PNA World Hypothesis
It has been hypothesized that the earliest life on Earth may have used PNA as a genetic material due to its extreme robustness, simpler formation and possible spontaneous polymerization at 100°C (while water at standard pressure boils at this temperature, water at high pressure—as in deep ocean—boils at higher temperatures). If this is so, life evolved to a DNA/RNA-based system only at a later stage. Evidence for this PNA world hypothesis is however far from conclusive. See RNA world hypothesis for related information.
Read more about this topic: Peptide Nucleic Acid
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—Alasdair Chalmers MacIntyre (b. 1929)