How life emerged from a mixture of lifeless chemicals remains one of the most profound scientific questions. Multiple origin scenarios have been proposed, from icy environments to hydrothermal systems. Yet many researchers converge on a central requirement: life could not begin without a molecule capable of storing information and copying itself.
The RNA World hypothesis argues that RNA preceded both DNA and proteins, serving simultaneously as genetic material and catalytic machinery. However, a major limitation of this model has been structural complexity. Known RNA polymerase ribozymes are typically large and intricate, making their spontaneous formation under prebiotic conditions statistically unlikely.
A recent study conducted at the MRC Laboratory of Molecular Biology in the United Kingdom introduces a compelling alternative. Philipp Holliger and colleagues screened a vast library of approximately 12 trillion random RNA sequences in search of minimal motifs capable of polymerase-like activity. Candidate sequences were subjected to iterative selection cycles under increasingly demanding conditions, favoring those able to extend RNA strands more efficiently.
From this molecular selection process emerged QT45, a remarkably small RNA motif composed of only 45 nucleotides. In laboratory simulations designed to mimic early Earth—using a partially frozen, saline environment—QT45 demonstrated the ability to synthesize a complementary RNA strand and subsequently use it as a template for further replication.
The findings indicate that complex replication-related functions do not necessarily require large ribozymes. Instead, compact RNA motifs may possess sufficient catalytic versatility to support template-directed synthesis. This expands the plausible chemical landscape in which life-initiating systems could have formed.
If functional polymerase activity can arise within such a small RNA sequence, then the probability of similar catalytic motifs existing in prebiotic environments may be significantly higher than previously estimated. The discovery redefines the lower boundary of molecular complexity required for self-replication and invites renewed consideration of minimalistic pathways toward the emergence of life.
.webp&w=3840&q=75)