Why are you surprised they follow the coast line.
All cultures follw the water and follow the food, as generations grow people expand the behaviour just like the Apes we are studying today.
X number follow a leader after a whie Someone else wants to be the leader so their followers either fight or go off to create their own life.
The only real surprise is how humans developed from the limited gene pool. In those remote places if cousin and incest are so bad.

