There is a very interesting article in the New York Times Magazine...

http://www.nytimes.com/2016/03/20/magazine/the-secrets-of-the-wave-pilots.html?emc=edit_th_20160320&nl=todaysheadlines&nlid=60003637

If you can't download the article (shame on you)...I've copied the text below....

The Secrets of the Wave Pilots

For thousands of years, sailors in the Marshall Islands have navigated vast distances of
open ocean without instruments. Can science explain their method before it’s lost forever?

By KIM TINGLEYMARCH 17, 2016

At 0400, three miles above the Pacific seafloor, the searchlight of a power boat swept through a warm June night last year, looking for a second boat, a sailing canoe. The captain of the canoe, Alson Kelen, potentially the world’s last-ever apprentice in the ancient art of wave-piloting, was trying to reach Aur, an atoll in the Marshall Islands, without the aid of a GPS device or any other way-finding instrument. If successful, he would prove that one of the most sophisticated navigational techniques ever developed still existed and, he hoped, inspire efforts to save it from extinction. Monitoring his progress from the power boat were an unlikely trio of Western scientists — an anthropologist, a physicist and an oceanographer — who were hoping his journey might help them explain how wave pilots, in defiance of the dizzying complexities of fluid dynamics, detect direction and proximity to land. More broadly, they wondered if watching him sail, in the context of growing concerns about the neurological effects of navigation-by-smartphone, would yield hints about how our orienteering skills influence our sense of place, our sense of home, even our sense of self.

When the boats set out in the afternoon from Majuro, the capital of the Marshall Islands, Kelen’s plan was to sail through the night and approach Aur at daybreak, to avoid crashing into its reef in the dark. But around sundown, the wind picked up and the waves grew higher and rounder, sorely testing both the scientists’ powers of observation and the structural integrity of the canoe. Through the salt-streaked windshield of the power boat, the anthropologist, Joseph Genz, took mental field notes — the spotlighted whitecaps, the position of Polaris, his grip on the cabin handrail — while he waited for Kelen to radio in his location or, rather, what he thought his location was.

The Marshalls provide a crucible for navigation: 70 square miles of land, total, comprising five islands and 29 atolls, rings of coral islets that grew up around the rims of underwater volcanoes millions of years ago and now encircle gentle lagoons. These green dots and doughnuts make up two parallel north-south chains, separated from their nearest neighbors by a hundred miles on average. Swells generated by distant storms near Alaska, Antarctica, California and Indonesia travel thousands of miles to these low-lying spits of sand. When they hit, part of their energy is reflected back out to sea in arcs, like sound waves emanating from a speaker; another part curls around the atoll or island and creates a confused chop in its lee. Wave-piloting is the art of reading — by feel and by sight — these and other patterns. Detecting the minute differences in what, to an untutored eye, looks no more meaningful than a washing-machine cycle allows a ri-meto, a person of the sea in Marshallese, to determine where the nearest solid ground is — and how far off it lies — long before it is visible.

In the 16th century, Ferdinand Magellan, searching for a new route to the nutmeg and cloves of the Spice Islands, sailed through the Pacific Ocean and named it ‘‘the peaceful sea’’ before he was stabbed to death in the Philippines. Only 18 of his 270 men survived the trip. When subsequent explorers, despite similar travails, managed to make landfall on the countless islands sprinkled across this expanse, they were surprised to find inhabitants with nary a galleon, compass or chart. God had created them there, the explorers hypothesized, or perhaps the islands were the remains of a sunken continent. As late as the 1960s, Western scholars still insisted that indigenous methods of navigating by stars, sun, wind and waves were not nearly accurate enough, nor indigenous boats seaworthy enough, to have reached these tiny habitats on purpose.

