A billion years of geological drama – Boring or brilliant?

• The study underscores the geological influence on the evolution of early complex life, particularly eukaryogenesis (or the origins of the eukaryotic cell). • We examine various Earth system processes, including plate tectonics, atmosphere–ocean redox conditions, nutrient availability, temperature and mineral evolution, and their potential impacts on biological evolution during the Boring Billion period. • The study adopts a geo-biological approach to explain how the Boring Billion period marks the foundation for all complex life on Earth. Used to describe the Paleo-Mesoproterozoic era (1800–800 Ma), the term «Boring Billion» is, in many ways, a misnomer. The conventional focus on the significance of pO 2 for life, along with the discovery of the first metazoans in the rock record around 800 million years ago (according to molecular clock estimates), and the enduring human interest in Ediacaran macroscopic fossils, are just a few factors contributing to this undeserved characterization. Initially perceived as a phase of geological inertia that may have hindered biological development, recent research has illuminated pivotal milestones in both environmental and biological domains throughout the ’Boring Billion.’ Through a thorough review of existing literature, we present a discussion encompassing plate tectonics, atmosphere–ocean chemistry, nutrient cycling, temperature fluctuations, and mineral evolution. Furthermore, we explore significant biological phenomena such as eukaryogenesis, predation, and potential metazoan origins, contextualizing these events within the broader geo-biological narrative of the period. Our discussion delves into the latest research within the realm of established notions about this era. We emphasize the abiotic factors that influenced life’s evolution, drawing parallels between contemporary geochemical trends and the evolution of complex life forms, including animals. We also delve into the prerequisites and origins of eukaryogenesis, exploring diversification during the Middle Proterozoic. Furthermore, we examine the role of environmental cues in driving biological innovation throughout this billion-year span. This research offers an alternative lens through which to interpret geological trends and the evolutionary trajectory of complex life. By spotlighting shifts in Earth system processes—such as plate tectonics, atmosphere–ocean redox dynamics, marine nutrient cycles, and biological evolution—during the “Boring Billion”, our study invites readers to critically assess this significant era in Earth’s history.