Please answer a question about the following article about Genocide:

Other authors have focused on the structural conditions leading up to genocide and the psychological and social processes that create an evolution toward genocide. Ervin Staub showed that economic deterioration and political confusion and disorganization were starting points of increasing discrimination and violence in many instances of genocides and mass killing. They lead to scapegoating a group and ideologies that identified that group as an enemy. A history of devaluation of the group that becomes the victim, past violence against the group that becomes the perpetrator leading to psychological wounds, authoritarian cultures and political systems, and the passivity of internal and external witnesses (bystanders) all contribute to the probability that the violence develops into genocide. Intense conflict between groups that is unresolved, becomes intractable and violent can also lead to genocide. The conditions that lead to genocide provide guidance to early prevention, such as humanizing a devalued group, creating ideologies that embrace all groups, and activating bystander responses. There is substantial research to indicate how this can be done, but information is only slowly transformed into action.

A history of what is just one factor that contributes to the probability of violence developing into genocide?
devaluation of the group