other words, if resources are readily available, then we already know that a creature that is too indulgent becomes fat thereby incurring a survival risk.  However, it may make sense that certain phenotypic structures exist precisely to ensure that the creature's caloric requirements can be safely met, with the additional physical traits requiring just enough calories to ensure a better balance.  This might readily be an extension of epigenetic functions, where the abundance or availability of food can determine the size or development of particular traits.  This could be a simple regulatory mechanism to ensure that animals optimal physical size is balanced against resource availability. Fewer resources results in smaller animals, while greater resources results in larger animals.  This ensures that such creatures don't have to have elaborate metabolic controls to avoid obesity.  It is their size which helps approximate their optimal caloric state.  While this can also become a liability such traits provide a high degree of variability without any need for specific selection.

    Often metabolic costs are associated with the loss of traits [such as eyesight in cave-dwelling creatures] and rationalized as a quest for greater efficiency, as if natural selection was simply waiting for an opportunity to dump this trait because it was expensive.  However, to make such a claim one would have to demonstrate that there is an actual metabolic difference.  This is especially relevant if one considers the requirements for dietary changes that might accompany such a transition.  In addition, one has to consider whether the loss of a trait is actually a loss, versus simply a "reassignment" where such a loss is offset by utilizing the existing capabilities in other capacities.  

    In another reproductive scenario, many creatures simply rely on probability by producing a sufficiently large enough number of offspring, so that there is no direct relationship between the offspring and any particular survival trait.  Clearly larger numbers of offspring can be a selectable trait, but this does not provide a link to any trait to promote survivability in offspring.

    These are some of the interpretive risks associated with overly simplistic considerations regarding the issue of such "costs".

    We know that creatures have adapted to a variety of environmental conditions, therefore it is reasonable to conclude that there are no inherent "costs" associated with survival in those environments that translates into much significance for individual populations (2).  Some may do slightly better than others, but it isn't sufficient to have an effect unless there is a specific environmental pressure that is capable of acting on a highly heritable trait.

    Competition between species can certainly raise the stakes and is generally dependent on the rate of reproduction being a primary factor that can overwhelm more slowly reproducing species.  In this situation, one finds that the competition will either force one species into extinction or into another environmental niche.  In turn, this will drive other selection pressures.

    It is very difficult to assess these types of changes purely on the basis of our interpretation of "costs".  Clearly the more extreme the environment the more volatile the survival of individuals of any species. This helps illustrate the point that the more resource rich the environment is, the less impact any concept of "costs" has on a population.  The harsher the environment, then the more specialized each species becomes, focusing their "costs" on the specific niches they occupy.  Using our economic analogy further, if conditions change radically, then the species essentially loses its "investment" and goes "bankrupt" [extinct].  

    ======================
    (1)  The distinction between fitness versus metabolic costs is largely arbitrary, so there should be no special significance assigned to what they are called.  Instead it is just a convenient way of trying to distinguish different aspects of the organism's "energy budget".

    (2)  It is important to remember that traits develop because they are beneficial.  Therefore if "costs" were a significant factor in evolution, then one would have to question how such traits can arise in the first place.  Instead, it is much more likely that such traits develop precisely because they are already well within the "energy budget" of such an organism. 

    Comments

    Bonny Bonobo alias Brat
    the question of biological costs is invariably mentioned in discussing evolution.  These costs are normally of the metabolic or fitness type.  Metabolic costs are associated with the existence of a particular trait and the energy necessary for the trait's existence, while fitness costs are those that have an impact on the organism's ability to survive and reproduce ....The harsher the environment, then the more specialized each species becomes, focusing their "costs" on the specific niches they occupy.  Using our economic analogy further, if conditions change radically, then the species essentially loses its "investment" and goes "bankrupt" [extinct].
    Surely it doesn't go completely bankrupt and lose its fitness costs, isn't this when the species then cashs in on the fitness cost investment, even if the conditions have changed radically? 

    For example, I have haemochromatosis which was fitness cost beneficial for the Scots and people of Northern European descnt for many years, nowadays with iron rich diets and no need to fight and shed blood or give birth each year, the gene is a big disadvantage and a bad cost investment that kills millions prematurely, often without them knowing why. 

