The thesis that I shall support is this. It is legitimate to speak of adaptations as being ‘for the benefit of’ something, but that something is best not seen as the individual organism. It is a smaller unit which I call the active, germ-line replicator. The most important kind of replicator is the ‘gene’ or small genetic fragment. Replicators are not, of course, selected directly, but by proxy; they are judged by their phenotypic effects. Although for some purposes it is convenient to think of these phenotypic effects as being packaged together in discrete ‘vehicles’ such as individual organisms, this is not fundamentally necessary. Rather, the replicator should be thought of as having extended phenotypic effects, consisting of all its effects on the world at large, not just its effects on the individual body in which it happens to be sitting.
I don’t know if that comes off as revolutionary to you as it does to me, couched as it is in language that tries to avoid metaphor for the sake of clarity. What he is essentially saying is that genes produce effects in the world beyond the individual organism in which they reside, and it is by these “extended phenotypic” effects that their survival and replication depend.
Dawkins himself, in his 1989 note to the Oxford Paperback Edition of The Extended Phenotype, gives this idea a singular honor:
I suppose most scientists -- most authors -- have one piece of work of which they would say: It doesn’t matter if you never read anything else of mine, please at least read this. For me, it is The Extended Phenotype. In particular, the last four chapters constitute the best candidate for the title ‘innovative’ that I have to offer.
Extended Phenotypes
One of the most common extended phenotypes, or at least one that practically everyone has a common understanding of, is the beaver’s dam. Indeed, a beaver is shown on the cover of the paperback I read. Whatever gene or combination of genes that exist in the beaver that codes for her dam-building behavior can claim not just the behavior but the resulting dam itself as its phenotype. Because it is, in fact, the dam, not the dam-building behavior, that increases the reproductive fitness of the beaver.
Once you start looking for extended phenotypes, there is a tendency to see them everywhere. Dawkins describes one of the more thought-provoking in a section on songbirds.
If a physiologist wants to bring a female canary into reproductive condition, increase the size of her functional ovary and cause her to start nest-building and other reproductive behavior patterns, there are various things he can do. He can inject her with gonadotropins or oestrogens. He can use electric light to increase the day-length that she experiences. Or, most interestingly from our point of view, he can play her a tape recording of male canary song. It apparently has to be canary song; budgerigar song will not do, although budgerigar song has a similar effect on female budgerigars.
Now suppose a male canary wanted to bring a female into reproductive condition, what could he do? He does not have a syringe to inject hormones. He cannot switch on artificial lights in the female’s environment. Of course what he does is sing. The particular pattern of sounds that he makes enters the female’s head through her ears, is translated into nerve impulses, and bores insidiously into her pituitary. The male does not have to synthesize and inject gonadotropins; he makes the female’s pituitary work to synthesize them for him. He stimulates her pituitary by means of nerve impulses. They are not ‘his’ nerve impulses, in the sense that they all occur within the female’s own nerve cells. But they are his in another sense. It is his particular sounds which are subtly fashioned to make the female’s nerves work on her pituitary. Where a physiologist might pump gonadotropins into the female’s breast muscle, or electric current into her brain, the male canary pours song into her ear. And the effect is the same.
So here the extended phenotype is not the male canary’s song, nor even the stimulation of the female canary’s pituitary, but the instigation of female’s reproductive behavior patterns. The male canary has genes “for” female reproductive behavior.
Extended Metaphors
But here again, as in The Selfish Gene, I wonder if the metaphoric language that Dawkins has chosen to communicate his idea is the very thing that gets in the way of it being clearly understood. By way of example, and the reason I had to put “for” in quotation marks at the end of the last section, is that genes don’t always create the phenotypes with which they are associated.
If I am homozygous for a gene G, nothing save mutation can prevent my passing G on to all my children. So much is inexorable. But whether or not I, or my children, show the phenotypic effect normally associated with possession of G may depend very much on how we are brought up, what diet or education we experience, and what other genes we happen to possess.
This is one of the scientific realities that belie the metaphor that we have genes “for” certain phenotypes. Just having a gene isn’t enough. A gene must be expressed in order for its phenotype to manifest, and gene expression is a process that is very much mediated by the environment for by what other genes are present on the chromosome.
Here’s another way of thinking about the implications of this.
When a geneticist speaks of a gene ‘for’ red eyes in Drosophila, he is not speaking of the cistron which acts as template for the synthesis of the red pigment molecule. He is implicitly saying: there is variation in eye colour in the population; other things being equal, a fly with this gene is more likely to have red eyes than a fly without the gene. That is all that we ever mean by a gene ‘for’ red eyes.
Did you get that? It’s another example of metaphoric language causing misunderstandings. Genes don’t automatically create their phenotypes, extended or otherwise.
But it goes deeper than that. Because despite what Dawkins himself proposed in his earlier groundbreaking work, genes are also not actually selfish.
