Complex sentence: Lev Nikolayevich Gumilyov (1 October 1912, St. Petersburg--15 June 1992, St. Petersburg), was a Soviet historian, ethnologist, anthropologist and translator from Persian, had a reputation for his highly non-orthodox theories of ethnogenesis.
Split into simpler sentences: Lev Nikolayevich Gumilyov (1 October 1912, St. Petersburg--15 June 1992, St. Petersburg) was a Soviet historian, ethnologist, anthropologist and translator from Persian. He had a reputation for his highly non-orthodox theories of ethnogenesis.