title: Hereditary blindness: a genealogical study among Al-gharahir, a jordan valley tribe.
abstract: BACKGROUND
  Hereditary diseases form an omnibus problem in Arab societies in general and in rural Arab societies in particular.
  
  
  OBJECTIVE
  Study of hereditary blindness and its relation to endogamous marriage among the Gharaghir tribe in the Jordan valley.
  
  
  METHODS
  The researchers carried out a fieldwork among the Gharaghir tribe in Al-Sawalha (the northern valley region, Deir Alla, the Hashemite Kingdom of Jordan) using participant observation, and intensive focussed interviews, in addition to the genealogical method. We gathered data on endogamous marriages, blindness, genealogy and the degrees of kinship between the spouses.
  
  
  CONCLUSIONS
  The results show that blindness among the Gharaghir was found to be associated with endogamous marriage. Marriage among the established ancestors of the clans used to be exogamous and kinship was unilineal-patrilineal. Through the shift to endogamy (marriage between close kin) there was a shift from uniliny (patriliny) to bilineal descent. This may have increased the probability of a recessive gene transmission from both parental sides. This is evidenced by the high inbreeding coefficient of 0.0687, one of the highest recorded.
authors.affiliation: Department of Anthropology, Yarmouk University, Irbid, Jordan.
authors.forename: M Y
authors.initials: MY
authors.lastname: Haddad
authors.forename: M Y
authors.initials: MY
authors.lastname: El-Najjar