" Since gorillas split off from our evolutionary branch slightly before chimps and bonobos, it’s been argued that whichever ape is more like the gorilla deserves to be called the original type. But who says that gorillas themselves resemble our last common ancestor? They have had plenty of time to change, too, over seven million years, in fact. What we are looking for instead is the ape that has changed the least over time. Takayoshi Kano, the premier expert on wild bonobos, has argued that since bonobos never left the humid jungle - whereas chimpanzees did so partially and our own ancestors completely - bonobos probably have encountered fewer pressures to change and may therefore look most like the forest ape from which we all descend. American anatomist Harold Coolidge famously speculated that the bonobo “may approach more closely to the common ancestor of chimpanzees and man than does any living chimpanzee. "

― Frans de Waal , Our Inner Ape: A Leading Primatologist Explains Why We Are Who We Are