Dr Yousuke Kaifu was working at an archaeological site on the Japanese islands of Okinawa when a question started to bubble in his mind. The pieces unearthed in the excavation, laid out before him, revealed evidence of humans living there 30,000 years ago, arriving from the north and the south. But how did they get there?
“There are stone tools and archaeological remains at the site but they don’t answer those questions,” Kaifu, an evolutionary anthropologist at the University of Tokyo, says.
