How did the ancient Polynesian navigators manage to populate the entirety of the Pacific Ocean with no instruments of any kind? We do know that they did manage it because here they are and we know that there is a certain amount of misinformation out there about how they accomplished it. Today we're gonna do a deep dive into their actual methods, and find out how they accomplished that which many people might assume would be impossible. And that's coming up right now on Skeptoid.
You are listening to Skeptoid. I'm Brian Dunning from Skeptoid.com. Facts and Fiction of Polynesian Navigation Part 2. This episode was sponsored by Frederic Raña, Skeptoid's Earl of Elixirs. To personally sponsor your own episode, come to skeptoid.com/sponsor. Welcome to the show that separates fact from fiction, science from pseudoscience, real history from fake history, and helps us all make better life decisions by knowing what's real and what's not.
For 4,000 years, the people who were to become the Polynesians, gradually migrated eastward across the Pacific Ocean from the region around Taiwan. Eventually they reached what is today French Polynesia, and from there they spread outward toward the three corners of the Polynesian Triangle: Hawaii, New Zealand, and Rapa Nui.
One of the greatest and most difficult migrations in human history had been successfully completed, and in doing so, they developed wayfinding -- traditional Polynesian navigating. It was a skill that easily rivaled any other ever created. And today we're gonna find out how it worked.
Last week in part one, we talked about the history of this skill and how it had almost become completely lost by the middle of the 20th century, and also dispensed with a few popular myths and misconceptions about it. Today we're gonna give an overview of what these navigators actually had to learn and actually did. Voyaging was typically done in their larger boats called voyaging canoes. These were typically large twin-hulled catamarans or single-hulled canoes with outriggers.
Several types of sails were used. Navigating with no instruments of any kind was accomplished with surprising accuracy. And since so much went into it, we're not gonna waste any time but jump right in. We'll start with what was by far the most important skill: Celestial Navigation. By far, the most important wayfinding technique was celestial navigation, just as it would be today for us if we lost our modern electronics. They did not of course have compasses.
In fact, they had no knowledge that such a thing as magnetic north existed. However, the system they developed was basically just as good. It was called the star compass. The Polynesian star compass had 32 houses comparable to our 360 degrees. They had a north, south, east, and west, each with seven points in between, giving eight steps from one cardinal direction to the next.
Just as we might say northeast, which divides into north, northeast, which divides into north, north, northeast as the first step clockwise from North. Each house had a name. Polynesian master navigators memorized a staggering 220 plus stars, and for each which house it would rise and set in and even understood how to adapt these positions based on the season. So with a glance at which stars were near the horizon, they knew exactly which direction they were headed.
That in itself is an astonishing accomplishment of memory, and even more impressive is the generational learning it was built upon. The star compass also incorporated the moon and the planets. They understood the difference between the planets and the stars, even if they didn't know what they actually are, which didn't matter. The differences in their movements and cycles was helpful and their greater brightness (plus that of the moon) helped when sky conditions made the other stars hard to see.
In daytime, the houses in which the sun rose and set gave them their heading. They had no clock, so they measured the time of day by the sun's height above the horizon, calibrated by season. They might use their hand a stick or anything, each according to individual preference to know how far along they were between noon and sunset or sunrise. The sun's reflection on the ocean drew a literal line from the canoe to the horizon.
At noon, it was due north and throughout the day, the navigator could easily tell in which house that line was in. All of this applies south of the equator. When they traveled north of the equator, everything was reversed. The knowledge base was doubled.
Obviously this is a simplified overview, but it effectively tells us two things: one, that the star compass was extremely accurate, rivaling the real compasses used by later European sailors; and two, that it required an immense amount of mentoring and experience. Pick any random Polynesian navigator, they could easily rival today's top celestial navigation experts. Ocean Swell Patterns.
So important was celestial navigation, that analysis of ocean swell patterns was a supplemental method, which any good navigator kept on top of constantly, assuming that some storm might obscure the sky unexpectedly at any time. Swells, as opposed to waves, are the deep, consistent wave systems generated by consistent tradewinds or distant storms and could be relied upon to maintain both their direction and their period for days or weeks at a time.
Their consistency comes from the fact that their primary cause is the equally consistent tradewinds. Navigators noted what directional house the swells were in and could recalibrate that every time celestial bodies were visible. Swells can also come from distant storms and swells in different directions are additive. They're nearly always multiple swell patterns going on at any given time. The prevailing swell is usually obvious to the eye, but to the Polynesian navigator, more data was needed.
The traditional way that they sensed multiple swells, including patterns too subtle to see, was to sit or lie in the very bottom of the canoe in direct contact with the hull, allowing the body to sense every movement. Experienced navigators are said to have been able to detect as many as five different swell patterns at once. Wave and Current Analysis. Waves, as distinguished from swells, are smaller and more localized.
They told a powerful story about nearby islands that might be obscured by dark or low visibility. Islands at sea influence wave patterns primarily through two processes: reflection and refraction, effects that in some cases can be detected as far as 50 kilometers away. Wave reflection occurs when waves strike the island and bounce back. Though the details depend on shoreline shape and energy absorption.
