Simplify the following text for a Grade 6 native English-speaking person.
Original: Robert Pershing Wadlow ( February 22 , 1918 -- July 15 , 1940 ) is the tallest person in history for whom there is irrefutable evidence .
Simplified: Robert Pershing Wadlow ( February 22 1918 â `` July 15 1940 ) was one of the tallest people who ever lived .