From the origin of life to pandemics: Emergent phenomena in complex systems

TL;DR

This paper reviews the concept of emergence in complex systems across physical, biological, and social domains, highlighting current understanding, challenges, and its relevance from origins of life to pandemics.

Contribution

It provides a comprehensive overview of emergence phenomena, discusses theoretical challenges, and connects these ideas to diverse systems from biological origins to disease spread.

Findings

Emergence occurs across physical, biological, and social systems.

Current theories lack a rigorous, universally accepted definition.

Emergence plays a key role in phenomena from life's origins to pandemics.

Abstract

When a large number of similar entities interact among each other and with their environment at a low scale, unexpected outcomes at higher spatio-temporal scales might spontaneously arise. This nontrivial phenomenon, known as emergence, characterizes a broad range of distinct complex systems -- from physical to biological and social ones -- and is often related to collective behavior. It is ubiquitous, from non-living entities such as oscillators that under specific conditions synchronize, to living ones, such as birds flocking or fish schooling. Despite the ample phenomenological evidence of the existence of systems' emergent properties, central theoretical questions to the study of emergence remain still unanswered, such as the lack of a widely accepted, rigorous definition of the phenomenon or the identification of the essential physical conditions that favour emergence. We offer here a general overview of the phenomenon of emergence and sketch current and future challenges on the topic. Our short review also serves as an introduction to the Theme Issue "Emergent phenomena in complex physical and socio-technical systems: from cells to societies", where we provide a synthesis of the contents tackled in the Issue and outline how they relate to these challenges, spanning from current advances in our understanding on the origin of life to the large-scale propagation of infectious diseases.