A digital rendering illustrating how LUCA was already under attack by viruses as early as 4.2 billion years ago. Credit: Scientific Graphic Design
or University of BristolThe lead study found that life on Earth, descended from a common ancestor called LUCA, flourished soon after the planet formed.
Through genetic analysis and evolutionary modeling, researchers pinpointed the existence of LUCA around 4.2 billion years ago, revealing it as a complex organism with an early immune system integral to Earth’s earliest ecosystems.
The LUCA Genetics Project and its Progeny
Everything alive today is descended from a single common ancestor affectionately known as LUCA (Last Universal Common Ancestor).
LUCA is the hypothesized common ancestor from which all modern cellular life is derived, from single-celled organisms like bacteria to giant redwood trees (as well as humans). LUCA represents the root of the tree of life before it split into the groups known today as Bacteria, Archaea and Eukarya. Modern life has evolved from LUCA from different sources: the same amino acids used to build proteins in all cellular organisms, the common currency of energy (ATP), the presence of cellular machinery such as the ribosome and others related to the production of proteins from information stored in DNAeven the fact that all cellular life uses DNA itself as a way to store information.
Research Methods and the Age of LUCA
The team compared all the genes in living genomes speciescounting the mutations that have occurred within their sequences over time since they had an ancestor in LUCA.
The time of the split of some species is known from the fossil record, so the team used a genetic equivalent of the well-known equation used to calculate velocity in physics to determine when LUCA existed, arriving at the answer of 4.2 billion years ago, about four. hundreds of millions of years after the formation of the Earth and our solar system.
Co-author Dr. Sandra Álvarez-Carretero of the Bristol School of Earth Sciences said: “We didn’t expect LUCA to be so old, within just hundreds of millions of years of Earth’s formation. However, our results fit modern views on the habitability of the early Earth.”
Physiological insights and evolutionary modeling of LUCA
The team then worked out the biology of LUCA by modeling the physiological characteristics of living species back through the genealogy of life at LUCA. The main author Dr. Edmund Moody explained: “The evolutionary history of genes is complicated by their exchange between lineages. We must use complex evolutionary models to reconcile the evolutionary history of genes with the genealogy of species.”
Co-author Dr. Tom Williams from the School of Biological Sciences at Bristol said: “One of the real advantages here is the application of the species-gene-tree reconciliation approach to such a diverse dataset representing the major life domains Archaea and Bacteria. This allows us to say with some confidence and estimate that level of confidence how LUCA lived.”
LUCA complexity and environmental impact
Co-author Professor Davide Pisani said: “Our study showed that LUCA was a complex organism, not very different from modern prokaryotes, but what is really interesting is that it clearly possessed an early immune system, showing that even 4.2 billion years ago, our ancestor was engaged in an arms race with viruses.”
Co-author Tim Lenton (University of Exeter, School of Geography) said “It is clear that LUCA was exploiting and changing its environment, but it is unlikely to have lived alone. Its waste would have been food for other microbes, such as methanogens, that would help create a recycling ecosystem.
Broader implications of the study on early life
“The findings and methods used in this work will also inform future studies that look in more detail at the subsequent evolution of prokaryotes in light of Earth’s history, including the less studied Archaea with their methanogenic representatives,” added co-author Professor Anja Twine. Royal Netherlands Institute for Marine Research).
Co-author Professor Philip Donoghue said: “Our work brings together data and methods from multiple disciplines, revealing insights into Earth and early life that could not be achieved by any single discipline alone. It also shows how quickly an ecosystem formed on the early Earth. This suggests that life may thrive in Earth-like biospheres elsewhere in the universe.”
Reference: “The Nature of the Last Universal Progenitor and Its Impact on the Early Earth System” by Edmund RR Moody, Sandra Álvarez-Carretero, Tara A. Mahendrarajah, James W. Clark, Holly C. Betts, Nina Dombrowski, Lénárd L Szánthó, Richard A. Boyle, Stuart Daines, Xi Chen, Nick Lane, Ziheng Yang, Graham A. Shields, Gergely J. Szöllősi, Anja Spang, Davide Pisani, Tom A. Williams, Timothy M. Lenton, and Philip CJ Donoghue, 12 July 2024, Nature Ecology and Evolution.
DOI: 10.1038/s41559-024-02461-1
The study also involved scientists from University College London (UCL), Utrecht University, the Center for Ecological Research in Budapest and the Okinawa Institute of Science and Technology.
The research was funded by the John Templeton Foundation. The views expressed in this publication are those of the author(s) and do not necessarily reflect the views of the John Templeton Foundation.