Final answer:
The RNA world hypothesis suggests that the first life-form on Earth was a self-replicating RNA molecule. RNA can both store genetic information and carry out chemical reactions. This hypothesis is supported by evidence and solves the 'chicken-and-egg problem'.
Step-by-step explanation:
The RNA world hypothesis suggests that the first life-form on Earth was a self-replicating RNA molecule, rather than DNA or protein. The main reason for this contention is that RNA can both store genetic information, like DNA, and carry out chemical reactions, like proteins. This solves the 'chicken-and-egg problem' of which molecule came first, as RNA can perform both functions.
Additionally, evidence suggests that RNA is the most ancient of the organic molecules. RNA molecules have been found to have catalytic properties, meaning they can speed up chemical reactions. This ability would have been crucial for early life, allowing for essential biochemical processes to occur.
In summary, the RNA world hypothesis proposes that the first life-form was a self-replicating RNA molecule due to its dual ability to store genetic information and perform chemical reactions. This hypothesis is supported by the fact that RNA is the most ancient of the organic molecules and has catalytic properties.