Centuries before Captain James Cook explored the South Pacific, Polynesian seafarers in canoes crossed vast swaths of water to colonize lonely islands from Samoa and New Zealand all the way to Hawaii. But how they managed such a feat remains something of a mystery.

Now, a roughly 600-year-old canoe discovered in New Zealand may shed some light on the Polynesians’ sailing technology. The vessel, described in the Proceedings of the National Academy of Sciences, is one of just two canoes dating back to such an early time period. A second paper in the same journal finds that shifting ancient wind patterns may have created ideal windows of opportunity for certain generations of sailing Polynesians.

The preserved canoe remains were discovered in 2012 on New Zealand’s South Island near the Anaweka estuary, pulled from a sand dune some time after a major storm. The 19.95-foot-long section of hull is part of what the authors call a "complex and robust composite canoe, carved from a single timber."

Few such vessels have lasted long enough to be found, because wood is organic matter and decays quickly. But the swampy, oxygen-poor spot it was buried in allowed the canoe to survive the centuries, researchers said. And the shape of it turned out to be very unlike the boats that early European explorers had described.

"It was one of those situations where it sort of took your breath away," said lead author Dilys Amanda Johns, a senior research fellow at the University of Auckland. "I’d never seen anything like it."

Using radiocarbon dating, the team found that the canoe was last caulked around the year 1400. The canoe, known as a waka, was probably at least 45.9 feet long when it was whole, Johns said.

The image of a sea turtle is carved into the hull — a symbol that is rarely found in the Maori culture of New Zealand but that featured widely in art, myths and ritual throughout Polynesia. (Sea turtles were held in high regard, known — perhaps fittingly — for their long voyages through open ocean.)

"A sea turtle on a 600-(year)-old Polynesian canoe is a unique and powerful symbol," the study authors wrote.

A few features, including four transverse ribs carved into the hull, haven’t been known historically in New Zealand, but have been featured in canoes in the Southern Cook Islands, described in 1913. The New Zealand canoe also shares some design elements with a canoe found about 30 years ago on Huahine in the Society Islands. It’s thought to be from around the same time period as the New Zealand canoe, even though it was discovered roughly 2,500 miles away. The canoes "could have come from the same design tradition," the authors wrote. Clearly, the Polynesians knew how to get around.

Scientists have tried to understand the kinds of boats and sailing technology that would have allowed seafaring Polynesians to brave the waters and winds. Without these kinds of archaeological finds, researchers have to rely on far less direct evidence, from linguistic reconstructions of the words for canoe parts to the much-later observations of European explorers.

A second study in PNAS takes a different tack at answering that question, by charting the "paleowind" patterns. Because the Polynesians appeared to travel against the wind patterns as we know them today, it’s thought that they would have needed sufficiently high-tech sailing canoes to navigate these unfavorable conditions.

But a team led by Ian D. Goodwin of Macquarie University in Sydney created a model of the paleoclimate in 20-year increments, showing that at key periods, the winds favored travel to distant islands. For example, based on their model, the winds favored sailing from central East Polynesia to New Zealand from 1140 to 1260, and travel to Easter Island from 1250 to 1280.

"Our reconstructed sailing conditions during the period of East Polynesian colonization would have enabled all of the known colonizing routes, and others, to have been negotiated at times proposed archaeologically by canoes lacking an upwind capability," the study authors wrote. "We do not assert that this ability was absent, although it may have been."

Timing wise, the papers don’t seem to quite line up. In the Goodwin paper, the window to New Zealand appears to have closed around 1300, but the canoe described in the Johns paper was dated to 1400.

While these trends may have been helpful, the closing of such wind windows don’t appear to have stopped the Polynesians, Johns said.

"We’re going to have to discuss, clearly," said Johns, who said she welcomed the other study’s insights. "We think Polynesians were really good sailors … we think they were able to sail down here with or without help."