No matter how hard 100 men work independently they can never achieve what that can cooperatively. And if they fight instead then the difference in assets between conflict and cooperation produces a measurement of the value of cooperation.
Or to fall back on Adam smith. A division of labor between ten is not ten times the productivity of on man but ten thousand times the productivity of one man.
Ergo, cooperation is so rewarding that it is not only impossible to survive without it but impossible to compete without it and foolish to exist without it.