Recently in a new study, scientists have suggested that the last universal common ancestor (LUCA) could have formed just 300 million years after the Earth formed.

• A recent study in Nature Ecology and Evolution, employing genomic analysis and the molecular clock, estimated LUCA’s origin to be around 4.2 billion years ago, soon after Earth’s formation.

Recent Studies and Findings

• LUCA’s Early Genome and Ecosystem: This study precedes earlier estimates and indicates that LUCA had a compact genome, potentially producing metabolites that shaped a distinct ecosystem.
• Origins: Fossil records from the Pilbara Craton indicate the emergence of early life forms around 3.4 billion years ago, but LUCA’s estimated origin, nearly a billion years earlier, sheds light on the early evolution of life.
• LUCA’s Immunity Genes: Researchers also hypothesize that LUCA may have harbored genes for immunity, indicating it possessed mechanisms to defend against viruses, enhancing our understanding of early microbial interactions.

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Early Experiments

• Oparin-Haldane Hypothesis: The origin of life on Earth remains a deep enigma, with several theories proposed but lacking definitive proof. In the 1920s, Alexander Oparin and J. B. S. Haldane formulated the Oparin-Haldane hypothesis, proposing that the first life molecules arose from a “primordial soup” of inorganic compounds in Earth’s early, turbulent environment.
• Earth Chemistry Experiment: The Miller-Urey experiment in 1952 provided evidence for the Oparin-Haldane hypothesis by showing that amino acids, essential building blocks of proteins, could emerge from inorganic compounds (such as methane, ammonia, and water) under simulated early Earth conditions, which included electrical discharges resembling lightning.
• Other Theories: Other theories suggest that organic molecules were delivered to Earth by meteorites, bolstered by findings of extraterrestrial organic material in meteorites and amino acids on asteroids such as Ryugu.

LUCA Theory

• Origin of Life: The theory of the Last Universal Common Ancestor (LUCA) proposes that all life forms — bacteria, archaea, and eukarya — originated from a single cell. While no fossil evidence of LUCA exists, genomic similarities among species imply shared ancestry.
• Molecular Clock Theory: Proposed by Emile Zuckerkandl and Linus Pauling in the 1960s, the molecular clock theory estimates evolutionary timelines by analyzing mutation rates in genomes. This approach calibrates mutation rates using known evolutionary events as temporal benchmarks.

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