so a socialist society would not survive unless the people in it acted cooperatively in a spirit of mutuality
Bingo, which is the most egregious flaw of socialist theory. Socialism grossly misreads human nature, presuming by some horrific miscalculation, that everyone wants to 'act cooperatively in the spirit of mutuality'. They don't, they never have, which is why socialism can only exist through the barrel of a gun, forcing you to be content with your lot in life and cooperate in the spirit of mutuality, e.g. "for the collective good".
All societies exist through the barrel of a gun to some extent, don't pay your taxes for several years and see if the tax collector comes bearing flowers, or a badge and a gun. But there would be exponentially more "force" in socialism, because there has to be.
The natural tendency of man is to think of himself or 'his own' when left to his own devices. Socialism can only succeed to the extent that, in the minds of everyone living under it, there is nothing better. Until man advances a few thousand years, or regresses a few thousand years, either way, this can only be accomplished by some heavy indoctrination, propoganda, oppression, and fear.
Even highly romanticized, if not misrepresented, tribal cultures such as Native Americans only existed in communal 'happiness' to the extend they didn't know there was anything better. When Europeans came with their trinkets, the Indians would come out of the wood work for them. Louis and Clark's memoirs and journals tell of Indian tribesmen who would show up at their camps butt naked from head to toe, deliberately exaggerating their own poverty, so that members of the expedition would give them material possessions, clothing, and food. lol!