From rides to homes and beyond, we're sharing everything these days, with the help of digital tools. But as modern and high-tech as the sharing economy seems, it's been alive in Africa for centuries, according to author Robert Neuwirth. He shares fascinating examples -- like apprenticeships that work like locally generated venture capital and systems for allocating scarce water -- and says that if we can propagate and scale these models, they could help communities thrive from the bottom up.