In 1947, against the best navigational advice, the Norwegian explorer Thor Heyerdahl and five crew members set sail from Peru on a balsa wood raft to test his theory that ancient South American cultures could have reached Polynesia. The frail vessel, called Kon-Tiki, crossed several thousand nautical miles of the Pacific in 103 days and showed that his anthropological hunch was at least feasible.

In 2019, in much the same spirit, a research team led by Yousuke Kaifu, an anthropologist at the University of Tokyo, built a dugout canoe in order to study another aspect of western Pacific migration: How did ancient humans, more than 30,000 years ago, navigate the powerful Kuroshio current from Taiwan to southern Japanese islands, such as Okinawa, without maps, metal tools or modern boats? “Since any physical evidence would have been washed away by the sea, we turned to experimental archaeology, in a similar vein to the Kon-Tiki,” Dr. Kaifu said.

Two new studies published on Wednesday in the academic journal Science presented the results of those experiments. In one report, advanced ocean models recreated hundreds of virtual voyages to pinpoint the most plausible routes for the crossing. “We tested various seasons, starting points and paddling methods under both modern and prehistoric conditions,” Dr. Kaifu said.

The other paper charts the 45-hour journey that Dr. Kaifu’s crew made from eastern Taiwan to Yonaguni Island in the southern Ryukyus. The mariners, four men and one woman, paddled the 25-foot canoe, a hollowed-out cedar log christened Sugime, for 122 nautical miles on the open sea, relying solely on the stars, sun and wind for their bearings. Often, they could not see their target island.