I'm currently writing a fantasy piece set on a frozen landscape with a few islands of trees and plant life. The inhabitants are primitive relatives of humans who have just started to mingle. There are three main tribal clusters living within 20 kilometers of one another, meeting every year to exchange stories, tribe memebers and discoveries. Now, I'm wondering just how varied would the cultures of each cluster be? Would they all have similar lifestyles and languages or have several major differences? Would the specie factor alter cultural development? Any help here is appreciated.