    If suddenly meat and iron rich food became very scarce and I was plunged into an apocalyptic society fighting for survival over the few available fruit and veggies, I would be at an advantage again. People with haemochromatosis can shed much more blood fighting and in childbirth and survive than people who don't have this genetic disorder, they can also extract much more iron from food in an iron depleted diet. So haemochromatosis is both a metabolic cost and a fitness cost that only becomes an advantage when the environment changes and others go bankrupt around them. 

    There must be thousands of now redundant genetic traits like this in our gene pool, that had metabolic and fitness advantages in the past and that are an unnecessary overhead and cost now but could be a useful fitness investments in the future. Especially when and if the environment reverts to past conditions from a previous time that positively selected for the gene back then. So how do these redundant and costly genes from the past fit into your metabolic and fitness genetic banking system's investments, costs and bankruptcies?
    My article about researchers identifying a potential blue green algae cause & L-Serine treatment for Lou Gehrig's ALS, MND, Parkinsons & Alzheimers is at http://www.science20.com/forums/medicine
    Gerhard Adam
    Sorry, but premature death is not a liability nor a fitness cost in biological terms.  If you survive long enough to reproduce and your offspring survive ... whatever happens afterwards isn't subject to selection.
    So haemochromatosis is both a metabolic cost and a fitness cost that only becomes an advantage when the environment changes and others go bankrupt around them.
    As I said in the article, everything has a cost.  It only matters if it affects your actual ability to reproduce in a material way.  If it doesn't then it isn't subject to selection and becomes irrelevant, regardless of what it "costs".

    If more extreme circumstances occurred and your fitness increased, then it would be advantageous, but since that isn't occurring and isn't likely to occur, then you will simply carry the trait and it will serve no purpose.
    So how do these redundant and costly genes from the past fit into your metabolic and fitness genetic banking system's investments, costs and bankruptcies?
    There is no quest for "efficiency".  So, if they do not impact your ability to reproduce and pass on heritable traits, then there is nothing to select out.  You've survived long enough.  As to how it fits?  You can consider it the same as walking around with a suit of armor or something else like that that could be considered protective but ultimately unnecessary.

    Yes, it takes energy and resources to support it, but if it doesn't affect you in a way that matters biologically, then it's not relevant.
    Mundus vult decipi
    Bonny Bonobo alias Brat
    There is a biological and evolutionary cost because people die younger, get cancer, cirrhosis, arthritis and diabetes from it and are not there to support their offspring. Its an investment from the past that has an ongoing fitness and metabolic cost at different points in evolution and time but it is also cash for the future when others go bankrupt if the environment changes or rather reverts. So does it therefore have the two defining elements that you say must be considered, which are value and affordability?

    What about the fact that there are many now useless genes like these still in the gene pool, how do they fit in with your biological, banking, cost system if they are giving value and affordability, I still don't get it? Don't worry, if I can't understand your next reply I will stop asking these questions here, as this is all a bit mind blowing to me and its definitely hurting my head :)
    My article about researchers identifying a potential blue green algae cause & L-Serine treatment for Lou Gehrig's ALS, MND, Parkinsons & Alzheimers is at http://www.science20.com/forums/medicine
    Gerhard Adam
    It seems that part of the problem is that you're assigning too much nuance to the system.  It cannot evaluate a trait, it is only based on whether the trait has a chance to be passed into future generations or not.  If not, then it will tend to disappear, if it can be passed on, then it will tend to persist in a population whether the individual possessing it likes it or not.
    There is a biological and evolutionary cost because people die younger, get cancer, cirrhosis, arthritis and diabetes from it and are not there to support their offspring.
    Unless their offspring survive in smaller numbers, then there is no fitness cost.  In other words, those with the trait are reproducing just as readily as those without it.  However, even if they weren't, unless there is specific competition for resources that would have a fitness impact on those with the trait, they can still persist in a population. 

    I thought of an analogy, although its not a very good one, it might help.  Suppose that a group of people were going to drive across the country in a variety of cars.  Some with high mileage per gallon of fuel [higher efficiency] and others with lower efficiency.  In our example, those with greater efficiency, the trip would cost less than in those without.

    Now suppose that this group left their beginning position and eventually arrived at their destination.  Perhaps some didn't make it.

