An active replicator is that which exerts at least some kind of influence over the likelihood of its being copied. A DNA molecule is a replicator; a piece of sheet music considered valuable enough to be xeroxed can be considered a replicator (Dawkins, p. 83); but an individual organism, sexual or asexual, cannot be considered a replicator.
Here's why.
Because we reject Lamarckism, we know that characteristics acquired during an organism's life cannot be passed down to its offspring. Even in the case of asexual reproduction in which the entire genome is passed down, any acquired features--a lost limb, developmental factors, etc.--is not replicated in the lineage, and in order for the organism as a whole to be called a replicator it must pass these on. "There is a causal arrow," writes Dawkins, "going from gene to bird, but none in the reverse direction." However, the genome of an organism that reproduces asexually could be a candidate for the term "replicator."
Can a species be considered a replicator? Again, Dawkins points out that a species, being mutable, is not comparable to a gene and its alleles. However, the gene pool of a reproductively isolated species could be a candidate.
In examining this possibility, Dawkins explores "differential lineage extinction"--for example, the statistical rates of extinction of ammonites and bivalves that have a high rate of evolving a larger size, say, than those who do not (those that more rapidly increase their size over successive generations are also more likely to die off). However, while these different rates of extinction are a form of selection, they do not drive "progressive evolutionary change" and thus these lineages are not replicators, either. They are merely, as Dawkins terms them, "survivors."
(And at this point, people, I confess I must read the chapter again.)
Part II: Punctuated Equilibrium and Memes
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36 comments:
"Because we reject Lamarckism, we know that characteristics acquired during an organism's life cannot be passed down to its offspring."
Can this definition accomodate symbiogenesis?
Sorry that I haven't gotten back to you guys--I had a busy day at work and I had class on Valentine's Day night!
Indexing class. Ewww. Gimme an hour on the bus to get home, and I shall answer. :)
for a complex adaptation to be built up, you need a steady generational replacement cycle
Exactly so. And I think Dawkins demonstrates this ably. I think his analogy was the evolution of the whale and the complex interrelationship that would accomplish this--hardly the stuff of species-level selection.
I get the idea that the concept of species selection annoys him as well, but that he includes it for the sake of fairness, because it seems to be theoretically possible (and I must say, Dawkins is one of the most scrupulously fair and even-handed writers that I have come across).
I think your characterization of Gould is correct. However, Gould had a thing about evolution not being progressive (or perhaps that's not the word to use). I always took issue with this. The essense of Gould's view was that the individual is the unit of selection, and that is what I took from his writings; it has created a great barrier for me in understanding Dawkins' view, but Dawkins keeps referring to the Necker cube as an analogy for how one can toggle between the concept of the individual and the concept of the individual's genome. I struggle with this, too.
I need to read what you've said about lineages more carefully because once again I feel that I'm in over my head.
Can this definition accomodate symbiogenesis?
I'm not sure that I understand the question. Are you asking if symbiogenesis is a form of Lamarckism? I don't have an answer for you--I don't know enough about the concept of symbiogenesis. (This isn't why Lynn Margulis came up with, is it?) I'll look it up.
:)
"Are you asking if symbiogenesis is a form of Lamarckism?"
It seems to me it is a kind of Lamarkism, though a very limited version.
I just think, with symbiogenesis in mind, that the statement, "we know that characteristics acquired during an organism's life cannot be passed down to its offspring," is too strong.
"There is a causal arrow," writes Dawkins, "going from gene to bird, but none in the reverse direction."
Os so we think we know. Did anyone see this?
That's an interesting discovery, John, which seems to be in the area of "evo-devo," not something I know anything about (yet). However, as dogscratcher said, perhaps I should revise my statement about Lamarckism because it could be taken to mean something more limiting than I meant it to (I'm an old dog myself, and the information about evolution has changed a lot since I last read Gould!).
But let me make this clear: what does not change during the organism's life is the genome. What is happening in the bird that receives a mother's care is a change (if I am understanding this correctly) in what genes are expressed. However, during the creature's life, broken legs and such do not have effects on the genome so that they could be passed down to subsequent offspring. That is what I mean by Lamarckism.
