Monday, December 25, 2006
Friday, December 15, 2006
Arms Races and Manipulation, Part 2
If evolution can be viewed as a sort of “arms race,” one often assumes that if an animal manipulates another, the victim will, via random mutation and natural selection, develop counterstrategies to escalate the arms race rather than capitulate. However, Dawkins shows several examples of how this is not necessarily so.
For example, the foster parents of the cuckoo continue to feed their changeling “child” despite the obvious absurdity of a tiny Garden Warbler straining to feed a cuckoo several times its size. Why doesn’t the Warbler recognize this incongruity, when apparently some host parents of cuckoos can indeed recognize flaws in the cuckoo’s egg mimicry? Why does the host parent recognize the parasitic egg but not the more obvious parasitic changeling fledgling bird?
Dawkins’s answer is that natural selection does not act uniformly at all times in any animal’s life. Selective pressure may be stronger at some points in the life cycle than others, or natural selection may have no effect on evolution even if a beneficial mutation were to arise. As an example of the first case, Dawkins points out that recognition of a cuckoo egg in one’s nest gives the host parent the chance to gain an entire breeding cycle, whereas recognition of the incongruous fledgling would buy at most a few days, and that probably too late for the host parent to breed again. Moreover, the actions of the cuckoo, its exaggeratedly gaping mouth, its size, could indeed act as a “drug” on the foster parent, no less than the song of a male nightingale acts as a drug on the female reproductive cycle (and, incidentally, upon the poet’s imagination).
However, a fascinating example of how an animal’s victimhood can be perpetuated is exemplified by slave-making ants. Some species of ants spend a great deal of their time raiding the nests of others and carrying off the larvae and pupae, which subsequently hatch in the new nest and begin to labor for their “masters.” This is a disturbing and puzzling development. Why don’t the enslaved worker ant colonies develop a resistance to the strange environment, filled with others not their genetic sisters—for example, by evolving a genetic disposition to cease work (to go on “strike”) when in a strange queen’s lair?
Remember that worker ants do not reproduce. Therefore, any beneficial mutation that arose in the enslaved ants would not be passed on to the rest of their home nest. At any rate, the raids do not happen often enough to destroy the victims utterly, who are under little selective pressure to evolve complex adaptive countermeasures against slave-making behavior on the part of others that, while aggressive, does not threaten the existence of the nest. An uneven battle ensues, in which the slave-making ants can be said to win the war.
Dawkins indicates that this situation is not unlike the phenomenon of a certain species of hybrid frog, which has one set of chromosomes that is jettisoned in meiosis and one set that is passed on to its offspring. The set of chromosomes (dead-end replicators) that is jettisoned in the hybrid frog is perpetuated in the pure bred species that carries two sets of these chromosomes (which become germ-line, not dead-end, replicators in this species). Thus, any beneficial mutation in the dead-end replicator line will be passed on in the pure bred species that contains two sets of these chromosomes (because in this species these sets of chromosomes are not dead-end replicators), but will not be passed on in the hybrid species. The situation of the enslaved ants is like that of the hybrid species of frog: their genes have phenotypic effects and can even be selected, but they will not be transmitted in the hybrid species, and thus are irrelevant to that particular species' evolution.
For example, the foster parents of the cuckoo continue to feed their changeling “child” despite the obvious absurdity of a tiny Garden Warbler straining to feed a cuckoo several times its size. Why doesn’t the Warbler recognize this incongruity, when apparently some host parents of cuckoos can indeed recognize flaws in the cuckoo’s egg mimicry? Why does the host parent recognize the parasitic egg but not the more obvious parasitic changeling fledgling bird?
Dawkins’s answer is that natural selection does not act uniformly at all times in any animal’s life. Selective pressure may be stronger at some points in the life cycle than others, or natural selection may have no effect on evolution even if a beneficial mutation were to arise. As an example of the first case, Dawkins points out that recognition of a cuckoo egg in one’s nest gives the host parent the chance to gain an entire breeding cycle, whereas recognition of the incongruous fledgling would buy at most a few days, and that probably too late for the host parent to breed again. Moreover, the actions of the cuckoo, its exaggeratedly gaping mouth, its size, could indeed act as a “drug” on the foster parent, no less than the song of a male nightingale acts as a drug on the female reproductive cycle (and, incidentally, upon the poet’s imagination).