    If we now consider that there is another group that is going, but the only information they can use to choose which vehicle to take is whether it arrived at its destination or not.  They cannot know anything about efficiency or anything.  For those vehicles that never made it, they are simply eliminated from the pool of choices.  Whereas all other vehicles that arrived, whether costly or not, could be chosen. 

    What we would find is that "cost" wouldn't matter, because as long as they arrived at their destination [our equivalent of fitness], then they would continue to appear as choices for the next group. 

    I don't know if that helps or is more confusing, but the point is that assessing value judgements and costs is not information that can be chosen.  The only criteria is whether you survived, reproduced, and whether your offspring survived and reproduced.  Beyond that the particular traits involved aren't particularly relevant. 
    Mundus vult decipi
    Bonny Bonobo alias Brat
    OK, that's a great analogy, I've got it now, I think :)
    My article about researchers identifying a potential blue green algae cause & L-Serine treatment for Lou Gehrig's ALS, MND, Parkinsons & Alzheimers is at http://www.science20.com/forums/medicine
    vongehr
    "and resources to support it, but if it doesn't affect you in a way that matters biologically, then it's not relevant."
    Yes, but how do you measure these ultimately but with the statistical "success" during natural selection, which is an accumulation of accidents large and small? In other words: much of your position comes down to what you accept to label "cost".
    vongehr
    If you want this to go against the picky females having to spend nine months cost theory about who makes the sandwiches and all that (you know my drift, I am sure): You are way out into the domain where such argumentation is always philosophy, and if philosophy is not seeing itself as philosophy, it is easily moralizing and all that. We make models, I can make you a numerical one if you like, but if I made it, I promise you, those nine months and the pretty peacock tail would be costly! And then you would blame me for making a biased model. ...
    Gerhard Adam
    We make models, I can make you a numerical one if you like, but if I made it, I promise you, those nine months and the pretty peacock tail would be costly! And then you would blame me for making a biased model. ...
    I don't have a problem with the models as long as we don't begin to presume that the model is the reality.  My concern is that while such models may show us how various traits are distributed, show correlations,  etc.  I find too many instances of where the models are being used to explain why they are distributed in such a fashion.  That's where the bias comes in.

    In the case of the peacock's tail, it has simply been assumed that it was the product of sexual selection, except actual observation doesn't find any indication that the female actually cares.  So we have the supposition of a costly trait being manifest for the express purpose of attracting females.  There are all kinds of stories about how males are risking their own fitness by such a trait, and that it must be sending some "signal" to the female about the males desirability.  Yet, in the final analysis, if the female doesn't actually find the tail relevant, then our story is just a story. 

    It is biased, because we chose to take a simple correlation and put our own value system on it.  That's the bias.

    It's no different than arguing that a bird giving out a warning call is behaving altruistically, because it is giving away it's position.  We are the ones presuming that this is a sacrifice and we are assigning human values to it, by presuming that it should act the way we might in the presence of a predator.

    Mundus vult decipi
    vongehr
    I don't have a problem with the models as long as we don't begin to presume that the model is the reality.
    But that is the point, namely that it is you who claims to know better about 'reality' than people making working models and calling certain parameters "cost", but what you present is no alternative, for example that traits are rather 'beneficial' (as if a 'benifit' parameter is not just a 'cost' with a minus sign in front). Your article again argues against 'cost' as a useful concept in evolutionary research, not about select overinterpretations of models. 'Costs' are ultimately more often than not reproducible negative effects on statistical outcome over the time span under consideration, NOT necessarily an amount of energy or resources or number of children during a single generation. But we discussed this before. ;-)
    Gerhard Adam
    But that is the point, namely that it is you who claims to know better about 'reality' than people making working models and calling certain parameters "cost", but what you present is no alternative, for example that traits are rather 'beneficial' (as if a 'benifit' parameter is not just a 'cost' with a minus sign in front).
    Actually my point is that concepts like "cost" or "benefit" are necessarily human value judgements.  We don't know anything of the sort, except that a particular trait exists.  If a species seems to do well with it, then we know that it isn't costly enough to impact fitness.  If a species doesn't do well, then perhaps we can identify something that points to where the liability is, but this is sketchy at best.

