The Last Universal Common Ancestor (LUCA), the theoretical single organism from which all life on Earth descends, is now believed to have emerged far earlier than previously estimated. This discovery challenges long-standing assumptions about the origins of life and suggests that biological evolution began under conditions that may have been radically different from what scientists once envisioned. If LUCA is significantly older than previously thought, it raises new questions about the geochemical environment of early Earth and the factors that allowed life to take hold and diversify.
According to a recent study published in Nature Ecology & Evolution, researchers have traced LUCA’s origins further back in time than earlier estimates, using molecular and genetic data to refine the timeline of life’s emergence.
A Deep Dive into LUCA’s Timeline
Scientists have long speculated that LUCA existed around 3.5 billion years ago, near the dawn of Earth’s biological history. However, new research suggests that LUCA could be hundreds of millions of years older, placing its emergence closer to 4 billion years ago. This shift in timeline dramatically changes how scientists view the origins of life on Earth.
By analyzing ancient genetic markers found across all living organisms today, researchers have been able to reconstruct the essential genes that LUCA likely carried. These markers suggest that LUCA was a simple, single-celled organism with the ability to thrive in extreme environments, likely near hydrothermal vents deep in the ocean.
According to “It’s clear that LUCA was exploiting and changing its environment, but it is unlikely to have lived alone,” Tim Lenton, a co-author of the study.
How Scientists Traced LUCA’s Age
This discovery stems from advancements in genomic analysis. Researchers examined the most ancient genes present in all living things, including bacteria, archaea, and more complex life forms. By estimating the rate of genetic mutations over billions of years, scientists have refined their models to push LUCA’s origins back significantly.
One of the strongest pieces of evidence comes from ribosomal RNA—a fundamental molecule found in every living cell. The structure and function of this molecule have remained almost unchanged for billions of years, making it a reliable marker for tracking the age of life’s earliest ancestor.
Martin’s research team identified 355 genes that are believed to have been present in LUCA. According to the research, these genes suggest that LUCA was an anaerobic, autotrophic organism—meaning it lived without oxygen and produced its own energy from hydrogen and carbon dioxide, much like the bacteria found today in hydrothermal vents.
Implications for Astrobiology
The idea that life emerged so quickly after Earth became habitable supports the “life everywhere” hypothesis—the notion that, if the right conditions exist, life will inevitably arise. This strengthens the argument that microbial life might exist on Mars, the ice-covered oceans of Europa, or the methane-rich atmosphere of Titan.
Edmund Moody, the lead author of the study, emphasizes that “ the evolutionary history of genes is complicated by their exchange between lineages, We have to use complex evolutionary models to reconcile the evolutionary history of genes with the genealogy of species”.
If life on Earth appeared almost immediately after the planet stabilized, then the same process could have happened elsewhere in the universe. Some scientists believe that we are on the brink of finding biosignatures—chemical markers of life—on exoplanets, making LUCA’s revised timeline a crucial piece of the puzzle.