Archaeological and DNA evidence (and replica voyages) have since proved that the Pacific islands were settled intentionally — by descendants of the first humans to venture out of sight of land, beginning some 60,000 years ago, from Southeast Asia to the Solomon Islands. They reached the Marshall Islands about 2,000 years ago. The geography of the archipelago that made wave-piloting possible also made it indispensable as the sole means of collecting food, trading goods, waging war and locating unrelated sexual partners. Chiefs threatened to kill anyone who revealed navigational knowledge without permission. In order to become a ri-meto, you had to be trained by a ri-meto and then pass a voyaging test, devised by your chief, on the first try. As colonizers from Europe introduced easier ways to get around, the training of ri-metos declined and became restricted primarily to an outlying atoll called Rongelap, where a shallow circular reef, set between ocean and lagoon, became the site of a small wave-piloting school.

In 1954, an American hydrogen-bomb test less than a hundred miles away rendered Rongelap uninhabitable. Over the next decades, no new ri-metos were recognized; when the last well-known one died in 2003, he left a 55-year-old cargo-ship captain named Korent Joel, who had trained at Rongelap as a boy, the effective custodian of their people’s navigational secrets. Because of the radioactive fallout, Joel had not taken his voyaging test and thus was not a true ri-meto. But fearing that the knowledge might die with him, he asked for and received historic dispensation from his chief to train his younger cousin, Alson Kelen, as a wave pilot.

Now, in the lurching cabin of the power boat, Genz worried about whether Kelen knew what he was doing. Because Kelen was not a ri-meto, social mores forced him to insist that he was not navigating but kajjidede, or guessing. The sea was so rough tonight, Genz thought, that even for Joel, picking out a route would be like trying to hear a whisper in a gale. A voyage with this level of navigational difficulty had never been undertaken by anyone who was not a ri-meto or taking his test to become one. Genz steeled himself for the possibility that he might have to intervene for safety’s sake, even if this was the best chance that he and his colleagues might ever get to unravel the scientific mysteries of wave-piloting — and Kelen’s best chance to rally support for preserving it. Organizing this trip had cost $72,000 in research grants, a fortune in the Marshalls.

The radio crackled. ‘‘Jebro, Jebro, this is Jitdam,’’ Kelen said. ‘‘Do you copy? Over.’’

Genz swallowed. The cabin’s confines, together with the boat’s diesel odors, did nothing to allay his motion sickness. ‘‘Copy that,’’ he said. ‘‘Do you know where you are?’’

Though mankind has managed to navigate itself across the globe and into outer space, it has done so in defiance of our innate way-finding capacities (not to mention survival instincts), which are still those of forest-dwelling homebodies. Other species use far more sophisticated cognitive methods to orient themselves. Dung beetles follow the Milky Way; the Cataglyphis desert ant dead-reckons by counting its paces; monarch butterflies, on their thousand-mile, multigenerational flight from Mexico to the Rocky Mountains, calculate due north using the position of the sun, which requires accounting for the time of day, the day of the year and latitude; honeybees, newts, spiny lobsters, sea turtles and many others read magnetic fields. Last year, the fact of a ‘‘magnetic sense’’ was confirmed when Russian scientists put reed warblers in a cage that simulated different magnetic locations and found that the warblers always tried to fly ‘‘home’’ relative to whatever the programmed coordinates were. Precisely how the warblers detected these coordinates remains unclear. As does, for another example, the uncanny capacity of godwits to hatch from their eggs in Alaska and, alone, without ever stopping, take off for French Polynesia. Clearly they and other long-distance migrants inherit a mental map and the ability to constantly recalibrate it. What it looks like in their mind’s eye, however, and how it is maintained day and night, across thousands of miles, is still a mystery.

Efforts to scientifically deduce the neurological underpinnings of navigational abilities in humans and other species arguably began in 1948. An American psychologist named Edward Tolman made the heretical assertion that rats, until then regarded as mere slaves to behavioral reinforcement or punishment, create ‘‘cognitive maps’’ of their habitat. Tolman let rats accustom themselves to a maze with food at the end; then, leaving the food in the same spot, he rearranged the walls to introduce shortcuts — which the rodents took to reach the reward. This suggested that their sampling of various routes had given them a picture of the maze as a whole. Tolman hypothesized that humans have cognitive maps, too, and that they are not just spatial but social. ‘‘Broad cognitive maps,’’ he posited, lead to empathy, while narrow ones lead to ‘‘dangerous hates of outsiders,’’ ranging from ‘‘discrimination against minorities to world conflagrations.’’ Indeed, anthropologists today, especially those working in the Western Pacific, are increasingly aware of the potential ways in which people’s physical environment — and how they habitually move through it — may shape their social relationships and how those ties may in turn influence their orienteering.

