Meet LUCA, the original ancestor

LUCA, or the Last Universal Common Ancestor, is no less than 4 billion years old, and was a single-cell organism


LUCA may have lived in really inhospitable environs like underwater volcanos. Photo: Wikimedia Commons
LUCA may have lived in really inhospitable environs like underwater volcanos. Photo: Wikimedia Commons

New Delhi: Step aside Adam and Eve—scientists have just discovered the ancestors of all living things on earth and its name is LUCA.

It’s the acronym for the Last Universal Common Ancestor, a key concept in the study of early evolution and life’s origin that has been tracked by scientists for years.

LUCA, according to a study published in Nature Microbiology on Monday, is no less than 4 billion years old, may have lived in really inhospitable environs (Just how inhospitable? Think moving tectonic plates) and was a single-cell organism.

To describe LUCA, a team of scientists led by William Martin from Heinrich Heine University Düsseldorf, investigated all clusters and genetic evolutionary trees for 6.1 million genes.

The team identified 355 genes that trace to the last ancestor by phylogenetic criteria.

The idea of how LUCA could be found came when a researcher from Martin’s group was giving her 20-minute summary of a Masters thesis in bioinformatics.

“That genomes have retained traces of life’s earliest history is an exciting prospect. Even more exciting is the prospect that we can decipher some of that history,” said Martin.

LUCA inhabited a “geochemically active environment” rich in hydrogen, carbon dioxide and iron. According to the paper, the data support the theory of an autotrophic or self-nourishing origin of life.

An autotroph is an organism that produces complex organic compounds from simple substances present in its surroundings, generally using energy from light or inorganic chemical reactions.

LUCA would have inhabited volcanically active places or areas where tectonic plates are moving apart, ocean basins, and hotspots. And it may have used carbon dioxide and hydrogen (rather than oxygen) to acquire energy.

The concept of LUCA is in line with the early evolutionary trees provided by the English naturalist Charles Darwin.

“The nature of the genes that are conserved tells an amazing story about the kind of environment in which this last common ancestor lived—including how it extracted energy to survive and thrive. The study suggests that the world inhabited by these organisms nearly four billion years ago was very different to the one we live in now,” said Professor Jeff Errington of Newcastle University in a comment on the university website.

“There was no available oxygen, but according to the genes, this common ancestor probably obtained energy from hydrogen gas, presumably made by geochemical activity in the Earth’s crust,” added Errington.

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