What is life?–This remains the quintessential puzzle of biological sciences, a question that embodies the intricate complexity and stunning diversity of life forms. This study suggests that one viable approach to address this extreme complexity is to conceptualize living matter as a cascade of machines producing machines. This cascade illustrates how cells are composed of smaller submachines, reaching down to the atomic level where molecular machines, such as ion pumps and enzymes, operate. In the other direction, it explains how cells self-organize into larger systems, such as tissues, organs, and populations, cumulating into the biosphere.
This new conceptual framework is a fruit of collaboration between Professors Tsvi Tlusty from the Department of Physics at 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. The study was inspired by the seventeenth-century polymath Gottfried Leibniz, who noted that "the machines of nature, that is living bodies, are still machines in their smallest parts, to infinity".
Tlusty and Libchaber constructed a simplified language that characterizes living matter as an (almost) infinite, double cascade, spanning eighteen orders of magnitude in space and thirty in time. The large-scale and small-scale branches of this cascade converge at a critical point of 1,000 seconds and 1 micron, corresponding to the typical temporal and spatial scales of microbial life. This paper explains the origins of the critical point based on fundamental physical and logical principles, identifying it as the minimum conditions necessary for a self-reproducing machine to interface with salty water.
This critical point marks the evolution from the construction of minimal self-replicating machines to the emergence of societies of such machines, ultimately leading to the formation of whole biospheres.
"This work lays the conceptual groundwork for developing mathematical languages that encapsulate the hallmarks of life " said Professor Tlusty. "Such formalisms are essential for constructing a theory of life."
The findings of this research have been published in the Proceedings National Academy of Sciences USA (PNAS) , on January 20, 2025.
Tsvi Tlusty
Distinguished Professor, Department of Physics
Ulsan National Institute of Science and Technology (UNIST)
JooHyeon Heo
Public Relations Officer, UNIST
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