Anyone who thinks about genes literally as molecular entities is in danger of being misled by passages like ‘What is the selfish gene? It is not just one single physical bit of DNA … It is all replicas of a particular bit of DNA, distributed throughout the world … a distributed agency, existing in many different individuals at once … a gene might be able to assist replicas of itself which are sitting in other bodies.’ The whole of kin selection theory rests on this general premise, yet it would be mystical and wrong to think that genes assist copies of each other because those copies are identical molecules to themselves. … Chimpanzees and gorillas are so similar that a gene in one species might be physically identical in its molecular details to a gene in the other. Is this molecular identity a sufficient reason to expect selection to favour genes in one species ‘recognizing’ copies of themselves in the other species, and extending them a helping hand? The answer is no, although a naive application of ‘selfish gene’ reasoning at the molecular level might lead us to think otherwise.
Dawkins is even more direct a few paragraphs on.
It is the incidence of phenotypes that we are interested in explaining, not the incidence of molecular configurations of DNA.
In other words, it is not genes that are the agents of evolution. In a world where natural selection dominates, it is the phenotypes that are the gene’s expression (extended or otherwise) that serve as the selection mechanism.
And Dawkins very next sentence, is the one that just about made my head explode.
And if any reader thinks that last remark contradicts my basic thesis, I must have failed to make my basic thesis clear!
Are you following this? For a book and a half, Dawkins has been advancing a theory about selfish genes, admittedly not as a description of reality but as a handy way of thinking about the mechanisms of reality. But it is only occasionally that he comes through with the kind of clarity that we see above. Remember, despite everything I’m saying, it is not the gene that is selfish, it is instead the phenotype that is better adapted to its environment.
The reader is cautioned not to fall into a similar trap when Dawkins discusses the concept of inclusive fitness.
Individual-level thinking is superficially attractive because individuals, unlike genes, have nervous systems and limbs which render them capable of working in obvious ways to maximize something. It is therefore natural to ask what quantity, in theory, they might be expected to maximize, and inclusive fitness is the answer. But what makes this so dangerous is that it, too, is really a metaphor. Individuals do not consciously strive to maximize anything; they behave as if maximizing something. It is exactly the same ‘as if’ logic that we apply to ‘intelligent genes.’ Genes manipulate the world as if striving to maximize their own survival. They do not really ‘strive’, but my point is that in this respect they do not differ from individuals. Neither individuals nor genes really strive to maximize anything. Or, rather, individuals may strive for something, but it will be a morsel of food, an attractive female, or a desirable territory, not inclusive fitness. To the extent that it is useful for us to think of individuals working as if to maximize fitness, we may, with precisely the same licence, think of genes as if they were striving to maximize their survival. The difference is that the quantity the genes may be thought of as maximizing (survival of replicas) is a great deal simpler and easier to deal with in models than the quantity individuals may be thought of as maximizing (fitness). I repeat that if we think about individual animals maximizing something, there is a serious danger of our confusing ourselves, since we may forget whether we are using ‘as if’ language or whether we are talking about animals consciously striving for some goal. Since no sane biologist could imagine DNA molecules consciously striving for anything, the danger of this confusion ought not to exist when we talk of genes as maximizing agents.
Sorry. This is all just a little too much for me. Dawkins writes about selfish genes that aren’t really selfish, that only act ‘as if’ they were selfish. And he also writes about individuals striving to maximize fitness that aren’t really striving to maximize fitness, that only act ‘as if’ they were striving to maximize fitness. And then, he criticizes people who fail to remember to add the ‘as if’. How, I wonder, are these metaphors helping me understand what is really going on? At the very least, Dawkins should be making the ‘as if’ explicit, but I think I would prefer if he dropped the metaphors altogether.
How Very British
One of the things I didn’t like about The Selfish Gene (at least the version I read, which contained the original 1976 text and new introductions and endnotes from Dawkins written in 2006) was how arrogant Dawkins came off; especially the 2006 Dawkins, who seemed to be writing explicitly to extract his rhetorical revenge on all the real and imagined critics of his work. Thankfully, no similar arrogant jerk can be found in the pages of The Extended Phenotype. Indeed, one paragraph in the author’s preface, written in 1981, jumped out at me as expressing quite the opposite state of mind. It has to do with his occasional use of feminine pronouns to refer to the generic reader.
The linguistic experiment of the last sentence reminds me that I wish I had had the courage to instruct the computer to feminize personal pronouns at random throughout the text. This is not only because I admire the current awareness of the masculine bias in our language. Whenever I write I have a particular imaginary reader in mind (different imaginary readers oversee and ‘filter’ the same passage in numerous successive revisions) and at least half my imaginary readers are, like at least half my friends, female. Unfortunately it is still true in English that the unexpectedness of a feminine pronoun, where a neutral meaning is intended, seriously distracts the attention of most readers, of either sex. I believe the experiment of the previous paragraph will substantiate this. With regret, therefore, I have followed the standard convention in this book.
My note in the margin upon reading this for the first time: How very British!
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This post first appeared on Eric Lanke's blog, an association executive and author. You can follow him on Twitter @ericlanke or contact him at eric.lanke@gmail.com.
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