The cognitive map is now understood to have its own physical location, as a collection of electrochemical firings in the brain. In 1971, John O’Keefe, a neuroscientist at University College London, and a colleague reported that it had been pinpointed in the limbic system, an evolutionarily primitive region largely responsible for our emotional lives — specifically, within the hippocampus, an area where memories form. When O’Keefe implanted electrodes in rats’ hippocampuses and measured their neural activity as they traveled through a maze, he detected ‘‘place cells’’ firing to mark their positions. In 1984, James B. Ranck Jr., a physiologist at the State University of New York, identified cells in an adjacent part of the brain that became active depending on the direction a rat’s head was pointing — here was a kind of compass. And in 2005, building on these discoveries, Edvard and May-Britt Moser, neuroscientists at the Kavil Institute for Systems Neuroscience in Norway, found that our brains overlay our surroundings with a pattern of triangles. Any time we reach an apex of one, a ‘‘grid cell’’ in an area of the brain in constant dialogue with the hippocampus delineates our position relative to the rest of the matrix. In 2014, O’Keefe and the Mosers shared a Nobel Prize for their discoveries of this ‘‘inner GPS’’ that constantly and subconsciously computes location.

The discovery that human orientation takes place in memory’s seat — researchers have long known that damage to the hippocampus can cause amnesia — has raised the tantalizing prospect of a link between the two. In the late 1990s, Eleanor Maguire, a neuroscientist at University College London, began studying London taxi drivers, who must memorize the city’s complex layout to obtain a license. Eventually, she showed that when cabbies frequently access and revise their cognitive map, parts of their hippocampuses become larger; when they retire, those parts shrink. By contrast, following a sequence of directional instructions, as we do when using GPS, does not activate the hippocampus at all, according to work done by Veronique Bohbot, a cognitive neuroscientist at McGill University.

Bohbot and others are now trying to determine what effect, if any, the repeated bypassing of this region of the brain might be having on us. The hippocampus is one of the first areas disrupted by Alzheimer’s disease, an early symptom of which is disorientation; shrinkage in the hippocampus and neighboring regions appears to increase the risk of depression, schizophrenia and post-traumatic stress disorder. On the other hand, the taxi drivers who exercised their hippocampuses so much that parts of them changed size were worse at other memory tasks — and their performance on those improved after they retired. Few of us spend all day every day navigating, however, as cabbies do, and Maguire doubts that our GPS use is extreme enough to transform our gray matter.

What seems clear is that our ability to navigate is inextricably tied not just to our ability to remember the past but also to learning, decision-making, imagining and planning for the future. And though our sense of direction often feels innate, it may develop — and perhaps be modified — in a region of the brain called the retrosplenial cortex, next to the hippocampus, which becomes active when we investigate and judge the permanence of landmarks. In 2012, Maguire and co-authors published their finding that an accurate understanding of whether a landmark is likely to stay put separates good navigators from poor ones, who are as apt to take cues from an idling delivery truck as a church steeple. The retrosplenial cortex passes our decisions about the stability of objects to the hippocampus, where their influence on way-finding intersects with other basic cognitive skills that, like memory, are as crucial to identity as to survival.

