What’s more, detailed studies of the Southeast Asian coastline of 50,000 years ago showed that an 800-mile-long stretch of islands and at least eight ocean straits separated the island continent from the Asian mainland. “By any route, you have to island-hop to Australia, with one water crossing greater than 44 miles,” Erlandson says. “So it is a real exercise to get across, and the magnitude of that is illustrated by the fact that, before anatomically modern humans made the leap, no large-bodied animal ever got all the way across.”
But modern humans possessed the wherewithal to paddle to Australia. With stone knives they could have felled Asia’s giant bamboo and then tied the canes together to make a raft large enough to carry several passengers. Moreover, they could have navigated by sight for most of the journey. As they set out from one island to the next, they could generally have spied at least a smudge of land on the far horizon.
Even where land lay beyond view, ancient mariners could have deduced its presence from natural indicators such as cloud formations that tend to gather over islands, mats of drifting land vegetation, and the flight paths of land-roosting seabirds. Traditional navigators in the Caroline Islands, northeast of New Guinea, make use of such signs today, and many researchers believe that our modern human ancestors possessed the cognitive skills both to perceive the significance of these indicators and to communicate them to potentially fearful passengers.
“It looks like seafaring capabilities and seafaring technology have a much greater antiquity than conventional wisdom among archaeologists would lead one to expect,” says James O’Connell, an archaeologist at the University of Utah.
“I think water crossing goes with modern language and with modern art,” says Geoff Irwin, an expert on ancient seafaring at the University of Auckland in New Zealand. “I think they are a package.”
Genes and tools around the Pacific rim
In the wake of the Australian finds, archaeologists are looking long and hard at other major migrations of ancient humans. For decades researchers have promoted the idea that the first Americans were clans of Siberian big-game hunters who trekked hundreds of miles on foot over a vast land bridge (where the Bering Strait is now) and came south from Alaska some 13,000 years ago. But were these Siberian hunters the first to explore the Americas? Or could they have been beaten there by skilled mariners exploring ice-choked northern coasts?
Erlandson has been examining this possibility since the late 1990s, when he read of a dig on the island of Okinawa, some 1,000 miles southwest of Tokyo. Poring over archaeological reports from the region, he learned that Japanese researchers had unearthed the 32,000-year-old bones of a child on Okinawa in the 1950s. He also examined studies of ancient sea levels and a detailed bathymetric map showing the depth of the seafloor between the islands of Okinawa and Japan. Some 32,000 years ago, a coastal plain joined Japan to the Asian mainland, allowing travelers to tramp back and forth by foot. But they could not have trekked to Okinawa, a distant island even then. “Several sea voyages would have been required to reach it from Japan,” explains Erlandson, “including one crossing roughly 46 miles long.” Intrigued, he delved further into Japanese archaeological reports. Other ancient mariners, he discovered, had ventured into stormier waters to the north: Some 21,000 years ago, people had paddled boats across 30 miles of choppy water from Honshu to Kozushima Island to fetch shiny black obsidian, a type of volcanic glass, for stone tools.
Almost certainly these voyagers traveled in small, sturdy boats—perhaps a type of kayak—and possessed sufficient seafaring skill to avoid spills that would lead to hypothermia and death. With such experience, the mariners and their children could well have headed northward at least 16,000 years ago. Crossing the straits by boat and walking the beaches, they could have gradually explored the coasts of the Kuril Islands, the Kamchatka Peninsula, and the Bering Land Bridge until finally reaching the west coast of the Americas, a journey of several thousand miles. A trail of distinctively shaped points and a telltale pattern of genes support this hypothesis.
Last November an international team of geneticists out of University College London and the University of Michigan at Ann Arbor published a key new study of genetic diversity among Native Americans. The researchers examined repetitive stretches of short DNA sequences known as microsatellites in DNA samples taken from 422 individuals, ranging geographically from Chipewyan and Cree individuals in northern Canada to Guarani and Huilliche people in South America. What they discovered was that genetic diversity decreased from north to south and was higher among tribal groups living along the Pacific coast than among those residing in the continent’s interior. This suggested to the team that the first Americans migrated down the west coast of the Americas; only later did smaller bands—with less genetic diversity—move inland. Moreover, another new genetic study by Brazilian researchers pegs the date for that coastal migration somewhere between 18,000 and 15,000 years ago.
Taken together, the genetic and archaeological evidence now strongly suggests that ancient mariners from northeast Asia could well have explored the coast of the Americas at least 12,000 or 13,000 years ago, and conceivably earlier. Erlandson has found two stone tools and a bone bead on San Miguel Island that may be 18,000 years old, but he has yet to confirm the date via further excavation. “We need to know more,” he says.
Just what drew ancient seafarers from northeast Asia to California remains a puzzle. As they ventured along the southern coast of the Bering Land Bridge, which was an arid grassland at that time, they could have pursued both terrestrial and marine prey. Then, as they moved into coastal North America after ice sheets there began retreating around 16,000 years ago, they could have continued to dine on a wealth of coastal foods.
Erlandson believes that kelp forests—rich oases of seaweed—were key to their success all along the route. Giant kelp grows nearly two feet a day, reaching lengths of 150 feet in the water. Kelp forests teem with abalone, rockfish, and other seafood delicacies. Furthermore, the fronds of kelp are edible, and its stemlike stipe can be cut to create fishing lines, making it possible to catch fish that live outside the kelp beds, such as halibut and cod.
Ice Age migrants journeying from kelp forest to kelp forest, Erlandson says, would have had no need to adjust to strange new ecosystems or devise brand-new hunting technologies as they pushed along the rim of the North Pacific. “I think they were just moving along and exploring,” he muses. “It was like a kelp highway.”