Jacob is over 2,000 years old, and his birth mother is from ancient Rome. Jacob's immortality comes from his role as the island's protector. Mark Pellegrino, who played Jacob, was born in 1965 and was 44 when he joined Lost.

Many of the underlying mysteries of Lost center around Jacob, extending even to his age. Teased throughout the first half of Lost's overarching storyline, Jacob's role in the latter seasons of the series revealed more about the island and the true nature of the unseen battle at the heart of the show. As a mysterious and seemingly mystical force behind the Others that appeared across Lost, almost everything about the character remained a mystery until the final stretch of the series.

This includes his age, with many fans wondering how old the character could really be when he finally joined the cast of Lost in season 5. Thanks to the mysterious qualities of the island,...