Individual Difference in Evolutionary Theory                                                                          

by Beth Metcalf

According to Deleuze (Difference & Repetition 247-8), interpretations of individuation that depend on qualities of species and extension of parts are inadequate.  Such hierarchical interpretations assume a quality in general and an extensity already formed.  Rather, individuation occurs in a pre-individual field of singularity.  That is, classification in a table of generality does not give rise to singular individual difference.  Individuation occurs in a pre-individual field of singularity that is actualized into species and parts.  Each time, a new singular-universal is actualized as a new functional use.

(DR 247) “….individuation precedes differenciation in principle…every differenciation presupposes a prior intense field of individuation.  .….  As a result, they then form the quality, number, species and parts of an individual in short, its generality ….. Individuation does not presuppose any differenciation; it gives rise to it.  Qualities and extensities, forms and matters, species and parts are not primary; they are imprisoned in individuals as though in a crystal.  Moreover, the entire world may be read, as though in a crystal ball, in the moving depth of individuating differences or differences in intensity.”

The idea of continuity is the prerequisite of possible taxonomic classification.  However, if we are to avoid interpretations that assume quality in general and extensity already formed, we must now ask how our idea of continuity needs to change.  How do we reach continuous variation of individuating differences in intensity?  Deleuze says,

 (DR248) “[The ‘characteristic’ in a continuous order of resemblances] ensures the greatest subordination of differences to the order of increasing and decreasing resemblances….so long as it is subordinated to the criteria of resemblance within perception, identity within reflection, analogy within judgement and opposition within the concept, difference is not regarded as individual difference.  It remains only general difference, even though it is borne by the individual.” 

Therefore, according to Deleuze, it is important that interpretations of individual difference do not depend upon a prior structure of quality in general and extensity already formed.  Only singularity is unique difference because no singularity is similar to any other.  Individuation occurs in a prior field of pre-individual singularity – in fields of difference in intensity.  Heterogeneous couplings of intensity reveal (DR 222) “the properly qualitative content of quantity”.

Deleuze says (DR 248) that Darwin’s novelty of thought was the inauguration of individual difference.  That is, we do not know what an individual body can do when natural selection connects small free-floating differences to accumulate in a given direction for the survival of the divergent.  Darwin knew that the taxonomic units of genera, families, orders, and classes are not related by conditions of resemblance, identity, analogy, or opposition.  Rather, taxonomic units are derived from the differenciating difference of natural selection.  But Deleuze says that Darwin did not yet give ‘individual difference’ a clear status.  He did not yet distinguish it from an indeterminate variability at the level of the fully formed individual organism. 

Deleuze credits Weissmann with making a further contribution to Darwinism (DR 249) by noticing that species, organic parts, and the sexes were substances that turn around the modes of individual difference.  This is the reverse of the usual notion that modes turn around substance.  It may appear that sexed reproduction depends upon the qualities and limits of species and the extension of organic parts.  However, sexed reproduction in the egg precedes species and parts.  The egg is differentiated in a pre-individual field that does not depend on already differenciated species and parts.  (So, here is one answer to the old riddle about which comes first, chicken or egg.)    

 (DR 249) “The egg reconstitutes the parts only on condition that it develops within a field which does not depend upon them.  It develops within the limits of the species only on condition that it also presents phenomena of specific de-differenciation.”

Differential genetic elements are expressed in processes of reciprocal and complete determination that constitute intensive potentiality.  Rhythms of speed and slowness produce spatial-temporal dynamisms that dramatize actualization into species and parts of actual organisms.  Therefore, intensive-singular difference is incarnated in species and parts of actual organisms.  (DR 251) Difference of intensity is implicated in the egg.  Intensive individuation is prior to actualization into species and parts.  Differentiation precedes differenciation.  There is no resemblance between them.  Therefore, individuating difference does not proceed from an already determined taxonomic classification of generalizing hierarchy.  Individual difference has its source in a field of the pre-individual singularity. 

(DR 253) “The enveloping intensities (depth) constitute the field of individuation, the individuating differences.  The enveloped intensities (distances) constitute the individual differences.  The latter necessarily fill the former.  Why is the enveloping intensity already a field of individuation?  Because the differential relation on which it is focused is not yet a species, nor are its distinctive points yet parts.  They will become so, but only in being actualised by the action of this field which it constitutes…” 

These intensive fields of singularity are never the same.  They are folded in disparate order, depth and distance.  The indivisible individual difference of intensive quantities cannot divide without changing in nature.  They can never maintain a same generality.  Depths and distances are folds of the enveloped and enveloping.  There is no totalizing general organization.  How could evolution create any real change in nature if there is only continuity from one already actual term to another?  There could be no real creative evolution.  If evolutionary theory is to account for creative novelty, there needs to be evolution of disparate-intensive difference that, with division or augmentation, changes in nature.  There cannot be merely a conceptual difference of generality of the particular that never reaches singular difference.  Deleuze finds singular different/ciation in intensive folding.  This intensive folding is not a mere folding in two.  Rather, folding is difference different/ciated.  It is decoding and deterritorialization.

