How did the expansion of the Roman Republic affect small farmers? Small farmers bought more land, allowing them to move into a higher social class. Small farmers could not compete with higher levels of production from large estates. Small farmers lost income because their farms were not connected to cities by roads.
I would say what was most important would be the adoption of agriculture. Humans no longer had to move around and spend their days solely focusing on finding food. Being able to settle down and make one's own food allowed humans to have free time, and create hierarchies and languages and art, creating societies and civilization.
