Individuality through ecology: Rethinking the evolution of complex life from an externalist perspective

Abstract

The evolution of complex life forms, such as multicellular organisms, is the result of a number of evolutionary transitions in individuality (ETIs). Several attempts have been made to explain their origins, many of which have been internalist (i.e., based largely on internal properties of these life form's ancestors). Here, we show how an externalist perspective, via the ecological scaffolding model in which properties of complex life forms arise from an external scaffold, can shed new light on the question of ETIs. Ultimately, we anticipate progress in the field will occur by recognizing the importance of both the internalist and externalist modes of explanation for ETIs. We illustrate this by considering an extension of the ecological scaffolding model by niche construction in which particles modify the environment which later becomes the scaffold giving rise to collective-level individuality.