II.1. ONE CAN'T BRING IN THE HARVEST ALONE

OR FISH WITH LARGE NETS OR HUNT BIG ANIMALS

So work must be collective. 

 The Harvesters by Pieter Breughel the Elder, Flanders, 1565 / zoom

When expanding towns lead to growing crops for market, lands used communally become private and the pursuit of individual gain weakens the community. Then people leave —"He went off to seek his fortune," is how many fairy tales begin.

Some migrants learn a craft or become merchants — that's how a middle class grows up — but most finish as vagabonds, mercenaries or thieves. 

Those who remain on the land become sharecroppers or serfs.

Ways to limit such change appear. 

Next,

2.2. 

Curbs on gain that villagers impose