Scientists have discovered that the ancestor of all living things was not the "start" of life, but rather the survivor of an even older, mysterious era.For years, biology has centered on LUCA-the Last Universal Common Ancestor. This single-celled organism, which lived roughly 4.2 billion years ago, is the "trunk" of the evolutionary tree from which all bacteria, plants, and humans grew.
However, a new study published in Cell Genomics reveals that LUCA inherited its most vital tools from "pre-LUCA" ancestors that have long been lost to history.
The Genetic Roots
Because fossils do not survive from four billion years ago, researchers from MIT and Oberlin College turned to "universal paralogs." These are rare, duplicated genes found in every living creature today. Since every branch of life has them, they must have doubled up before the branches split. If LUCA is the trunk of the tree, these genes represent the buried roots. They prove that before our common ancestor existed, there was already a "modestly productive" world of primitive cells swapping DNA and building complex biological machinery.
A Complex Beginning
The study highlights that these "super-old" genes weren't just backups; they handled the fundamental "tech" of life, such as:
- Protein Factories: Ancient enzymes that link amino acids together.
- Cell Security: Proteins that maintain biological membranes.
"Genetics is written by the victors," the researchers explain. While many early lineages died out, these specific genes were so successful they became the permanent foundation for everything that followed. This discovery suggests the journey to the modern genetic code was far more ancient and sophisticated than previously thought.