    For every species that has gone extinct, I'm sure we could point to something and claim that "this" was the primary factor involved in them going extinct, and yet it would still tell us nothing about why the trait developed in the first place.  All we might surmise is that, at some point, it appears to have become a liability.

    Yet, even then, it could be something completely different.
    'Costs' are ultimately more often than not reproducible negative effects on statistical outcome over the time span under consideration...
    Perhaps, but in the end, we don't need a value judgement of either costs or benefits.  It is straightforward enough to consider a mismatch between traits and the environment the organism is now in.   So unless a trait is heritable, then such cost/benefit assessments are moot.  In other words, a "choice" [something that can be favored] must already be present in the population.
    Mundus vult decipi
    vongehr
    Actually my point is that concepts like "cost" or "benefit" are necessarily human value judgements.
    Who else important but you does the '"human value judgement"? You argue against "cost" because people in other posts used that word to support evolution scenarios. Sometimes wrong models, like perhaps that for the peacock tail, are put forward. That does not make the large investment of pregnancy a theory to be rejected in favor of feminist literature studies. Those costs are at the basis of the evolution of rape - I have never seen an argument against this very well working model but politically motivated pseudoscience. You argued that women never make as many children as they physically could and thus gestation time cannot be a factor. Was I to interpret that as suggesting that all is fine if we call it "parameter c" instead of "cost"?
    Gerhard Adam
    No, but as you've seen in other posts.  When cost is assigned, it creates the impression that it is a singular, stand-alone definition.  It becomes to easy to miss the interconnections between all the factors that are actually responsible for success, so we begin to see pronouncements about the "cost" of x, or the "investment" of y.

    Whether this is ultimately just a terminology argument, or at least a call to be more stringent with the parameters and the meaning we derive from them, that may well be the case.

    I didn't say that gestation time isn't a factor, but when you hear "fitness cost" and the total fitness [maximum reproductive potential] hasn't even been established, much less demonstrated to ever occur, one can't help but wonder what the basis is for presuming there is a fitness cost.

    Mundus vult decipi
    Thor Russell
    I don't think your reasoning about costs is right either, but I'll try discussing it from a different angle.
    You argue that efficiency can be a liability, however as you later seem to concede efficient metabolism + epi-genetic (or genetic of course) ability not to store fat would be better than a single metabolic state as it would allow adaptation to a range of circumstances.
    So as you say, there could be a simple regulatory mechanism to ensure that animals optimal physical size is balanced against resource availability. Well when resources are scarce, that is impossible unless the animal is capable of entering a state with efficient metabolism and therefore has genes to do so. Now if we take the view that genes rather than being "selfish" or whatever instead represent a toolkit that an animal can use to adapt to different situations it is pretty obvious that genes for efficient metabolism will be in that toolkit as it will let the animal/population survive in times of resource scarcity. You can then ask whether the most efficient metabolism setting will be turned on all the time, with instructions not to make excess fat also turned on, or the most efficient metabolism only becoming available in times of food scarcity. Both could work.


    Thor Russell
    Gerhard Adam
    While I understand what you're saying, I don't see that it makes any difference.  The only time "costs" might be relevant is if one is comparing the variations of the same trait within a species.  That would render it selectable [assuming it was heritable]. 

    A trait under selection could certainly be assessed from the perspective of whether those possessing it can operate more flexibly under different environmental conditions.  Invariably it is the environment that will dictate those conditions though.

    Genes cannot be in that "toolkit" because they can't simply be turned on later if a particular trait proves to be a liability.  At best, there may be some epigenetic effects that can help, but unless these are heritable traits, they aren't relevant.  Animals cannot choose to express their traits.

    Once the essential development is done, it is committed.  There is no undoing it because conditions change.

    In fact, we already know that animals possess many kinds of traits to deal with such environmental variation.  That's the purpose of fat stores, for example.  There are many such traits that establish the priority of systems to be preserved, versus those that may be sacrificed during periods of hardship.  Freezing to death has a hierarchy of organ systems that must be preserved.  Just like the mammalian reflex when submerged in water.

    So, while perhaps fortuitous circumstances and a lucky combination of traits allows an animal to survive when others die ... that's fine.  Again, unless it's a heritable trait then it's irrelevant.  It's just dumb luck.  Just like an animal with superior genetics isn't exempt from getting struck by lightning.

