Digital image showing how LUCA was already under viral attack 4.2 billion years ago. Credit: Science Graphic Design
a University of BristolThe led study found that life on Earth descended from a common ancestor called LUCA and thrived soon after the planet formed.
Through genetic analysis and evolutionary modeling, the researchers determined that LUCA existed about 4.2 billion years ago and was a complex organism with an early immune system essential to Earth’s oldest ecosystems.
LUCA’s genetic blueprint and descendants
All living organisms today descend from a single common ancestor nicknamed LUCA (Last Universal Common Ancestor).
LUCA is hypothesized to be the common ancestor of all modern cellular life, from single-celled organisms like bacteria to giant sequoia trees (and us humans). LUCA represents the root of the Tree of Life, which existed before the split into the groups of bacteria, archaea, and eukaryotes recognized today. Modern life evolved from LUCA, from the same, but from a variety of different sources. amino acid The shared energy currency (ATP) used to make proteins in all cellular organisms, the presence of cellular machinery such as ribosomes, and other things involved in making proteins from information stored within the cell DNAThen there is the fact that all cellular life uses DNA itself as a means of storing information.
Research Methods and the Age of LUCA
The research team compared all the genes in the organisms’ genomes. seedWe count the mutations that have occurred in the sequence over time since they shared a common ancestor, LUCA.
The times when some species split off are known from the fossil record, and the team used a genetic equivalent of a familiar equation used in physics to calculate speed to calculate when LUCA existed, arriving at an answer of 4.2 billion years ago, about 400 million years after the formation of Earth and the solar system.
Co-author Dr Sandra Alvarez Carretero, from the University of Bristol’s School of Geosciences, said: “We did not expect LUCA to be so old, within just a few hundred million years of Earth’s formation, but our findings are consistent with modern views of the habitability of the early Earth.”
Physiological insights and evolutionary models of LUCA
The team then worked out LUCA’s biology by tracing the lineage of life back to LUCA and modelling the physiological traits of extant species. “The evolutionary history of genes is complicated by exchanges between lineages,” explains lead author Dr Edmund Moody. “Reconciling the evolutionary history of genes with the lineage of species requires the use of complex evolutionary models.”
Co-author Dr Tom Williams, from the University of Bristol’s School of Biological Sciences, said: “One of the real advantages here is that we’ve applied the gene tree species tree reconciliation approach to a diverse dataset representing the major domains of life, Archaea and Bacteria. This allows us to make statements with some confidence about how LUCA may have lived, and to assess our level of confidence.”
LUCA’s complexity and environmental impact
Co-author Professor Davide Pisani said: “Our study shows that LUCA was a complex organism not too different from modern prokaryotes, but what’s really interesting is that LUCA clearly had an early immune system, suggesting that by 4.2 billion years ago our ancestors were engaged in an arms race with viruses.”
Co-author Tim Lenton from the University of Exeter’s Department of Geography said: “LUCA clearly used and transformed its environment, but it is unlikely to have lived in isolation – its waste would have provided food for other microorganisms, such as methanogens, helping to create a circular ecosystem.”
Broader implications of early childhood research
“The insights and methods provided by this study will also inform future studies looking in more detail at the subsequent evolution of prokaryotes in the context of Earth’s history, including the less-studied archaea and their methanogens,” added co-author Professor Anja Spang of the Royal Netherlands Institute for Marine Research.
Co-author Professor Philip Donoghue said: “Our study brings together data and methods from multiple disciplines to reveal insights into the early Earth and life that could not be achieved by any single discipline alone. It also shows how quickly ecosystems were established on the early Earth, suggesting that life may be thriving in an Earth-like biosphere somewhere in the universe.”
Reference: “The nature of the last universal common ancestor and its implications for the early Earth system”, Edmund R.R. Moody, Sandra Alvarez Carretero, Tara A. Mahendrarajah, James W. Clark, Holly C. Betts, Nina Dombrowski, Leonard L. Zandt, Richard A. Boyle, Stuart Daines, Xi Chen, Nick Lane, Zhiheng Yang, Graham A. Shields, Gergely J. Sorosi, Anja Spang, Davide Pisani, Tom A. Williams, Timothy M. Renton, Philip C.J. Donohue, 12 July 2024, Natural Ecology and Evolution.
DOI: 10.1038/s41559-024-02461-1
The study also involved scientists from University College London (UCL), Utrecht University, the Budapest Centre for Ecological Research and the Okinawa Institute of Science and Technology Graduate University.
This research was funded by the John Templeton Foundation. The opinions expressed in this publication are those of the authors and do not necessarily reflect the views of the John Templeton Foundation.
