Analyzing the evolutionary changes in these genes offers insights into the era when LUCA existed.
The researchers suggest that 2600 protein-coding genes can be linked back to LUCA, a stark contrast to earlier estimates as low as 80.
Additionally, they propose that LUCA existed approximately 4.2 billion years ago, a significantly earlier timeframe compared to previous assessments, placing it in close proximity to Earth’s formation 4.5 billion years ago.
Other genes suggest LUCA fed on hydrogen, which is in line with previous studies.
“I think it’s naive in the extreme to think that LUCA would have existed on its own,” says Donoghue.
The organism that gave rise to all life present on Earth may have evolved much earlier than once thought, just a few hundred million years after the planet formed, and been more sophisticated than previous assessments have suggested.
The DNA found in all present-day organisms, ranging from E. coli to blue whales, shares numerous similarities, implying a lineage that extends billions of years back to a single ancestral source – LUCA. Despite numerous attempts to unravel LUCA’s mysteries, a recent comprehensive study has yielded unexpected findings.
“What we’ve been trying to do is bring people representative of different disciplines together to come up with a holistic understanding of when LUCA existed and what its biology was,” says Philip Donoghue at the University of Bristol in the UK.
Genetic Insights: Reconstructing LUCA
Genes present today across all major branches of life could have descended in an uninterrupted lineage from LUCA, enabling us to deduce the genetic makeup of this ancient ancestor. Analyzing the evolutionary changes in these genes offers insights into the era when LUCA existed. READ MORE: Antibiotic Tablet Led To Allergy, 15 Admitted To Hospital In Andhra Pradesh
In reality, this task is more challenging than it appears due to the complexities of gene loss, acquisition, and transfer between different evolutionary branches. Donoghue explains that the team has developed an intricate model to address these complexities and determine the genes that were likely present in LUCA. “We come out with an organism which was much more sophisticated than many people have argued in the past,” he says.
The researchers suggest that 2600 protein-coding genes can be linked back to LUCA, a stark contrast to earlier estimates as low as 80. Additionally, they propose that LUCA existed approximately 4.2 billion years ago, a significantly earlier timeframe compared to previous assessments, placing it in close proximity to Earth’s formation 4.5 billion years ago. “It suggests evolving life may be simpler than people have argued in the past because it occurred so early,” says Donoghue.
Scientific Debate: Interpreting LUCA’s Significance
The earlier estimation is attributed in part to the team’s improved methodology. Unlike previous studies, the researchers do not assume that LUCA could have only emerged after the late heavy bombardment, a period around 3.8 billion years ago when Earth was possibly bombarded by space debris, which could have hindered early life. This dating is based on lunar rock samples, but Philip Donoghue notes significant uncertainty surrounding this timeframe.
“Because their reconstruction suggests that LUCA had genes for protecting against UV damage, it is most likely that it lived at the surface of the ocean, the researchers think. Other genes suggest LUCA fed on hydrogen, which is in line with previous studies. It may have been part of an ecosystem of other kinds of primitive cells that died out, the team speculates. “I think it’s naive in the extreme to think that LUCA would have existed on its own,” says Donoghue.
“I find this compelling from an evolutionary perspective,” says Greg Fournier at the Massachusetts Institute of Technology. “LUCA is not the beginning of the story of life, but just the last shared ancestor state that we can work backwards to using genome data.”
“The results also suggest LUCA had a primitive version of the bacterial defence system known as CRISPR, to fight off viruses. “Even 4.2 billion years ago, our earliest ancestors are fighting off viruses,” says team member Edmund Moody, also at the University of Bristol.
“Peering back into the deep past is fraught with uncertainty, and Donoghue is the first to admit that his team may have missed the mark. “It’s almost certainly all wrong,” he says. “What we’re trying to do is push the envelope, and create the first kind of attempt at integrating all of the relevant evidence.”
“It won’t be the last word,” he says. “It won’t even be our last word on this topic, but we think it’s a good start.”
