Complex sentence: Reining's field of specialization was centered mainly on the sub-Saharan region of Africa; she worked for several years with the Haya people located in Tanzania in the early 1950's becoming one of the uppermost authorities on the village life of sub-Saharan peoples.
Split into simpler sentences: Reining's field of specialization was centered mainly on the sub-Saharan region of Africa. She worked for several years with the Haya people located in Tanzania in the early 1950's becoming one of the uppermost authorities on the village life of sub-Saharan peoples.