ONE CAN'T BRING IN THE HARVEST ALONE...

OR FISH WITH LARGE NETS 
OR HUNT BIG ANIMALS

So unmechanized work must be collective --
think of the Harrison Ford film Witness,
where Amish meet to build a barn

Noon by Pieter Breugel the Elder, about 1550

Pursuing individual gain weakens the community.

Worse, communal lands become privately owned.
Then many leave --
"He went off to seek his fortune"

A few become merchants in the growing towns -- that's how a middle class grows up -- but most finish as vagabonds, mercenaries or brigands. 

Those who remain become sharecroppers or serfs. 

That menace explains the universal brakes on gain,
which villagers begin and centralized power extends.  

*      *      *

Next,
When chiefs become kings