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team of scientists from the University of Bristol studied the earliest ecosystem on Earth to understand when life began flourishing on our planet, just a hundred million years after planetary formation.
The new study was published in Nature Ecology & Evolution. The living beings are said to have come from a single common ancestor known as LUCA (Last Universal Common Ancestor), according to the scientists.
LUCA is a hypothesised common ancestor from which it is believed all modern cellular life has descended.
The living beings that evolved from LUCA also came from different sources: the amino acids which had built proteins in other cellular organisms, cellular machinery like the ribosome and others, and the shared energy currency (ATP).
The team compared all the genes in the genomes of living species, counting the mutations that have occurred within their sequences over time since they shared an ancestor in LUCA.
Some species' time of separation was understood from the fossil record and a genetic equivalent of the familiar equation was used by the team to understand when LUCA existed, which was found to be 4.2 billion years ago - nearly four hundred million years after the Earth and our solar system was formed.
LUCA was a complex organism, exploiting its environment: scientists
The study's co-author Dr Sandra Álvarez-Carretero said, "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."
The researchers also worked on LUCA's biology by modelling the physiological characteristics of living species with the genealogy of LUCA's life.
Explaining the process, lead author Dr Edmund Moody said, "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."
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"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," said co-author Professor Davide Pisani, while speaking about the features of LUCA.
Taking this discussion further, co-author Tim Lenton said, "It's clear that LUCA was exploiting and changing its environment, but it is unlikely to have lived alone. Its waste would have been food for other microbes, like methanogens, that would have helped to create a recycling ecosystem."
