Research into the origin of life and its possible presence in the universe has never been more intense. To detect it, specialists from all fields (biologists, geneticists, chemists, physicists and astrobiologists) attempt to define and study its properties: chemical composition, metabolism, reproduction, evolution, self-organisation and complexity. However, whilst small rovers scour the Martian surface in search of it, the most obvious aspect of life on Earth has, paradoxically, never been formally defined: its geometry. Indeed, there is currently no comprehensive inventory of the morphological diversity and complexity of organisms that would enable us to define its fundamental properties. Consequently, essential questions as ‘what kinds of forms can living beings produce?’, ‘how can we recognize life on another planet?’ or ‘are there general limits or rules governing the morphological evolution of life?’ currently have no satisfactory answers at the scale of the biosphere. The reason for this is very simple: there is no theoretical framework that allows us to rationally compare and quantify geometries and structures as complex and diverse as those of the living beings inhabiting our planet.

In this presentation, I will outline a new method based on the structural and fractal properties of shapes, designed to quantify and compare the morphology of all living beings on Earth (e.g., bacteria, ants, whales, sequoias, office colleagues), regardless of their level of complexity and size. By applying this method to all known phyla, we will explore how body size influences the form of life on a large scale and discuss the role of chance and necessity, as well as the constraints and general trends in the evolution of life on Earth (and perhaps in the Universe…).