For around 150 years, Darwinism and the modern synthesis have endured as theoretical approaches in the field of evolutionary biology. Over this period, biologists have made unprecedented progress as regards to their concepts, methods and instruments. By way of example, when Darwin postulated his theory on the origin of species, it was not yet possible to see a chromosome, much less to see how it worked during the different stages of the cell division. Strikingly, the modern synthesis has generated a set of hypotheses that keep the core of Darwinian theory intact, as put forward in Marta Linde Medina’s (2010) interesting target article.Facultad de Ciencias Naturales y Muse

Dressino, Vicente

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CRITIQUE OF THE INTERNALISM/EXTERNALISM APPROACH AS A WAY OF EXTENDING THE SYNTHETIC THEORYVICENTE DRESSINOFor around 150 years, Darwinism and the modern synthesis have enduredas theoretical approaches in the field of evolutionary biology. Over thisperiod, biologists have made unprecedented progress as regards to theirconcepts, methods and instruments. By way of example, when Darwinpostulated his theory on the origin of species, it was not yet possible to seea chromosome, much less to see how it worked during the different stagesof the cell division. Strikingly, the modern synthesis has generated a setof hypotheses that keep the core of Darwinian theory intact, as putforward in Marta Linde Medina’s (2010) interesting target article. A key concept in the theoretical structure of Darwinism and in themodern synthesis is that of ‘natural selection,’ which has yet to be scien-tifically defined in a clear-cut and verifiable manner. Thus, initially, naturalselection was tautologically defined as the ‘survival of the fittest,’ andMayr subsequently conceptualized it as ‘differential reproductive success.’This shift entails much more than a mere semantic transformation. It alsoimplies a conceptual shift from selection based on the organism’s potentialto a reproductive conception. In other words, what is ‘selected’ is theorganism that leaves the most descendents or, to use current terms, thegenes or sets of genes that pass on the most traits to future generations.This concept would be related to multicellular organisms that reproducesexually, but would thus be inapplicable to organisms that reproduceasexually or by parasexual reproduction mechanisms. According to Dress-ino (2010), organisms that reproduce through these mechanisms are tech-nically clones and do not present any genetic variation for naturalselection to act upon. Another controversial aspect of natural selection isits metaphysical character, which Mayr (1998) himself asserts by statingFacultad de Ciencias Naturales y Museo, Universidad Nacional de La Plata, Argentina. /vdressino@gmail.com; vdress@fcnym.unlp.edu.arThis text comments the article ”Natural selection and self-organization: A deep dichotomy inthe study of organic form,” by Marta Linde Medina, Ludus Vitalis, vol. XVIII, num. 34, 2010,pp. 25-56. Available at www.ludusvitalis.org/debates.Ludus Vitalis, vol. XIX, num. 35, 2011, pp. 319-324.that evolutionary explanations would not vary if ‘God’ were referred toinstead of ‘natural selection’. That is to say, if the causal factor werechanged, the core structure of the theory would remain intact. On theother hand, Salthe (2010) conceptualizes natural selection as ‘the physicalprinciple of maximal energy gradient dispersion’ (p. 227). This definitionposes a thermodynamic approach to natural selection but it is very difficultto apply empirically.In turn, Linde Medina proposes the internalism/externalism dichotomyas an argumental strategy through which to analyze the debate on theextension of the synthetic theory and the role of natural selection. Never-theless, this controversy is becoming less significant as biology now relieson more integrated approaches, either deriving from or included in com-plexity theory. Thus, according to García-Azkonobieta (2005), the internal-ist perspective arises from material principles as a dynamic and systemicproperty that results from the interaction between simple units. On theother hand, according to the externalist approach, organization is theresult of a historical selection process of functional adaptation to theenvironment, in which the organism is broken down into a series offeatures that can ultimately be considered as emerging manifestations ofthe genes they are made of. From this viewpoint, the autonomous char-acter of organisms is weakened, since they are assumed to derive from anexternal organizing principle that brings about order. Therefore, the ideathat the internalism/externalism debate itself might extend the synthetictheory is meaningless. Who would call into doubt that an organism is theresultant of self-organizing forces facing responses to environmental pres-sures? At present, the existence of a constant two-way exchange betweenorganisms and their environment is widely recognized, thus bringing anend to the internalism/externalism controversy. Nevertheless, the domi-nance of the reductionist aspect of genetics avoids this interaction and, onthe other hand, epigenetics seems to uncover the error of this approach.Therefore, the internalism/externalism dichotomy constitutes a methodo-logical approach rather than an epistemological or philosophical one. Infact, the choice between an internalist (genetic, physiological, etc.) ap-proach and an externalist (ecological, paleobiological, etc.) one is deter-mined by the focus of the researcher when