Deleuze (DR 249) credits Baer with understanding that epigenesis proceeds from a high level of generality.  But this is not an abstract generality.  It is generality as lived by the embryo.  It is pre-individual and singular.  The egg is the field of individuation.  The embryo is the pure individuation prior to actualization of species and parts.  The embryo is a unique and singular source of new functional structures.  Individual difference is inseparable from its species and parts.  It is inseparable variation because, when there is separation, there is a real change in the singular conditions of actualized species and parts. 

(DR 250) “It is not the individual which is an illusion in relation to the genius of the species, but the species which is an illusion – inevitable and well founded, it is true – in relation to the play of the individual and individuation.  The question is not whether in fact the individual can be separated from its species and its parts.  It cannot.  However, does not this very ‘inseparability’, along with the speed of appearance of the species and its parts, testify to the primacy in principle of individuation over differenciation?  It is the individual which is above the species, and precedes the species in principle.  Moreover, the embryo is the individual as such directly caught up in the field of its individuation……” 

Intensive folding cannot happen at the level of a general classification of differences and resemblances.  Cuvier was right that folding cannot happen at that level of already formed species and parts.  But Geoffroy (DR184-5) was not thinking about folding at that level.  Geoffroy was thinking of elements that were not distributed in a general form.  Structure is not at the level of already actual anatomical elements.  Structure is a virtual domain where differential elements and ideal connections have a different determination. 

(DR 214-18) Embryology is that domain of pre-individual folding.  Such folding creates the individual difference of the embryo.  Only the embryo can withstand intensive folding.  Therefore, intensive folding does not produce a totalizing general difference.  There are spatio-temporal dynamisms as the lived of the embryo beneath the extensities and qualities of species and parts.  Intensive folding creates singular conditions actualized in species and parts.  Therefore structure is pre-individual.  If structure is mistaken to be inside an already general table of classification, then the virtual is mistaken for the limitations of the possible.  However, actualization does not go from one actual element to another.  The process goes from the virtual to its actualization. 

Deleuze says (DR 279-80) that there are two dissimilar halves.  There is the ideal half of the virtual (differential relations and corresponding singular points).  The other half is the actual qualities of species (actualizations of the virtual relations) and actual parts (actualizations of the singular points).  Individuation embeds the two dissimilar halves as interpenetrating singular multiplicities – virtual differentiation and actual differenciation – in which there can be no resemblance, identity, analogy, or opposition.  If evolutionary theory is to account for real creative novelty, there must be variation of singular individual difference from which nature can select.  Natural selection must act upon variations of singular pre-individual difference that, with division, changes in nature. Different/ciation precedes causal selection.   

Evolution is a fact of biological science.  Natural selection is theorized to be a causal mechanism.  However, does current evolutionary theory reach recognition of singular pre-individual difference?  There seems to be debate among evolutionary biologists.  ‘What is the individual unit of selection?’  Does selection occur at the level of the gene -- the gene as already individuated and self-ish, as if it were making calculations of exchange?  Or, is the unit of selection the individual organism, group, species, or cross-level* effects?  All sides of this debate seem to assume an already generalized taxonomy.  They assume (DR 247-8) that classification is the problem of ordered differences --- a continuity of resemblances.  But don’t these levels form an already generalized hierarchy?  Wouldn’t any such individual unit presuppose actual terms in a general taxonomic structure of identity, resemblance, analogy and opposition?  Under these conditions of mere generalizing difference, individual difference can only be conceived as the generality of the particular.  Such concepts never reach singular pre-individual difference.  Under generalizing conditions, there could be no real change in nature.  There could be no accounting for truly creative evolution.  So we must ask, ‘Is evolutionary biology (under such generalizing assumptions) able to develop an adequate theory to explain the biological fact of evolutionary novelty?’**

It seems that, with the new discoveries of evolutionary developmental biology (evo-devo), there is imperative for interpretation to break away from generalizing biases.  Prior to the discoveries of evo-devo, the assumption was that development of different parts of different species would involve different genes.  However, evo-devo has discovered evidence that all life on earth is built from the same genetic toolkit.  This common toolkit was already present in a common ancestor and regulates development of different species.  Evo-devo reveals that there are not equivocal genera whose lines of differentiation are determined by different genes.  During embryonic development, the on-off switching of genetic ingredients regulates how genes are expressed.  The same genes are the basic ingredients for the expression of dissimilar parts of different species.  On/off switching differentiates structural development.  Genes are expressed in different combinations and timing.  Genes are switched on or off in virtual differentiation.  At the level of the embryo, in its early stages of development, very different species look similar in a deep homology.  Then, at later stages of development, differences appear. 

