Somalia has had no effective government since 1991. According to the UN refugee agency, UNHCR, Somalia is the most pressing humanitarian emergency, even worse than the crisis in Darfur, Sudan. The current instability in Somalia is rooted in many factors such as war, famine, corruption, warlords and external interventions. The Somali society is based on a patriarchal lineage system, in which the origins of all Somalis can be traced back to six principal patriarchs. Competition for water and grazing lands has often been the source of conflict among clan families.