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The Physics of Life: Exploring Information as a Distinctive Feature of Living Systems

Stuart Bartlett, Andrew W. Eckford, Matthew Egbert, Manasvi Lingam, Artemy Kolchinsky, Adam Frank, Gourab Ghoshal

TL;DR

The paper probes whether information, specifically semantic information, is a distinctive feature of life by arguing that living systems uniquely acquire, process, and utilize environmental information to sustain viability. It develops two formal frameworks—the semantic information approach and the fitness value of information—grounded in mutual information and rate-distortion theory to link information to survival and growth, with $I(X;Y)$, $I(Z;Y)$, and $d(x,z)$ as core constructs. It discusses implications for origins of life and astrobiology, including information-driven transitions, informational constraints on habitability, and information-centric biosignatures, while proposing experimental platforms such as flow reactors, synthetic cells, and active matter to test predictions. The work emphasizes integrating theoretical and experimental approaches to reveal universal informational dynamics that may span biology, chemistry, and potentially digital life, thereby informing how we search for life beyond Earth and understand life's emergence. It also highlights threshold phenomena and learning dynamics as key features of information processing in living systems, suggesting concrete experiments to quantify the value and limits of semantic information in complex environments.

Abstract

This paper explores the idea that information is an essential and distinctive feature of living systems. Unlike non-living systems, living systems actively acquire, process, and use information about their environments to respond to changing conditions, sustain themselves, and achieve other intrinsic goals. We discuss relevant theoretical frameworks such as ``semantic information'' and ``fitness value of information''. We also highlight the broader implications of our perspective for fields such as origins-of-life research and astrobiology. In particular, we touch on the transition to information-driven systems as a key step in abiogenesis, informational constraints as determinants of planetary habitability, and informational biosignatures for detecting life beyond Earth. We briefly discuss experimental platforms which offer opportunities to investigate these theoretical concepts in controlled environments. By integrating theoretical and experimental approaches, this perspective advances our understanding of life's informational dynamics and its universal principles across diverse scientific domains.

The Physics of Life: Exploring Information as a Distinctive Feature of Living Systems

TL;DR

The paper probes whether information, specifically semantic information, is a distinctive feature of life by arguing that living systems uniquely acquire, process, and utilize environmental information to sustain viability. It develops two formal frameworks—the semantic information approach and the fitness value of information—grounded in mutual information and rate-distortion theory to link information to survival and growth, with , , and as core constructs. It discusses implications for origins of life and astrobiology, including information-driven transitions, informational constraints on habitability, and information-centric biosignatures, while proposing experimental platforms such as flow reactors, synthetic cells, and active matter to test predictions. The work emphasizes integrating theoretical and experimental approaches to reveal universal informational dynamics that may span biology, chemistry, and potentially digital life, thereby informing how we search for life beyond Earth and understand life's emergence. It also highlights threshold phenomena and learning dynamics as key features of information processing in living systems, suggesting concrete experiments to quantify the value and limits of semantic information in complex environments.

Abstract

This paper explores the idea that information is an essential and distinctive feature of living systems. Unlike non-living systems, living systems actively acquire, process, and use information about their environments to respond to changing conditions, sustain themselves, and achieve other intrinsic goals. We discuss relevant theoretical frameworks such as ``semantic information'' and ``fitness value of information''. We also highlight the broader implications of our perspective for fields such as origins-of-life research and astrobiology. In particular, we touch on the transition to information-driven systems as a key step in abiogenesis, informational constraints as determinants of planetary habitability, and informational biosignatures for detecting life beyond Earth. We briefly discuss experimental platforms which offer opportunities to investigate these theoretical concepts in controlled environments. By integrating theoretical and experimental approaches, this perspective advances our understanding of life's informational dynamics and its universal principles across diverse scientific domains.
Paper Structure (9 sections, 4 figures)

This paper contains 9 sections, 4 figures.

Table of Contents

  1. Introduction
  2. Theoretical frameworks
  3. Semantic information
  4. Fitness value of information
  5. Implications for origins of life research
  6. Implications for astrobiology
  7. Informational Constraints on Habitability
  8. Information-Centric Biosignatures
  9. Summary and future directions

Figures (4)

  • Figure 1: Semantic thresholds. Semantic Information identifies "semantic thresholds" where only specific mutual information between an agent and its environment impacts viability. ( a) The foundational study kolchinsky2018semantic introduced this concept through counterfactual simulations assessing viability as information is scrambled. ( b) Forager models Sowinski:2023vf demonstrated such thresholds by adding noise to food detection sensors, revealing a peak in viability per bit of information at the threshold. ( c) Similar thresholds appear in biosphere models like Daisy-World, responding to stellar forcing Sowinski2024eDW.
  • Figure 2: Semantic information in a flow reactor. A proposed experiment for studying semantic information inspired by the "fitness value of information" from Ref. pinero2024information. (a) The system consists of a population of simple replicators, such as the photocatalytic molecular replicators synthesized by Liu et al. liu2024light. (b) The replicators are placed in a flow reactor and subjected to fluctuating environments which favor different replicators, e.g., weak (green) light or strong (orange) light. The population is also allowed to re-equilibrate during "inactive" periods (no growth). (c) Productivity (replicator production per time) depends on environmental statistics as well as internal parameters, such as exchange reactions and re-equilibration timescale $\lambda$. At intermediate timescales, the system's memory may provide a source of side information, increasing productivity in proportion to the mutual information between successive environments pinero2024information.
  • Figure 3: Example schematic for an origins of life experiment focusing on information measures. Consult the text for full details. Reproduced with permission from bartlett2019probing.
  • Figure 4: Signal-to-noise (SNR) associated with chemosensing plotted as a function of cell radius for Earth's oceans (blue) and the hydrocarbon lakes of Saturn's moon, Titan (red); the dotted and dashed lines correspond to spatial and temporal modes of sensing LM21. A heuristic minimum cell radius may be inferred by determining when the SNR exceeds the value of unity (horizontal black line).