An international team of scientists from France and Norway explored the origins of the renowned Great Ordovician Biodiversity Event, a pivotal period when a remarkable array of marine and terrestrial life began to flourish. The researchers reported their findings in a peer-reviewed science journal.
The Great Ordovician Biodiversity Event spans roughly 25 million years, starting about 471 million years ago. During this interval, marine life diversified at an extraordinary pace: species numbers rose sharply, numerous families appeared, and oceanic life achieved a level of variety that echoes today’s plenteous ecosystems. This burst of diversification set a new baseline in the history of life on Earth.
Historically, scientists offered several explanations for this dramatic rise in biodiversity. Hypotheses included rising oxygen levels in the atmosphere driven by land plants, shifts in planetary configuration due to continental drift, and meteorite impacts that could have reshaped ecological systems. Yet none of these ideas alone fully accounted for the scale and timing of the event.
In the new study, researchers propose an alternative driver: a long-term cooling of global sea surface temperatures. The team reconstructed past climates and simulated conditions from roughly 440 million to 490 million years ago, providing a window into the planet’s ancient climate system. The climate model suggests a pronounced cooling trend, beginning with very warm ocean waters and gradually lowering toward the equator. This gradient fostered new ecological niches and created stable, productive marine environments that could sustain rapid expansion of life.
The analysis indicates that as surface temperatures dropped from about 40°C to near 30°C, water masses at higher latitudes became more hospitable to diverse organisms. Colder conditions likely affected ocean chemistry, nutrient cycling, and predator-prey dynamics in ways that promoted specialization and speciation. In turn, these processes can help explain why the Ordovician seas supported such a broad and persistent wave of evolutionary innovation.
The research adds a climate-driven narrative to the collection of factors considered in global paleoecology. By modeling the interplay between atmospheric and ocean temperatures and the distribution of life, the study offers a cohesive mechanism linking environmental change to biological diversification. It also underscores the value of climate reconstructions in understanding the deep-time dynamics that shaped Earth’s biosphere. The findings contribute to a broader appreciation of how shifts in climate regimes can influence the tempo and mode of evolution across vast geological timescales.
Overall, the results emphasize that the Great Ordovician Biodiversity Event was likely the product of interconnected environmental changes rather than a single cause. The cooling trend created conditions favorable to the emergence and expansion of many marine lineages, while also setting the stage for continued diversification as the climate continued to evolve. This perspective aligns with emerging views that climate context plays a central role in major phylum and ecosystem transitions throughout Earth’s history.
As scientists refine climate reconstructions and integrate them with fossil records, new insights into the Ordovician period will emerge. The study’s approach highlights how century-spanning climate shifts can leave lasting imprints on the trajectory of life, helping researchers trace the links between physical oceans, atmospheric chemistry, and the rich tapestry of organisms that once populated ancient seas.