Each village has a "generation pole" erected in the center of the village. Every 18 years a new pole is added to the existing poles marking the start of a new generation. That way you can tell the age of the village. There is also a large stone that is used to determine if a young man is ready to marry. He has to lift the stone (it's really heavy) above his head and drop it behind him. If he is successful, he can choose a bride. If not, he has to wait a year.