Mobility without a motor or even the sight of a steed or a haggard old horse tends to be confounding to people in modern times. But it is true: Our hominid ancestors, predating Homo sapiens, had to rely on their own two legs, and that is how hominids spread from Africa to the farthest reaches of eastern Asia and Europe, beginning some 2 million years ago. On foot.
Shank's mare, i.e., using their feet is also how anatomically modern humans spread from northern Europe to the Americas starting around 20,000 years ago. But how the devil did early humans reach islands that remained isolated even in scenarios of low sea levels at the height of the Ice Age?
Any boats or rafts that may have existed tens of thousands of years ago have long since decayed. Speculation about ancient maritime mobility has ranged from unfortunates swept out to sea by tsunamis or storms who clung to serendipitously available tree trunks, to deliberate locomotion on primitive rafts made of bamboo, reeds or branches lashed together. But some have long suspected that early humans (and maybe even proto-modern-humans too) could sail, properly, in actual durable boats.
Anybody can cling to a palm tree swept out to sea and with luck reach an island, but it takes a lot of such instances for a population to become established. So that has been largely dismissed as an explanation for how islands became populated. Now a team of scientists has demonstrated, by proving a negative, that while early modern humans may have wandered the seas floating on rickety rafts, they had to have mastered the art of proper boating.
The team proved the negative by showing that it was not possible to reach the current-whipped Ryukyu island chain in Japan using reed rafts. Yet early modern humans did in fact reach the Ryukyu chain some time between 30,000 to 40,000 years ago.
The culmination of the research, which began in 2013, was published this week in the Cambridge University Press journal Antiquity by the anthropologist Yousuke Kaifu of the Japanese National Museum of Nature and Science, with an international team.
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The mystery surrounding hominid dissemination was partly resolved by the realization that during the Ice Age, sea levels were lower than today. Ergo, more land was exposed, including land bridges between continents. At the peak of the last Ice Age, sea levels were about 120 meters (400 feet) lower than today. That explains how anatomically modern humans crossed from Asia (from Siberia) to the Americas (to Alaska) around 20,000 years ago: They trekked over the now-submerged Bering Bridge.
The British Isles were also graced with the occupation of both early humans and Neanderthals who walked there. Doggerland, a low-lying land bridge between Europe and Britain, only sank beneath the briny around 8,000 years ago. Low sea levels may also explain how archaic humans reached the Greek island of Naxos about 200,000 years ago.
Fine, but then how exactly did modern humans reach Australia 65,000 years ago? And how did they reach the Ryukyu chain of islands, surrounded by violent seas, between 30,000 to 40,000 years ago?
Regarding Australia, separate studies suggest that much of the journey from Indonesia was actually possible on foot. From roughly 70,000 to 59,000 years ago Indonesia was part of a continent called Sunda, and Australia and New Guinea were part of a continent called Sahul.
The two ancient continents practically touched, and the spans between them could have theoretically been crossed on primitive reed rafts. Now much of that land is underwater. In any event, researchers suggest that the distance could have been crossed using primitive proto-crafts, such as bamboo rafts, which can travel over 800 kilometers (500 miles), previous studies have shown.
But the case of the Ryukyu Islands (called Nansei in Japan), stretching from Japan’s south to Taiwan, is different. For one thing, at no point in the history of the genus Homo were the islands connected to the mainland, Kaifu, the lead author of the Ryukyu raft research, told Haaretz.
“The geology and biology and everything support that. The animals living on those islands are unique,” he said, adding that the islands lack major East Asian species such as monkeys and bears.
For another, there is the obstacle of the north-flowing surface current called Kuroshio, the Black Current. Though not quite a household word like the Gulf Steam, the Kuroshio Current, the researchers say, is “one of the strongest in the world, and it may have been even stronger during the time these islands were colonized.”
The point is that rafters can’t possibly vanquish the Kuroshio to reach the Ryukyu Islands. The researchers know that because they tried, very hard, to recreate a Stone Age-type voyage to the islands on a bamboo craft, and it did not work. They just could not make headway from island to island on their bamboo rafts. Then they tried to improve on the raft’s design, but their repeated attempt still proved unsuccessful.
If anything the current may have been even stronger in the past, they add.
“It seems the Stone Age sailors had better naval technology than archaeologists expected,” they concluded.
And maybe even earlier types could sail properly too. How exactly did Homo erectus spread to Indonesian islands including Flores a million years ago, in the process apparently spawning the population of meter-tall hominids popularly known as hobbits? Or the other population of weird tiny hominids who once lived on Luzon, an island in the Philippines? And what about the Neanderthals? Stone tools generally associated with the Neanderthal Mousterian tool culture industry have been found on the islands Zakynthos, Lefkada and Kefalonia in the Mediterranean. They are around five to twelve kilometers from the shores of Greece. Mousterian tools have also been found on Crete.
Maybe Neanderthals could have swum to the nearby islands, but they probably couldn’t do the crawl to Crete, which today is 40 kilometers off the mainland.
Again sea levels were apparently key to much of that movement. Water levels have fluctuated with the coming and going of ice masses. The wanderlust was clearly there, but maybe archaic human naval prowess was much greater than we tend to imagine, and developed much earlier than we generally think.
The projects reenacting how ancient humans crossed the sea to the Ryukyu Islands were organized by the National Museum of Nature and Science in Tokyo and the National Museum of Prehistory in Taiwan.