Recently, Maguire and colleagues proposed a new unified theory of the hippocampus, imagining it not as a repository for disparate memories and directions but as a constructor of scenes that incorporate both. (Try to recall a moment from your past or picture a future one without visualizing yourself in the physical space where that moment happens.) Edvard and May-Britt Moser have similarly hypothesized that our ability to time-travel mentally evolved directly from our ability to travel in the physical world, and that the mental processes that make navigation possible are also the ones that allow us to tell a story. ‘‘In the same way that an infinite number of paths can connect the origin and endpoint of a journey,’’ Edvard Moser and another co-author wrote in a 2013 paper, ‘‘a recalled story can be told in many ways, connecting the beginning and the end through innumerable variations.’’

Disorientation is always stressful, and before modern civilization, it was often a death sentence. Sometimes it still is. But recent studies have shown that people who use GPS, when given a pen and paper, draw less-precise maps of the areas they travel through and remember fewer details about the landmarks they pass; paradoxically, this seems to be because they make fewer mistakes getting to where they’re going. Being lost — assuming, of course, that you are eventually found — has one obvious benefit: the chance to learn about the wider world and reframe your perspective. From that standpoint, the greatest threat posed by GPS might be that we never do not know exactly where we are.

Genz took his thumb off the radio receiver’s talk button and waited for Kelen’s reply. He could make out on deck John Huth, a Harvard physicist and member of the international team that discovered the Higgs boson particle, vomiting volubly off the port side. The last time Genz checked, Gerbrant van Vledder, an oceanographer at Delft University in the Netherlands, one of the world’s foremost institutions for wave modeling, was huddled miserably behind the abandoned galley, where a lone cabbage thudded against the walls of the sink. Compounding their digestive distress, a booby, ignoring the limitations of its webbed feet, had crash-landed on the deck, barring the men’s access to the head. Sometimes Genz felt that all his decade of research on wave-piloting had taught him was that he could never hope to predict what might go wrong next.

Genz met Alson Kelen and Korent Joel in Majuro in 2005, when Genz was 28. A soft-spoken, freckled Wisconsinite and former Peace Corps volunteer who grew up sailing with his father, Genz was then studying for a doctorate in anthropology at the University of Hawaii. His adviser there, Ben Finney, was an anthropologist who helped lead the voyage of Hokulea, a replica Polynesian sailing canoe, from Hawaii to Tahiti and back in 1976; the success of the trip, which involved no modern instrumentation and was meant to prove the efficacy of indigenous ships and navigational methods, stirred a resurgence of native Hawaiian language, music, hula and crafts. Joel and Kelen dreamed of a similar revival for Marshallese sailing — the only way, they figured, for wave-piloting to endure — and contacted Finney for guidance. But Finney was nearing retirement, so he suggested that Genz go in his stead. With their chief’s blessing, Joel and Kelen offered Genz rare access, with one provision: He would not learn wave-piloting himself; he would simply document Kelen’s training.

Joel immediately asked Genz to bring scientists to the Marshalls who could help Joel understand the mechanics of the waves he knew only by feel — especially one called di lep, or backbone, the foundation of wave-piloting, which (in ri-meto lore) ran between atolls like a road. Joel’s grandfather had taught him to feel the di lep at the Rongelap reef: He would lie on his back in a canoe, blindfolded, while the old man dragged him around the coral, letting him experience how it changed the movement of the waves.

But when Joel took Genz out in the Pacific on borrowed yachts and told him they were encountering the di lep, he couldn’t feel it. Kelen said he couldn’t, either. When oceanographers from the University of Hawaii came to look for it, their equipment failed to detect it. The idea of a wave-road between islands, they told Genz, made no sense.

Privately, Genz began to fear that the di lep was imaginary, that wave-piloting was already extinct. On one research trip in 2006, when Korent Joel went below deck to take a nap, Genz changed the yacht’s course. When Joel awoke, Genz kept Joel away from the GPS device, and to the relief of them both, Joel directed the boat toward land. Later, he also passed his ri-meto test, judged by his chief, with Genz and Kelen crewing.

