I thought the theory was we're from both? We got the sex desire from bonobos and the aggression from chimps? I'm not well versed so I admit I could be very wrong
Chimps also have sex for fun, I don't know about frequency. What sets bonobos apart from chimps and humans is that they use sex for conflict resolution. If humans or chimps have a territorial dispute, then it's going to lead to a violent war. If bonobos have a territorial dispute, then they usually sex it out (somehow, I don't know how they decide who comes out on top, if someone has to come out on top that is, maybe post nut clarity is enough to convince everyone that it's not worth the fuzz).
I only know one instance in human history where (maybe) something similar happened: Richard Lionheart and Philip of France.
It's not cross-group. Bonobos fight with other bonobos. Intergroup conflict is settled with sex instead of violence, it's about group cohesion.
Example: Human pisses off their neighbor. The "advanced" human approach is to take it to court and allow the whole to decide who was in the wrong. The chimp approach is to just beat the shit out of your neighbor and take some food from his fridge to rub salt in the wound. The bonobos approach is to fuck his wife, his daughter, and his son, to which his only response will be so mad he'll fuck you then everyone is happy because sex.