Ancient Rocks Unveil “Lost World” of Early Ancestors Dating Back a Billion Years

A multinational team of researchers has unearthed ancient protosteroids in rocks, indicating the existence of complex life as far back as 1.6 billion years ago. These molecules provide a unique glimpse into the evolution of complex organisms and bridge the gap between traditional fossil records and lipid fossils.

The abundance of these newly discovered protosteroids in rocks from Earth’s Middle Ages is surprising. These primordial molecules were produced during the early stages of eukaryotic complexity, expanding the known record of fossil steroids beyond 800 million years ago to as far as 1.6 billion years ago. Eukaryotes are a category of life that includes animals, plants, and algae. They are distinguished from bacteria by their complex cell structure, which includes a nucleus and intricate molecular machinery.

Christian Hallmann, a scientist from the German Research Center for Geosciences (GFZ) in Potsdam, highlights the significance of this finding, stating, “The extension of the molecular record of eukaryotes is not the only noteworthy aspect. Considering that the last common ancestor of all modern eukaryotes, including humans, was likely capable of producing ‘regular’ modern sterols, it is highly probable that the eukaryotes responsible for these rare signatures belonged to the root of the phylogenetic tree.”

The “root” represents the common ancestral lineage that predates all extant branches of eukaryotes. Although these representatives are long extinct, understanding their nature could shed light on the conditions that shaped the evolution of complex life. Further research is needed to determine the proportion of protosteroids that may have originated from bacteria. Nonetheless, the discovery not only reconciles the geological records of traditional fossils and lipid molecules but also offers a rare and unprecedented glimpse into a lost world of ancient life. The decline of the stem group eukaryotes, marked by the emergence of modern fossil steroids approximately 800 million years ago, may signify one of the most pivotal events in the evolution of increasingly complex life.

Benjamin Nettersheim, one of the lead authors of the study, investigates high-resolution elemental and molecular maps of 1.64 billion-year-old rock samples at the Geobiomolecular Imaging Laboratory at MARUM. The ongoing research focuses on mid-Proterozoic biomarker signatures conducted by MARUM, GFZ, and the Australian National University. Nettersheim’s goal is to gain an unprecedented resolution of the cradle of eukaryotic life.

Nearly 30 years ago, Nobel laureate Konrad Bloch speculated about such biomarkers in an essay. Bloch proposed that short-lived intermediates in modern steroid biosynthesis might not have always been intermediates, suggesting that lipid biosynthesis evolved alongside changing environmental conditions throughout Earth’s history. Unlike Bloch, who believed that these ancient intermediates would never be found, Nettersheim embarked on a search for protosteroids in ancient rocks deposited during a time when these intermediates could have been the final product.

However, how does one identify such molecules in ancient rocks? Jochen Brocks explains, “We employed a combination of techniques to convert various modern steroids into their fossilized equivalents. Otherwise, we wouldn’t have known what to look for.” For decades, scientists overlooked these molecules because they did not match typical molecular search criteria. “Once we identified our target, we discovered that numerous rocks from billion-year-old waterways worldwide contained similar fossil molecules.”

The oldest samples containing the biomarker were found in Australia’s Barney Creek Formation and date back 1.64 billion years. Over the next 800 million years, the rock record reveals only fossil molecules from primordial eukaryotes until the molecular signatures of modern eukaryotes appear during the Tonian period. According to Nettersheim, “The Tonian Transformation emerges as one of the most significant ecological turning points in our planet’s history.” Hallmann adds that “both the primordial stem groups and modern eukaryotic representatives, such as red algae, may have coexisted for hundreds of millions of years.” However, during this time, Earth’s atmosphere became increasingly oxygen-rich—a byproduct of cyanobacteria and the earliest eukaryotic algae—which would have been toxic to many other organisms. Later, global “Snowball Earth” glaciations occurred, and the protosterol communities largely perished. The last common ancestor of all living eukaryotes likely lived between 1.2 and 1.8 billion years ago. Its descendants likely possessed greater resilience to heat, cold, and UV radiation, outcompeting their primordial relatives.

Nettersheim concludes, “For much of Earth’s history, it was a microbial world that left few traces.” Research at the Australian National University, MARUM, and GFZ continues to trace the origins of our existence. The discovery of protosterols brings us closer to understanding the lives and evolution of our earliest ancestors. Dr. Nettersheim and his international collaborators employ a laser coupled with an ultra-high-resolution mass spectrometer at MARUM’s unique Geobiomolecular Imaging Laboratory to examine ancient rocks. Through these efforts, they aim to delve into the cradle of eukaryotic life with unprecedented resolution, further enhancing our understanding of our early ancestors in the future.

Reference: “Lost world of complex life and the late rise of the eukaryotic crown” by Jochen J. Brocks, Benjamin J. Nettersheim, Pierre Adam, Philippe Schaeffer, Amber J. M. Jarrett, Nur Güneli, Tharika Liyanage, Lennart M. van Maldegem, Christian Hallmann and Janet M. Hope, 7 June 2023, Nature.
DOI: 10.1038/s41586-023-06170-w

Participating Institutions:

• Research School of Earth Sciences, The Australian National University, Canberra, Australia
• MARUM – Center for Marine Environmental Sciences, University of Bremen, Bremen, Germany
• Faculty of Geosciences, University of Bremen, Bremen, Germany
• Université de Strasbourg, CNRS, Institut de Chimie de Strasbourg, Strasbourg, France
• Northern Territory Geological Survey, Darwin, Australia
• German Research Center for Geosciences (GFZ), Potsdam, Germany

MARUM conducts fundamental scientific research to understand the role of the ocean and the ocean floor in the Earth system. The dynamics of the ocean and its floor significantly influence the entire Earth system through geological, physical, biological, and chemical processes. These interactions impact climate, the global carbon cycle, and create unique biological systems. MARUM is dedicated to unbiased and fundamental research that serves the interests of society and the marine environment, aligning with the United Nations’ Sustainable Development Goals. The institution publishes quality-assured scientific data, making it publicly available. MARUM also engages with the public, sharing new discoveries in the marine environment and providing practical knowledge through dialogue with society. In accordance with its mission to protect the marine environment, MARUM collaborates with commercial and industrial partners.

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More about protosteroids

• Nature: “Lost world of complex life and the late rise of the eukaryotic crown”