Answer:
Gathering and Hunting Requirements
Step-by-step explanation:
I'm not sure how early we are talking but if we are talking like cavemen then it's due to food, you have to move around constantly to gather and hunt food it's not just sit in one spot and hope something comes to you, if we are talking later in time just before the feudal era it's usually to branch out into other groups of humans to find a partner or form their own little clan / country.