However, a fascinating example of how an animal’s victimhood can be perpetuated is exemplified by slave-making ants. Some species of ants spend a great deal of their time raiding the nests of others and carrying off the larvae and pupae, which subsequently hatch in the new nest and begin to labor for their “masters.” This is a disturbing and puzzling development. Why don’t the enslaved worker ant colonies develop a resistance to the strange environment, filled with others not their genetic sisters—for example, by evolving a genetic disposition to cease work (to go on “strike”) when in a strange queen’s lair?
Remember that worker ants do not reproduce. Therefore, any beneficial mutation that arose in the enslaved ants would not be passed on to the rest of their home nest. At any rate, the raids do not happen often enough to destroy the victims utterly, who are under little selective pressure to evolve complex adaptive countermeasures against slave-making behavior on the part of others that, while aggressive, does not threaten the existence of the nest. An uneven battle ensues, in which the slave-making ants can be said to win the war.
Dawkins indicates that this situation is not unlike the phenomenon of a certain species of hybrid frog, which has one set of chromosomes that is jettisoned in meiosis and one set that is passed on to its offspring. The set of chromosomes (dead-end replicators) that is jettisoned in the hybrid frog is perpetuated in the pure bred species that carries two sets of these chromosomes (which become germ-line, not dead-end, replicators in this species). Thus, any beneficial mutation in the dead-end replicator line will be passed on in the pure bred species that contains two sets of these chromosomes (because in this species these sets of chromosomes are not dead-end replicators), but will not be passed on in the hybrid species. The situation of the enslaved ants is like that of the hybrid species of frog: their genes have phenotypic effects and can even be selected, but they will not be transmitted in the hybrid species, and thus are irrelevant to that particular species' evolution.
Arms Races and Manipulation, Part 1
Dawkins' purpose in his book The Extended Phenotype is to dash the concept that the individual is the unit of selection, that is, the idea that, among other things, individuals act in a manner as to increase copies of itself. (Ann Coulter, for example, in her crap book Godless asks why, if evolution is true, she doesn't want to have children. Once again, she has mistaken evolutionary theory for a naive "for the good of the species" caricature of evolution. I should think that organisms (i.e., Dembski) manipulating other organisms (i.e., Coulter) into believing in creationism would be a prime example of said manipulation.)
Organisms may consistently work against their own interests (inclusive fitness) through being manipulated by another organism. Examples of manipulators are angler fish and cuckoos.
Although it's easy to assume that one animal manipulating another is only a temporary phenomenon until the other animal evolves some method of fighting back (that is, that the manipulation is a "time-lag" phenomenon--see my post on constraints on perfection), in reality the manipulator can in fact succeed continuously under certain conditions. An example of this is intraspecific manipulation (manipulation within the species, particularly kin-manipulation). Examples are parents manipulating their offspring, and offspring manipulating their parents.
Altruism is defined here, in a biological sense, as a behavior that favors other individuals (their inclusive fitness) at the expense of the actor.
Dawkins believes that parents who manipulate their children have an advantage over parents who do not, but states that parents do not have any built-in advantage over their children by the mere fact of their being parents.
Organisms may consistently work against their own interests (inclusive fitness) through being manipulated by another organism. Examples of manipulators are angler fish and cuckoos.
Although it's easy to assume that one animal manipulating another is only a temporary phenomenon until the other animal evolves some method of fighting back (that is, that the manipulation is a "time-lag" phenomenon--see my post on constraints on perfection), in reality the manipulator can in fact succeed continuously under certain conditions. An example of this is intraspecific manipulation (manipulation within the species, particularly kin-manipulation). Examples are parents manipulating their offspring, and offspring manipulating their parents.
Altruism is defined here, in a biological sense, as a behavior that favors other individuals (their inclusive fitness) at the expense of the actor.
