The Central African Rainforest (as distinct from the West African Rain Forest) spans an area from the Atlantic coast to nearly Lake Victoria in Uganda and Tanzania. In fairly recent times (the mid Holocene) this forest was probably continuous all the way to Victoria, and probably extended farther north and south than one might imagine from looking at its current distribution.Within the forest are major rivers, including the Congo. The Congo River is the only major river in the world that crosses the Equator twice. This trans-equatorial configuration guarantees that the rivers picks up rain from both of the equatorial rainy seasons, making it a huge and virtually uncrossable barrier for terrestrial mammals. During glaical periods, the forest is believed to have shrunk to either small refugia, or to have virtually disappeared entirely with only riverine forest remaining. Between the shrinkage of the forest and the major riverine barriers, terrestrial (non-flying, non-swimming) forest-dwelling animals that might have had a more continuous distribution would have been broken into many smaller units. Likely, many of these small populations would have gone extinct, but others may have changed over time such that when the forest was re-established, they may have constituted different subspecies or species. This breaking up and rejoining of the rain forest, over and over again, during the Pleistocene is thought to have caused much of the modern day variation we see among closely related forest species of primates, small carnivores, and forest ungulates such as duikers. Continue reading Scientists Investigate Gorilla Biogeography →