Latest / Skeptoid / Skeptoid #1009: Facts and Fiction of Polynesian Navigation, Part 2

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Skeptoid #1009: Facts and Fiction of Polynesian Navigation, Part 2 · Skeptoid

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