Wednesday, January 17, 2007

The Active Germ-Line Replicator

What is a "gene"? Dawkins admits to using the term loosely. In this chapter he tries to nail down the term more precisely, in order to give a clearer, "gene's eye-view" of the replicator as the unit of selection.

In 1957 S. Benzer split the gene into three units: the muton (minimum unit of mutational change); the recon (minimum unit of recombination); and the cistron (roughly equivalent to the unit need for one polypeptide synthesization). Dawkins proposes the optimon (and Ernst Mayr the selectron) as the unit of natural selection.

Dawkins briefly describes Gould's objection to his proposal, and critiques Gould't characterization of the selfish gene replicator as located "below" the level of the individual (which for Gould was the unit of selection), as the species group-unit is located "above" the level of the individual. Dawkins points out that this "single-dimensional ladder" analogy is not apt in that genes are replicators, whereas vehicles (individuals and species) are not. Individual vehicles are selected, but they are not replicators (more on this later). Likewise, replicators are selected by proxy as individuals (vehicles) are selected.

The issue of species versus individual selection is a question of what is to be properly considered a vehicle; the issue of individual/species versus gene selection is a question of what is to be considered a replicator.

"I define a replicator as anything in the universe of which copies are made," says Dawkins. These may be active (displaying some ability to influence their being copied) or passive, "germ-line" (such as gametes), or "dead-end" (somatic). It is the active, germ-line replicator that Dawkins names as his optimon.

Because chromosomes, and the genes within them, are subject to splitting due to crossing-over in sexual reproduction, replicators may consist of various codon lengths, but, depending upon their length and the strength of the particular selective pressure on them, various replicators will have different "half-lives," and the most successful replicators will, by exerting their phenotypic effects, have the longest half-lives with respect to their alleles.

It now becomes obvious why no individual, nor even an individual's genome, can be considered a replicator.

In the next chapter, Dawkins explains what individuals and species are, and why species also cannot be defined as replicators.

15 comments:

llewelly said...

wonderful post, thank you.

Kristine said...

Hey, Llewelly, thanks for reading. I'm glad that people are enjoying this series.

Lui said...

You're an absolute champion. Finally, someone else who's read The Extended Phenotype! It was the most fascinating, compelling read ever for me (with lines and lines of red ink to prove it). The Selfish Gene rocked, too. I'm finally reading The Ancestor's Tale in its entirety (I'm up to Rendezvous 36).

It's great that you grew up reading Gould. I'm very much a "Dawkinsian", and I'd love to get a "Gouldian" perspective. (I will read more of his stuff in due time)

Kristine said...

Thanks, Lui. I've just started The Structure of Evolutionary Theory and may blog that, too.

I'd love to get a "Gouldian" perspective

I must confess that while I adore Gould I am taken aback to find that he probably overstated the “revolutionary” aspects of P.E. It's really just a compression of the geologic timetable (see Ken Miller, Finding Darwin's God). I put off reading Dawkins for so long because of Gould’s characterization of him, and that’s unfortunate. I am leaning toward Dawkins’ take on things at this point, although I see many problems with his “meme” idea.

Here’s a discussion that I had with another commenter at the mother ship, Amused Muse, regarding Dawkins vs. Gould. The issue is still unresolved for me.

Lui said...

Cool. Dawkins wrote a chapter about PE in The Blind Watchmaker called "Puncturing Punctuationism", where he made it clear that it's still a gradualistic model, and is emphatically not a radical break from orthodox Darwinism. Daniel C. Dennett also wrote a chapter in "Darwin's Dangerous Idea", where he did much the same, along with some other criticisms of Gould.

In case you're interested, there's a book called "Dawkins vs Gould: Survival of the Fittest", by Kim Sterelny (the author is himself "much closer to Dawkins than Gould", though he sees PE as a truly novel contribution and agrees with Gould on some other things).

I'd love to read The Structure of Evolutionary Theory, though personally, I don't see how, when you really think about it, the selfish gene school can be as seriously mistaken as Gould might have had us believe.

Finally, what do you see as being wrong with memes?

Kristine said...

My problem with memes is that I do not see ideas as replicators. I see no such phenomenon in actual human behavior.

The issue is not the replication of an idea (say, “Jesus is your lord and savior”) in the mind of another person, for research and studies show us that each person filters and recreates any new information entering the brain. People are not blank slates upon which to copy (replicate) memes. The issue is—as Dawkins points out so succinctly—the manipulation of one person by another.

