Moss - What genes cant do - 2003, страница 4

There was for Aristotle no exceptionalism,no miracles, or divine interventions. The possibilities of an adapted formwere understood to be constrained by the properties of the elements ofwhich it was composed and by an implicit principle of material conservation. It was in this interplay of the telos of the organism—i.e., thatadapted way of being for-the-sake-of-which it takes on the form that itdoes and such material constraints—that Aristotle found the heuristickey with which to elaborate his taxonomy, anatomy, and physiology.3As certain contemporaries might wish to point out, Aristotle, forwhom the universe was eternal, did not have a theory for the ultimateorigins of adapted form, that is, for the origin of species.

So then in whatway could he address the question of how adapted, complex, life-formsarise from nature? He did so through a theory of epigenesis. Complex,highly organized, adapted life-forms were understood to be the6Chapter 1achievement of an ontogeny in each and every case.

Epigenesis—thetheory of the progressive, step-wise acquisition of adapted form duringthe developmental life history of an organism—was a hallmark and centerpiece of Aristotelian biology.By considering what has been the relevant locus of interest for understanding how so-called simple nature can acquire complex, adaptedform, one can bring into focus just what the real demarcation is betweenwhat became orthodox neo-Darwinist perspectives of the twentiethcentury and their most significant antecedents.

The idea that the realfocus ought not be upon the organism and its ontogeny but rather inprocesses that occur over many generations, and in relation to whichindividual organisms are naught but pawns, is unique to the twentiethcentury. The principal distinction to be made is not between creationismand evolutionism but rather between a theory of life which locates theagency for the acquisition of adapted form in ontogeny—that is, in sometheory of epigenesis versus a view that expels all manner of adaptiveagency from within the organism and relocates it in an external force—or as Daniel Dennett (1995) prefers to say, an algorithm called “naturalselection.” [Darwin himself (as you can see by my chronology) does notfall into this neo-Darwinian camp].4Aristotle’s Substantive SoulAs suggested above, Aristotle, for whom the universe was eternal, didnot have a theory of the origin of species or a theory of the transmutation of species, but that is not to say that the seeds of a transmutationtheory can’t be located in an ontogenetically centered perspective.

Aristotle’s biology was a kind of functionalism. The telos of developmentfor Aristotle was not just a matter of the reproduction of parental morphology but also that of an ability of the developing organism to adaptto shifting conditions of existence. Aristotle himself did not hold thatenvironments were constant or that changes in the environment were“designed” for the good of the organism. As David Depew (1996) pointsout “this gives us new insight into why Aristotle, in acknowledging thatenvironmental fluctuations are not always well-tuned to organisms, laysdown as a matter of principle that organisms differ from inanimateGenesis of the Gene7objects because they are substantial beings, whose souls at the same timemake them into unified forms and enable them to act appropriately tomeet environmental contingencies in behaviorally plastic ways.”But what did Aristotle mean by a soul? What he didn’t mean was someform of disembodied spirit or idea.

What Aristotle perceived as the definitive sine qua non of being alive was physical process—that selforganized movement of heat and matter that takes in “nutriment, concocts it,” and in so doing sustains itself. He referred to this as the “nutritive soul.” Aristotle’s nutritive soul did not tell the matter of the organismwhat to do. It was not a blueprint or an idea. It simply was that movement of heat and matter which, owing to its absence, distinguishes awooden arm, albeit with all the right shapes, colors, and textures, froma bona fide living arm.A sense of similarity between Aristotle’s hylomorphic understandingof soul and much more recent descriptions of self-organizing dynamicsystems is not entirely accidental.

Aristotle may not have been privy tocomputer simulations of theoretical, nonlinear adaptive systems, but theidea that epigenesis was achieved by self-organizing movements drivenby an internal orientation toward an adapted form was entirely consistent with his metaphysics. It was the nature of Aristotle’s nature to inherein purposes. Nature as a whole for Aristotle was lifelike—conceptuallymodeled not by the example of inertness but rather by the example ofliving activity.This kind of outlook changed dramatically during the metaphysicalshift that took place over the course of the seventeenth century.

Naturebecame stripped of its capacity to self-organize as an end unto itself. Finalcause, the for-the-sake-of-which a creature possessed the form that itcomes to have, was not lost but rather relocated. Seventeenth centurymetaphysicians moved final cause from within nature to the mind of God.It was not by the hand of Aristotle but rather due to natural philosophersof the seventeenth century that final cause came to carry the sense of intelligent design and livings beings thereby the character of artifacts (Osler1994).

