The study explores the evolutionary histories of domesticated capsid (CA) genes derived from Metaviridae in mammals. Using a complete human genome and 25 additional vertebrate genomes, researchers analyzed the evolutionary trajectories and functional potential of these genes. They identified five independent domestication events from diverse Metaviridae, resulting in three universally retained single-copy genes under purifying selection and two gene families unique to placental mammals, with some showing rapid evolution. The SIRH/RTL family exhibits diverse amino-terminal domains, widespread loss of protein-coding capacity in RTL10, and differential utilization of a programmed ribosomal frameshift in RTL3. The PNMA family encodes a conserved putative RNA-binding domain (RBD) both adjoining and independent from domesticated CA domains. The study corrects previous annotations of the CCDC8 gene, revealing a novel protein domain configuration in retrotransposons. Collectively, the study reveals divergent outcomes of multiple domestication events from diverse Metaviridae in the common ancestor of placental mammals. Key findings include the retention of CA-like structures in genes like ARC and dArc1, the functional convergence of independently domesticated genes, and the evolutionary retention of CA-like genes in placental mammals. The study also highlights the structural diversity of domesticated genes, including distinct N-terminal domains and the presence of RNA-binding domains. The findings suggest that these genes play important, nonredundant roles in mammalian biology, with some genes evolving under purifying or positive selection. The study provides insights into the structural and evolutionary diversity of domesticated CA genes derived from Metaviridae in mammals.The study explores the evolutionary histories of domesticated capsid (CA) genes derived from Metaviridae in mammals. Using a complete human genome and 25 additional vertebrate genomes, researchers analyzed the evolutionary trajectories and functional potential of these genes. They identified five independent domestication events from diverse Metaviridae, resulting in three universally retained single-copy genes under purifying selection and two gene families unique to placental mammals, with some showing rapid evolution. The SIRH/RTL family exhibits diverse amino-terminal domains, widespread loss of protein-coding capacity in RTL10, and differential utilization of a programmed ribosomal frameshift in RTL3. The PNMA family encodes a conserved putative RNA-binding domain (RBD) both adjoining and independent from domesticated CA domains. The study corrects previous annotations of the CCDC8 gene, revealing a novel protein domain configuration in retrotransposons. Collectively, the study reveals divergent outcomes of multiple domestication events from diverse Metaviridae in the common ancestor of placental mammals. Key findings include the retention of CA-like structures in genes like ARC and dArc1, the functional convergence of independently domesticated genes, and the evolutionary retention of CA-like genes in placental mammals. The study also highlights the structural diversity of domesticated genes, including distinct N-terminal domains and the presence of RNA-binding domains. The findings suggest that these genes play important, nonredundant roles in mammalian biology, with some genes evolving under purifying or positive selection. The study provides insights into the structural and evolutionary diversity of domesticated CA genes derived from Metaviridae in mammals.