However, wars still happened before the introduction of borders

The concept of borders did not exist yet but the earliest wars was definitely about territories control for accessing more natural resources . It's basically the same

https://www.smithsonianmag.com/science-nature/ancient-brutal-massacre-may-be-earliest-evidence-war-180957884/

This implies that the resources the people of Nataruk had at the time were valuable and worth fighting for, whether it was water, dried meat or fish, gathered nuts or indeed women and children. This shows that two of the conditions associated with warfare among settled societies—control of territory and resources— were probably the same for these hunter-gatherers, and that we have underestimated their role in prehistory.