An international team of researchers led by the University of Bristol has shed more light on LUCA (Last Universal Common Ancestor). LUCA is the hypothesized common ancestor from which all modern cellular life evolved, from single-celled microbes such as bacteria to giant redwood trees (as well as us humans). LUCA is the node on the Tree of Life from which the original prokaryotic domains (Archaea and Bacteria) diverge.
Highlights of the Research
- Researchers believe all three branches of life namely bacteria, archaea, and eukarya originated from a single cell, called the last universal common ancestor (LUCA).
- LUCA had a small genome with about 2.5 million bases and 2,600 proteins, sufficient for survival in its unique environment.
- LUCA’s metabolites might have created a secondary ecosystem for other microbes to emerge, and it possibly had immunity genes to fight off viruses.
- Though there is no fossil evidence to support the existence of LUCA, modern genomes share so many features that provide some insights.
- However, the theory of the molecular clock allowed scientists to reconstruct the ‘tree of life’.
- As per theory, the rate at which mutations are added or removed from a population’s genome is proportional to the rate of acquiringnew mutations, which is constant.
- The mutation rate varies between species. Based on the findings, researchers created a method to estimate the time between
- evolutionary events by using known mutation rates and linking genomes to specific events like the evolution of the first mammal or the age of fossils as benchmarks.
- Based on the earlier findings of fossils in the Pilbara Craton in Australia, the earliest life forms were believed to be date back to 3.4 billion years ago.
Significance of Findings
- Overall, these findings are crucial for understanding how life began and evolved on
- Earth and for seeking similar life forms elsewhere in the universe.
- These evolutionary insights will boost efforts to engineer synthetic organisms for
- various processes on Earth and to create or manage ecosystems on other planets in the future.
Various Competing Theories of Life’s Origin
- Oparin-Haldane Hypothesis: In 1924 and 1929, Oparin and Haldane respectively suggested the first molecules making up the earliest life forms gradually self-organised from a “primordial soup” in a young earth’s tempestuous, prebiotic environment. This idea is today called the Oparin-Haldane hypothesis.
- Miller-Urey Experiment: It showed that in the right conditions, inorganic compounds could give rise to complex organic compounds.
- Under it methane, ammonia, and water were mixed and applied an electric current to produce amino acids, the building blocks of proteins.
- Panspermia Hypothesis: It suggests that meteorites could have brought life’s building blocks to Earth, supported by discoveries of extraterrestrial organic material and amino acids on asteroids.
- In 2019, French and Italian scientists reported discovering extra-terrestrial organic
- material 3.3 billion years old.
- Japan’s Hayabusa 2 mission to the asteroid Ryugu also indicated the presence of more than 20 amino acids there.