    You're playing a bit fast and loose regarding the idea of efficiency being a liability.  My only point was that success is achieved by striking a reasonable balance.  The point about a regulatory mechanism, was simply to suggest that perhaps the availability of food during development could trigger a growth pattern that might, at least in part, be helpful in regulating such caloric input, so that instead of simply getting fatter, the animal could exploit getting bigger in the ready availability of food or be smaller when food is in short supply.  However, these are developmental and not regulatory once the animal is grown.
    Mundus vult decipi
    Thor Russell
    Well you seem to have a different understanding as to what epi-genetics capable of and how it works to me, but anyway back to the main point.
    "The only time "costs" might be relevant is if one is comparing the variations of the same trait within a species.  That would render it selectable [assuming it was heritable].  "
    Yes obviously, however there are always variations, and genetic differences in metabolism are inheritable. So I consider this to be very common, if not the default situation. 

    My prior position is that efficiency is an obvious trait to be selected for and genetically inherited. I don't know why this isn't yours also as it is with everyone else I have spoken to. Now we may not have the exact measurements that you require, but some things are obvious. There is no scientific evidence with a control that a company in which every person was required to spend 10 mins of every 30 running around in circles would do worse than one that wouldn't but it is obviously the case.

    I find your comments about fat stores quite bizarre. Fat stores will evolve, but the most efficient use of water and energy won't in camels, elephants cats etc? The most likely way for things to go would seem to be evolution towards the most efficient metabolism, (that is where efficiency doesn't have other costs such as lack of speed etc) then other techniques to ensure an animal did not get too fat in times of plenty. Even if such water and food stresses only affect 1% of generations I would still expect this. There would be selection pressure in times of stress, none without, so the efficient metabolism would stay once selected for. To argue effectively to me  against this you will need to do a lot more than just speculate on alternative mechanisms, but provide evidence to show that this seemingly obvious adaption is not happening. Pointing out that  "cost" is not as well defined as you would like is a long long way from doing that.
    Thor Russell
    Gerhard Adam
    Yes obviously, however there are always variations, and genetic differences in metabolism are inheritable.
    Based on what?  What differences are you alluding to?  You may consider it to be common, but you're suggesting that there is a sufficient genetic difference within a population to where selection can operate on metabolism.  I don't think you have any evidence for such a thing.
    My prior position is that efficiency is an obvious trait to be selected for and genetically inherited.
    Again, so what?  Such a trait would have long gone to fixation and therefore is irrelevant as a cost consideration.  Unless there is variation within a population, then it is pointless to talk about "costs".  They are the same for all members of the species.  Most beneficial traits will have gone to fixation in the population so that there is very low heritability.
    The most likely way for things to go would seem to be evolution towards the most efficient metabolism ...
    Wrong, now you're assigning a direction to evolution that doesn't exist.  The problem is exacerbated by your comparing across species.
    There would be selection pressure in times of stress, none without, so the efficient metabolism would stay once selected for.
    Perhaps, perhaps not.  That's precisely why many species simply go extinct.

    Regarding the size/calorie point, I'm not arguing that this is an alternative mechanism.  It is pure speculation on my part to even mention it as a possible regulatory mechanism.  However, there are no costs involved here.

    Unless you can give me an example of where "costs" would play a role, then they are largely nonsensical descriptions. 

    You're trying to advance some sort of "engineering" type argument that somehow evolution is striving for efficiency and therefore even minor variations are sufficient to improve an animal's fitness.  Sorry, but it just ain't so.  Unless you can demonstrate that there is sufficient variation of a trait and that it is heritable, then you've got nothing.  In which case, a trait under active selection could be assessed a "cost" or relative advantage when the population is being examined for the same traits.  However, that would also only follow within the same environment.  You can't simply assume that everything is under selection.   

    I don't know where you got that fat stores will evolve but metabolism won't.  I simply said that fat stores is already an existing adaptation to account for environmental variability.  I'm not sure you're understanding the point about heritability.  This is a mark of variation within a population that is accountable by genetics.  Some traits have higher heritability [such as size] while others have low or almost zero heritability [such as your having lungs].    Some may have extremely high heritability but be trivial [i.e. eye color].  So you can't presume that the majority of the traits are under selection. 

