Advanced tools and expanded fossil datasets have painted a clearer picture of the eukaryotic diversity of the Proterozoic eon, which has been hard to quantify. The findings show that Earth's severe Cryogenian glaciations catalyzed a pivotal shift in the evolution and diversity of early eukaryotes during this eon, 2500 to 538 million years ago. This work underscores the interplay between Earth's environmental perturbations and the evolutionary trajectories of early life. Quantifying global fossil diversity provides valuable insights into the evolutionary history of life on Earth and its relationship with environmental changes. This is exemplified by the well-known mass extinction events and associated environmental perturbations during the Phanerozoic Eon (538 Ma – present day). The Proterozoic Eon also saw significant tectonic and environmental shifts on Earth – from the formation and disassembly of supercontinents to an extensive and severe glaciation that froze nearly the entire planet solid. However, our understanding of global fossil diversity of Proterozoic life, particularly for eukaryotes, has been limited by inconsistent fossil data and poorly defined age constraints. This has hindered efforts to unravel the evolutionary trajectories of early eukaryotes. Recent advancements in paleontological and geochronological datasets, along with the application of new tools like the Constrained Optimization (CONOP) algorithm, have enabled more precise reconstructions of fossil diversity; these methods help integrate diverse stratigraphic data and circumvent the limitations of undated fossiliferous sections. Using the CONOP program and a global compilation of fossil eukaryotes, Qing Tang and colleagues constructed a high-resolution diversity curve of Proterozoic and early Cambrian eukaryotic fossil species. The findings revealed a gradual increase in species richness during the "Boring Billion" – a period marked by stable Earth system conditions with very little biological innovation. However, the Cryogenian glaciations that followed profoundly influenced eukaryotic life. According to the findings, the Cryogenian was a key driver of biodiversity shifts and marked a pivotal transition to the Ediacaran period, which saw greater diversity, more rapid turnover, and multiple radiations and extinctions.
For reporters interested in research integrity issues, the authors note, "In [the] field of paleontology, transparency data sharing is a key priority. Because paleontology is largely a specimen-based science, reproducibility is critically dependent on accessibility of specimens and data (CT data, images, databases, etc.). Thus, a detailed protocol for specimen and data repository is of paramount importance. Most journals… have requirements for specimen and data availability. Such practice should become universal for all peer-reviewed journals."
