New Research Unveils LUCA: The Last Universal Common Ancestor of All Life on Earth

All living things on earth are related to each other. Now a research team has counted back in evolution and been able to recreate an organism from which all other organisms come. It is called LUCA, after the English Last Universal Common Ancestor. It lived 4.2 billion years ago, just a few hundred million years after Earth was formed, and got its energy from hydrogen and carbon dioxide, which were abundant at the time.

So he survived

LUCA has a genome that codes for around 2,600 proteins, which makes it similar to a bacterium. In addition, the genes show what characteristics the organism had to survive on the very young Earth. The research is published in Nature & Evolutionary Ecology.

Ulf Ellervik, professor of organic chemistry at Lund University, has read the study and thinks it is compelling.

– I think it is exciting that genes have been found that provide UV protection. It could mean that it has been exposed to the sun’s UV radiation, he says.

Close to the surface of the water

This in turn means that LUCA may have stayed close to the surface of the water and therefore had to develop protection against solar radiation. So he didn’t live near hot springs on the sea floor, where many suspect that life first took root.

So much indicates that LUCA was not the first life on Earth.

– We were very surprised when we discovered a cluster of proteins called Crispr Cas. We didn’t expect that at all, says Edmund Moody at the University of Bristol, who led the study.

Crispr cas is part of the bacteria’s DNA that makes up their immune system. Our oldest common ancestor therefore had built up defenses against others, perhaps viruses or other organisms that are no longer traceable.