The highly endangered solenodons, endemic to Cuba (Solenodon cubanus) and Hispaniola (S. paradoxus), comprise the only two surviving species of West Indian insectivores1,2. Combined gene sequences (13.9 kilobases) fromS. paradoxusestablished that solenodons diverged from other eulipotyphlan insectivores 76 million years ago in the Cretaceous period, which is consistent with vicariance, though also compatible with dispersal. A sequence of 1.6 kilobases of mitochondrial DNA fromS. cubanusindicated a deep divergence of 25 million years versus the congenericS. paradoxus,which is consistent with vicariant origins as tectonic forces separated Cuba and Hispaniola3,4. Efforts to prevent extinction of the two surviving solenodon species would conserve an entire lineage as old or older than many mammalian orders.