Comparative Analyses of 35 Marine Mammal Genomes Provide Insights into the Evolution of Aquatic Life

Marine mammals, whose ancestors once roamed the land, have intrigued scientists for centuries. Although they share many similar morphological characteristics, the innovations for mammalian aquatic life were independently acquired at least seven times. Extant marine mammals are found in three orders: Artiodactyla, Sirenia, and Carnivora. To better understand the evolution of marine mammals, we generated the genomes of 17 marine mammals (11 cetaceans and six pinnipeds). Comparing these with publicly available marine mammal and terrestrial taxon genomes provides new insights into the evolutionary history of these iconic species. Focusing on the oldest groups of living marine mammals, the cetaceans, pinnipeds, and sirenians, we uncover genomic variations in marine mammals, including brown fat cell differentiation regulatory gene, NFIA, and forelimb development related genes, Xylt1 and Fam20b, which could underlie marine adaptations across these diverse taxonomic lineages.