Approximately every 14 years a significant event known as Yokalar Rang occurs in Nyoongar country. It is signalled by Yokalar (Pleiades constellation) and the conjunction of the planet of Jupiter. This planet becomes known as the seventh sister in the constellation. For Yokalar Rang, girls born during that Nyoongar year go through a process that determines which of them will sacrifice their genes and be married to the Yamatji people to the north and the Wongai people to the east. This practice — governed by marriage law — ensures Nyoongar, Yamatji and Wongai gene pools remain strong.