Complex sentence: Most inhabitants of Diego Garcia through the period from 1793 to 1971 were plantation workers, but also included Franco-Mauritian managers, Indo-Mauritian administrators, Mauritian and Seychellois contract employees, and in the late 19th Century, Chinese and Somali employees.
Split into simpler sentences: Most inhabitants of Diego Garcia through the period from 1793 to 1971 were plantation workers. There were several categories of workers, including Franco-Mauritian managers, Indo-Mauritian administrators, Mauritian and Seychellois contract employees, and in the late 19th Century some Chinese and Somali employees.