Kenneth Loi shows how VIPR RNA (in pink) snakes around the double helix of DNA (yellow and green) to form a unique triplex structure.
Photo: Glenn Ramit.
One of the recurring mistakes in creationist arguments is to assume that a complex biological system must always have performed its present function. If its components now work together, the argument goes, they must have been created together for that purpose. Evolution, however, can recruit existing machinery for new roles. Two papers in *Science* now provide evidence that this process may help explain the origin of an important form of microbial immunity—with the intriguing possibility that bacteria acquired the precursors of their antiviral weapons from viruses themselves.
To appreciate the discovery, it helps to understand what CRISPR immunity actually is. Although CRISPR is familiar as a tool for editing genes, its natural role is defence. Many bacteria and archaea possess CRISPR–Cas systems that retain molecular records of past invaders. Short pieces of foreign DNA are incorporated into the cell’s genome, between repeated sequences. These stored fragments provide templates for small RNA molecules, which guide CRISPR-associated—or Cas—proteins to matching genetic material during subsequent infections. Depending on the system, the resulting response can destroy invading DNA or RNA. This is adaptive immunity: protection directed against particular threats, with a genetic memory that can pass to descendants.
CRISPR stands for “clustered regularly interspaced short palindromic repeats”, a description of the DNA arrangement in which those memories are stored. The best-known gene-editing protein, Cas9, belongs to class 2, whose targeting machinery centres on one large protein. Class-1 systems instead use assemblies of several proteins to recognise their targets. It is the evolutionary origin of this latter machinery that the new research addresses.
The studies, published on 17 September 2026 investigate a compact system called VIPR, short for viral interference programmable repeat. Found in viruses and bacteria, it combines a small protein with a guide RNA. The researchers propose that an ancestral VIPR-like system involved in competition between viruses was recruited into bacterial defence, eventually contributing to the evolution of class-1 CRISPR. This would be evolutionary co-option: machinery favoured in one context becoming useful in another.




































