A critical review on the origin of the genetic code——who built the informative bridge between proteins and nucleic acids?

As the core informative bridge linking nucleic acid and amino acid sequences, the genetic code represents a central pillar of life, making its origin one of the most fundamental questions in science. Since the decipherment of the genetic code in the 1960s, dozens of hypotheses have been proposed to explain its emergence. However, these hypotheses are often either overly reductionist or excessively broad, lack integration across hierarchical levels, and fail to address the deep-level question of why and how the codon system first arose. To overcome these limitations, this paper systematically reviews and critically assesses existing hypotheses, focusing on what constructed the informative bridge between proteins and nucleic acids. It aims to offer a novel perspective for establishing a unified framework that delineates the sequential and synergistic stages of genetic code origin in future research.