Simplify the following text for a Grade 7 native English-speaking person.
Original: Due to lack of reliable documentation there is a great degree of debate over Waldo 's role in the Waldensian sect which may have existed before his leadership , while the French historian Thuanus dated his death to the year 1179 .
Simplified: Also , the French historian Thuanus thought Waldo died in the year 1179 .