Jacob Is Approximately 2,000 Years Old In Lost
Jacob is the ancient being at the heart of many of Lost's mysteries, and is over 2,000 years old during the events of the series. For most of the show, Jacob remains a mystery. His origins aren't even explored until after his death. As revealed in season 6's "Across the Sea," Jacob and his twin brother were the children of Claudia. Surviving a boat crash on the island in ancient times, Claudia was killed by a mysterious Woman. The Woman raised Jacob and his brother as her own, grooming them to serve as the next guardians of the Island.
While the exact date of the flashbacks from "Across the Sea" can be hard to confirm, the episode suggests that Claudia hails from the Classical Roman era, making Jacob thousands of years old. When Jacob's brother sided with the island's other boat survivors against the Woman, their villAge was shown to be rudimentary and fitting for such an ancient period. This is the earliest chronological flashback in Lost, highlighting just involved Jacob is with the show's lore. With Jacob assuming the Woman's role as the island's protector following her demise, he was able to become functionally ageless.
Why Jacob Doesn't Actually Age
Jacob is immortal for much of Lost, seemingly due to his role as the guardian of the Island. After going through a small ritual with the Woman, Jacob gained a connection to the Island. Jacob's understanding of this power allowed him to live long beyond his mortal lifespan. Like many of the mysteries surrounding the Island's true nature, the exact way this works is left somewhat ambiguous. However, Jacob seems more than capable of sharing his Immortality, such as when he granted immortality to Richard. Notably though, his extended life-span doesn't actually make him fully immortal.
While the Man in Black is prevented from killing Jacob, he is able to manipulate others into doing so. While Jacob was initially content to protect the Island, the knowledge that his brother — by this point transformed into the Smoke Monster — would try to find a way to kill him led him to search around the world for candidates who could replace him. This became the central throughline of their feud, and played into Jacob's ability to appear in the lives of all of Lost's primary characters and influence their lives, as revealed in season 5's "The Incident" two-part episode.
How Old Jacob's Actor Mark Pellegrino Was In Lost
Mark Pellegrino plays Jacob in Lost, joining the cast in season 5's "The Incident." Although Jacob had been teased for several seasons, his on-screen debut (and subsequent death) in Lost set the show's endgame into motion. Mark Pellegrino was born in 1965, and had been active in the film and television industry for decades before taking on the role of Jacob. Lost's Mark Pellegrino has since appeared in shows like Lucifer. When "The Incident" aired in 2009, Mark Pellegrino was 44 years old.
This fits into the show's approach to the character, as well as the impact he has on the rest of the setting and cast. It helps separate the younger Jacob who appears in "Across the Sea," highlighting his maturity and growth into a true protector. It also gives him a natural aura of calm seniority over the more desperate and chaotic survivors at the heart of the show. Therefore, it makes sense why Lost would cast someone with a steady and calm approach to the character, like Mark Pellegrino.