Worlds away, Huth, a worrier by nature, had become convinced that preserving mankind’s ability to way-find without technology was not just an abstract mental exercise but also a matter of life and death. In 2003, while kayaking alone in Nantucket Sound, fog descended, and Huth — spring-loaded and boyish, with a near-photographic memory — found his way home using local landmarks, the wind and the direction of the swells. Later, he learned that two young undergraduates, out paddling in the same fog, had become disoriented and drowned. This prompted him to begin teaching a class on primitive navigation techniques. When Huth met Genz at an academic conference in 2012 and described the methodology of his search for the Higgs boson and dark energy — subtracting dominant wave signals from a field, until a much subtler signal appears underneath — Genz told him about the di lep, and it captured Huth’s imagination. If it was real, and if it really ran back and forth between islands, its behavior was unknown to physics and would require a supercomputer to model. That a person might be able to sense it bodily amid the cacophony generated by other ocean phenomena was astonishing.

Huth began creating possible di lep simulations in his free time and recruited van Vledder’s help. Initially, the most puzzling detail of Genz’s translation of Joel’s description was his claim that the di lep connected each atoll and island to all 33 others. That would yield a trillion trillion paths, far too many for even the most adept wave pilot to memorize. Most of what we know about ocean waves and currents — including what will happen to coastlines as climate change leads to higher sea levels (of special concern to the low-lying Netherlands and Marshall Islands) — comes from models that use global wind and bathymetry data to simulate what wave patterns probably look like at a given place and time. Our understanding of wave mechanics, on which those models are based, is wildly incomplete. To improve them, experts must constantly check their assumptions with measurements and observations. Perhaps, Huth and van Vledder thought, there were di leps in every ocean, invisible roads that no one was seeing because they didn’t know to look.

Early last year, Genz and Kelen, grants in hand, saw a chance to show Huth and van Vledder the di lep. Kelen is the director of Waan Aelon in Majel, or Canoes of The Marshall Islands, a nonprofit organization that teaches students to build canoes using traditional methods and modern materials. If the students hurried, the first sailing canoe to be built in the Marshalls in decades — the Jitdam Kapeel, which can be roughly translated as ‘‘the sharing of knowledge’’ — could be ready by summer’s sailing season. Kelen’s goal is for his students to build, staff and maintain a fleet that will transport goods and passengers between atolls and islets without using fossil fuels. Despite the expectation that the Marshalls will be one of the first countries to disappear beneath rising seas, Kelen envisions a renaissance of sailing: a means for his students to reclaim their heritage while creating jobs that don’t contribute to their own destruction.

Huth and van Vledder bought plane tickets to Majuro while Genz and Kelen made arrangements for the journey. At the last minute, Joel's leg became infected, and Kelen offered to pilot in his place. The scientists embraced this new plan: Talking with Joel before and after, they figured, would be almost as useful as having him onboard.

Soon after arriving, they visited him at home, where he was confined to bed, and eagerly showed him their maps and simulations while posing detailed queries about various properties of the di lep. Although this was the scientific investigation Joel had been pushing for, he seemed reluctant to respond. He asked Huth and van Vledder if they believed in the di lep; they still weren’t sure, they replied. Holding a rudimentary map that Huth had made of wave frequencies between Majuro and Aur, the captain traced a shaded region with his finger. ‘‘Di lep here,’’ he said.

The next afternoon, Kelen and his five-man crew set out for Aur. A breeze rattled the palms, blowing the Jitdam past a fleet of slumbering cargo ships anchored in the lagoon. The power boat Jebro puttered in pursuit. At the mouth of the opening between islets into the Pacific, the setting sun threw a flickering train on the water. ‘‘Now we get the truth,’’ Huth cried, thrusting a sextant toward the sky. ‘‘The moment of reckoning!’’

Twelve hours later, Huth was seasick, bent over the deck rail, to which he had bound himself with a harness and tether. ‘‘If anyone said the di lep was subtle, they were wrong,’’ he said, wiping his mouth. Nevertheless, he was doggedly recording on the hour the boat’s GPS coordinates, the wind speed and direction and his observations of the waves in a waterproof notebook. This data would allow him to map the journey with wind and wave details at each coordinate; van Vledder could later add wind data collected by satellite and local bathymetry, using programs written at Delft, to create a computer model of the seas they were currently in.

