Researchers have made a groundbreaking discovery, tracing the origins of life on Earth back to a single ancestor that emerged approximately 4.2 billion years ago. Scientists pinpointed the emergence of the last universal common ancestor (LUCA) by analysing the genomes of present-day organisms, Science Alert reported. To put this in perspective, Earth itself is approximately 4.5 billion years old, indicating life originated when the planet was still in its infancy.
"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 evolutionary biologist Sandra Álvarez-Carretero of the University of Bristol in the UK.
In its early stages, Earth possessed a vastly different atmosphere, one that would be considered highly toxic by today's standards. The emergence of oxygen, crucial for current life forms, occurred relatively late in the planet's evolutionary timeline, possibly as recent as 3 billion years ago.
Despite this, life appeared even earlier; evidence in the form of microbial fossils dates back 3.48 billion years. Scientists speculate that Earth's conditions could have been conducive to life as early as 4.3 billion years ago. However, the planet's geological and biological processes make it extremely challenging to uncover traces of life from that era.
The team of scientists then sought answers from new sources: the genomes of living organisms and the fossil record. They uncovered new insights into LUCA's nature and its ability to survive in the harsh conditions of early Earth.
Their research suggested that was a primitive, single-celled organism without a nucleus, which relied on non-oxygen-based metabolic processes to produce acetate. Additionally, LUCA likely possessed a rudimentary immune system and was part of a larger ecosystem, paving the way for the diverse range of life forms that exist today.
"Our study showed that LUCA was a complex organism, not too different from modern prokaryotes. But what is 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,'' said phylogenomicist Davide Pisani of the University of Bristol.
LUCA's metabolic waste products could have supported the growth of other life forms, implying that ecosystems can emerge in a relatively short time frame during a planet's evolutionary history. This finding suggests possibilities for the development of life beyond our planet.
"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,'' explained paleobiologist Philip Donoghue of the University of Bristol.
