BBC Future: There are a handful of people left on Earth who have been alive in three separate centuries, says Rachel Nuwer. What can they – and those of a similarly extreme age – teach us?

• “Doug Boyd, director of the Louie B Nunn Center for Oral History at the University of Kentucky Libraries – That’s why Boyd is digitising his entire collection of oral histories, with 9,400-plus recordings into a searchable, freely available database. Instead of 500 people accessing the collection each year, now users top 8,000 per month. As those stories make their way into high school classrooms, podcasts and social media, they could start to shape the way we think about history – and the lifetime’s worth of knowledge and experience held within older people. “I really do think that a more informed, dynamic public memory is going to emerge as we start to see the walls of oral history archives coming down,” Boyd says. “The recorded human voice telling stories and grappling with life’s questions firsthand will take on an ever increasing cultural value.”