Searching for LUCA, the first life-form from which all other life descended
- July 17, 2024
- Posted by: OptimizeIAS Team
- Category: DPN Topics
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Searching for LUCA, the first life-form from which all other life descended
Sub : Sci
Sec : Msc
Context:
- In a new study, scientists have said the last universal common ancestor (LUCA) could have formed just 300 million years after the earth formed.
What is LUCA?
- 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.
- The concept of LUCA is based on the phylogenetic relationship among all the organisms.
- LUCA is not the first living form on earth or the first living ancestors.
- There is no fossil evidence to support the existence of LUCA, but the fact that modern genomes share so many features provides some insights.
- The first universal common ancestor (FUCA) is a hypothetical non-cellular ancestor to LUCA and other now-extinct sister lineages.
Which is older: LUCA or fossils?
- According to the journal Nature Ecology and Evolution, researchers at the University of Bristol and Exeter in the U.K. constructed a phylogenetic tree of 350 bacterial and 350 archaeal genomes and using a molecular clock, they estimated that LUCA could have originated around 4.2 billion years ago, just 300 million years after the earth itself formed.
- The team also reported that LUCA may have had a small genome, of some 2.5 million bases and encoding around 2,600 proteins, which help it survive in a unique environmental niche.
- The team also suggested the metabolites produced by LUCA — compounds produced as a result of its metabolism — could have created a ‘secondary’ ecosystem in which other microbes could have emerged.
- Researchers have found fossil records of the earliest life-forms in the Pilbara Craton in western Australia, one of the few places on the planet where archaean rocks are exposed aboveground and accessible.
- Studies of these fossils have suggested the life that lived on the rocks emerged around 3.4 billion years ago.
- The current study has pushed this date back by almost a billion years, almost on the heels of the birth of our planet itself.
- The researchers also found that LUCA may have had genes responsible for immunity, suggesting it had to fight off viruses.
What is a Molecular Clock?
- The molecular clock is a figurative term for a technique that uses the mutation rate of biomolecules to deduce the time in prehistory when two or more life forms diverged.
- The biomolecular data used for such calculations are usually nucleotide sequences for DNA, RNA, or amino acid sequences for proteins.
- To calibrate the molecular clock to a particular rate of mutations, researchers establish links between a genome with known events, such as the ‘date’ on which the first mammal evolved or with the age of certain fossils. These links act like temporal benchmarks.
Origin of Earth
- Earth formed around 4.54 billion years ago, approximately one-third the age of the universe.
- There are a number of competing theories but all of them lack conclusive proof.
- Oparin-Haldane hypothesis:
- In 1924 and 1929, Oparin and Haldane respectively suggested the first molecules making up the earliest life forms gradually self-organized from a “primordial soup” in a young earth’s tempestuous, prebiotic environment.
- Miller-Urey experiment:
- Miller-Urey experiment in 1952, showed that in the right conditions, inorganic compounds could give rise to complex organic compounds.
- Miller and Urey mixed methane, ammonia, and water, and when they applied a strong electric current — like a lightning strike might have — the mixture contained amino acids, the building blocks of proteins.