|mind, matter, meaning and information|
Living structures such as cells, organs and organisms embody physical information just as do non-living structures like molecules, rocks and solar systems. But genetic information, the design of these living structures, would seem to be something else. This chapter examines the relationship between simple physical and genetic types of information. (Genetic information turns out to be physical, but not simple.)
A rock survives only as long as all of its elements, down to the very lowest level, remain together—but life, with self-reproduction, transcends that limitation. The pattern survives, even though the substrate might be long gone. Patterns survive at various levels: cells in the human body are replaced on a cycle of a few years, and one generation of a species replaces another—the species survives even after all its previous members have died.
Mere matter cannot replicate itself, but particular configurations of matter can reproduce themselves. Replication of matter itself would violate some of the most basic laws of physics, regarding conservation of matter and energy. It cannot be multiplied, but matter can be rearranged. What can self-replicate—rearrange existing matter to make copies of themselves—are certain structures, particular configurations of matter. What is replicated is not the matter, but the pattern in which it is organised: its structure or form.
The basic unit of this replicating and thus surviving biological information is the gene, the complete set of which (the “genome”) can be viewed as the blueprint of an individual. Many biologists (probably most of them, these days) agree with Richard Dawkins, who explained in The Selfish Gene that gene survival is the main “driving force” of evolution—humans like all other organisms are in effect mere machines for the propagation of genes. (This is a form of reductionism—link to come.)
The essential elements of evolution are replication, variation, and selection. Replication is imperfect, and some variants (those that are “fit”) are selected in the sense that they survive and replicate themselves, whilst others do not. The Selfish Gene suggests that biological evolution is best understood when neither species, nor individual organism, nor any other biological entity but the gene, is viewed as that which replicates, varies and is selected. Replication on other levels does take place—organisms replace themselves by producing offspring, for instance—but replication of the gene is absolutely central, the axis around which all else revolves. The gene is the replicator par excellence.
Do genes control anything in the usual sense of that word: are they active agents, with a goal or goals in mind, towards which they make plans and then attempt to execute them? Of course not—only organisms, and intelligent ones at that, can do such things—but what is the alternative? If the genome is the blueprint, who or what uses it as such?
What's important about genes is their survival—or their failure to survive, as the case may be. In fact, surviving (or failing to do so) can be said to be all that genes do. They are best understood as lying at the still centre of a storm of biological activity. Their nature determines the character of that activity, but in themselves they are quite passive, like a chemical catalyst. They direct the development of the organism, yes, but that is merely a byproduct of their survival, and they do it merely by being what they are, rather than by any activity of their own. This is how their role is best understood at this stage, but it is not the absolute truth. In fact, the distinction between activity and passivity [link to come] is a relative one. But it is the centrality of genes in the storm of biological activity, their long-term stability, their very stillness, in fact, that gives them their importance in our understanding of biological evolution.
You might ask: what is this genetic information about—if we could read a strand of DNA, what would it tell us? In very loose terms, it could be said that genetic information is “about” the survival of the gene, the information itself, and that of the other genes with which it cooperates. But genetic information is not really about anything—it exists for its own sake—it is a form of physical information.
Life first emerged when a molecule, or a small group of them, simply by virtue of the way it was arranged—its form—happened somehow to be capable of reproducing itself. Genetic information has that sort of stability. It is an item of information that is sufficiently stable, in a given environment—by being able to reproduce itself, or by associating with those that will arrange the copying of a cluster of which they are part—that it can survive the destruction of the medium upon which it is encoded—the death of the individual organism carrying the gene. It will survive if other individuals also carry it, which will almost always be the case, though it is most likely where there are offspring.
Genes can be viewed as biological blueprints, but the DNA molecule just reacts with its environment, as any other molecule might do. That environment—the highly complex and structured biochemistry of the cell—is just as important in practice as is the DNA. Offspring do not inherit only DNA, but also its context—the rest of the cell—and the whole package is essential. We can only view DNA as a blueprint if we put ourselves in the position of that which uses the DNA that way, which is its biochemical context. In fact, it is only our subjective view that brings the DNA to the foreground and relegates the rest of the mechanism to the background, because we are most interested in the particular characteristics that the DNA encodes. Information about the organism is encoded in the DNA as interpreted by the cellular mechanisms with which it interacts. Dennett makes this point very well in Darwin's Dangerous Idea.
The DNA carries the information required for the development of the organism in coded form, while the remainder of the cellular mechanism is the decoding device. Here we see the utility of the formal stance. Just as physical information is not special, separate stuff, but merely an aspect of matter, so information processing such as decoding is not a special sort of operation, but just an aspect of any physical process.
The discipline of genetics is the result of taking the formal stance towards biological phenomena, focusing on its design. That design, the genetic information, is physical information, but rather than being in “clear” form, it is encoded.
The genetic information that we think of as carried by a strand of DNA specifies the result of the interaction between the DNA molecule and its biochemical environment. And there is nothing magical about such prediction, because the outcome is predetermined by the laws of physics and chemistry—otherwise, DNA could not reliably code for any biological structure, and life could not exist.
So genetic information is encoded physical information, being not explicit, as is the information considered in physics, but implicit in the relationship between a number of physical things, where time is part of that picture. It is neither static structure, nor energy flow, but information that's embodied in a certain sort of process, a dynamic but relatively stable structure.
How does genetic information get encoded? One way would be Lamarckism: the inheritance of characteristics acquired during the lifetime of the individual organism. This could only take place if such characteristics somehow became encoded in the DNA, but it has been very widely accepted for many years that there is no way this could happen. The ultimate genetic encoding operation would be divine design: when God created all living things, he obviously put that design into the genes, so they could reproduce. But that myth has no part in this story. What actually encodes genetic information is the process of evolution.
What is so special about genetic information? Given that “encoded” is applicable to any predetermined state of affairs, there is obviously a very great deal of encoded information out there, only a tiny proportion of which is genetic. What is “special” about genetic information is that it survives the destruction of the medium upon which is it encoded: life is the survival of encoded physical information.
Copyright © 1998--2005 by Robin Faichney.
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Last modified 19-Feb-2005 18:37:42 by Robin Faichney .