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.