- "Those with my specialty are chosen as infants in order to develop their minds to specifically serve the Traveler program. Some days I felt like an experiment, other days like a super-human [...] The Director has kept watch over my entire life, knowing the outcome of every decision, crafting my path forward, but here, I see people every day who still believe in free will. They don’t know any better."
- — Philip Pearson
Historians are modified humans capable of memorizing massive amounts of information. Their abilities prove vital to adaptation and survival in an unfamiliar time: they are able to finance the team's operations by knowing the outcomes of sporting events and market trends, locate incoming Travelers by remembering host candidates, and relay complicated messages from the Director.
As the Traveler program continued over the course of fifteen years, the future began to change. Many of the historians who had arrived previously found that much of the data they'd memorized had become obsolete. For example, Philip Pearson won every bet he placed shortly after arriving. Soon he noticed that sporting event outcomes were starting to deviate from the historical record he'd memorized. Ultimately the team's investments began to suffer, imperiling their ability to finance missions. (Update)
Not long afterward, he was ordered to attend an "update" - a movie theatre screening of relevant data related to the new, alternate timeline the Travelers had created. The attending historians learned the new history of the future - including the historical deaths of their team members. The dates of their own deaths were omitted from the presentation "for obvious reasons." This was referred to as Update Four, implying the future has changed a great deal.
The attendees received medication to cope with side effects of the update, which include visions of alternate timelines. Philip began experiencing alternate visions shortly after attending the update. Historians who receive an update are bound by Protocol 2H never to discuss the update with anyone.
The Faction did not have access to any historians, preventing them from ascertaining the effects of interference in the 21st century. With assistance from the turncoat historian Kyle and his teammate Luca, they kidnapped every historian present at Update Five, along with the attending archivist. The historians were rescued by the core Traveler team.