Moss - What genes cant do - 2003, страница 3

TheMendelian units as such, taken per se are powerless.—Wilhelm Johannsen, 1923The full understanding of the nature of the genetic program was achieved bymolecular biology only in the 1950’s after the elucidation of the structure ofDNA. Yet, it was already felt by the ancients that there had to have been something that ordered the raw material into the patterned system of living beings. . . One of the properties of the genetic program is that it can supervise its ownprecise replication and that of other living systems such as organelles, cells, andwhole organisms.—Ernst Mayr, 1982The gene is by far the most sophisticated program around.—Bill Gates, 1994The Gene—An Unusual Portfolio with a Compounded LegacyThe gene, to say the very least, is a most peculiar member of our currentmolecular menagerie.

We may now speak of genes as “defined sequencesof nucleic acids” with as much empirical support as when we speak ofproteins, lipids, or even cells and tissues. Yet, the gene concept isroutinely extended in directions that other biomedical entities are notlikely to be taken. We would certainly be surprised, for example, to hearsomeone attribute some aspect of their personality to the fact of havingtheir father’s oligosaccharide for stubbornness.

Oligosaccharides, likegenes, are present in every living cell. Is it possible that two biologically2Chapter 1ubiquitous types of molecules could be so fundamentally different thatit would make perfect sense to speak of one as a determinant of, forexample, one’s stubborn disposition, but only humorous to ascribe asmuch to the other? How can it be sensible to speak of one species ofbiochemical but patently inappropriate and silly to speak of another asa determinant of human characteristics, let alone as the blueprint for allorganisms?The concept of the gene, unlike that of other biochemical entities, didnot emerge from the logos of chemistry. Unlike proteins, lipids, and carbohydrates, the gene did not come on the scene as a physical entity atall but rather as a kind of placeholder in a biological theory. As theobvious etymological link with the word genesis suggests, the very senseof being a gene is that from out of which other things arise.

The conceptof the gene began not with an intention to put a name on some piece ofmatter but rather with the intention of referring to an unknown something, whatever that something might turn out to be, which was deemedto be responsible for the transmission of biological form betweengenerations.Since Watson and Crick, the gene is no longer just an abstract placeholder or a hypothetical address on a cytological structure known as achromosome; rather, it has attained a specific physiochemical reference,i.e., as DNA.

As such it is more than just a placeholder for “that whichis responsible for a trait,” but as an empirical entity it is also certainlyother than just that which is responsible for a trait and, it will be argued,it is indeed also considerably less than that which is responsible for atrait. At once a molecule, yet also the heir to the premolecular scienceof transmission genetics, the gene carries a peculiarly multifaceted portfolio. Genes, like oligosaccharides, are molecular, but unlike oligosaccharides they are also conceived of as information, blueprints, books,recipes, programs, instructions, and further as active causal agents,as that which is responsible for putting the information to use as theprogram that runs itself.The implications of there being one kind of physical matter, one kindof molecule—which is unique in this way, which is simultaneously physical “stuff” and information, a chemical and a program for running life—is hardly trivial.

The task of explaining how simple matter can becomeGenesis of the Gene3organized into living beings, if so it does, has been one of the most fundamental and challenging questions of the entire Western philosophicoscientific tradition. Can the gene be the answer? Is it the bridge betweensimple physical matter and organized biotic form? It is clear from theepigraphs above that there are those who believe it is. The existence ofthe Human Genome Project attests to the seriousness of this belief.Ontology TodayThe attempt to explain an always messy reality on the basis of envisaging ontologically antecedent Forms or Ideas is hardly new to the westernphilosophical tradition, extending at least as far back as Plato.

Curiously,ironically even, just as the metaphysics of transcendental forms, ideas,categories, and the like, have come to lose favor with many philosopherswho increasingly set out to grapple with the unavoidably contextualaspects of truth and rightness (and for whom notions such as that ofembodied and distributed cognition have become veritable watchwords),a new, putatively “naturalized” metaphysics of predeterminism hasgained increasing influence—not from the lofty heights of God, Mind,Reason, or Being, but rather, as it were, from below.

