They had had a long battle with what looks to be hundreds of participants and there were a few wounded, but nobody died. Compare with e.g. battles in the ancient Mediterranean, where the fighting would have continued until one side panics and tries to flee, and the winning side kills anyone who can't run away fast enough. Now maybe they're simply bad at warfare, but I think a more likely explanation is that they're intentionally not escalating to that level of violence and mostly stay at a standoff distance where fatalities are unlikely. The narrator also calls it a "formal battle" at one point.
In any case, I don't think you can ascribe much of their bow-and-arrow tactics to base instincts.
In any case, I don't think you can ascribe much of their bow-and-arrow tactics to base instincts.