The Organic Codes: An Introduction to Semantic Biology
Most scientific publications deal with problems that can be explained in a straightforward manner and with solutions that can be evaluated as a matter of routine. But scientific progress often occurs when somebody tries to reformulate the problem, or to suggest a different kind of solution. When that happens, it may be necessary to dwell as much upon the questions as upon the answers, and to show how a novel approach might give further significant results.
Barbieri finds that biology has been able to deal with information and with structure, but not with the connection between them. Something has been left out, and that is meaning. Semantics is the branch of logic that deals with meaning: hence the term “semantic biology”. Meaning is a difficult concept to analyse, even though we find it in everything we read or listen to, including imaginative literature. To understand a poem one needs all sorts of background information. Poetry is rich in literary allusions, so just knowing the words will not do. Meaning is largely a matter of context, and that makes it hard to pin down.
The contextuality of meaning may be called a “principle”, for it is neither a brute fact nor a law of nature. But exactly what is meant by a principle is hard to specify. We can give some familiar examples of course. In ecology there is the well-known “competitive exclusion principle”, which explains why organisms occupying exactly the same niche cannot coexist for more than a brief period of time. In logic we all use, whether we know it or not, the “principle of contradiction”, which states that two propositions that really contradict each other cannot both be true. And since, by implication, at least one of them must be false, we justify the kind of hypothetico-deductive scientific method that Barbieri (an admirer of Popper) endorses. Principles are very important in science, more important than may seem obvious. Usually we adopt them implicitly, without giving them much thought. Principles are perhaps the most important components of Barbieri’s theoretical, or perhaps better, metatheoretical, system. One might even say that such principles are what the book is really all about.
Barbieri enunciates four general principles, all of which relate to the problems of development. He begins by considering epigenesis, and redefines it as the property of a system to increase its own complexity. He goes so far as to make the capacity for attaining such convergent complexity both a fundamental principle and a defining property of life itself. One might question that, but his definition is at least as good as any of the ones that are quoted in the Appendix. The second principle tells us that achieving such convergent complexity amounts to reconstructing a structure from incomplete information. That in turn provides a new definition of “epigenesis”. Then we get a third principle, according to which organic epigenesis requires organic memories. Here “memory” is a technical term indicating that there has to be some repository of information. And as a final principle, such epigenesis requires organic codes. Indeed codes and memories exist only because they are necessary for producing epigenetic systems. Barbieri is a scientist, not a philosopher. He justifies his ideas on the basis of their ability to make sense out of the material universe. This he accomplishes by means of four “models”, as he calls them. Why “models” rather than “theories”? Evidently because they serve to illustrate the principles. Of course it really matters whether the particular interpretations are correct. But the point of the book could be made just as well if the hypotheses being discussed were modified in some respects. The more basic message is not the examples as such, but rather the kind of theory that might be expected to emerge out of a semantic approach to biology. Let us have a brief look at these models from that perspective.
First, Barbieri presents a theory about the origin of life. Extant organisms possess both genotype, in the form of DNA molecules, and phenotype, in the form of proteins, cells, and other products of epigenesis. Previous scenarios treated proteins or DNA as coming first. Both of these alternatives ran into difficulties because the one cannot exist without the other. For that very reason there must have been something additional to genotype and phenotype, which he calls the ribotype. It is RNA that bridges the gap between genotype and phenotype, and it does so by endowing the system with meaning. Cells contain all three. Those who want to define life as either as genes or as gene products will find no comfort in this view of it.
The second model illustrates the point that more than one kind of memory can be responsible for the reconstruction from incomplete information that takes place during the (epigenetic) formation of an organism. Barbieri proposes that two kinds of memory are in fact responsible for the development of multicellular animals – one for the earlier stages, the other for the later ones. He shows how the existence of these two kinds of memory might account for the pattern of macroevolution, notably the Cambrian explosion.
The third model is an application of similar considerations to mental development, especially with respect to language. One kind of organic memory accounts for the acquisition of the capacities that appear early in the ontogeny of language, then a second takes over. Again, codes are absolutely indispensable, and the emergence of new ones has been a key innovation in the history of both life and mind. And finally, the semantic theory applies to culture as well. Cultures are like species, insofar as they are supraorganismal wholes, and real concrete things. There are codes in both life and culture, and both life and culture have evolved through natural selection and natural conventions. In culture we find something analogous to genotypes, though they depend upon an extrasomatic memory. We also find something analogous to phenotypes, such as artifacts. But, if we are to extend Barbieri’s basic vision of organised beings to culture, there is also something more. Consider a village with its buildings. Is it blueprints that explain the existence of buildings, or buildings that explain the existence of blueprints? Barbieri suggests that we might ask more edifying questions.
Barbieri’s most ambitious claim is that life evolves through natural conventions as well as natural selection. The importance of such conventions as major evolutionary innovations becomes increasingly obvious as he discusses one example after another. Yet let us not get carried away. There is nothing here that portends the fall of Darwinism or its replacement by an alternative paradigm. The book is, after all, concerned with the fundamental principles of development, and with how they relate to the grand picture of evolution. It belongs to the mainstream of biological thought, and finds its proper place among the works of Karl Ernst von Baer, Charles Darwin, and August
October 2001 Michael T. Ghiselin
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