In the cabin, Genz heard Kelen’s voice on the radio again. Kelen could see the lights of the Jebro behind him, he said, and he thought they were about 10 miles east of Aur. Because they were approaching its reef too fast, his plan was to overshoot it, then look for it to his west after sunrise. Genz glanced at the boat’s GPS device and realized that Kelen, over the last decade, might have learned more than he had ever let on. He wanted to shout congratulations.

‘‘Copy that,’’ he said instead.

The sky grew lighter, revealing more sky, a flock of seabirds fishing and, finally, far ahead, the canoe, battered but intact, struggling to head downwind. After getting a brief tow from the Jebro, it reached Aur under its own power. An empty beach came into view, then children running on it. ‘‘This is feeling like an adventurer,’’ van Vledder said. ‘‘Coming to a new place, and people out to welcome you.’’

The entire village was waiting in a palm-frond-thatched pavilion, having been alerted by ham radio. A woman put leis around the necks of the sailors and scientists as they entered. The community had piled a long table with lobster, fish, breadfruit, plantains and rice balls with coconut. The acting chief of the island made a speech. He said the local children had never seen a sailing canoe before. The islanders wanted to learn to build them again; they had only one motorboat, and gasoline there cost more per gallon than most of them made in a month of selling fish and handicrafts in Majuro.

Two mornings later, Kelen stood outside a cinder-block schoolhouse on Aur that the chief had offered as a dormitory, looking up at an overcast sky and weighing again — as he had when he first met Genz — how much of his knowledge to share in order to keep it alive. Now in his late 40s and newly a grandfather, he had lived his early childhood on the atoll nearest Rongelap, Bikini, where the hydrogen bomb and dozens of other nuclear weapons were exploded. Later, as part of a program to test the effects of radiation on humans, American officials told the people from Bikini and Rongelap that their islands were safe to resettle, so they returned for several years. During this period, Kelen’s father taught him to sail in a traditional canoe made by Kelen’s grandfather. When Kelen was 10, the Americans finally evacuated the islanders to Kili, an uninhabited island bedeviled on all sides by violent ocean swells too rough for the canoe, which rotted away.

Eventually, Kelen’s parents moved to Majuro, home to half of the nation’s 50,000 citizens — an urban hub compared with the outer islands. They sent Kelen, a top student, to boarding school in Honolulu. There, when he was 19, he went with his class down to the docks to watch the world-famous Hokulea return from a trip to New Zealand. Later, he came back to Majuro as a young man and dedicated himself to the preservation of fading skills, like weaving and canoe-building. But he felt tremendous ambivalence about what gaining resources to preserve his culture, or any native culture, seemed to require: allowing outsiders, whether academics or reporters, to commodify it. Secrecy and hands-on training is integral to the tradition of wave-piloting; explaining the di lep would disrupt those features of it even while immortalizing it in books and journals, perhaps inspiring more Marshallese children to become ri-metos.

The tide was on its way out as the sailors and scientists began to load up for the 70-mile journey back to Majuro. The villagers sang again and prayed for their safe return. They laid another feast and stocked the canoe with provisions, packed in woven pandanus baskets, and handicrafts, including a toy sailing canoe, a perfect imitation, small and light as a bird. Until now, because his crew and canoe were untested, Kelen had deemed it unsafe to have any passengers aboard the Jitdam. One more person could fit, however, and he invited me on board.

‘‘Youp, youp,’’ called Binton Daniel, the master builder who had supervised the construction of the Jitdam, and the sail shot up. The sailors waved in overhead arcs at the people on the beach. The people waved back. Gradually, the sound of swells rushing against the coral rim of the lagoon grew louder. With a thunk, the bottom of the canoe hit the top of the reef and slid across, and we were out in open water.