    As to your point about epigenetics, it isn't a mechanism that an organism can turn on or off.  It is a response to environmental conditions that allows adjustments outside of what the genes control.  Even then, it isn't clear on how heritable such adjustments are for the long-term.  In my view, such short term adjustments could exert a significant influence, but again, these are developmental, not occurring well after maturation.
    Mundus vult decipi
    Thor Russell
    Don't think there is much new here that I havn't already addressed. Not convinced at all, but I don't think there is any way I can make you reconsider things.
    Thor Russell
    Gerhard Adam
    You haven't described anything.  You keep insisting that there's some goal of efficiency, yet it should be clear that such objectives as make a difference in fitness will already have been attained by the organism in its environment.

    The minor variations that occur otherwise aren't realistic.  If circumstances are so harsh as to enable such small changes to be selectable, then it is unlikely that offspring will survive, or that pregnancy won't terminate prematurely. 

    So, there's no dispute that traits that are under selection will tend to become more distributed, ultimately becoming fixed within a population.

    However, what does this have to do with cost?  Except in the case where I indicated that you could use something like that to evaluate the variation in one trait over another within the same species dealing with the same environment, then what else is there?

    Also don't overlook the fact that many traits associated with energy extraction from food are outside the scope of evolution; in other words many are in natural selection's "blind spot".  These traits are never selected for, because they are addressed by the microbiota.  As a result, there is no genetic influence since the genome doesn't even recognize that a "problem" exists to be selected for.  For example, most animals can't digest cellulose, so there can be no natural selection to improve the ability to digest it, since that is handled by commensal bacteria.

    Perhaps if you could provide an example of what you mean where you believe cost provides you more or better information.  Then, perhaps you might consider how you would quantify that cost.

    Again, let me give you some examples of where cost is invoked to see what I'm saying.  One obvious one is the peacock's tail, but there is no evidence to suggest that this is a trait that varies in the population producing difference results among peacocks.  As a result, how can one assess a cost when they all possess it?  More importantly, when there is no evidence to suggest that it detrimentally affects the peacock, the argument becomes even more tenuous.

    Another point often made is the biological costs of a human female's pregnancy versus the male's commitment.  As a result, the erroneous conclusion is reached that males are looking to impregnate the largest number of females while females are choosier.  It's complete rubbish, but it sounds plausible because most people considering it confuse sex with reproduction.  Yet, there are no fundamental biological costs associated with any of these things, because they are representative across the entire population and there is no appreciable variation in those traits across human beings. 

    Of course, one could raise the issue of a fitness cost when someone doesn't reproduce and that can certainly play a role in specifically defined circumstances, but it is the opposite of what is alleged in the previous paragraph.  In addition, among humans it becomes harder to assert genetic influences as opposed to behavioral and cultural effects.
    Mundus vult decipi
    Thor Russell
    Sigh, what Sascha said about pregnancy seems not to have got through either. 
    Thor Russell
    Gerhard Adam
    All you have to do is find an example.  It's all well and good to discuss the value in terms of statistics, yet if all the members of the species have the same traits, then how does statistics help you?

    You've mentioned the efficiency argument several times yet have no example of such efficiency, since that isn't actually a trait.  That's much too vague a concept, so it should be easy for you to come up with something that would render a species metabolism more "efficient" and then demonstrate how this would be selected for [even if it's a tiny portion of the population].  After all, that's what natural selection is all about. 

    It's easy enough to illustrate when using microbes where there is an opportunity to express certain traits over others.  In those cases, an argument can be made that traits like antibiotic resistance are more "costly" for an organism to maintain over those that don't have it, as a result it isn't a trait that is likely to go to fixation overall.

    Even the point about pregnancy explains nothing.  All human females take 9 months for development.  So, if you're going to assign a "cost", then what is it measured against?  As for an investment of time, compared to what?  Since the majority of females hardly maximize the number of potential offspring anyway, then where is the cost?  As can readily be seen by the immense size of the human population, there is no fitness cost involved for the species. 

