LUCA ancestor may have existed 4.2 billion years ago

An international team of researchers has published a study in the journal Nature Ecology & Evolution suggesting that the Last Universal Common Ancestor (LUCA) lived approximately 4.2 billion years ago. This timeline places the emergence of this common ancestor only about 400 million years after the formation of Earth.

LUCA is not considered the first living organism, but rather the most recent common ancestor from which all current cellular life forms—including bacteria, archaea, plants, animals, and humans—descended. To estimate this date, scientists analyzed shared genes in modern organisms and used mathematical models known as “molecular clocks” to calculate accumulated mutations since different lineages diverged.

The findings suggest LUCA existed during the Hadean eon, a period characterized by intense geological transformations and extremely hostile environmental conditions. Researchers estimate LUCA was likely a simple prokaryote without a cell nucleus, yet it may have possessed sophisticated features, such as a rudimentary immune system, suggesting an early evolutionary struggle against viruses.