Lui, I have to read your post again, once I complete all my homework! :) I'm facing another marathon session in the library today.
Hi, Lui. I was literally just thinking about you, and feeling a little guilty because I haven't replied for a while.
I'm facing midterms--which means projects. I'm indexing the book Innumeracy: Mathematical Illiteracy and its Consequences for my Indexing and Abstracting class (I can't believe this book has no index!), and learning the database Dialog for my Reference class.
Since I made a dent in my work today (because we had a snow day!), I hope to return to this tomorrow (Saturday), I promise! Thanks for hanging in there.
I think Dawkins has no problem with a limited form of it, though, it's just that, in his words, "it doesn't seem to do very much".
I agree with you; in fact I think it probably does diddly-squat in the long run.
I haven't gotten through The Ancestor's Tale and so have not grasped "evolution of evolvability"--it makes me a little confused, perhaps "evolution of adaptability" would be a good substitute? (Or would this actually be a different phenomenon?)
Species don’t strive towards cladogenesis, it just happens for arbitrary reasons.
Got it. I agree totally.
I think what he must have meant was that the contingencies that our ancestors found themselves living under were essentially random
Yes, of course. But I think he was also saying that consciousness did not necessarily reveal anything deep and true about the cosmos, and that the evolution of it did not represent a progression or a giant leap forward for nature. It is an adaptation like any other, but it's not the pinnacle of evolution. Therefore, to wonder about the long odds of evolution producing consciousness is no different that wondering about the long odds of evolution to produce any specialized adaptation. In addition, animals have degrees of consciousness; it is we who separate consciousness from the list of unlikely adaptations and wonder about it (because we can!), when in fact who besides ourselves benefits from it (and do we, really, at this point?).
I think that is what Gould meant when he characterized evolution as not progressive, because he saw people, including scientists, imparting a special status and value to consciousness that it really doesn't have. That seems like a harsh statement to make, but it isn't, really.
I agree with you; given billions of years, evolution will accomplish something, but the chances of it creating any one particular thing are small (like the chance that you get a certain hand in poker are extremely small, but nevertheless you will get something, itself quite unlikely).
Thank you. I just read "Human Chauvinism and Evolutionary Progress" and you're right, it helped immensely. I'll get a hold of Gould's article when I can (if you visit the Mother Ship, you'll see me crowing about my midterm. Gould was also a literary nut. :-) )
I must have read this particular chapter of The Extended Phenotype six times! Do you know what my problem is? My "problem" is, despite reading Gould I didn't end up like the "American nonspecialists who unfortunately...get their evolutionary knowledge almost entirely from Gould, [and] have been deeply misled." Small wonder I was confused at the relationship between "species selection" and punctuated equilibrium - I never understood it in the manner that Dawkins criticizes, but in the manner that he describes it! "The theory of punctuated equilibrium itself is gradualist (by Gad it had better be)." Damn straight, Professor Dawkins!
So, I got confused because I was never confused? Well--how confusing. :-)
Groups within the species can still be capable of interbreeding, but the species taken as a whole must still be pretty homogenous. (right? Well, that’s what I got from it. If this book had been written for a more general audience, we might not even be having this discussion)
I've just gotten through that part for the sixth time and I think I, too, get it now--and you're right. (I am a general audience. *wink*) But I think that Dawkins is being careful here to the point of overscrupulousness. I actually don't see species level selection at all. The more I look at it, I don't even see the genome of the asexual stick insect as a replicator, the reason being that, aren't they still subject to genetic mutation?
{I wanted to save my comment before my crappy connection lost it.)
Random mutation is happening all the time. I think Dawkins is onto something in his description of speciation events, but frankly, it is the selection of the mutuation, and not the mutation itself (which is always happening), that leads to speciation. So, even though a gene-pool can remain stable for a long time, that does not mean that it is not mutating and changing, but that the changes are weeded out, kept to a minimum - until circumstances force speciation - and I don't think that parallels the selfish gene explanation, really. I could be wrong.