conceptually delimiting thesystem to be studied. In any case, an expansion of the synthetic theorycould not be determined through these approaches. The development of models based on the concept of modules is areflection of this. In this sense, Schlosser (2002) proposes that, undercertain conditions (which he does not specify), modules act as ‘units ofevolution’. He thus asserts that modules are more important in delimitingunits of selection than either organisms or genes because they are lesseasily disrupted by recombination. However, Schlosser does not explain320 / LUDUS VITALIS / vol. XIX / num. 35 / 2011how a module can be selected or what definition of natural selection he isadhering to in order to justify this.On the other hand, the modular perspective has also been applied tophysiological adaptation—another important component of this theory,together with adaptation in its broadest sense—by means of a formaldefinition (Dressino 2005) and by a more general framework aimed at amodular theory of adaptation (Dressino and Lamas 2010). These authorshave revealed the conceptual problems underlying traditional under-standings of adaptation and the usefulness and biological sense of modu-lar proposals relating to adaptation. In short, the scenario has moved froma strictly reductionist viewpoint (the traditional understanding of thegene) to an integrationist approach represented by modules. The main problem of the synthetic theory is its reductionism, which isstrongly based on the conceptual framework of “gene-centrism” (Dressino2010) and the exclusive role of natural selection as a ‘mechanism’ or‘process.’ It is evident that mechanism and process represent completelydifferent ideas, but this is part of the conceptual polysemy proper to thesynthetic theory in particular, and of biology in general (Folguera 2008).At any rate, regardless of whether natural selection is conceptualized as amechanism or as a process, there is no doubt that it should be possible toenumerate or refer to its constituent elements. Yet this cannot be carriedout since natural selection is, at best, a complex system very difficult tocharacterize. Several authors (Maturana and Varela 1984) have pointed out theideological connotations of the expression ‘natural selection’, also impliedin the statements of Mayr’s discussed above. One way of eliminating theideological nature of this concept would be to use the expression naturaldrift, as proposed by Maturana and Varela (1984) and Maturana andMpodozis (2000). According to these authors, ‘natural drift’ is the result ofinvariance of autopoiesis (self-organization of living systems) as well as ofadaptation. It then follows that natural drift would constitute the mostappropriate hypothesis for a module-based biology that would be thus inline with complex systems, as was previously stated.Building on the modular argument, Newman and Bhat (2008) putforward the concept of “dynamical patterning modules” (DPMs) consistingin products of the ‘toolkit’ genes that characterize mechanical and chemi-cal processes of cellular aggregates such as cohesion, viscosity, elasticity,diffusion, etc. This theoretical approach represents a major breakthroughin the understanding of the physical and genetic determinants of multicel-lular systems’ development and evolution. These authors claim that thebody plans and organ forms generated by these DPMs have been stabilizedand consolidated by natural selection and genetic drift. Proving thisassertion empirically is very difficult, due to the following basic reasons.DRESSINO / CRITIQUE TO THE APPROACH / 321First, DPMs include physical phenomena over which natural selectionexerts no power whatsoever. Second, the concept of ‘gene’ itself is under-going a deep crisis, according to the authors belonging to the ‘HumanGenome Project’ consortium (Gerstein, et al. 2007; Gingeras 2007). In thisregard, genes no longer represent particle units with a specific location onthe DNA strand, but are instead conceptualized as modules or ‘transcrip-tors.’ Thus, the current understanding of genes involves a number ofelements that are often far apart from one another in the DNA strand aswell as molecules of diffuse origin such as small RNA (RNAs), non-codingRNA (ncRNAs), interfering RNA (siRNA), etc., which render the work ofnatural selection—or at least the classical conception of this—untenable.Furthermore, this understanding gives rise to another question, namely,which genic unit natural selection acts upon, taking into account the deepinterconnection between genic modules.Moreover, Linde Medina (2010) affirms that part of Evo-Devo is com-patible with the Darwinian paradigm if development is defined as amechanism, which is genetically controlled by switching on and off genes.This has been questioned by Salthe (2008) on the grounds that naturalselection is a weak force during embryonic development. Nevertheless, indevelopmental biology growth and development are not usually concep-tualized as being exclusively controlled by switching on and off genes.Besides, development is a process that responds to a complex dynamicsthat goes beyond the individual action of specific genes. In this sense,epigenetics has shown that the switching on and off of genes may be theresult of methyl groups incorporated into certain positions on the DNAstrand. As such, the author’s assertion that Evo-Devo represents a gene-centric perspective compatible with the synthetic theory is questionable.Additionally, the problems posed by the modern synthesis are made morecomplex by the presence of numerous