Such philosophersostensibly seeking empirical moorings, as well as other investigators fromthe human sciences, have been increasingly looking to take their cuesfrom biology. Biologists, in turn, having “gone molecular” and imbibedof a rhetorical soup flavored by ancillary developments in cybernetics,computer science, and linguistics, have come to adopt and adapt to arather ethereal idiom of so-called information.

And it is precisely in termsof information, with the aid of the rhetorical and metaphorical resourcesthat this concept provides, that the gene is construed to be that whichspans the chasm between physical matter and organized, biotic form. Asa code, a program, a text, a blueprint, and so forth, inscribed in theone-dimensional array of DNA sequences, its meaning is understood tobe self-contained. As an entity, its existence is now widely believed to besomehow temporally, ontologically, and causally antecedent to organismic becoming. The gene (or genetic program) envisaged as contextindependent information for how to make an organism appears to havebecome the new heir to the mainstream of western metaphysics.4Chapter 1The Phylogenetic Turn and the History of OntogenyAlthough continuous with one long-standing tradition, the rise of thegene concept marks a radical break with another.

For over 2000 years,from Aristotle through the nineteenth century, the living organism withinthe confines of its own life span had been at the center of naturalisticunderstanding and explanation. I will refer to a radical shift of perspective, which begins neither with Darwin nor with Mendel (although thework of both are contributing factors) but very early in the twentiethcentury, as the “phylogenetic turn.” The intent of this phrase is to highlight the idea that as the gene and genetic program became understoodto be the principal means by which adapted form is acquired, the theaterof adaptation changed from that of individual life histories, that is,ontogenies, to that of populations over multiple generations, that is,phylogenies.

As the genetic program moved to the explanatory centerstage, the individual organism, with its own adaptive capacities, beganto recede from view.To adequately clarify and critically consider current usage of the wordthe “gene” we must locate it, as well as the associated assumptions ofthe phylogenetic turn in this larger context of the history of westernefforts to reconcile the tension between the experiences of nature assimple physical matter and as organized life-forms.

And to begin todo this we must start by exposing a shibboleth of recent philosophy ofbiology.1 The shibboleth I have in mind is one that evokes the menace ofcreationism and insinuates that there have been only two basic organizing principles in the study of life: that of Darwinian evolution and thatof creationism.

Espousals of this sort continue to be ubiquitous in thephilosophy of biological literature. A recent article concerned with theconcepts of function and adaptation suggested that “originally, teleologywas controversial because it was associated with pre-Darwiniancreationist views about organisms” (Allen and Bekoff 1998). Now, infact, the teleology of Aristotle as well as that of Immanuel Kant haveboth played extremely important roles in the history and advancementof our understanding of life, and dismissing them with the label “creationism” is not only misguided but also markedly misleading.

It servesto create an arbitrary boundary beyond which many good neo-Genesis of the Gene5Darwinians dare not cross. In another example, a recent book by aleading (and not even particularly orthodox) neo-Darwinian philosopherbegins as follows: “The existence of adaptations, the fit between organisms and their environments, is one of the most striking features of thebiological world. Before Darwin (1859) numerous accounts were offeredto explain adaptation, the most prominent among them being the creationist account.

According to this account, organisms were designed byGod to fit the demands of their environments. Darwin offered an alternative proposition, the theory of evolution by natural selection.”2What are we to make of such a statement? The two most influentialthinkers about the nature of adaptation, i.e., the fit between an organism and its surroundings, have certainly been Darwin and Aristotle. Doesthat mean that Aristotle was a creationist? Unless one’s entire frameof reference is Victorian England and one is perhaps speaking only ofcertain Victorian friends of Aristotle (or really Plato), then the answermust be a resounding no! Aristotle was not a creationist; indeed, therewere no references to external causation in Aristotle’s biology at all.

Aristotle labored to understand the nature of living beings in terms of theelements and movements from which they were constituted. He foundin an organism’s adapted form—that is, in its mode of existence andattunement to its environment, the organizing principle of the organism,its final cause or purpose unto itself, the for-the-sake-of-which it undergoes its formative processes.