Convergence by Necessity: Sensory Systems and the Three-Level Architecture of Biological Organisation

Abstract King and Gray (2026) propose that functional degradation in disorders of consciousness follows a systematic pattern across three organisational levels — biological regulation, integrated experiential awareness, and recursive self-modelling — with ordered vulnerability from the highest to the lowest: recursive self-modelling fails first, biological regulation last. Is this three-level architecture a deep organisational principle, or a contingent feature of vertebrate neuroanatomy? This paper offers a converging line of evidence from comparative sensory physiology. Seven sensory systems — four of which represent independent evolutionary origins (vision, olfaction, gustation, and infrared sensing), with audition and the lateral line as divergent elaborations of a shared mechanoreceptive ancestry, and mammalian touch as an independently evolved mechanoreceptive system — exhibit a common three-level organisational structure. The first level consistently contains three distinct sub-functions: noise disposal, signal preservation, and signal transformation. I argue that each level solves a distinct thermodynamic problem — the hierarchy is not arbitrary but thermodynamically constrained. While this paper stops short of formal mathematical proof, it establishes the heuristic and structural groundwork required to map these biological architectures to formal rate-distortion bounds. By establishing this conceptual and structural territory, this paper lays the groundwork for future quantitative modelling of biological information processing. Simpler organisms may exhibit only Levels 1 and 2 without Level 3, which requires sufficient organisational complexity. If this analysis is correct, then King and Gray's ordered vulnerability and the sensory convergence are two independent manifestations of the same thermodynamic principle: three levels, with the properties both frameworks observe, because any entropy-reducing biological system that does not implement those levels is at a severe selective disadvantage; simpler organisms implement subsets — Level 1 alone, or Levels 1 and 2 — that are metabolically viable but informationally limited. This is a research synthesis that integrates comparative sensory physiology with thermodynamic principles of biological organisation. It generates hypotheses regarding the role of Level 2 metabolic stress in neurodegenerative conditions. The work is intended to stimulate discussion and further empirical investigation. Keywords: thermodynamic constraints, three-level architecture, sensory systems, convergent evolution, hierarchical organisation, ordered vulnerability, disorders of consciousness, biological information processing