Biological hierarchical complexity

Heim et al. (2017). "Hierarchical complexity and the size limits of life." Proceedings of the Royal Society B (Biological Sciences), 284. 

The above article was referenced in Koonin et al (2021) as one that described the hierarchical organization of biological life. It distinguishes between two forms of complexity, vertical and horizontal. The former "is the number of levels of nestedness or levels of organization in an organism," whereas the latter "is the number of part types within a given level." In that sense it is much akin to the Model of Hierarchical Complexity's (MHC) distinctions. 

This study explores the sizes of various life forms relative to their vertical complexity: "(i) virus, (ii) single-celled prokaryote, (iii) single-celled eukaryote and (iv) non-colonial multicellular eukaryote." Obviously the more complex an organism is, meaning the more components it has to coordinate, requires a larger size to accommodate it. Their "results suggest that there are constraints on both the minimum and maximum sizes for each level of complexity," but also with "the hypothesis that minimum size constraints arise from physical factors while constraints on maximum size arise from physiological factors."

"In summary, body size data spanning all major branches on the tree of life reveal discrete macroevolutionary modes for different levels of vertical complexity. The individual size distributions for multicellular eukaryotes, protists, prokaryotes and viruses are approximately unimodal and symmetric, but the combined distribution is multimodal and highly asymmetric. Evolutionary innovations associated with new levels of complexity therefore appear to be fundamentally different in nature from those that arise within complexity levels."

The MHC's levels are purely abstract and not grounded in this sort of biological complexity. Hence in the abstract such levels can increase ad infinitum without the biological constraints noted above. And yet our bodies and brains do have these constraints, therefore our own complexity is indeed limited by our embodiment. My previous article (Berge 2019), using our embodied cognitive constraints, contextualized the MHC's limitations given its abstract divorce from that embodiment.

I suggest that if we are to have a more meaningful measure of hierarchical complexity it must be tied to our biological constraints. Our models themselves have to operate within these constraints. Infinite abstract complexity and growth seems more a sign of dysfunctional growth like we're seeing in our current crises. And per above and Koonin (2021), each level, while unimodal and symmetric within itself, is different from the other levels and multimodal when comparing the other levels collectively. Hence we need much more that a self-similar fractal measure to model it. That is, if it's to remain human.

I've also suggested that perhaps there is a time for us to decomplexify. It might be appropriate given that our current socio-economic system is depleting natural resources faster than they can be regenerated. This on top of the fact that our fossil-fuel energy system is destroying the atmosphere and oceans at an alarming rate. All of which is directly tied to this notion of unlimited growth, as is not coincidentally our models of complexity. Hence the degrowth movement advises us to live within our means and our ecological limits. All of which might very well require us to take a step back on our complexity obsession to survive. As both articles make clear, biological evolution has repeatedly become simpler when necessary. Instead of thinking that more complexity is the answer to our so-called meta-crisis it just might be that it is the cause and that we might need to engage more voluntary simplicity at this point in our evolution.

I can hear the cries already. But that would be a regression! It would be going backwards! But only if we unconsciously accept the premise of unlimited growth and complexity in one direction. It would after all be in line with evolution itself, which the complexity crowd purports to claim as their own premise. Perhaps we should listen to what evolution actually does instead of following our current dysfunctional obsession with ever-increasing complexity and growth? There's a move in Tai Ji Quan called Step Back and Repulse Monkey. This seems the right time to practice it.