Everything Flows

Everything Flows cover

Process philosophy has really just recently come on my radar, and I’m not sure what to make of it. I have written before that I don’t have a particularly strong background in philosophy, and so I’m hesitant to judge what I may not understand. At least some of the descriptions I’ve seen strike me as quasi-mystical word salads:

In short, a becoming actual entity prehends, or “feels,” not only other, past actual entities (which may be seen as the metaphysical basis for causality wherein one entity becomes part of another entity’s formation process), but also eternal objects (i.e., “pure possibilities”), which introduces novelty into the process. –Lukasz Lamza in Nature Alive – Essays on the Emergence and Evolution of Living Agents

But it’s entirely possible that this is a deep insight into the nature of reality that I simply lack the training to understand. At any rate, process philosophy has popped up again as a result of my search alert for “Volvox“. This time it’s in Argyris Arnellos’ chapter “From organizations of processes to organisms and other biological individuals” in a new edited volume by Daniel J. Nicholson and John Dupré, Everything Flows: Towards a Processual Philosophy of Biology. The entire book is open access; you can download a pdf of it here (but if you want the hardcover, I’ll get a buck or two if you buy it here).

I will get to what Arnellos has to say about Volvox, but first I have a couple of nits to pick. The chapter opens

Even though our world is continuously changing, contemporary thought is still dominated by a ‘substance-’ or ‘particle-based’ metaphysics, according to which static individuals composed by basic bits of matter constitute the world. [p. 199]

This seems a bit of a straw man to me. Who exactly is it who believes this? Maybe, MAYBE you could name a biologist who has said that individuals are static. I couldn’t. But contemporary thought is “dominated by” this view? Ridiculous. And just to stave off the criticism that Arnellos didn’t specify biological individuals, the whole chapter is about biological individuality.

Dupré (2012) has suggested that a process ontology is the most appropriate kind of ontology for thinking about life, organisms, and the organization of the biological world in general. The main claim is that the biological realm consists of processes rather than things. [p. 201]

Processes rather than things? I always assumed it was both.

Below I elaborate on this claim [that multicellular systems fail as integrated individual organisms] by considering examples of bacterial, early eukaryotic, and early eumetazoan multicellularity. [p. 209]

My only complaint here is a subtle one. The “early eukaryotic” example is Volvox, which is in no way an early eukaryote. Volvox probably evolved after mammals, certainly long after the origin of multicellularity in animals. Eukaryotes had been around for well over a billion years before Volvox came on the scene.

Aside from this, Arnellos gets most of the Volvox discussion right.

4.2. A case of early eukaryotic collaboration

A well-studied case of relatively simple eukaryotic collaboration is Volvox carteri. In its adult stage, this MC [multicellular] alga normally consists (a) of almost 2,000 biflagellate, terminally differentiated somatic cells engaging in phototaxis and (b) of sixteen germ cells, which are non-motile but can grow through photosynthesis and reproduce (Kirk 2005). [p. 211]

The number of germ cells is, of course, variable, but 16 is within the range of variation.

The way interaction is organized in V. carteri is qualitatively different from the one found in biofilms (see Arnellos and Moreno 2015 for details). There is no known direct communication among the somatic cells (Ueki et al. 2010). So, without considering the anatomical characteristics of the spheroid, the whole organization of interaction is of the type of swarms; each somatic cell swims according to its own detection of the local environment. [p. 211]

That is, as far as we know, true.

However, because of the morphological and anatomical constraints introduced during development (the spheroid’s polarity and asymmetry, combined with the immersion of all cells in the extracellular matrix; a proper orientation of the cells with respect to one another; and the reorientation of the flagella, beating in each cell towards the always heavier posterior), the collaboration in V. carteri is tighter and much stricter than in the myxobacteria. This structural arrangement is necessary for the proper execution of phototactic swimming and will stay unaltered during the MC alga’s lifetime. It could be considered collaboration on the basis of functional interdependence. The movement of the flagella of each somatic cell requires the movements of the other cells, in the sense that proper phototaxis is the net effect of all cells’ movements. [p. 211]

Also true, due to hydrodynamic interactions.

In accordance with the account we have discussed, V. carteri exhibits a more integrated organization than biofilms. Contrary to M[yxococcus] xanthus biofilms, the alga’s constitutive identity is compatible with its interactive dimension, and its MC [multicellular] organization cannot be reversed to the unicellular stage of its constituents because of the absolute germ/soma division of labour. However, compared to the organismal integration of a cell, the integration achieved by this MC alga is weak. Isolated germ cells of V. carteri would still grow and divide under euphotic conditions (Koufopanou and Bell 1993). This means that the constitutive identity of the MC alga could be reproduced and maintained even without its interactivity; in other words, unlike unicellular organizations, the alga’s relatively weak interdependence between constitution and interaction is not indispensable for the development and maintenance of its organization. This type of early eukaryotic collaboration results in a recursively self-maintaining organization but it still does not achieve the form of integration its constituents entertain when in their unicellular form. [pp. 211-212]

In the section entitled “Organisms and other biological individuals,” Arnellos concludes

According to the analysis offered here, MC organizations such as the one exhibited by V. carteri do not achieve organismal status, but are nevertheless evolutionary individuals. Each cell type needs the other for the whole colony to be maintained and to reproduce its organization. Somatic cells are necessary for the spheroid to be moved into euphotic conditions and germ cells are needed for the reproduction of the colony. [p. 215]

I’m not going to get into an extended discussion of what constitutes an individual here (biologists and philosophers have been arguing about that much longer than I’ve been alive). I’ve previously written about the takes of Julian Huxley, David QuellerEllen ClarkeBeckett SternerSonya BaharLukasz Lamza, Karen Kovaca, Erik Hanschen and Dinah Davison, Derek Skillings, and myself, and I haven’t scratched the surface. Suffice it to say that opinions vary.

Arnellos’ opinion that Volvox doesn’t qualify as an organism, as best I can tell, is based on a lack of central coordination:

…although the alga’s swimming is adaptive (it manages to stay or move to euphotic conditions), there is no central functional coordination in the sense of a regulatory system (like the TCST [E. coli two-component signal transduction subsystem]) that would switch the MC [multicellular] system between two different organizational regimes. [p. 211]

The other given example of central coordination is the central nervous system of eumetazoans. Personally, I think this is too high a bar. Lots of animals lack a central nervous system, and I think a definition of organism that excludes echinoderms, ctenophores, and cnidarians (among many others) would be silly. But it seems Arnellos only intends the central nervous system as an example of a way that high levels of integration can be achieved:

…the control of eumetazoan behaviour cannot be achieved without functional coordination of all its different local regulatory subsystems. What is required is higher-order integration. This is what a regulatory centre provides: it functionally integrates all local norms according to a higher-level normativity. This is precisely the role of the NS [nervous system] in eumetazoa. It does not only regulate contractile epitheliomuscular tissues that generate sensorimotor interactions; it also regulates processes of development, growth, and global homeostasis. [p 212, references omitted]

I’m not convinced. Coordination among parts seems a reasonable (though by no means the only reasonable) criteria for organismality, but I can’t see why that coordination needs to be “central.” The process of inversion in volvocine algae seems to me a pretty striking example of coordination among cells, though Arnellos is probably right that there’s no central control. I think, though, that lots of developmental processes in things that are uncontroversially considered organisms similarly lack central control. Of course, I’m biased.


Stable links:

Arnellos, A. 2018. From organizations of processes to organisms and other biological individuals. pp. 199-221 in Nicholson, DJ and Dupré, J Everything Flows: Towards a Processual Philosophy of Biology. Oxford University Press.


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