Dawkins believes that parents who manipulate their children have an advantage over parents who do not, but states that parents do not have any built-in advantage over their children by the mere fact of their being parents.
The Extended Phenotype - Constraints on "Perfection"
One of the flaws in Ann Coulter's arguments in Godless is the fact that she believes that mutations arise already labeled neutral, beneficial, or non-beneficial, as if God had willed it so. Mutations do not arise in a vacuum, however, and any mutation is potentially any of these. When one says that a mutation (or adaptation) is beneficial, this must be taken in context with the vehicle's (organism's) genetic structure, environment, the existence of predators and competitors, the potential costs of this benefit as opposed to other benefits that could have evolved instead, etc. That a mutation carries an advantage in its particular context does not mean that the resulting adaptation is perfect, or that "things came together in perfect harmony" (as I often hear people say), or that the adaptation would even be considered adequate given fewer external constraints!
"It is simply meaningless to speak of an absolute, context-free, phenotypic effect of a given gene."--Dawkins
6 Constraints on "Perfection," or 6 Objections to Naive Adaptationism
-Time lags--the animal observed is "out of date," built under the influence of genes selected in an earlier era under different conditions. (The "lag load")
-Historic constraints--natural selection, having no foresight, modifies existing structures for new uses, leading in many cases to an obviously suboptimal formation, which nevertheless carries an advantage over no such formation at all.
Two species can respond to the "same selective forces in slightly different ways." --Lewontin
-Available genetic variation--"No matter how strong a potential selection pressure may be, no evolution will result unless there is genetic variation for it to work on."
-Constraints of Costs and Materials--adaptive organization is a "tangle of compromises."-Imperfections at one level due to selection at another--again, natural selection has no foresight.
-Mistakes due to environmental unpredictability or "malevolence"--adaptation to conditions is statistical in terms of success; moment-by-moment changes in an environment can trip up even the most successful animal. Moreover, manipulation of one animal by another can exploit the victims abilities, which in this context become disadvantages. The "loser" of this arms race may develop the ability to resist such manipulation; may find the manipulation beneficial to itself as well or may shape it to be such; or may actually go extinct, which does not necessarily benefit the aggressor.
"It is simply meaningless to speak of an absolute, context-free, phenotypic effect of a given gene."--Dawkins
6 Constraints on "Perfection," or 6 Objections to Naive Adaptationism
-Time lags--the animal observed is "out of date," built under the influence of genes selected in an earlier era under different conditions. (The "lag load")
-Historic constraints--natural selection, having no foresight, modifies existing structures for new uses, leading in many cases to an obviously suboptimal formation, which nevertheless carries an advantage over no such formation at all.
Two species can respond to the "same selective forces in slightly different ways." --Lewontin
-Available genetic variation--"No matter how strong a potential selection pressure may be, no evolution will result unless there is genetic variation for it to work on."
-Constraints of Costs and Materials--adaptive organization is a "tangle of compromises."-Imperfections at one level due to selection at another--again, natural selection has no foresight.
-Mistakes due to environmental unpredictability or "malevolence"--adaptation to conditions is statistical in terms of success; moment-by-moment changes in an environment can trip up even the most successful animal. Moreover, manipulation of one animal by another can exploit the victims abilities, which in this context become disadvantages. The "loser" of this arms race may develop the ability to resist such manipulation; may find the manipulation beneficial to itself as well or may shape it to be such; or may actually go extinct, which does not necessarily benefit the aggressor.
Women Not Funny? Now, That's Funny!
Christopher Hitchens needs to get out more. He's turning into a pompous old fart. He doesn't think women are funny - can you imagine? hasn't he ever watched Judge Judy? - and he invokes pop evolutionary psychology to defend his point.
Hoo-boy, the next batch of self-help books (Men are from Mars, Women are from Penis, uh, Venus) are going to be something else (Men are Happyloids, Women are Dippyloids)!
Kristine launches her silly salvo.
I love to make people laugh. (And to inspire "sudden art." I am, after all, the Amused Muse.)
