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The Identity of Living Beings, Epigenetics, and the Modesty of Philosophy

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Abstract

Two problems related to the biological identity of living beings are faced: the who-problem (which are the biological properties making that living being unique and different from the others?); the persistence-problem (what does it take for a living being to persist from a time to another?). They are discussed inside a molecular biology framework, which shows how epigenetics can be a good ground to provide plausible answers. That is, we propose an empirical solution to the who-problem and to the persistence-problem on the basis of the new perspectives opened by a molecular understanding of epigenetic processes. In particular, concerning the former, we argue that any living being is the result of the epigenetic processes that have regulated the expression of its genome; concerning the latter, we defend the idea that the criterion for the persistence of its identity is to be indicated in the continuity of those epigenetic processes. We also counteract possible objections, in particular (1) whether our approach has something to say at a metaphysical level; (2) how it could account for the passage from the two phenotypes of the parental gametes to the single phenotype of the zygote; (3) how it could account for the identity of derivatives of one living being that continue to live disjoined from that original living being; (4) how it could account for higher mental functions.

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Notes

  1. According to genetic essentialism, we are our genes, as it was paradigmatically stated by Gilbert (1992) who observed that, since our sequenced genome can be contained in a CD, we may take the latter out of the pocket and claim: “Here is a human being: it’s me!”. At the present day, we suspect that no biologically informed and philosophically critical scholar could rationally support any form of genetic essentialism, and therefore we do not devote much time to objecting to it. Incidentally, the entire content of this paper could be seen as a “long argument” against genetic essentialism. Note, however, that if it were true that the identity of a living being cannot be reduced to its genes, ‘genetic identity’ is not a void concept, since it refers to that kind of identity that relies only on the genotype. For example, two homozygotic twins are, at least in the first stages of their life, genetically identical. Note that genetic essentialism can be objected in a variety of different ways and from several different perspectives; for instance, see (Lewontin et al. 1984; Berkowitz 1996; Mauron 2003; Hauskeller 2004; Boniolo and Vezzoni 2006).

  2. In other words, the persistence-problem regards the following question: “Which is the set of r-properties (p 1, …, p r) of a living being A, such that if (p 1, …, p r)t ≡ (p 1, …, p r)t then A t ≡ A t, where t’ and t indicates two successive times (t’ > t) at which the set of properties and the living being A are given?”. Of course, here there is an existential quantification over the properties (∃p: p tp tA t ≡ A t). If we were dealing with qualitative identity, we would have a universal quantification over the properties: ∀p, p tp tA t ≡ A t.

  3. There is also an interesting renaissance of the immunological identity analysis (cf. Pradeu 2009). As we will see, our approach encapsulates it.

  4. Note that there are many different definitions of ‘development’. For example, ‘development’ can be meant as the set of modifications occurring in a living being from its zygote stage to its adult stage or to its sexual maturation. We accept the definition proposed by those evo-devo biologists (for instance, Minelli 2003) who consider development as the set of modifications occurring over the entire life span of a living being. Some could object that the more correct term should be ‘ontogeny’. Actually there exist many different definitions also of this term. According to some authors, the two terms could be superimposed; according to others, ontogeny has to do with both origin and development. In this case, the development of a living being would be a sub-period of its ontogeny.

  5. Here, we should pay attention that an intergenerational process can be among successive generations of cells either belonging to a given organism (in case of multicellular living beings), or being themselves an organism (in case of unicellular living beings). But it can be also among successive (multicellular) organisms.

  6. Certainly one could ask what we intend by ‘living being’. On this issue, see Boniolo and Di Fiore (2008).

  7. On the other hand, this “alternative” perspective based on empirical sciences has a long history and is raising a renewed interest in the philosophical community, as evidenced by the recent analyses of boundaries (Boniolo et al. 2009) or causation (Boniolo et al. 2011). Of course, this approach does not deny any possible metaphysical commitment. There could always be metaphysical presuppositions in a scientific theory and in an epistemological perspective, as has been clarified by the debate on the relationships between science and metaphysics made almost 40 years ago by philosophers such as K. R. Popper, J. Agassi, J. Watkins, W. W. Bartley III, Th. S. Kuhn, and P. K. Feyerabend, etc.

  8. It was thought that neurogenesis stops at a certain moment of foetal development. Yet it has been found that it continues in certain brain areas throughout life (cf. Altman 1963; Eriksson et al. 1998; Kempermann 2002).

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Acknowledgments

We want to thank Matteo Mameli and Maria Kronfeldner for their comments on previous versions of this paper and the many who have raised questions in the seminars in which the ideas here contained have been presented. Moreover, we wish to acknowledge two anonymous reviewers, whose extremely scrupulous reading of the paper and helpful suggestions have permitted us to improve it. To finish, we have to thank Rosalind Gunby and the Scientific Writing Team at the IFOM-IEO Campus.

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Boniolo, G., Testa, G. The Identity of Living Beings, Epigenetics, and the Modesty of Philosophy. Erkenn 76, 279–298 (2012). https://doi.org/10.1007/s10670-011-9308-9

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