Would the empirical results of evo-devo seem to imply that, as Deleuze hypothesized, there is a pre-individual field of univocal differentiation in widely divergent species at early stages of embryonic development?  Under the assumptions of univocal being, what would be the new unit of selection?  The unit of selection, itself, could no longer be conceived as belonging to some level of a generalizing hierarchy.  The unit of selection, itself, would be virtual in the embryo (all differentiation of the singular) that becomes actual (differenciated in species and parts).  The actualized species and parts would not be already formed units of a general structure or hierarchy.  Every actualization would be individuated at the pre-individual level of the embryo.  Each actualization would be a new singular-universal unit of selection – a new functional structure with its own singular conditions.  Selection could no longer be thought to occur within an already generalizing structure.  Selection would always effectuate a real change in the nature (functional structures) of species and parts.  Could it even be said that there is a general structure (genus and species) that draws the distinction between a unit of selection and its environment?  Such distinction itself would be a product of degrees of different/ciation. 

A generalizing taxonomy is classification according to units of genera, families, orders, and classes that are related by conditions of resemblance, identity, analogy, and opposition.  But it would seem that deep homology (if it is to escape conditions of generality) must reach the univocality of pre-individual singularity of inseparable variations of intensity.  Doesn’t evo-devo present science with empirical data that now makes it imperative for new theoretical interpretations to reach a singular source of variation from which nature makes its selections?  Could there be a univocal source of singular difference that generates variation?  With the new deep homology of univocal being, there are no oppositional relations.  Internal and external are folded together.  Structure and function are no longer in opposition.  Functional structures are actualized according to singular conditions, each time – a new singular unit of selection, each time.  Actualization is differenciation.  Actualized structures are not derived from predetermined taxonomic units of genera, families, orders, and classes.  Rather, species and parts are actualized in functional structures with singular conditions, each time.  Only singular pre-individual difference could create real evolutionary change.

Also, our idea of continuity would need to change.  Our ideas would need to reach a continuous variation that does not depend upon any prior conceptual relations of identity, resemblance, opposition, or analogy.  Our ideas of continuity would need to reach a pre-individual source of individual difference. 

According to Deleuze, the embryo is the source of individual difference – differentiated, not yet differenciated – virtual, not yet actual.  All singular differentiation is one ontologically singular body-without-organs.  The virtual organism is singular-universal.  Isn’t this a singular-universal that, each time, is actualized into a new singular unit (species-parts) of selection with its own singular conditions?  Individuation (the real relations and singular points) precedes actualization (species and parts).  Now, the unit of selection is singular rather than general.  Singular difference is the new unit of selection.  It allows theories about natural selection to reflect a more truly creative process of novelty.  

Therefore, under the assumptions of univocity, the new unit of singularity is the actualization of a pre-individual source.  Each actualization is a new functional structure – a new singular use of generality – even though there is no totalizing general structure.  This fulfills the first criterion of univocal being. 

(D&R 35) “Being is univocal….What is important is that we can conceive of several formally distinct senses which none the less refer to being as if to a single designated entity, ontologically one….”

However, in order to reach univocal being, there is something else that must be added.

(D&R 35-6) “….We must add that being, this common designated, in so far as it expresses itself, is said in turn in a single and same sense of all the numerically distinct designators and expressors.” 

Therefore, under Deleuze’s concept of univocal being, there is another prediction that can be made.  Not only does a pre-individual source (at the level of embryology) become actualized in new structures of creative generality, but the world is an egg.  Every numerically distinct designator and expressor is a singularity – another singular unit of selection.  That is, any intensive expression or designation not already formed within a prior general structure (i.e. not in relations of identity, resemblance, opposition, and analogy) can be said in a single and same sense.  For example, as long as a plant (like an orchid) and an insect (like a wasp) are not already in a prior classification of generality, together they may be regarded as a new assemblage – a new unit of singular selection – the orchid-wasp as individual unit of intensive difference upon which natural selection may act.    