We can still see the earmarks of this legacy in the design talk ofcertain neo-Darwinists like Richard Dawkins (1976) and Daniel Dennett(1995) who want to tell us that it’s now OK, even perspicuous, to speakin the idiom of design because we have a natural algorithm with which to8Chapter 1do it. The most vituperative purveyors of the neo-Darwinian shibbolethare, it turns out, in closest agreement with contemporary creationistswhen it comes to the “as-if-by-intelligent-design” character of life. Aristotle, by contrast, and epigenesists ever since, have endeavored to explainlife-forms not as artifacts designed from without but as self-organizing,“autopoietic,”5 ends-unto-themselves.The Antinomies of Early Modern Preformationism and EpigenesisThe advent of an explanatory crisis in biology brought forth by the newscience and metaphysics of the seventeenth century was not immediate.Descartes, in particular, had no difficulty imagining that epigenesis, andeven spontaneous generation, could occur simply on the basis of the newlaws of matter in motion.

Subsequent Cartesian mechanists, however,could no longer countenance the possibility of adapted form arisingspontaneously from an unorganized nature newly construed as essentially passive. They offered, in place of epigenesis, a theory of preformation consistent with a deistic theology. In their view the embryos ofall the organisms which would and could ever be had come into existence with the creation of the world and its first creatures, as so manyRussian dolls, fully formed miniatures nested and encased one inside theother. Subsequent generations were deemed to “evolve” from the old onthe basis of the purely mechanical unfolding and elaboration, the inflating really, of parts already in place.Theories of epigenesis made a comeback during the eighteenth century,inspired by the example of Newton’s discovery of gravitational force.The success of Newtonian physics meant that the natural sciences could,and did, countenance causes of action beyond the mechanics of directcollision.

Where “Cartesian matter” lacked the wherewithal to becomeself-organized, “Newtonian matter” by contrast could yet contain somenew principle, some vital force, which could account for self-organizingepigenesis (Farley 1974, Roe 1981). New epigenesists seeking to discoverjust such an organizing force aspired to become the Newton of naturalhistory.Eighteenth century attempts at addressing the problem of how naturecould produce complex, adapted life-forms thus oscillated between twoGenesis of the Gene9positions, both of which were problematic. On the one hand preformationists could not account for the production of hybrids that bore thecharacteristics of both parents, nor could they meet the increasing challenge of empirical observation, that is, of being able to reveal miniatureadults in eggs.

Epigenesists, on the other hand, couldn’t solve theirsource-of-organization problem without referring to intangible, occultsounding forces (Kraft, vis essentialis, nisus formativus, and so forth).The Critical Solution—Teleology Turned HeuristicWhat enabled nineteenth century biologists to get beyond this impasseand provide the heuristic groundwork that ultimately led to much ofwhat became the foundation of modern biology—that is, the elaborationof developmental morphology, a histology, and embryology based on atheory of germ layers, the discovery of the mammalian ovum, the formation of cell theory and the elaboration of cellular histopathology—was not the theory of natural selection but, in effect, a renewal ofAristotelian final cause given an epistemological turn.

Immanuel Kantand his Göttingen interlocutor, biologist, and ethnographer, JohannFriedrich Blumenbach, found an enabling passage through the quagmireof reconciling the fact of complex, adapted life forms with a nature construed to be mechanistic all the way down, through Kant’s notion of areflective judgment.In his third critique, The Critique of Judgment, Kant observed that tobehold a living organism unavoidably entailed regarding it as a selfsustaining, and hence internally purposeful, end unto itself.

Unlike themechanistic processes of the nonliving world which lack any internaldirectionality, living beings exhibit, in Kant’s view, a circular causalityconstituting an ongoing status of being both the cause and effect of themselves. Using the example of a tree Kant observed the fact of circularcausality in the following three ways:1. As a member of species the tree is both cause and effect of other treesof its kind.2.

The tree is the cause of assimilation of nutrients into tree constituentsand thus the cause of the chemical changes that these nutrients undergoand their subsequent effects as they become the matter of the tree.10Chapter 13. The parts of the tree exist in a relation of reciprocal interdependence—roots dependent upon shoots (foliage), shoots dependent uponroots. The parts are thus cause and effect of each other.This kind of circular causality for Kant could not be conceived of asthe result of random, mechanistic processes. We are, says Kant, compelled to draw reflectively on a “concept of reason,” that is, one of purposiveness, but we do so not as a form of natural explanation but onlyfor regulative or heuristic usage. In reflective judgment, for Kant, thesubject projects “his or her own principle,” the causality of reason, ontoan object of nature in order to gain a conceptual handle; however, thisprinciple, derived as it is from the subject, cannot be considered constitutive that is, explanatory of the object.