Therefore, what Dawkins calls “memes” has no existence for me as replicators, but the phenomenon of a religious belief (“Jesus is your lord and savior”) is an attempt by one organism to manipulate the behavior of another to the benefit of the manipulator (and often, though not always, to the disadvantage of the manipulated party). What is replicated is a certain behavior—not the idea. Each person has his or her own ideas about the idea, and responds in his or her own unique manner to it—and yet this idea can fill megachurches.

Whole cultures, too, seek to manipulate other cultures. Remember that this is not necessarily a conscious phenomenon, either individually or culturally.

Therefore, I do not see “memes” in culture, either employed by individuals or groups. What I do see is the equivalent (especially with regard to religion) of the giant cuckoo chick being fed by the diminuative garden warbler. (Think of the huge, rich churches in Africa being funded by millions of poor Africans. Obviously, the beneficiaries of such largess do not seek to “replicate” their ideas about God in the minds of the masses, for then the masses would all seek to become rich, and would consider themselves just as worthy to receive God's “grace” as these rich pastors do.)

The “idea” passing between them is a fantasy with an infinite number of variations. Ideas don’t replicate, but behavior is manipulated (by the pastor), rationalized (by the believer) and thus replicated, and it is the behavior that creates cultures.

Lui said...

Thanks for the thoughtful reply, Kristine.

While I can see what you're saying, I think that perhaps you overstate the importance of individual differences in interpreting ideas. Each individual will have their own perception of an idea (like the one you suggested) but we can still talk about an average effect in the presence of other ideas in the "meme-pool" over time as well as the rest of the environment they happen to find themselves in (like the personality of the person, their gullibility, their experiences and traumas, and so on). Memes, like genes, don't exist and act in isolation. You're right to say that humans are not blank slates, but that might be a point in favour of the meme, not a point against it, for humans come pre-packaged with certain predispositions which will make it easier for some ideas to proliferate at the expense of others. To the extent that certain ideas can tap into these predispositions and effectively co-opt them, they may be favoured by selection. For example, there are certain ideas that are more intuitive and comforting than others, and hence might be favoured accordingly (of course, those ideas need not be true, even if they have features that assist their replication). Of course there will be exceptions - some people will resist the worst indoctrination that is thrown at them - but when talking about selection, we need only invoke an overall, statistical effect.
A meme should be distinguished from its phenotypic effects – namely, behaviour. A meme can potentially be an active replicator, as it can have an effect on its prospects of getting copied, for example through the behaviours it compels its “hosts” to carry out (on average). One form of behaviour that is deemed virtuous by most religions is the indoctrination of children. This is of course going to have an effect on that religion’s prosects of getting copied from one brain to the next (and definitely will tend to have a strong effect in getting that particular idea – that indoctrination is a good thing – in getting itself copied). Another behaviour that is deemed virtuous by most religions is the building of places of worship.
In The God Delusion, Dawkins talked about meme fidelity by contrasting the game of simple Chinese whispers with the Chinese Junk. In the former, the message is likely to be distorted after a few “whispers”, whereas in the latter, each child passes on a simple set of instructions by demonstrating to the next child in the line how to build the Junk (actually, I think Dawkins was using this example to illustrate the concept of digital information). The actual Junks might be a little different to one another - one might be a bit crooked, another might be folded rather clumsily - but the underlying instructions, the information - will be preserved and are much more resistant to distortion.
Finally, religions might be said to evolve in a quasi-Darwinian fashion, as they adapt to local conditions. Religions that fail to adapt are in danger of becoming extinct. In Breaking The Spell, Daniel Dennett even suggests that the reason some religious beliefs are so prevalent is precisely because they are irrational. You need faith to take them seriously (faith being itself explicitly endorsed, since religion has little else going for it), and it takes a red-blooded Christian or Muslim, for example, to devoutly adhere to the rituals, customs and beliefs therein, even if those rituals, customs and beliefs make little sense and contribute nothing substantial to everyday existence and are even potentially dangerous to the person practising them. Religions that lack such traits will be too easy to shirk and people might start to break away from their orbit, because it doesn’t ask them to pay any price, so what’s the point? Pretty perverse, if you ask me.
Anyway, these are just some reasons why I think that the concept of memes, if not actually convincing or even compelling, is at least not obviously silly. In any case, Dawkins’ original motivation for invoking them was not to make a contribution to sociology, but to emphasise the notion that genes need not be the only replicators in the universe, and that Darwinian or quasi-Darwinian evolutionary processes might be extended to other entities that exhibit the right properties.

Kristine said...

