If you look at the bottom of the Tree of Life in our poster you will see the words ‘Life Begins’. A natural question might be: what was the first life form?
Scientists have been trying to answer this question for a long time. Now in 2026, researchers think they may have an answer to how life emerged from the chemistry of the ancient earth and what that life might have been.
Take another look at the bottom of our poster. On one side you see a branch for Bacteria, and the other Archaea. According to a new study, “bacteria and archaea, the first two branches of the tree of life, each sprung separately from something not really alive.” Their last common ancestor, known as LUCA (for “Last Universal Common Ancestor”), was dependent on metals deposited in hydrothermal vents to live.
Bacteria and Archaea are single-celled organisms without a distinct nucleus. All of them evolved from a single-celled ancestor that lived about 4 billion years ago. Researchers used genetic data that suggest that LUCA, the single-celled ancestor, existed about 4.2 billion years ago.
The scientists who did the study looked at the known protein-coding genes of bacteria and archaea. They found 355 genes that “pointed quite precisely to an organism that lived in the conditions found in deep sea vents.”
Hydrothermal Vents
Deep sea hydrothermal vents are extreme, hot places found throughout the oceans where unique ecosystems and animals thrive based on chemistry, not light. The 355 genes the researchers say are from LUCA include some that metabolize hydrogen as a source of energy as well as a gene for an enzyme called reverse gyrase, found only in microbes that live at extremely high temperatures.
But modern life’s last common ancestor is not the same thing as the origin of life says Betül Kaçar, director of a NASA astrobiology center “How chemistry and geology passed the baton to biology remains unknown. Further experiments will be needed to test the ideas raised by this study.”
Others scientists are also skeptical of the LUCA theory. It seems that LUCA can be traced back to deep sea vents. But that does not mean life originated there, they say. The debate between life originating at hydrothermal vents in the ocean or on land continues. Other scientists think that ultraviolet light from the sun was an essential energy source to get the right biological reactions underway, and so pools on land are the most likely environment in which life began.