What I find interesting about the Necker Cube analogy is that it is itself an abstraction. It refers to, but is not, a real cube. I understand what he is saying, but I find it interesting that he must make an analogy that is itself a two-dimensional representation to make another abstraction, his argument, more sensible. I'm not sure where I'm going with that - remember, my degree is in English literature and not in science - but it struck me that Dawkins is using an optical illusion to explain an abstraction, which says something about our inability to just see reality--really, it highlights the bogusness of the claims of intelligent design theorists who would have us believe that our naive view of the world (it looks designed, so it is) is true when it is false. Michael Behe uses a concrete example, a mousetrap, as an analogy for intelligent design, and it suddenly struck me that I was initially perceiving the Necker Cube as a concrete analogy when it is not. And perhaps that means that we humans can only understand the world, and our own abstractions, in terms of abstractions.
...
Sorry. It's late, and I've gotten off on a philosophical tangent. Thanks for hanging in there, and I'll tangle with the question of the central dogma tomorrow!
Okay, I need to read what you said about Lamarkism again, because I'm getting mixed up again. (I make things more difficult for myself than they need be - I read more into things than is there - that's why, for example, I never passed calculus when I always excelled at algebra and trig.) But here's Dawkins' definition of Lamarkism from the glossary:
Regardless fo what Lamarck actually said [and for pity's sakes I can't remember anymore], Lamarckism is nowadays the name given to the theory of evolution that relies on the assumption that acquired characteristics can be inherited. From the point of view of this book, the significant feature of the Lamarckian theory is the idea that new genetic variation tends to be adaptively directed, rather than 'random' (i.e. non-directed) as in the Darwinian theory. The orthodox view today is that the Lamarckian theory is completely wrong.
And I believe that it is wrong. I don't think this is referring to the acquisition of mitochondria or to the success of genes in proximity to other, reciprocally successful genes. I'm not sure that I would agree that the existence of genes in another body that appear to cooperate with one's own is "incidental." It is the apparent cooperation that is incidental - which is to say, the genes are not "cooperating" any more than color pixels in a photograph "cooperate" with the black one to produce a color photograph instead of a black-and-white one. The presence of the color pixel changes the overall pattern, and the presence of the aphid genes changes the phenotype of the ants and visa versa, but it changes their genes only by proxy, through natural selection.
However, that may be what you've already said, and I may have simply misunderstood you.
There is something cleansing about thinking about all this, I must say. It is a discipline.
Rowers that work well in each other's presence (speak the same language, communicate well, train together etc) will tend to do better than rowers who do perform poorly in each other’s presence.
*More flights of fancy alert* I have been thinking about PE in terms of quantum theory, specifically in terms of wave interference, with periods of "stasis" (even though they're not really) representing the troughs, and speciations the peaks. Is this a plausible connection? Your mention of the rowers made me think of it - I envisioned two sets of rowers becoming, due to circumstances, briefly entangled (this isn't a good image, because boats and rowers don't split off) and their rhythms becoming erratic and chaotic, spurring a speciation event.
I agree that the selfish gene could not exist without the environment, and I cannot understand how anyone could make such an accusation of Dawkins. What do they think he's talking about when he mentions replication? The replicator is successful because it's selected, and it must perform well in its envrionment to do so.
At any rate, thanks for hanging in there, Lui. I've finished the chapter and shall post on it soon.
Dawkins is wrong again. There is probably not a single organism on this earth that is capable of any further evolution. Phylogeny, like ontogeny, has proven to be self-limiting and self-terminating. The extinction of the species is the counterpart to the death of the individual. There is every reason to believe that Homo sapiens is the last mammalian species that will ever appear on the planet.
I agree with Robert Broom that there was a Plan, a word he had the temerity to capitalize. I further contend that the Plan has been realized with the ultimate evolutionary product - ourselves.
All that remains is extinction, the ultimate fate of nearly every species that ever existed. There are no reasonably large "living fossils" and Homo sapiens is very definitely on the large size.
Sorry about that.
It is hard to believe isn't it?
I love it so!
"A past evolution is undeniable, a present evolution undemonstrable."
John A. Davison
Well, John, I remember someone telling me "You could bleed to death and I won't show up [at your blog]," but being that you inadvertently inspired this blog (especially its title), what can I say but thanks for stopping by.
