2 million years ago. Divergence between chimpanzees and bonobos.
Around 2 million years ago, bonobos and chimps, which were two of the species of primates living in central Africa, suffered allopatric speciation after being separated by the formation of the Congo River. They became isolated from each other and diverged in different directions. Bonobos evolved south of the river and chimps evolved in the north. Since these species do not swim, there has been no genetic interchange from 2 million years. They have even developed very different behaviors.
Researchers have dedicated much more time and resources to study chimpanzees than to study bonobos. By far the best chimpanzee expert is Jane Goodall. She has studied them for many decades and was able to demonstrate that chimpanzees make and use tools. There are some populations which fish termites using tree branches. Other groups break open nuts using small stones as hammers and large ones as an anvil.
Bonobos have been less studied but are known to be much more peaceful than chimpanzees. One of the experts on bonobos is Vanessa Woods.