Daniel eased the mainsheet and let the boom swing out. The first mate, Jason Ralpho, a stern-looking man in gray socks who worked with Kelen at the Ports Authority, and Ejnar Aerok, a plump, professional karaoke singer, secured the line to a cleat. The youngest, Elmi Juonran, lifted a lid off one of two hatches and, muttering, disappeared to boil water for ramen in a big silver teakettle. ‘‘He says he’s the only one who knows the password to these doors,’’ Kelen said. Juonran’s cousin, Sear Helios, named for the department store his parents visited on a trip to Honolulu, steered from the stern of the canoe with a 50-pound wooden paddle.

Kelen leaned back against the mast and looked at the front of the outrigger float and the back, estimating our speed. He checked his wristwatch. The wind was coming from the northeast, and the current, he said, would take us farther east that night. Ostensibly, he was dead-reckoning — to do that you must know where you started, where you’re going, how fast you’re moving and in what direction. Wave-piloting, if Genz, Huth and van Vledder are right, is more precise; theoretically, a wave-pilot, dropped blindfolded into a boat in Marshallese waters, could follow a set of seamarks — waves of a particular shape — alone to land.

‘‘Majuro should be that way,’’ Kelen said, pointing. ‘‘I’m closing my eyes and looking at the wind. This is a very short distance. Again, I’m only a student. I’m entitled to a few mistakes.’’

Swells glided, smooth and gentle, beneath us. Sunset cracked yolk on a puffy lavender sky. The horizon appeared infinite and also very near, as if we had fallen into a mixing bowl. Around us, the crew faded into shadow. Ralpho lit a cigarette, and its tip burned orange in the dark. The sail luffed.

‘‘This is kind of scary smooth,’’ Kelen said. ‘‘Does it feel like we’re moving anywhere? That’s not good. We have to move or we’ll drift away from the islands.’’ Yet he didn’t sound worried. We lay back. The sky was foggy with stars.

As a young man, Kelen said, he spent some time on the West Coast, picking strawberries in Oregon, working in a turkey plant, then driving a Rent Town USA truck up and down Highway 101. He described long days of sweet berries, of cutting the necks of birds, of truck-stop sloppy Joes and giant cups of coffee. We lost sight of the Jebro and missed three call-ins. Kelen could still remember fishing as a child on Bikini, its long white beaches. In his memory, everyone there was happy. Periodically, a government ship brought provisions, and men in white lab coats tested him and the other islanders with a huge machine. When the ship came to take them away for good, Kelen thought they were going for a ride.

Aerok began to sing in a high, lonely tenor. Ralpho added baritone harmony. ‘‘It’s kind of like a country-music song,’’ Kelen said. ‘‘ ‘I see you as beautiful as a sunset, and I cry when I leave the beach that you stand on.’ It’s kind of like a sailors’ leaving-home song. It’s a song when you start singing it, everyone knows it.’’

I closed my eyes. The sounds of the canoe — creaking, sloshing, rippling — traced its shape like fingers moving over a face in the dark.

I awoke to Aerok and Juonran singing about Majuro, another sad song. The sky spilled radiance onto the water. Beside me, Kelen was awake, too. ‘‘Every time I look up at heaven, I wonder, How many Earths are out there?’’ he said. ‘‘How many planets like ours? There’s millions of galaxies. There must be something.’’

We saw one star drop, then another. ‘‘Every time I see a falling star, I make a wish and I don’t tell nobody,’’ he said. ‘‘I don’t believe very many things, but this is something that makes me feel good, even if it isn’t true.’’

By 9:30 the next morning, the sun was high and the sailors had grown quiet. Kelen rested his shoulder against the mast, peering into the distance. If we didn’t see Majuro by 10, he said, the current had pushed us too far to the west. At 9:50, Juonran pointed, and everyone else followed his finger to the faintest of tints on the horizon. Kelen swatted him on the butt. The sailors laughed.

‘‘Another good guess,’’ Kelen said to me.

All maps are but representations of reality: They render the physical world in symbols and highlight important relationships — the proximity of one subway stop to another, say — that are invisible to the naked eye. If storytelling, the way we structure and make meaning from the events of our lives, arose from navigating, so, too, is the practice of navigation inherently bound up with storytelling, in all its subjectivity.

