Simplify the following text for a Grade 9 native English-speaking person.
Original: Ernst Walter Mayr ( July 5 , 1904 -- February 3 , 2005 ) was one of the 20th century 's leading evolutionary biologists .
Simplified: Ernst Walter Mayr ( 5 July 1904 , Kempten , Germany â `` 3 February 2005 , Bedford , Massachusetts U.S. ) , was one of the 20th century 's leading evolutionary biologists .