Around 1.5 million years ago, the ancestors of today’s bonobos and chimpanzees became isolated from one another, likely due to the formation of the Congo River. This geographical barrier separated populations of the genus Pan, which ultimately evolved into two distinct species: bonobos (Pan paniscus) south of the Congo River, and chimpanzees (Pan troglodytes) to the north. The river’s formidable width and strong currents created an insurmountable boundary, preventing these populations from interbreeding and leading them down separate evolutionary paths!