‘‘When I was young, we had canoes,’’ Kelen told me one afternoon on Aur. ‘‘We didn’t have TVs. In evening time, my father would open his arm, like this, and say lie there,’’ he tapped the inside of his elbow, ‘‘and he would tell me the legends of sailing. Some people have those heroes, like Superman, and they’re picturing they are Superman. When my dad talked about sailing, I was on that canoe.’’

To teach way-finding, the Marshallese use stick charts, wood frames crosshatched like dream catchers to represent swells coming from four cardinal directions, with shells woven in to symbolize the position of the atolls. These meant nothing to the first European explorers to see them, just as Mercator projections meant nothing to the Marshallese. Even today, local schoolchildren visiting the historical museum in Majuro are sometimes baffled when they’re told that the blue and green pictures on the walls are pictures of where they are.

If ‘‘where’’ is both subjective and physical, what do you need to know, precisely, to figure out where you are? From the moment our nomad ancestors wandered out of Africa until a few decades ago, locating yourself required interacting in some way with the environment: following the stars or a migrating herd of wildebeests, even reading a compass or a street sign. Then, in the time it took to transition from rotary phones to smartphones, we became the first unnatural long-distance migrants, followers of step-by-step instructions that obviated the need to look around at all. Over the last several years, organizations like the United States military and the Federal Aviation Administration have expressed concern about their overwhelming reliance on GPS and the possibility that the network’s satellite signals could be sabotaged by an enemy or disabled by a strong solar flare. The United States Naval Academy has once again begun training midshipmen how to take their position from the stars with a sextant.

As researchers urgently explore what GPS is doing to our minds, wave-piloting — a technique that seems to involve the subtlest environmental cues a person can detect — is slipping, virtually unnoticed, from human consciousness. Even if Huth and van Vledder could figure out how it worked, they admitted, it didn’t mean they could feel it or teach others how to do so.

Back on Majuro, they spent several days typing notes and crunching data, barely emerging from their rooms. Huth created a preliminary map of the route and approximate wind and sea conditions to show Korent Joel to see if he could identify a pattern that might be the di lep. But when they arrived at his home again, they learned that he had checked into the hospital the previous afternoon. Several weeks later, he was flown to Honolulu, where surgeons determined that his leg was gangrenous and amputated it below the knee. In his absence, Kelen and Genz helped Huth and van Vledder quiz Joel’s Rongelapese uncle for stray clues to di lep’s features, but nothing they recognized as epiphanies.

Until November, when van Vledder visited Cambridge, Mass., where he and Huth sequestered themselves in Huth’s office. As they mapped the coordinates Huth had recorded atop van Vledder’s model of sea conditions, they found that the path they had taken was exactly perpendicular to a dominant eastern swell flowing between Majuro and Aur. And at places where the swell, influenced by the surrounding atolls, turned slightly northeast or southeast, the path bent to match. It was a curve. Everyone had assumed that a wave called ‘‘backbone’’ would look like one. ‘‘But nobody said the di lep is a straight line,’’ van Vledder said.

What if, they conjectured, the ‘‘road’’ isn’t a single wave reflecting back and forth between every possible combination of atolls and islands; what if it is the path you take if you keep your vessel at 90 degrees to the strongest swell flowing between neighboring bodies of land? Position your broadside correctly, smack in the di lep’s path, and your hull would rock symmetrically, side to side — in a manner that would turn a loose cabbage into a pendulum and teach an anthropologist, a physicist and an oceanographer a hard lesson about the human gastrointestinal system’s adaptation to life at sea. In other words, it was as Joel’s uncle had, it turned out, told them: The di lep feels like pidodo, diarrhea. We might have been riding it all along.

Correction: March 18, 2016

An earlier version of this article misstated part of the name of the organization that teaches students to build canoes using traditional methods and modern materials. It is Canoes of the Marshall Islands, not Canoes of These Islands.