The Fostering

Among the Dras the potential choice of a mate is taken very seriously. Their numbers are small enough that without careful attention to the genealogies, close kin marrying and producing offspring could result in an increase in mortality among the already marginal population base. 
The Matriarchs and the Matchmakers meet just before the thawing begins in late spring to evaluate the young people who will enter the Fostering that year. These are young boys and girls, usually about twelve years old. Each boy is considered, his lineage, his abilities, and his interests. He is then sent to live with one of the other clans until he is considered a man. 
By doing this the young man is exposed to others of the Dras, ones where he can safely learn and grow, but more importantly, where he will be around young girls that are suitable potential mates. He is safely away from those females most closely related to him and in the majority of cases, propinquity takes care of the rest.
The girls do not take part in the fostering. It is expected that they will remain within their own clan, living with and learning from their mothers and aunts. New boys come from the other clans so there is no loss of new faces, but each girl has the potential to become Matriarch and they are kept close to their nearest kin.
The actual ceremony happens the week following the sun's return to the sky. Each boy is brought to the communal eating house and presented to the clan. Their skills and talents as well as their genealogies are recited and the Matriarch places a daub of ochre upon their foreheads and pronounces their destination. Several of the fathers are selected to travel with the boys to the assigned clan, often the one they came from themselves.  The fathers make the journey, but do not stay. Most years the numbers sent away and the numbers arriving are similar, so no clan suffers from lack of working hands.
After a year of life in a different clan, some few of the boys may be rotated again, but not back to their clan of birth.