The western black rhino emerged about 7 to 8 million years ago. It was a sub-species of the black rhino. For much of the 1900s, its population was the highest out of all the rhino species at almost 850,000 individuals. There was a 96% population decline in black rhinos, including the western black rhino, between 1970 and 1992. Widespread poaching is concluded to be partly responsible for bringing the species close to extinction, along with farmers killing rhinos to defend their crops in areas close to rhino territories.