Hi John
You, I see, disagree with Dave Springer's (and presumably Dembski's too, silence giving consent) stance on climate change. I have seen comments from you expressing concern about the environment
Oops pressed "publish" instead of "preview". (Out of practice :))
... about the environment, so you must be pretty disgusted with Springer's attempt to conflate ID with denial of global warming.
John wrote:
Dawkins is wrong again.
The Extended Phenotype is an excellent read for anyone wanting to get a good insight into evolutionary theory, and The Ancestor's Tale a rewarding wide-ranging work that is also a useful reference book for the layperson. You could do worse than emulate his integrity and patience in promoting his views.
BTW it looks like Jason Rennie is back-tracking on publishing your interview, and editing it down to a few "highlights". I was looking forward to the unexpurgated version.
Hello, gentlemen. Due to our past entanglements I just want to issue a friendly reminder that, unlike at the Mother Ship, Amused Muse (where just about anything goes, except some things, for example if I get too wigged out), this blog confines its subjects to on-topic comments about science. If people want to start a global warming thread I would be happy to. Thank you for visiting.
Falan Ox
I have been assured by Jason Rennie tht my interview will appear with little or no editing. I believe it will appear soon. I have no idea where you got the notion that he didn't intend to publish it. Perhaps you will enlighten us. But then perhaps you won't.
I love it so!
"A past evolution is undeniable, a present evolution undemostrable."
John A. Davison
Do keep the tone neutral, please.
Jason has assured me that I'll be notified when the interview comes out.
I am impatiently waiting to hear where Fox got the notion that Rennie does not plan to present my interview. I presume Kristine would join me in that request. Right Kristine?
"A past evolution is undeniable, a present evolution undemonstrable."
John A. Davison
Keep the tone neutral and quit attacking people, or you're gone, and I mean it. Alan Fox has his own blog, as you are well aware, if you want to confront him about this niggling point. It seems that there were many misunderstandings about your interview, which will be cleared up when it airs.
How tired I am of these personal recriminations! This is not your blog. You once told me I was not a lady - maybe you should model the behavior that you want to see in other people instead of criticizing them. Believe me, John A Davison, I have not lacked for abusive and relentless criticism in my life. So take it elsewhere.
I am attacking no one. I am simply claiming that nothing Dawkins, Gould or Mayr have ever written had anything whatsoever to do with speciation or the formation of any of the highet taxonomic categories.
All of organic evolution was emergent from within the evolving forms and took place on a predetermined schedule independent of the environment. In a word it was "prescribed" as my 2005 paper claimed. In other words Darwinian evolution is a hoax. Besides, evolution isn't even going on any more beyond the elaboration of varieties, none of which are incipient species in any event.
"A past evolution is undeniable, a present evolution undemonstrable."
John A. Davison
Darwinism is now in its terminal death throws with Richard Dawkins its last champion. It has been nearly a century and a half of nothing but mass hysteria. It is the biggest hoax in the history of science and Dawkins is now all alone holding the empty Darwinian bag.
On the other side are the IDists led by William Dembski, another loser, who has reinvented Intelligent Design and has even claimed to have proved it mathematically!
It is hard to believe isn't it?
The first IDer was William Paley who claimed, long before Darwin -
"Where there is design there is a designer."
Sorry Paley, but you are wrong also. All that can be said with certainty is -
Where there is design there WAS a designer.
That cannot be denied and that is all that can be substantiated. That is also all that is required by my Prescribed Evolutionary Hypothesis. There is not a shred of evidence for a living God and never has been. That does not mean that such a God does not exist, but it does mean that IT or THEY have no role in science. I know of not a single scientific advance that ever depended on a God of any description.
Christopher Wren designed and rebuilt Saint Paul's cathedral. Wren is dead and the cathedral remains. Need I say more? Get it? Probably not.
"God is dead."
Frederich Nietzche
Right on Fred!
And so you see both sides of this idiotic debate are dead wrong.
Naturally,
I love it so.
