What Genes Can't Do

This is, by turns, an important and a frustrating book. It is important because if its arguments are correct, we need to rethink the notion of the gene, as it has been accepted in popular and bioethical thought. But it is frustrating because Moss never really clarifies – perhaps because he cannot yet know – what is really at stake in the debate. What are the implications, for medicine, for bioethics, and for environmental debates, if his deflationary view of the gene is correct?  The importance of this work turns on these questions, and these questions are left largely unexplored.

Moss’s primary concern is the very widespread notion of the gene as a cause of phenotypic traits, and of the genome as the ‘book of life’ or ‘blueprint’ for the organism. As a cell biologist turned philosopher, he is very well placed to assess this concept of the gene. His approach is, initially at least, historical. George Gaylord Simpson, one of the architects of the modern synthesis of Mendel and Darwin, famously stated that all attempts to try to understand the human being prior to 1859, the year of the publication of The Origin of Species, were worthless and should be ignored. Moss believes that this is false, even if we restrict ourselves just to biology. In fact, earlier debates in biology played and continue to play a subterranean influence, in shaping the concepts through which biologists understand life. We cannot understand contemporary biology, fully, except by coming to grips with its history.

One of the perennial temptations in this history has been the idea of preformationism: the notion that the adult is contained, in toto and in detail, in the ‘seed’ from which it grows. In previous centuries, this notion was taken literally: at least some biologists believed that eggs or sperm contained entire individuals, in miniature, each of which contained in itself eggs or sperm, which contained entire individuals, and so on. Preformationism has as its perennial opposition the idea of epigenesis, according to which more and more complex traits arise during development, in a manner that is responsive to the local context.

The gene concept which dominates our discussion today is, Moss argues, the result of the conflation of two distinct, separately permissible, notions. The first he calls the Gene-P (for preformationist); the second G-D (for development). A Gene-P is a gene for a phenotypic trait. But a Gene-P is not a physical entity. There is a sense in which there are (some) genes for phenotypic traits, but it is not a simple sense. A Gene-P is not a molecular entity. Rather, its physical base is the absence of some molecular entity. Thus, when we say that someone has the “gene for” a cancer, for instance, we mean that they lack the ability to make a protein. Since there are indefinitely many ways to lack something, we do not thereby pick out anything specific at a molecular level. Someone has blue eyes not because they have the gene for blue eyes, but because they lack the structures that result in brown eyes, and blue eyes are what human beings have when they lack these molecular structures.

We can search for Genes-P by looking at the genome for one of the many variant molecular structures which people have been found to have when they lack the stretch of DNA in question, But the variant stretch is not a “gene for” the trait, since it is not necessarily causally involved in producing it (or at least, not to any greater extent than a great many other cell structures and stretches of DNA). Genes-P are not physical structures at all, but predictive devices, instrumentally defined.

Genes-D, in contrast, are physical features of the genome, defined by their molecular structures. But Genes-D are not genes for phenotypic traits. They are one more developmental resource, among many others. Moss argues that our largely preformationist gene concept, encapsulated in metaphors like the genome as the blueprint for the human being, is the result of the illegitimate conflation of these two senses of gene. There are (some) genes for traits, but they are not physical entities. There are genes correctly identified with a particular stretch of DNA, but they are indeterminate with regard to phenotype. The gene concept foisted upon us is the idea of a gene as a physical entity that codes for traits. But there is no such gene: no gene is simultaneously a Gene-P and a Gene-D.

Moss spends much of the rest of the book defending something akin to the view associated with developmental systems theory (DST), according to which the genome is not a privileged repository of information. DST argues that there is no sense in which genes contain information in which other cellular machinery, and even environmental influences, do not contain information as well. Moss argues that the discovery of the Human Genome Project that human beings have far fewer genes(-D) than predicted is evidence that the complexity of higher organisms is not a product of their genes. Rather, it is the result of the modular architecture of organisms as a whole. A long and detailed chapter is devoted to work on the biology of cancer. Despite all the recent emphasis upon genetic susceptibility to cancer, Moss argues, the mainstream of oncology is gradually moving toward a more epigenetic view of its etiology. Genetic mutuations, and genes(-P) are part of the explanation of the origins of many cancers, but more important are adaptive, but destabilizing, changes in cells and tissue. Why the ever-increasing emphasis on genetic screening, in this context, then? Moss has two explanations. One is the drunk looking for his keys under the lamppost story: that’s where the light is. Though genes(-P) may be an important part in the origin of only a small number of tumors, and almost never sufficient by themselves, at least we know how to look for them. Moreover, genetic screening can be marketed to patients, and Moss believes that this fact is an important ingredient in explaining its success.

 What are the implications, for society, for medicine, and for bioethics if Moss’s attack upon the gene concept is vindicated? Unfortunately, he is not very forthcoming on this score (though he obviously believes that the gene concept has been a negative influence, not only on science but on society at large). Perhaps Moss believes that we cannot understand the implications, until we have a better grasp of the epigenetic theory which will replace the gene concept. Nevertheless, we can make a beginning on drawing the consequences.

If Moss is right, and the basis of heritable traits lies in many different and interwoven components of the organism and not in an easily isolable molecule, then the genetic engineering of particular traits, foretold on all sides, sometimes welcomed and sometimes condemned, just doesn’t seem to be a technical possibility. We won’t be designing kids for height or intelligence, not for a very long time at least and perhaps not ever. If this is right, however, we are left wondering about the real importance of genetic modification. Consider the range of genetically altered crops. Are scientists simply mistaken in thinking that improved yields, or pest resistance, or whatever, is the result of genetic modification? Is this another example of the preservation of a veneer of Mendelian rhetoric, which is belied by the actual scientific practice? It has been suggested to me that if DST is correct, then we no longer have a reason to oppose GMOs. If genes are not the essence of organisms, then altering them cannot be all that important. Does this follow?

It is the mark of an important book that it raises as many questions as it answers: that it causes us to think again about fundamental issues. To this extent, perhaps the fact that Moss leaves us with so many questions is a mark of the significance of his work, and not its limitations. This is far from an easy book (its appearance in a series entitled ‘Basic Bioethics’ notwithstanding). Nevertheless, it will repay careful reading, for it may lead us to rethink the fundamentals of medicine and our approach to it, of reproduction, and of life itself.

© 2002 Neil Levy

Dr Neil Levy is a fellow of the Centre for Applied Philosophy and Public Ethics at Charles Sturt University, Australia. He is the author of two mongraphs and over a dozen articles and book chapters on Continental philosophy, ethics and political philosophy. He is currently writing a book on moral relativism.