How the Breakup of Supercontinent Nuna May Have Created ‘Incubators’ for Complex Life

Breakup of Nuna may have created ecological "incubators" for complex life

New research suggests the fragmentation of the ancient supercontinent Nuna during Earth's so-called "Boring Billion" triggered geological and chemical changes that helped make coastal seas warmer, oxygen-rich and more stable — conditions that could have promoted the rise of more complex organisms.

What was the "Boring Billion"?

The "Boring Billion" spans roughly 1.8 billion to 800 million years ago. Although previously characterized as a long interval of apparent geochemical and biological stability, recent work reveals it included important tectonic and evolutionary changes.

How the study was done

Published Oct. 27 in Earth and Planetary Science Letters, the study led by Dietmar Müller (University of Sydney) used advanced plate-tectonic simulations to reconstruct continental movements and associated carbon fluxes over the past 1.8 billion years. The model provides a finer resolution of carbon storage and emissions than many earlier approaches.

Key findings

During about 350 million years of the Boring Billion, the total length of shallow seas along continental margins roughly doubled to about 81,000 miles (130,000 km) — a combined extent greater than three times Earth’s equatorial circumference. At the same time, global subduction zones contracted as plates rearranged.

Because subduction carries seawater into the mantle and promotes melting that releases volcanic carbon dioxide (CO2), a reduction in subduction length led to lower CO2 outgassing. That decline in greenhouse gases would have cooled global climates and, together with expanded continental shelves, fostered more oxygenated, temperate coastal environments.

In addition, the breakup formed extensive young ocean crust where hydrothermal alteration and fluid circulation converted dissolved carbon into carbonate minerals. This process buried carbon in seafloor sediments and helped draw down atmospheric CO2 further.

"We think these vast continental shelves and shallow seas were crucial ecological incubators," said co-author Juraj Farkaš (University of Adelaide). "They provided tectonically and geochemically stable marine environments with elevated nutrients and oxygen, which were critical for more complex lifeforms to evolve and diversify."

Implications for life

These changes — expanded shallow seas, reduced volcanic CO2 emissions, and increased carbon burial — together created cooler, oxygen-richer coastal habitats that may have accelerated the diversification of eukaryotes (cells with membrane-bound nuclei and organelles). Eukaryotic fossils from about 1.05 billion years ago indicate the group existed during this interval, and the new study offers a plausible environmental driver for their rise.

Next steps

The authors emphasize the need for additional well-preserved eukaryote fossils to better document early evolutionary history and to further test links between tectonic change, ocean chemistry and biological innovation.

Study reference: Dietmar Müller et al., Earth and Planetary Science Letters, published Oct. 27.