Why did bonobos (Pan paniscus) evolve from common chimps (Pan troglodytes)?
The flippant answer is that we never really know or care why one species gives rise to another, we just see that it happens and document it. But underlying this question is the presumption that bonobos have interesting features that we do not expect to see in apes, and this is an opportunity to think interesting thoughts about evolution. Bonobos are different from chimps in a few ways that we can presume are derived … meaning that they are novelties found in bonobos that arose as part of their differentiation from the common chimps, or subsequently. Since none of these features have a fossil record at this time it will be hard to say which known differences, if any, account for the speciation event itself. The differences (that we’ll talk about now … this is not an exhaustive list): • Bonobos have a female matriline in which dominance ranking of the females determines the dominance ranking of the female’s male offspring. • The “chief bonobo” in a group is typically the highest ranking
