Living matter has long been one of the most perplexing questions in biological sciences. The sheer complexity and diversity of life forms, from the tiniest microbe to the largest organism, continue to challenge our understanding. A recent study presents an innovative approach to this challenge by conceptualizing living matter as a cascade of machines producing machines—a framework that could revolutionize how we think about the origins and organization of life. This new perspective offers a clearer picture of how the individual components of cells and organisms work in tandem to create the larger structures that make up the living world.
A Cascade of Machines: From Atoms to Biosphere
The idea of life as a cascade of machines was developed by Professors Tsvi Tlusty from the Department of Physics at the Ulsan National Institute of Science and Technology (UNIST), South Korea, and Albert Libchaber from the Center for Physics and Biology at Rockefeller University, New York. Their collaborative study proposes that living organisms can be understood as a hierarchy of smaller and smaller machines, all working in tandem to produce larger, more complex systems. At the bottom of this cascade, one finds molecular machines—such as ion pumps, enzymes, and ribosomes—which are responsible for basic cellular functions. These machines interact and work together to sustain life on the smallest scales, down to the atomic level.
As we move upward in this cascade, we encounter increasingly larger systems. These molecular machines aggregate into cells, which, in turn, form tissues, organs, and even entire populations of organisms, ultimately leading to the formation of the biosphere. The study provides a framework for understanding how these different levels of organization in living matter are not separate from each other but are interconnected through a continuous and self-sustaining process of machine production and interaction.
This conceptualization draws on a powerful analogy that was first proposed by the seventeenth-century polymath Gottfried Leibniz, who suggested that living bodies, or the “machines of nature,” were composed of ever-smaller machines, continuing “to infinity.” Leibniz’s insight forms the philosophical backdrop for this new study, which expands on his idea by presenting a more detailed and formal model of how life is organized and how it operates.
The Mathematical Language of Life
To explore this cascade of machines, Tlusty and Libchaber developed a simplified mathematical language that encapsulates the behavior of living matter. Their model presents life as an (almost) infinite, double cascade, spanning a staggering eighteen orders of magnitude in space and thirty orders of magnitude in time. This vast range captures everything from the smallest molecular interactions within cells to the largest biological processes that shape ecosystems and entire biospheres.
However, what sets this study apart is the identification of a critical point where the two branches of the cascade—large-scale and small-scale—converge. This point occurs at 1,000 seconds and 1 micron, the typical temporal and spatial scales at which microbial life operates. The critical point represents the minimum conditions necessary for a self-replicating machine to interact with its environment, specifically salty water. At this point, the dynamics of life shift, marking the transition from simple molecular interactions to the formation of more complex systems, such as cells that self-organize into tissues and larger organisms that form populations.
In essence, the critical point represents the threshold at which life, in its most basic form, transitions from isolated self-replicating units to interconnected societies of machines. It is here that the first embryonic forms of biological systems emerge, eventually leading to the formation of entire biospheres. This insight helps bridge the gap between molecular biology and larger-scale ecological processes, offering a unified framework for understanding how life evolves and self-organizes across vastly different scales.
The Evolution of Self-Reproducing Machines
One of the most intriguing aspects of this study is the way it links the evolution of self-replicating machines to the emergence of complex biological systems. The study suggests that the transition from simple machines—such as molecules and molecular machines—to more complex life forms, such as cells and organisms, follows a logical progression dictated by fundamental physical and logical principles.
At the heart of this idea is the concept of the self-replicating machine—a machine capable of making copies of itself. This idea is central to the origins of life, as the earliest forms of life were likely simple self-replicating molecules or structures. The study shows that the minimum conditions necessary for the formation of such machines are related to the ability to interface with the environment, specifically salty water—a characteristic shared by most forms of life on Earth.
By focusing on this critical point, the study provides new insights into the very nature of life. It suggests that the evolution of life did not occur in a random or arbitrary fashion, but rather followed specific, predictable principles. The cascade of machines framework helps explain how simple molecular interactions give rise to more complex forms of life, from individual cells to the vast array of ecosystems that make up the biosphere.
A Framework for the Theory of Life
Professor Tlusty believes that this work lays the conceptual groundwork for the development of a more formal and mathematical theory of life. “This work lays the conceptual groundwork for developing mathematical languages that encapsulate the hallmarks of life,” he said. “Such formalisms are essential for constructing a theory of life.” The study suggests that a deeper understanding of life’s complexity can be achieved through the development of mathematical models that capture the underlying principles governing the self-organization of living systems.
These models could ultimately help us better understand not just the mechanics of living systems, but also their origins and evolution. With the proper mathematical tools, scientists could develop a unified theory that explains the intricate processes that give rise to life, from the molecular to the global scale. This could lead to profound breakthroughs in fields like synthetic biology, biotechnology, and artificial life, where the goal is to create self-replicating systems or even entire artificial organisms.
Implications for Biology and Physics
The implications of this study extend far beyond biology. By framing life in terms of machines producing machines, Tlusty and Libchaber’s work draws on ideas from physics, information theory, and mathematics to offer a new way of understanding biological systems. The concept of living matter as a cascade of machines fits well with the principles of thermodynamics, statistical mechanics, and complex systems theory, which all deal with how simple components interact to produce larger-scale behaviors.
The study also touches on a number of profound questions about the nature of life and its place in the universe. Is life merely a collection of molecular machines, or is there something more to it—something that cannot be reduced to a set of physical laws? This question remains one of the central debates in the philosophy of biology. However, the cascade of machines model offers a framework for addressing this question, showing how life can emerge from simple physical principles while still exhibiting complex, self-organizing behavior.
Conclusion
The study by Tsvi Tlusty and Albert Libchaber marks a significant step forward in our understanding of life and its origins. By conceptualizing living matter as a cascade of machines, they provide a novel framework for understanding how life organizes itself across multiple scales. This approach brings us closer to a unified theory of life—one that incorporates both the physical and biological aspects of existence.
In the years to come, this conceptual framework could have far-reaching implications for fields ranging from synthetic biology to artificial intelligence. It may one day help us construct life-like systems or understand the fundamental nature of biological processes. Most importantly, it offers a fresh perspective on the ultimate question of what it means to be alive, providing new insights into the mysterious and awe-inspiring world of living matter.
Reference: Tsvi Tlusty et al, Life sets off a cascade of machines, Proceedings of the National Academy of Sciences (2025). DOI: 10.1073/pnas.2418000122