What is life? Defining life in the context of emergent complexity.

Abstract

Erwin Schrödinger defined life not only as a "self-reproducing" aperiodic crystal of DNA coding for proteins but within the context of living entities increasing their order by dissipating matter/energy gradients to maintain themselves away from equilibirium. Since then most definitions of life have focused on the former. But living cells do more than replicate their DNA. Cells also have membrane barriers across which metabolites must move, via which energy transduction as well as information processing occurs, and within which metabolic transformation occurs. An approach of complex systems dynamics, including nonequilibrium thermodynamics, may provide a more robust approach for defining life than a "naked replicator" at the origin of life. The crucial issue becomes the process of emergence of life from pre-biotic chemistry, concomitant with the emergence of function, information, and semiosis. Living entities can be viewed as bounded, informed autocatalytic cycles feeding off matter/energy gradients, exhibiting agency, capable of growth, reproduction, and evolution. Understanding how life might have emerged should sharpen our definition of what life is.