Refraction is subtler: as waves pass near the island, they slow in shallower water and bend, altering their direction beyond the island. The result is interference in surrounding wave patterns guided by the same physical rules, yet uniquely shaped by each island's size, form, bathymetry and geology. These changes relative to the wave's normal uninterrupted directions were evident by the way they'd change from house to house.
This could tell the navigator which direction the island was in and how far away it was. And since every island changed wave patterns differently, in many cases they could even identify the island. Marshall Islanders developed the most sophisticated such system, creating "stick charts" made of palm frond ribs and shells. These were teaching tools that represented wave patterns around specific islands. Atmospheric and Cloud Phenomena.
Clouds take distinctive forms above different kinds of islands. For example, mountainous islands create thermal updrafts that produce tall cumulus clouds, allowing many islands to be spotted from far away even while they're still below the horizon. All islands present warmer surfaces than the open ocean during daylight hours, resulting in localized weather patterns above them. Clouds can also help the navigator in other ways.
In the right conditions, clouds can reflect the color of the water below. When there's a broad patch of light turquoise water in a shallow lagoon, this can sometimes lend a subtle hue to clouds above it. Just as nighttime clouds above a city can reflect the prevailing color of streetlights over various parts of the city. Birds. Birds turn out to be the island hunter's best friends. The white tern in particular came in handy.
White terns would fly far out to sea in search of fish each morning, sometimes as much as 200 kilometers. Then in the evening, they would fly straight back. So if a navigator was lucky enough to spot a white tern, the bird provided a heading either directly from or toward an island, depending on the time of day. Brown terns also provided a similar service, only closer to the island.
They made similar ventures -- out in the morning, back in the evening -- but generally stayed within about 60 kilometers of land. Sometimes white terns were carried aboard in cages and could be released if the navigator suspected they were near land. They would fly up, often circle for a short time, and then beeline straight for the nearest island. Marine Life and Debris Indicators. Fish and flotsam were more than just things in the sea; they were indicators of how far from land you were.
The Polynesians understood that certain fish species preferred certain depths of water, certain water temperatures, and distances from land. If coastal fish were spotted, it meant you couldn't be too far from reefs or lagoons. When deep water species appeared, it meant you were still out in the open ocean. Marine animal behavior was also a clue. Dolphins and porpoises often frequent certain places around islands, and during migratory seasons, whales would provide directional references.
Floating vegetable matter helped navigators in at least two ways. First, its condition: if it was fresher, it meant you had to be pretty close to land; if it was more degraded and weathered, you could still be quite far away.
driftwood, leaves, coconut husk, and seaweed all indicated different types of island vegetation, giving an early identifier to which type of island (or which specific island) you were approaching. If the water was more cloudy or had a brown hue, that meant river runoff, again indicating type or identification of a nearby island. Wind Pattern Analysis. Understanding the wind patterns of the Pacific Ocean was not so much a part of navigating during a voyage, but of planning in advance.
Over the centuries, the Polynesians came to understand these patterns very
northeast tradewinds above the equator, southeast tradewinds below. Captain Cook found that their knowledge was so complete that they knew to wait for the summer monsoons -- when these patterns all changed rather drastically -- to make trips northward from New Zealand to Fiji or from Samoa to the Society Islands; journeys that would otherwise be both difficult and inefficient if attempted during the rest of the year.
Dead Reckoning. The master navigator held in their head an extensive database of as many islands as each had ever visited or been taught about. They commonly knew the relative positions of over 100 islands.
Distances between them was tracked in "canoe days." The route from one island to the next was often established as a doglegged path, going in one direction for so many canoe days, often trying to arrive at a point directly up wind from the destination, which would be another known number of canoe days ahead. Tracking progress against these measurements was done with dead reckoning.
Often mischaracterized as an experience-driven hunch or gut feeling about how far you've come, dead reckoning is actually a calculation. It's a relatively simple time-speed-distance calculation. The Polynesians did understand mathematics, mainly driven by the needs of wayfinding. They had no system of writing, and so they used what we term ethnomathematics, like measuring the height of a star with your thumb using whatever the local geography and culture provides.
Polynesian navigators knew how long they'd been traveling. They were both excellent judges of their speed through the water and were able to measure it against waypoints like islands, or changes in wave patterns. And they knew the canoe day distances. They were in fact calculating -- ethnomathematically.
Every last bit of this skillset, from knowing the relative positions and spacing in canoe days of a hundred different islands, to learning all the wind patterns at all the times of the year throughout all the latitudes of the Polynesian triangle, to clouds and birds and marine life, to how the interaction of waves with islands will look 100 kilometers away, to learning the ways different swells feel against your body through the hull of a canoe, to memorizing in
which house would 220 different stars rise and set in every season had to be taught and passed down from generation to generation without any system of writing. Navigators were apprentices for decades. Every one of them who ever voyaged developed an amount of knowledge that would put any modern PhD program to shame. And so we conclude our two-part series on ancient Polynesian navigation.
It was an art, it was a craft, and it was a science, and it is being brought back to life by groups such as the Polynesian Voyaging Society throughout the Pacific and by the master navigators there who train the next generation to ensure that this incredible, amazing, intricate, elegant, and wonderful skill, responsible for so much history and for populating such a huge geographical chunk of our beautiful blue planet, will always find its way home.
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