LUCA: The last common universal ancestor to all life on Earth

Isn’t it incredible how all life forms on our planet share a common ancestor? From the humble bacteria to the majestic redwoods, and yes, even us humans – we all spring from the same source, a creature fondly referred to as LUCA (Last Universal Common Ancestor).

An international team of researchers has fired up their curiosity engines to illuminate the corners of Earth’s earliest ecosystem.

Their efforts have led to some riveting discoveries, not just about LUCA, but about life’s first steps on Earth itself.

Light from the past

This study from the University of Bristol has revealed that life was already booming a few hundred million years after our planet’s birth. Among these life forms, our forebear LUCA was establishing its presence.

LUCA, a name that now holds much scientific significance, is theorized to be the common root from which the tree of life bifurcates into three main groups: Bacteria, Archaea, and Eukarya. Co-contributor

“We did not expect LUCA to be so old, within just hundreds of millions of years of Earth formation. However, our results fit with modern views on the habitability of early Earth,” said Co-author Dr Sandra Álvarez-Carretero of Bristol’s School of Earth Sciences.

Strands of LUCA’s life

Understanding LUCA is no easy feat. Our team of scientists embarked on a meticulous journey through time, comparing the genes in the genomes of living species.

They charted the mutations within these sequences since they shared a common ancestor in LUCA.

Using the genetic equivalent of the equation common in physics to calculate speed, the researchers calculated the age of LUCA to be about 4.2 billion years.

That’s a mere four hundred million years post the formation of Earth and our solar system!

Tracing back evolution

The scientists proceeded to reconstruct LUCA’s biology by tracing back through the genealogy of life.

“The evolutionary history of genes is complicated by their exchange between lineages. We have to use complex evolutionary models to reconcile the evolutionary history of genes with the genealogy of species,” noted lead author Dr Edmund Moody.

“One of the real advantages here is applying the gene-tree species-tree reconciliation approach to such a diverse dataset representing the primary domains of life Archaea and Bacteria,” added Co-author Dr Tom Williams from Bristol’s School of Biological Sciences.

“This allows us to say with some confidence and assess that level of confidence on how LUCA lived.”

LUCA was not so different after all

What did LUCA look like? How did it live?

“Our study showed that LUCA was a complex organism, not too different from modern prokaryotes, but what is really interesting is that it’s clear it possessed an early immune system, showing that even by 4.2 billion years ago, our ancestor was engaging in an arms race with viruses,” added co-author Professor Davide Pisani.

The conclusion is that LUCA was already exploiting its environment and influencing its surroundings. Yet, it was certainly not living alone. Its waste probably served as nourishment for other microbes, aiding in creating a recycling ecosystem.

Universal perspective

The findings suggest that life might be present on Earth-like biospheres elsewhere in the universe. Is it possible that as we read this, life is flourishing on a distant planet? Only time and further research will tell.

The team’s revelations ensure a bright future for studies examining the subsequent evolution of prokaryotes in light of Earth history, specifically the less studied Archaea with their methanogenic representatives.

“The findings and methods employed in this work will also inform future studies that look in more detail into the subsequent evolution of prokaryotes in light of Earth history, including the lesser studied Archaea with their methanogenic representatives,” added co-author Professor Anja Spang (the Royal Netherlands Institute for Sea Research).

“Our work draws together data and methods from multiple disciplines, revealing insights into early Earth and life that could not be achieved by any one discipline alone. It also demonstrates just how quickly an ecosystem was established on early Earth. This suggests that life may be flourishing on Earth-like biospheres elsewhere in the universe,” added co-author Professor Philip Donoghue.

Isn’t it breathtaking how we are all tied together by the strands of evolution? Our journey of understanding life, on Earth and beyond, has only just begun!

The study also received contributions from researchers at University College London (UCL), Utrecht University, Centre for Ecological Research in Budapest, and Okinawa Institute of Science and Technology Graduate University (OIST).

The study is published in the journal Nature Ecology & Evolution.

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