A digital representation illustrating how LUCA was invaded by viruses as early as 4.2 billion years ago. Credit: Scientific Graphic Design
AND University of BristolThis 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, scientists have determined 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 oldest ecosystems.
The LUCA genetic blueprint and its descendants
Everything alive today is descended from a single common ancestor affectionately known as LUCA (Last Universal Common Ancestor).
LUCA is the presumed common ancestor from which all modern cellular life, from single-celled organisms like bacteria to giant sequoias (just like us 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 evolved from LUCA from various different sources: the same amino acids used to make proteins in all cellular organisms, shared energy currency (ATP), the presence of cellular machinery such as the ribosome and others associated with making proteins from information stored in DNAand even the fact that all cellular life uses DNA itself as a way of storing information.
Research methods and the age of LUCA
The team compared all the genes in the genomes of life speciescounting the mutations that have occurred in their sequences over time since they shared an ancestor in LUCA.
The time of separation of some species is known from the fossil record, so the team used the genetic equivalent of a well-known equation used to calculate velocity in physics to work out when LUCA existed and arrived at the answer at 4.2 billion years ago, about four hundred million years after its formation Earth and our solar system.
Co-author Dr. Sandra Álvarez-Carretero, from Bristol’s School of Earth Sciences, said: “We didn’t expect LUCA to be so old, within just hundreds of millions of years since the Earth was formed. However, our results are consistent with modern views on the habitability of the early Earth.”
Physiological insights and evolutionary modeling of LUCA
Next, the team worked out the biology of LUCA by modeling the physiological characteristics of living species back through the genealogy of life to LUCA. Lead 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 Bristol’s School of Biological Sciences, said: “One of the real advantages is using a gene-tree-species-tree reconciliation approach to such a diverse dataset representing the primary domains of life in Archaea and Bacteria. This allows us to say with some certainty and assess this level of confidence in how LUCA lived.”
The complexity of LUCA and its impact on the environment
Co-author Professor Davide Pisani said: “Our study showed that LUCA was a complex organism not very different from modern prokaryotes, but what’s really interesting is that it clearly had an early immune system, showing that even 4.2 billion years ago years ago, our ancestor joined the virus arms race.”
Co-author Tim Lenton (University of Exeter, School of Geography) said: “It is clear that LUCA used and changed its environment, but it is unlikely to have lived alone. Its waste would be food for other microbes such as methanogens, helping to create a recycling ecosystem.
Broader Implications of the Early Years Study
“The findings and methods used in this work will also inform future studies that look more closely 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 Spang (Royal Netherlands Institute for Marine Research).
Co-author Professor Philip Donoghue said: “Our work brings together data and methods from a variety of disciplines, revealing insights into the early Earth and life that could not be achieved by any single discipline. It also shows how quickly an ecosystem formed on early Earth. This suggests that life may flourish in Earth-like biospheres elsewhere in the universe.”
Reference: “The Nature of the Last Universal Common Ancestor and Its Implications for 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, Ecology and evolution of nature.
DOI: 10.1038/s41559-024-02461-1
Scientists from University College London (UCL), Utrecht University, the Center for Ecological Research in Budapest and the Okinawa Institute of Science and Technology Graduate University were also involved in the study.
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.