Diego Olstein (also known as Diego Holstein, born 24 March 1970) is professor of history and department chair at the University of Pittsburgh. He was Associate and Interim Director of the World History Center (2011–2017) and member of the Executive Boards of the European Network of Universal and Global History (2005-2011) and the World History Association (2016-2018). Biography Diego Olstein, grandson of Jewish immigrants from Poland and Russia, was born and raised in Bahía Blanca, Argentina. Upon graduation from Colegio Nacional and Seminario Dr. Hertzl high schools, he migrated to Israel. He earned a BA in history and psychology at the Hebrew University of Jerusalem, where he continued to graduate studies. He wrote his MA thesis (1995-1996) and PhD dissertation (1998-2003) on medieval Spanish history under the supervision of Benjamin Ze’ev Kedar. During these formative years he worked in close collaboration with Moshe Zimmerman and Nathan Sussman at the Hebrew University, and Reyna Pastor, Ana Rodriguez López, and Eduardo Manzano while residing at the Universidad Complutense and Centro de Investigaciones Científicas (CSIC) in Madrid, and with Thomas Glick at Boston University. In 2004, Olstein returned to Israel and joined the faculty of the Hebrew University as a member of the Department of History until 2011. In 2009-2010 he was a visiting professor at the University of Wisconsin, Madison, and in 2011 he was appointed Associate Professor at the Department of History at the University of Pittsburgh, where he also became Associate Director of the World History Center. In 2017, he was appointed Full Professor. Olstein is married to Irit Lerner-Olstein. They are the parents of Racheli, Ariel, and Maya. Research Medieval Spanish History Olstein’s work on Medieval Spanish history concentrates on the processes of conquest and settlement, cultural diffusion, acculturation, and assimilation that unfolded during the twelve and thirteenth centuries in the city of Toledo and its rural area in the wake of the Castilian conquest (1085). He focused on the patterns of interaction between the two largest groups in both city and hinterland: the Christian settlers from the north and the local Mozarabs, i.e. Arabized Christians. In his book La Era Mozárabe, Olstein asserts that after a century of self-imposed segregation, by the 1180s a process of intermingling between these two societies started evolving, reflected in the gradual demographic homogenization of the landscape, the growth of economic and neighboring relationships between communities, and the increasing rate of inter-community marriages.