Thank you. I could be quite mistaken. I just read the chapter in which Dawkins introduces memes and I'm wondering if I am confusing memes with their phenotypic events (behavior). No, I do not think that the concept of memes is silly--it's so intuitively "right" at first blush (I liked the idea at first)--but the problem is, memes, if they exist, are constructions--not specific areas of the brain (because all brains are neurologically individual) that have clear alleles--they are snippets of information existing in pieces all over the brain and recombined each time the person accesses the information. ("Remembering" is exactly that--re-membering.) They are harder to nail down than genes (which as the unit of selection are hard to nail down themselves, and are to some degree conceptual).

I need to read that chapter again, frankly, because this is the one in which he deals with PE as well and I'm not grasping it all. I think this is a key part of the book for me. However, I do have a problem with Dawkins referring to a tune as a meme in one breath, and then talking of "Marxist" or "National Socialist" memes. He is so careful to define what we are even talking about when we say the word "gene" that I was taken aback by his, well, flamboyance about memes here.

Another possible objection is that he is assuming that thought drives behavior, whereas there is a lot of evidence that the opposite is true--behaving in a certain manner can "rewire" the brain. For example, behaviorist techniques, rather than analysis, are effective with changing the behavior of those who suffer from obsessive-compulsive disorder. Antonin Artaud (French playwright and theorist) said, "It is the action which shapes the thought" and being that mind evolved from mindless matter I agree with him.

When I have some time I'll have to look up what is said about memes in the literature--in my reference librarian class we're examining studies and hypotheses about cognitive learning styles and theories of teaching, etc. I may have to have an entire post devoted to memes!

Lui said...

Yes, now that you've brought it up, the issue of how memes are stored seems to be one of the best objections to them, or at least for regarding them as actual "things". Genes - even in the broader, less restrictive sense advocated by Dawkins - are proper sequences of information. Who knows how memes might be stored? If they differ substantially in their physical constitution from person to person, it may well be best to regard them only in the most abstract terms, certainly not like genetic fragments. Be that as it may, I can still imagine that treating memes as thought they did exist as discrete units of hereditary information can potentially be useful to all sorts of people, from politicians to PR pundits to advertisers to dictators. Some ideas really do have a way of spreading and taking off, often for perverse reasons that have to do with peoples' psychology and wishful thinking, and religions really do seem to me to have "adaptations" that make them thrive at the expense of other religions.

Anyway, here's the wikipedia entry. The study of memetics per se has apparently floundered for some time now. The Journal of Memetics is trying to regroup and revitalise the study of memes, but only time will tell if memetics is a worthwhile pursuit.

JohnADavison said...

Richard Dawkins is to Darwinian evolution what Paul Kammerer was to the Lamarckian version eighty odd years ago, a perfect charlatan.

Both have been exposed. The only difference is that Dawkins hasn't killed himself. Since he hasn't yet, I suspect he never will. I certainly hope not bas I love his fantasies.

It is hard to believe isn't it?

I love it so!

"A past evolution is undeniable, a present evolution undemonstrable."
John A. Davison

johnadavison said...

I thank Kristine for allowing me to post here. It is decent of her and I hope our past differences may be forgotten. I only wish I could post at EvC, ARN, Uncommon Descent and Panda's Thumb. Forums that must ban their critics are of no value to the search for ultimate truth.

"A past evolution is undeniable, a present evolution undemonstrable."
John A. Davison

Kristine said...

I know practically nothing about Paul Kammerer so I'll have to look him up when I have some time.

johnadavison said...

I am already on internet record as identifying Stephen Jay "intelligence was an evolutionary accident" Gould, Ernst "a dyed-in-the-wool Darwinian" Mayr and Richard "the blind mountaineering watchmaker" Dawkins as the "Three Stooges" of evolutionary science. The first two were fortunate to die before they were properly exposed, leaving Dawkins gamely still clutching the empty Darwinian bag.

It is hard to believe isn't it?

I love it so!

"A past evolution is undeniable, a present evolution undemonstrable."
John A. Davison

Alan Fox said...

Ooh, John,

You old hypocrite, you.

I don't know how you can post such stuff as "Forums that must ban their critics are of no value to the search for ultimate truth." and not be immediately struck by a thunderbolt from God.

You are never going to be taken seriously if you continue to use your definition of species. Did you look at John Wilkins' list?

Hi, Kristine, interesting you should quote Dawkins talking about what constitutes a gene, as John will tell you, "IT IS NOT THE GENES BUT THE CHROMOSOMES THAT DO THE EVOLVING".


How

Alan Fox said...

Re Paul Kammerer, John, I suspect has read Arthur Koestler's "The Case of the Midwife Toad". Kammerer is believed to have tampered with a preserved specimen of a toad in an effort to produce evidence of acquired inheritable characteristics (Lamarkism). What this has to do with Dawkins, the Lord only knows.