Hoo-boy, the next batch of self-help books (Men are from Mars, Women are from Penis, uh, Venus) are going to be something else (Men are Happyloids, Women are Dippyloids)!
Kristine launches her silly salvo.
I love to make people laugh. (And to inspire "sudden art." I am, after all, the Amused Muse.)
The Extended Phenotype - Introductory Summary
-There is survival value in the "packaging of life into discrete units" called "vehicles" or organisms.
-We can speak of "adaptations as being 'for the benefit of' something, but that something is best not seen as the individual organism" but the "active, germ-line replicator" which are not selected directly, but by proxy.
-A behavior pattern "can be treated like an anatomical organ."
-A species or "group" is not the unit of selection, and gene selectionism is not genetic determinism.
Regarding the defining of what constitutes an adaptation, Dawkins first takes on the concept of extreme adapationism and identifies three proposed constrants on "perfection" (or optimal function) that he finds less persuasive:
-Neutral mutations, which are changes in polypeptide structure having no effect on enzymatic activity of the protein, and thus having no phenotypic effect at all.
(Biochemical controversy: Do all gene substitutions have phenotypic effects?)
(Adaptationist controversy: Is this phenothypic effect the result of natural selection?)
Though it is possible to a phenotypic effect to be selectively neutral, beware human subjectivity in these judgements. Genetic drift plus natural selection may result in more optimal function than just the effects of natural selection alone.
-Allometry, which is the disproportionate growth of a characteristic (such as a large head in small humans and in large ants).
-Pleiotropy, which is the possession by one gene of more than one phenotypic effect.
-We can speak of "adaptations as being 'for the benefit of' something, but that something is best not seen as the individual organism" but the "active, germ-line replicator" which are not selected directly, but by proxy.
-A behavior pattern "can be treated like an anatomical organ."
-A species or "group" is not the unit of selection, and gene selectionism is not genetic determinism.
Regarding the defining of what constitutes an adaptation, Dawkins first takes on the concept of extreme adapationism and identifies three proposed constrants on "perfection" (or optimal function) that he finds less persuasive:
-Neutral mutations, which are changes in polypeptide structure having no effect on enzymatic activity of the protein, and thus having no phenotypic effect at all.
(Biochemical controversy: Do all gene substitutions have phenotypic effects?)
(Adaptationist controversy: Is this phenothypic effect the result of natural selection?)
Though it is possible to a phenotypic effect to be selectively neutral, beware human subjectivity in these judgements. Genetic drift plus natural selection may result in more optimal function than just the effects of natural selection alone.
-Allometry, which is the disproportionate growth of a characteristic (such as a large head in small humans and in large ants).
-Pleiotropy, which is the possession by one gene of more than one phenotypic effect.
Thursday, December 14, 2006
Introducing a New Blog - Science and Women
John A Davison told me: "Why don't you join up with the other two multisexual femme fatales to complete the female triumvirate of evolution experts. Then you might found a colony on the island of Lesbos where you can spend the rest of your useless lives admiring one another with GAY abandon."
To me, that rather reeks of, "I'm not into girls." Well, neither am I, not in the pre-biblical sense that JAD means. However, this comment, plus a debate going on about women in science gave me an idea.
How about a blog devoted to science--just science--by women--just women?
Men can view and comment, but this is about (smashing) women smashing stereotypes. How about it?
Of course, I wish to have more than three women posting, so I suppose the triumvirate could refer to the concept of triangulation.
I will keep my posts on The Extended Phenotype at Amused Muse but will migrate them here as well.
To me, that rather reeks of, "I'm not into girls." Well, neither am I, not in the pre-biblical sense that JAD means. However, this comment, plus a debate going on about women in science gave me an idea.
How about a blog devoted to science--just science--by women--just women?
Men can view and comment, but this is about (smashing) women smashing stereotypes. How about it?
Of course, I wish to have more than three women posting, so I suppose the triumvirate could refer to the concept of triangulation.
I will keep my posts on The Extended Phenotype at Amused Muse but will migrate them here as well.
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