"Never underestimate human stupidity," says historian Yuval Harari whose fans include Bill Gates and Barack Obama

Historian Yuval Harari says the study of the past has taught him an important lesson for the future.

"One things that history teaches us is that we should never underestimate human stupidity," said Harari, a professor at The Hebrew University of Jerusalem and author of books that have been recommended by the likes of Microsoft co-founder Bill Gatesand former U.S. President Barack Obama.

"It's one of the most powerful forces in the world," he added.

Speaking with CNBC's Martin Soong, Harari expressed concern about the ability of populist leaders — a group he described as "selling people nostalgic fantasies about the past instead of real visions for the future" — to solve today's biggest global problems.

While acknowledging that such leaders likely have many insights and answers on the national level, Harari said the three biggest "existential" problems faced by the world today are global in nature: Nuclear war, climate change and technological disruption.

"These problems have only global solutions, and so far, we haven't heard anything on the global level from these kinds of leaders that offers a real solution," Harari said. ...