Life is competition
So the first biological lesson of history is that life is competition. Competition is not only the life of trade, it is the trade of life — peaceful when food abounds, violent when the mouths outrun the food. Animals eat one another without qualm; civilized men consume one another by due process of law. Cooperation is real, and increases with social development, but mostly because it is a tool and form of competition; we co-operate in our group — our family, community, club, church, party, “race,” or nation — in order to strengthen our group in its competition with other groups. Competing groups have the qualities of competing individuals: acquisitiveness, pugnacity, partisanship, pride.
Will Durant, 1968, from the book The Lessons of History