Simplify the following text for a Grade 5 native English-speaking person.
Original: Alexander Selkirk ( 1676 â `` 13 December 1721 ) was a Scottish sailor who spent four years as a castaway when he was marooned on an uninhabited island .
Simplified: Alexander Selkirk , also known as Alexander Selcraig was a Scottish sailor . He was born in 1676 , and died on the 13th December 1721 .