Scientists have discovered the “lost world” of our early ancestors in billion-year-old rocks

Artist’s imagination of a group of primitive eukaryotes from the “Protosterol Biota” living on a bacterial mat on the ocean floor. Based on molecular fossils, the Protosterol Biota organisms lived in the oceans from about 1.6 to 1.0 billion years ago and are our oldest known ancestors. Credit: Organized on MidJourney by TA 2023

A multinational research team has found ancient protosteroids in the rocks, indicating that complex life existed as long as 1.6 billion years ago. These molecules provide new insight into the evolution of complex life and reconcile discrepancies between the traditional and lipid fossil records.

It turns out that the newly discovered record of so-called protosteroids was surprisingly plentiful throughout the Middle Ages of the Earth. Primordial molecules were produced at an early stage in the complexity of eukaryotes – extending the current record of fossil sterols beyond 800 and even 1,600 million years ago. Eukaryotes is a term given to the kingdom of life including all animals, plants, and algae and is separated from bacteria by having a complex cellular structure that includes a nucleus, as well as a more complex molecular mechanism.

“The highlight of this discovery is not simply an extension of the current molecular record of eukaryotes,” says Christian Hollmann, one of the co-scientists from the German Research Center for Geosciences (GFZ) in Potsdam. “Given that the last common ancestor of all modern eukaryotes, including us humans, was likely able to produce ‘regular’ modern sterols, it is likely that the eukaryotes responsible for these rare signatures belong at the trunk of the phylogenetic tree.”

Benjamin Nettersheim, one of the study’s lead authors, examines super-resolution elemental and molecular maps of 1.64-billion-year-old rock samples analyzed in the Geobiological Molecular Imaging Laboratory at MARUM. Credit: MARUM – Center for Marine Ecology, University of Bremen; in Descamps

This “stump” represents the common ancestral lineage that was the precursor to all living branches of eukaryotes. Its representatives are long extinct, but details of their nature may shed more light on the circumstances surrounding the evolution of complex life. Although more research is needed to assess what percentage of protosteroids may have a rare bacterial source, the discovery of these new molecules not only reconciles the geological record of traditional fossils with that of fossil fat molecules, but gives a rare and unprecedented glimpse into the world. lost from the old life. The competitive demise of stem-group eukaryotes, marked by the first appearance of modern fossil stromals around 800 million years ago, may reflect one of the most enduring events in the evolution of increasingly complex life.

adds Benjamin Nittersheim from Marom, University of Bremen, who co-first authored the study with Jochen Brooks from[{” attribute=””>Australian National University (ANU) – “due to potentially adverse health effects of elevated cholesterol levels in humans, cholesterol doesn’t have the best reputation from a medical perspective. However, these lipid molecules are integral parts of eukaryotic cell membranes where they aid in a variety of physiological functions. By searching for fossilized steroids in ancient rocks, we can trace the evolution of increasingly complex life.”

Dr. Nettersheim inserts a thin section and rock slices of 1.64 billion-years old rocks into the 7T solariX XR FT-ICR-MS equipped with a MALDI source at the Geobiomolecular Imaging Laboratory at MARUM. As part of ongoing research into mid-Proterozoic biomarker signatures at MARUM, GFZ and the Australian National University, Dr. Nettersheim aims to zoom into the cradle of eukaryotic life in unprecedented resolution. Credit: MARUM – Center for Marine Environmental Sciences, University of Bremen; V. Diekamp

Nobel laureate Konrad Bloch had already speculated about such a biomarker in an essay almost 30 years ago. Bloch suggested that short-lived intermediates in the modern biosynthesis of steroids may not always have been intermediates. He believed that lipid biosynthesis evolved in parallel with changing environmental conditions throughout Earth history. In contrast to Bloch, who did not believe that these ancient intermediates could ever be found, Nettersheim started searching for protosteroids in ancient rocks that were deposited at a time when those intermediates could actually have been the final product.

But how to find such molecules in ancient rocks? “We employed a combination of techniques to first convert various modern steroids to their fossilized equivalent; otherwise, we wouldn’t have even known what to look for,” says Jochen Brocks. Scientists had overlooked these molecules for decades because they do not conform to typical molecular search images. “Once we knew our target, we discovered that dozens of other rocks, taken from billion-year-old waterways across the world, were oozing with similar fossil molecules.”

The oldest samples with the biomarker are from the Barney Creek Formation in Australia and are 1.64 billion years old. The rock record of the next 800 million years only yields fossil molecules of primordial eukaryotes before molecular signatures of modern eukaryotes first appear in the Tonian period. According to Nettersheim “the Tonian Transformation emerges as one of the most profound ecological turning points in our planet´s history“. Hallmann adds that “both primordial stem groups and modern eukaryotic representatives such as red algae may have lived side by side for many hundreds of millions of years”. During this time, however, the Earth’s atmosphere became increasingly enriched with oxygen – a metabolic product of cyanobacteria and of the first eukaryotic algae – that would have been toxic to many other organisms. Later, global “Snowball Earth” glaciations occurred and the protosterol communities largely died out. The last common ancestor of all living eukaryotes may have lived 1.2 to 1.8 billion years ago. Its descendants were likely better able to survive heat and cold as well as UV radiation and displaced their primordial relatives.

“Earth was a microbial world for much of its history and left few traces,” Nettersheim concludes. Research at ANU, MARUM and GFZ continues to pursue tracing the roots of our existence – the discovery of protosterols now brings us one step closer to understanding how our earliest ancestors lived and evolved. Shooting at the ancient rocks with a laser coupled to an ultra-high resolution mass spectrometer in MARUM’s globally unique Geobiomolecular Imaging Laboratory, Dr. Nettersheim and his international collaborators aim at zooming into the cradle of eukaryotic life in unprecedented resolution to further improve 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 produces fundamental scientific knowledge about the role of the ocean and the ocean floor in the total Earth system. The dynamics of the ocean and the ocean floor significantly impact the entire Earth system through the interaction of geological, physical, biological and chemical processes. These influence both the climate and the global carbon cycle, and create unique biological systems. MARUM is committed to fundamental and unbiased research in the interests of society and the marine environment, and in accordance with the Sustainable Development Goals of the United Nations. It publishes its quality-assured scientific data and makes it publicly available. MARUM informs the public about new discoveries in the marine environment and provides practical knowledge through its dialogue with society. MARUM cooperates with commercial and industrial partners in accordance with its goal of protecting the marine environment.