Scientists find Earth’s common ancestor

A team of researchers in Germany believe that they may have found the common ancestor linked to all life on earth.

The last universal common ancestor (LUCA) is a four billion year old single-cell bacterium-like organism. It is believed to have lived near a deep sea vent. Researchers have long been engaged in debate about whether life began near an extreme environment or something more akin to a small pond.

James McInerney, from the University of Manchester and was not involved in the study, said: “When we look at the inferred metabolism of LUCA, we are looking at the dominant and most successful kind of metabolism on the planet before the Bacteria and Archaea diverged. This new study provides us with a very intriguing insight into life four billion years ago.”

William Martin and colleagues at Heinrich Heine University Dusseldorf, researched the evolutionary relationships of more than six million prokaryotic protein-encoding genes to search for genes that may have originated from LUCA. After finding 355 protein groups, they were able to determine that LUCA was anaerobic, thermophilic and used CO₂, N₂ and H₂ to sustain its metabolic pathway. The organism required transition metals such as iron and used elements such as selenium.

LUCA would have eventually given rise to two types of simple cell types, bacteria and archea. This means the three domains of life —eukaryotes, bacteria and archea — didn’t have a single point of origin. The scientists believe that LUCA lived similarly to how Clostridia bacteria and archaeal methanogens still present on Earth do.

The research was published in Nature Microbiology.