Deleuze and Guattari write about Spinoza’s univocal difference (A Thousand Plateaus 253-4).  They say that Spinoza arrives at abstract but real elements with neither form nor function.  They are distinguished only by movement and rest, slowness and speed (like the switches that constitute the gradients in the embryo’s field of individuation or determine developmental timing).  Depending on their degree of speed or relation of movement within their plane of composition, they belong to a given Individual which is itself part of a more complex Individual, and so on to infinity.  The whole of Nature is a multiplicity of individuated multiplicities. 

(ATP 253) “There is therefore a unity to the plane of nature, which applies equally to the inanimate and the animate, the artificial and the natural.  This plane has nothing to do with a form or a figure, nor with a design or a function.  Its unity has nothing to do with a ground buried deep within things, nor with an end or a project in the mind of God.  Instead, it is a plane upon which everything is laid out and which is like the intersection of all forms, the machine of all functions; its dimensions, however, increase with those of the multiplicities or individualities it cuts across.  It is a fixed plane, upon which things are distinguished from one another only by speed and slowness.  A plane of immanence or univocality opposed to analogy.  The One expresses in a single meaning all of the multiple…..Being expresses in a single meaning all the differs.  What we are talking about is not the unity of substance but the infinity of the modifications that are part of one another on this unique plane of life.” 

The plane of life is univocal.  It is the intersection of all forms and the machine of all functions.  It cuts across dimensions (like the orchid-wasp).  This plane of univocal immanence is not a totalizing organism.  It is a body-without-organs.  And couldn’t what D&G write about Spinoza’s univocity also be said about the more recent findings of evo-devo?  Genetic switches generate spatio-temporal patterns or gradients in the embryo that are expressed and differenciated in the body plans of different organisms.  Now, isn’t it necessary for theoretical interpretation to consider a pre-individual field that actualizes a univocal homology?  Not unlike Spinoza’s plane of immanence-univocality, evo-devo includes every combination of differential relations of the virtual -- the Idea of the Universal Abstract Animal that is always the real difference of singularity – the ontological singularity of the whole of being.  This virtual is expressed with real difference that can never be totalized into a generalizing structure of analogy.  There is a deep homology of univocal being that, in every degree of singularity, changes nature.  The creativity of evolution may now find a more adequate theoretical foundation.  I take the empirical discoveries of the science of evo-devo to be consistent with what I believe Deleuze means when he says “being is univocal”.  Being is creative.  It is the expressive articulation of asignifying elements.  It is not a general signifying structure.    

Homologous being is univocal -- the world as an egg -- a body without organs – singularity in all its varieties.  Real evolutionary change in nature is the creativity of singular individual difference.  Of course, there are genetic and developmental constraints on selection.  But, if our theories are to reflect a truly creative evolution, these constraints must not be regarded as pre-determined in a structure of generality.  Singular difference creates the constraints.  Natural selection must work on variations of singularity that are not pre-determined.  Evo-devo finds that ancient genetic pathways still determine constraints in phylogenetic descent.  But, these constraints are part of a deep structure of homology.  That is, there are not equivocal differences that unite continuous resemblances in the maintenance of a general structure.  Rather, there is univocal singularity that differentiates difference into multiplicities of creative novelty. Taxonomic structure does not resemble the body without organs that conditions it.

Even though Darwinian Theorists have always known that all life arises from a common ancestor and is therefore in the structure of deep homology, theoretical interpretations have still presupposed a framework of generality.  But doesn’t evo-devo now show us that, in order to reach a truly deep homology, generalizing biases must be overcome.  Perhaps univocal interpretations of deep homology are consistent with the new empirical findings of evo-devo.  Of course, that is for evolutionary biologists to judge. 


* I admire Stephen Jay Gould’s grasp of the problem.  He attempted to reach a theory of radical contingency as an ontological property of nature.  He was not satisfied with the uniformitarian extrapolations of traditional Darwinian Theory.  However, in trying to solve the problem, he depended upon cross-level effects of an expanded hierarchical theory.  That is, he questioned extrapolation of macroevolutionary effects from micorevolutionary causes.  Yet it seems that, from Deleuze’s point of view, Gould is still hindered by assumptions of a general hierarchical structure.  Gould says (The Structure of Evolutionary Theory p. 1294), “The explanation of macroevolution requires structuralist and hierarchical inputs from various scales, and cannot be rendered as an extension of organismal adaptation, smoothly scaled up through the immensity of geological time.”

**Population is a unit of selection only when not confused with a general type.  Nor are differential relations to be confused with degrees of generality.  (ATP 54)  “As long as pre-established forms were compared to pre-determined degrees, all one could do was affirm their irreducibility….”  A generalizing structure must not be presupposed.  Rather, evolutionary biology is a science of multiplicities.   

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