As for the rest of you Darwinian mystics, go right on worshipping Dawkins, the last champion of the biggest and most long-lived hoax in the history of science. It has been nothing more than nearly a century and a half of sustained mass hysteria, produced and then perpetuated by generation after generation of those poor souls who were "prescribed" to be congenital atheists.
Einstein put it this way -
"Then there are the fanatical atheists whose intolerance is the same as that of the religious fanatics, and it springs from the same source... They are creatures who can't hear the music of the spheres."
and
"Everything is determined... by forces over which we have no control."
You now have my permission to continue with your cozy litte "groupthink."
Ask not for whom the bell tolls. It tolls for Godless Darwinism, the biggest joke in the history of science.
"A past evolution is undeniable, a present evolution udemonstrable."
John A. Davison
Lui, check here for some context:
http://amused-muse.blogspot.com/2006/09/genetic-algorithms-for-uncommonly.html#c115771725486356226
Paste the link in your browser - everything will become clear then.
;-)
Another post coming soon, I promise.
Since this is supposed to be a scientific discussion, I would appreciate some scientific objections to the points I raised.
Lui, evolution truly will come to an end before you get an answer! ;-)
It breaks my heart, too. But he's actually behaving himself here so whatever, I'll let him spout.
This "evolution is finished" stuff seems to be his unique take on a "theory" that I've heard before, that being that the universe is "winding down." Usually the proponents are anti-evolutionist physicists.
Sorry kristine but you won't "let me spout." I have washed my hands of your mindless little Dawkins fan club. Enjoy one another. I have much better things to do than to try to educate evolutionary illiterates. Richard Dawkins is a "prescribed," congenital, homozygous loser.
"A past evolution is undeniable, a present evolution undemonstrable."
John A. Davison
Well, thanks for being a good sport and take care of yourself John.
Lui, shhhh! Let him go. ;-)
I'm glad it went as well as it did. He was really restrained here, after I laid down the law. John can get quite vituperative and I didn't want that.
You're not going to convince him. It's beyond argument; health issues, cognitive, I don't know what it is. (I'm trying to say this nicely.) In a way I love the guy.
Kristine.
Alan Fox has banned me from posting on his shabby little blog just vas David Springer has on Uncommon Descent. They are each nothing but hired goons for their masters. Wesley Elsberry and William Dembski respectively.
The reason I am banned is because these clowns are scared to death of me and my sources. If they have the balls they may communicate with me either on my blog or at Brainstorms.
I sure as hell am not going to interact with either of these phonies here on your blog. They can both go to hell as far as I am concerned.
"A past evolution is undeniable, a present evolution undemonstrable."
John A. Davison
David Springer does not come here as he has agreed, as a gentleman, not to visit my other blog anymore. I wish you would show the same restraint and gentlemanliness and quit baiting people here in an obvious attempt to draw them in.
You are not banned, but unless you have a point, make with the bye-bye.
This is for you Dawkins fans,
https://www2.blogger.com/comment.g?blogID=4412672427182333335&postID=7556043756485780134
Comments #14 and #15
Enjoy!
A past evolution is undeniable, a present evolution undemonstrable."
John A. Davison
I do not bait my several adversaries. They are much too cowardly to show up. I simply expose them as the mindless ideologues that they all are. It gives me pleasure to do so. Now go read some more Dawkins, the biggest charlatan in the history of evolutionary science.
"Study Nature not books."
Louis Agassiz
Got that? Write that down.
"A past evolution is undeniable, a present evolution undemonstable."
John A. Davison
I certainly shall read more Dawkins. Good idea. I daresay considering your behavior people fear for you rather than fear you.
He does. ;-)
Don't let it get to you, Lui. This stuff goes way back. He's deleting everything from his blog, because he thinks he's been banned from Alan Fox's blog when he's not (but he was banned from Uncommon Descent - I saw the comment that did it, I will not repeat it because it's icky, and I agreed with DaveScot for kicking him off). So now he's getting his "revenge." Let him. He's an old man and frankly, as I said, it's a mental illness.
You are an incredibly charitable person, Kristine.
Aside to John:
You have never been, are not, and will never be banned from my blog, no matter how hard you try, so there!
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