Stone Age humans crossed the sea from Taiwan to the Ryukyu islands of south-west Japan tens of thousands of years ago - and it looks like they did so deliberately, even though the islands are too far away to be reliably visible from Taiwan.
     Archaeological sites on several of the Ryukyu islands suggest humans had reached the islands by about 30,000 to 35,000 years ago. Yosuke Kaifu at the University of Tokyo and his colleagues suspect the ancient people did so by travelling north-east from Taiwan - a journey that involved ocean crossings of tens to hundreds of kilometres. The researchers have even repeated some of these ocean crossings themselves using bamboo rafts of the kind that Stone Age humans might have built.
     But it hadn't been clear whether the crossing occurred deliberately or by accident. The Kuroshio current, which flows from Luzon in the Philippines past Taiwan and Japan, is one of the strongest ocean currents in the world. To find out if people could have arrived at the islands by drifting on this current, the researchers looked at existing data from 138 satellite-tracked buoys that drifted past Taiwan or Luzon between 1989 and 2017.
     Kaifu and his colleagues found that the Kuroshio current directs drifters away from, rather than towards, the Ryukyu islands. Because the flow of the current is thought to have stayed the same for the past 100,000 years, it seems likely that Stone Age people reached the Ryukyu islands through deliberate voyaging rather than accidental drifting.
     "Now we can tell with confidence that Palaeolithic people set sail deliberately even to a remote invisible island," says Kaifu.
     
Edited from NewScientist (3 December 2020)