Their wars are legendary. They never give up. Never surrender. And the cycle never ends. Children of war.
The end game of "the replacement theory" when everyone fully commits.
Shared social structures and behaviors can last through much longer periods of time than 8 million years. For example take bees and ants sharing a common ancestor in the 100 of millions of years age.
Animals have inner lives as well. They have their own thoughts and feelings. And sometimes those feelings are anger and their thought is to kick the shit out of those assholes over there.
Fuck man, my cats occasionally scrap with each other. I know it's not anything they've learned from the people in my house because we don't go full Wrestlemania on each other.