    So, give me an example of what you're envisioning or are you merely arguing about an abstraction?
    Mundus vult decipi
    Thor Russell
    But you just gave a concrete example yourself relating to bacteria. If the principle applies to them, then it won't be the case that it doesn't apply anywhere else in the animal kingdom. Finding a second example isn't anything special. Making up other possible explanations ad-hoc for different circumstances as to why cost doesn't apply doesn't cut it, you would have to give some very good reason why it just couldn't possibly apply to anything else but bacteria. Its like accepting bacteria are made of atoms but claiming camels and every other animal isn't. 
    Thor Russell
    Gerhard Adam
    That's not the same thing.  Antibiotic resistance is conferred by plasmids, which are not part of the standard DNA, but are independently capable of replication..  The principles are NOT the same. 
    Its like accepting bacteria are made of atoms but claiming camels and every other animal isn't.
    Oh stop it.  You know that bacteria belong to a group that doesn't even have a nucleus, so I'm not sure what point you're trying to make.  I can certainly say they are NOT the same thing.  I'm equally sure that you have heard about horizontal gene transfer, and recognize that such an ability makes the entire premise of natural selection just a bit more dicey when applied to this situation.  In other words, such organisms are capable of picking up traits without the need to have them "evolve" within a group. 

    However, you will recall that I specifically mentioned that cost may be applicable when there is a variation in a given population for the same trait.  You seem to want to apply it to everything.

    I suspect you don't actually have an example.  It seems that no one is shy about invoking cost for virtually every evolutionary example they point to, but when I ask for an example, there isn't one?  Everything from the original "selfish gene" concepts to inclusive fitness are rife with talk of "costs".  So, I'm asking ... give me an example of where there is a demonstrable use for the concept and not merely an anthropomorphic value assignment.

    My point is simple.  Don't simply indicate a trait and say ... it "costs" something.  As I said in the beginning.  Everything "costs" something, so the question is whether such an assessment adds any meaning to the discussion.  Is there something to compare it to that "costs" less?  Is it a trait that is actually under selection?  What is the basis for assuming that the cost is relevant to anything?
    Mundus vult decipi
    Bonny Bonobo alias Brat
    My point is simple.  Don't simply indicate a trait and say ... it "costs" something.  As I said in the beginning.  Everything "costs" something, so the question is whether such an assessment adds any meaning to the discussion.  Is there something to compare it to that "costs" less?  Is it a trait that is actually under selection?  What is the basis for assuming that the cost is relevant to anything?
    I think you are making a very important point here, it took me a while to get it because everyone is always talking about evolution and costs, when it really is the wrong analogy, but what is the right analogy? Cars racing across the desert doesn't cover all of the many aspects of genetic evolution and survival of the 'fittest' does it?
    My article about researchers identifying a potential blue green algae cause & L-Serine treatment for Lou Gehrig's ALS, MND, Parkinsons & Alzheimers is at http://www.science20.com/forums/medicine
    Gerhard Adam
    I don't know that there is a right analogy beyond asking if it works. 

    Certainly if we are comparing variations of a particular trait within the same species in the same environment, then we might argue that the trait is under selection and that one manifestation over another appears to be more advantageous.

    I suppose examining "cost" might be one such thing, but then we also have to consider that perhaps there is no difference in any measurable "cost", but it's just that the trait is manifesting itself differently.

    What if a new trait is metabolically more "expensive"?  We know this had to occur with some regularity, otherwise life would just be one-celled organisms.

    So, my question, is that if all the "higher animals" evolved the traits they have, despite "costing" more to produce, then what can we derive from claiming something costs something, except in the simple case of a direct comparison.

    In my view though, the direct comparison can already be accommodated by simply noting whether a trait is advantageous or not.  I don't see that trying to translate into some kind of "cost" adds any meaning and it certainly confuses things if it "costs" more.

    I guess, the concept of "costs" carries a connotation.  So, are we to surmise that evolution's "goal" is to reduce costs?  exploit them for efficiency?   As I said, we already know that evolution isn't particularly conscientious regarding "costs", so that seems to be a weak argument (1).  I realize that evolution has no "goal", but even if we were to argue that it simply appears like a goal and is useful for statistical modeling ... my question is ... show me a use for it, beyond simply saying that x is better than y.

    (1)  Just consider all those animals that have evolved the means of reproduction by creating millions of eggs from which millions will die in the hopes that a few survive.  How does one quantify this in terms of "costs" or "efficiency", beyond simply saying ... it works.
    Mundus vult decipi