Every few years we discover that life is older than previously thought. Since Earth is thought to be 4.5 billion years old, it looks as if life evolved on Earth just a few billion years later. There is controversy in the claim though.
The origins of life on Earth might have occurred much earlier and been more complex than previously thought. Recent research suggests that the organism from which all life descended, known as the last universal common ancestor (LUCA), may have emerged just a few hundred million years after the Earth formed, and it was more sophisticated than earlier estimates indicated.
The DNA of all living organisms today, from bacteria like E. coli to massive blue whales, shares significant similarities, hinting at a common ancestry billions of years ago. This ancestral link traces back to LUCA. While many studies have tried to unravel LUCA’s mysteries, a new interdisciplinary approach has yielded surprising insights.
Anybody recognizing that everything gets earlier and earlier? 🤔😳
‘By studying the genomes of organisms that are alive today, scientists have determined that the last universal common ancestor (LUCA), the first organism that spawned all the life that exists today on Earth,… pic.twitter.com/cBjnrD7Rhs
— Troubled Minds (@TroubledMindsR) July 13, 2024
“We’ve aimed to bring together experts from various fields to achieve a comprehensive understanding of LUCA’s timeline and biology,” says Philip Donoghue from the University of Bristol in the UK.
Genes shared across all major life branches today may have been inherited directly from LUCA, providing clues about its genetic makeup. By examining the evolution of these genes, researchers can estimate LUCA’s existence. However, this process is complex due to gene loss, acquisition, and exchange among life branches. To address this, Donoghue’s team developed a sophisticated model to determine which genes LUCA likely possessed. Their findings suggest LUCA was far more advanced than previously thought.
The team identified around 2600 protein-coding genes traceable to LUCA, significantly higher than some past estimates of just 80. They also propose that LUCA lived around 4.2 billion years ago, closer to Earth’s formation 4.5 billion years ago. “This suggests life’s emergence was simpler than previously believed because it occurred so early,” says Donoghue.
The last universal common ancestor (LUCA) is the hypothesized common ancestral cell from which the three domains of life, the Bacteria, the Archaea, and the Eukarya originated.
According to this theory, all forms of life come from a single and unique ancestor. pic.twitter.com/yvfzUiWLKz
— Dreams N Science (@dreamsNscience) July 3, 2024
This early timeline results from the team’s enhanced method and their departure from the assumption that LUCA appeared only after the late heavy bombardment (LHB) – a period around 3.8 billion years ago marked by intense asteroid impacts thought to have sterilized early Earth. Donoghue points out the uncertainty of this date, based on lunar rock analysis.
The study also indicates that LUCA had genes for UV protection, implying it lived near the ocean’s surface. Additional genes suggest it consumed hydrogen, consistent with earlier studies. The researchers speculate LUCA was part of a broader ecosystem of primitive cells that eventually died out. “It’s naive to think LUCA existed alone,” Donoghue asserts.
Greg Fournier from MIT finds the study compelling from an evolutionary perspective. He notes that LUCA represents not the beginning of life but the most recent common ancestor discernible through genomic data.
Interestingly, the findings suggest LUCA had a primitive CRISPR system, a bacterial defense mechanism against viruses. “Even 4.2 billion years ago, our ancestors were battling viruses,” says Edmund Moody, also from the University of Bristol.
The Last Universal Common Ancestor (LUCA): Unraveling the Foundations of Life
In the vast and intricate web of life on Earth, all living organisms—whether they are towering redwoods, elusive deep-sea creatures, or microscopic bacteria—share a common heritage. At the root of this… pic.twitter.com/mLRnne94kx
— Niels Groeneveld (@nigroeneveld) May 20, 2024
Despite the intriguing results, Donoghue acknowledges the uncertainties. “It’s almost certainly all wrong,” he admits. “We’re pushing the envelope and integrating all relevant evidence for the first time.”
“This isn’t the final word,” he adds. “It’s just a starting point.”
Patrick Forterre from the Pasteur Institute in Paris, who coined the term LUCA, agrees that LUCA wasn’t isolated but disagrees with the early timeline. “The idea that LUCA existed before the LHB is unrealistic to me,” Forterre states, suggesting flaws in the team’s methodology for dating LUCA and determining its gene content.
Major Points
- LUCA, the last universal common ancestor, may have emerged just a few hundred million years after Earth formed.
- LUCA was more genetically sophisticated than previously thought, with around 2600 protein-coding genes.
- The study suggests LUCA lived around 4.2 billion years ago, earlier than prior estimates.
- LUCA likely lived near the ocean’s surface and fed on hydrogen, part of a broader ecosystem of primitive cells.
- Despite compelling findings, researchers acknowledge uncertainties and aim to integrate all relevant evidence for a comprehensive understanding.
TL Holcomb – Reprinted with permission of Whatfinger News
