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Context: A new study suggests that the last universal common ancestor (LUCA) may have formed around 4.2 billion years ago.

Origins of Life Theories

Primordial Soup Hypothesis	●In the 1920s, Alexander Oparin and J.B.S. Haldane independently proposed the idea that life originated from a "primordial soup" of organic molecules in a young Earth's prebiotic environment. This idea, now known as the Oparin-Haldane hypothesis, suggests that simple organic compounds gradually formed more complex molecules, eventually leading to the first life forms.
Miller-Urey Experiment	●In 1952, Stanley Miller and Harold Urey conducted a famous experiment that supported the Oparin-Haldane hypothesis. They mixed methane, ammonia, and water, simulating early Earth conditions, and applied an electric current to mimic lightning strikes. This experiment produced amino acids, the building blocks of proteins, demonstrating that inorganic compounds could give rise to organic molecules under the right conditions.
Extraterrestrial Origins	●The theory suggests that life’s building blocks could have arrived on Earth via meteorites. This is supported by discoveries of extraterrestrial organic material, such as the 3.3-billion-year-old organic material found by French and Italian scientists and the presence of more than 20 amino acids on the asteroid Ryugu, as indicated by Japan’s Hayabusa 2 mission.

Last Universal Common Ancestor (LUCA)

• LUCA is the hypothetical last common ancestor from which all current life forms, including bacteria, archaea, and eukarya, descended. Understanding LUCA is crucial for unravelling the evolutionary history of life on Earth.
• Molecular Clock Theory: It explains that the rate of genetic mutations is relatively constant over time. This allows scientists to estimate the timing of evolutionary events by comparing genetic sequences.

Recent Findings

• A recent study by researchers at the University of Bristol and Exeter used a phylogenetic tree of 350 bacterial and 350 archaeal genomes, combined with the molecular clock method, to estimate that LUCA originated around 4.2 billion years ago, just 300 million years after Earth’s formation. This significantly predates previous estimates of life’s origin, suggesting LUCA existed almost immediately after the planet's formation.
• The study suggests LUCA had a small genome of about 2.5 million bases and encoded around 2,600 proteins, which were sufficient for survival in a unique environmental niche. LUCA's metabolites might have created a secondary ecosystem for other emerging microbes. LUCA may have possessed genes responsible for immunity, indicating it faced viral threats.

LUCA's Early Origin

• Earlier Origin of Life:
  • The discovery that LUCA could have existed 4.2 billion years ago challenges previous fossil evidence from the Pilbara Craton in Western Australia, which dated the earliest life forms to around 3.4 billion years ago. This new timeline suggests life began nearly a billion years earlier than previously thought.
• Impact on Scientific Understanding and Technology:
  • Understanding LUCA’s early origin and characteristics enhances our knowledge of life’s evolution and opens up possibilities for discovering similar life forms across the universe.
  • Insights into LUCA’s genetic makeup and metabolism could also drive advancements in biotechnology, such as engineering synthetic organisms for industrial, chemical, and biological applications on Earth and potentially creating or moderating ecosystems on other planets.

Hydrothermal Vents and Ancient Life

• The ‘Candelabra’ hydrothermal vent on the Mid-Atlantic Ridge, where ancient life forms have been found in precipitates around such vents. These environments provide clues about the conditions in which early life may have originated, supporting the idea that hydrothermal vents could have been cradles for the first life forms on Earth.

Conclusion

• The recent study pushing back the origin of LUCA to around 4.2 billion years ago provides a new perspective on the early development of life. It highlights the early emergence of life in Earth's history and advances our understanding of how life might have evolved under extreme conditions. These insights not only inform our knowledge of Earth’s biological history but also have implications for the search for life beyond our planet and for advancements in synthetic biology.

Source:

The Hindu

PRACTICE QUESTION Q. Which of the following characteristics are believed to be true about the Last Universal Common Ancestor (LUCA) based on recent studies? 1. LUCA is thought to have lived in a high-temperature, hydrothermal environment. 2. LUCA is estimated to have existed around 4.2 billion years ago. Select the correct answer using the codes given below: A) 1 only B) 2 only C) Both 1 and 2 D) None Answer: C