substances in the environment thatact as endocrine disruptors that compromise the development and differ-ential reproductive success of the exposed species, regardless of theirgenetic make-up (Gilbert and Epel 2009). The historical development ofEvo-Devo thus clearly proves that it did not emerge as a line of researchrelated to the modern synthesis. Furthermore, the efforts made so far tounite Evo-Devo and synthetic theory have not succeeded for the reasonsdiscussed above.In short, as was mentioned above, if the internalism/externalism dichot-omy has to do with a methodological decision, then an extension basedon this categorization would be impossible since, as has already beenexplained, it is up to the researcher to strategically decide or propose themethodology of their approach. Moreover the main reason for the ‘Altenberg 16’ meeting of July 2008was supposedly the paper written by Bossdorf and others on the role of322 / LUDUS VITALIS / vol. XIX / num. 35 / 2011epigenetics. However, this was just an excuse, since there were severalresearch papers on epigenetics prior to that by Bossdorf, et al. (2008). Ashas been already explained, the problem is that we are still using a150-year-old theory, the core of which remains largely unchanged. Wecontinue to refer to concepts such as ‘adaptation’ and ‘natural selection’,though they no longer mean what they did in 1859. Which means that theliterature uses the same terminology to refer to a wide range of differentconcepts.At this point, it seems reasonable to raise some questions. Is it necessaryto extend or resynthesize the synthetic theory? The brief discussion pre-sented above leads me to reflect that the overwhelming amount of avail-able empirical data justifies the need for either a resynthesis or thedevelopment of a new theory that would include, in an appropriatemanner, the progress made in all fields. Further, why do we biologistsinsist on resorting to the concept of natural selection, even, for example,when carrying out experimental research from which natural selectionshould supposedly be absent? A plausible answer to this question has todo with something mentioned above, namely that we are facing a theo-retical-conceptual vacuum, in which the lack of new and more suitableexplanations leads us to resort to ancient ones. Even so, this is a contro-versial point since some concepts can effectively help us to explain numer-ous empirical problems, many of which are becoming important in certainfields. This is the case with, for example, directed mutagenesis (applied inoncology), horizontal gene transfer (a concept used in phylogenies),epigenetics as an explanation in cases of speciation and in medical oncol-ogy, and so forth. Nevertheless, it is likely that these issues are alsoinfluenced by factors related to the sociology of science and which lie farbeyond the scope of this discussion. DRESSINO / CRITIQUE TO THE APPROACH / 323BIBLIOGRAPHYBossdorf, O., Richards, C. L., Pigliucci, M. (2008), “Epigenetics for ecologists,”Ecology Letters 11: 106–115.Dressino, V. (2005), “Theoretical and semantic aspects of the modular physi-ological adaptation,” Rivista di Biologia / Biology Forum 98: 265-278.Dressino, V. (2010), “La encrucijada de la teoría sintética: expansionismo o nuevasíntesis teórica,” Revista Argentina de Antropología Biológica 12(1):15-25.Dressino, V., Lamas, S. G. (2010), “Una perspectiva modular de la adaptaciónbiológica,” Ludus Vitalis XVIII (33): 13-24.Folguera, G. (2008), “La polisemia en la Biología: implicaciones científicas yepistemológicas,” Revista Colombiana de Filosofía de la Ciencia IX: 155-164.García-Azkonobieta, T. (2005), “Evolución, desarrollo y (auto) organización. Unestudio sobre los principios filosóficos de la Evo-Devo,” Doctoral thesis.Universidad del País Vasco. San Sebastián. Spain.Gerstein, M. B., Bruce, C., Rozowsky, J. S., Zheng, D., Du, J., Korbel, J. O.,Emanuelsson, O., Zhang, Z.D., Weissman, S., Snyder, M. (2007), “What is agene, post-ENCODE? History and updated definition,” Genome Res. 17: 669-681.Gilbert, S. F., Epel, D. (2009), Ecological Developmental Biology: Integrating Epige-netics, Medicine and Evolution, Massachussets: Sinauer Associates Inc.Gingeras, T.R. (2007), “Origin of phenotypes: Genes and transcripts,” GenomeRes. 17: 682-690. Linde Medina, M. (2010), “Natural selection and self-organization: a deep di-chotomy in the study of organic form,” Ludus Vitalis XVIII (34): 25-56.Maturana-Romesín, H., Mpodozis, J. (2000), “The origin of species by means ofnatural drift,” Revista Chilena de Historia Natural 73: 261-310.Maturana-Romesín, H., Varela, F.G. (1984), El árbol del conocimiento: las basesbiológicas del entendimiento humano.Chile: Editorial Universitaria.Mayr, E. (1997), This is Biology: The Science of the Living World. USA: HarvardUniversity Press.Newman, S. A., Bhat, R. (2008), “Dynamical patterning modules: physic-geneticdeterminants of morphological development and evolution,” Phys. Biol, 5015008.Salthe, S. N. (2008), “Natural selection in relation to complexity,” Artificial Life 14:363-374.Salthe, S. N. (2010), “Limits to Darwinism,” Ludus Vitalis, XVIII (34): 227-235. Schlosser, G. (2002), “Modularity and the units of evolution,” Theory Biosci. 121:1-80.324 / LUDUS VITALIS / vol. XIX / num. 35 / 2011

Critique of the internalism/ externalism approach as a way of extending the synthetic theory

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Critique of the internalism/ externalism approach as a way of extending the synthetic theory

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