The primary impetus for going to the considerable trouble and expense of developing the technology of sail-powered watercraft was to overcome the limitations of human muscle power and endurance for propulsion. Two developments pressured for that: a) the desire to travel longer distances; and b) the desire to carry more cargo and/or people, which required bigger, heavier vessels, more difficult for humans to power with paddles, or even oars, for extended voyages.
The only voyaging for which we can say with confidence that sail was necessary was the crossing of oceans. It is true that, even for coastal work, larger vessels were going to be easier to power with sail—if wind patterns were conducive to its use—but for work close inshore, and into bays, harbors, and estuaries, auxiliary power was probably necessary anyway, for maneuverability in narrow waterways where the wind was likely not available from a usable direction—if it was available at all.
To cross any of the world’s oceans is a challenge to human survival. Humans are land creatures; we are primates. We evolved on the African savanna. A human trying to survive in the ocean, without technological aid, would be akin to a dolphin trying to survive on the savanna. And the technological aid we need to cross an ocean has to satisfy more than propulsion requirements. It has to carry all the food and water the crew of that vessel need to survive a voyage of whatever duration it might be. This would be easier if we were reptiles; reptiles are highly efficient predators, especially the big ones. They can slow down their metabolism, use far less energy, and go weeks or even months without eating. We, however, are mammals, and we burn energy the way a ’74 Eldorado burns gas. We require, as a rough rule of thumb, a liter of water a day to remain properly hydrated. Water weighs 1 kg per liter. It takes up 1,000 cm3 of space per liter. For a voyage of any length, then, the amount of drinking water required precludes the use of most small craft. And then there’s food. Fishing has always been considered a supplement to, not a guaranteed basis of, a seaman’s diet. Sufficient rations to sustain the crew for the voyage take up more space and add more weight—considerably more.
So, not only are we setting off across a distance long enough that we do not want to count on our stamina for paddling or rowing to get us there; we also need a craft big enough, and capacious enough, to carry us, our food, and our water—in addition to whatever it is we may be carrying as the purpose of the voyage to begin with.
All of these requirements pressured for a propulsion technology that took advantage of wind energy. For thousands of years, humans crossed oceans in watercraft we would consider somewhat larger than boats—up to those we would straight-up call ships—powered primarily by sails.
But, even if you can put to sea in a craft sturdy enough and powerful enough to execute the intended voyage, and you have a competent crew to run it, and enough food and water for that crew, you have one other major challenge that you do not face near the coast: all you can see around you is water, from horizon to horizon. There are no “landmarks”—consider the term itself. How do you get where you want to go? Mariners figured out a suite of techniques, but the primary technique used by all ocean voyages under sail was navigation by the stars. You sailed from and to a point on the surface of the Earth, but you got there by sailing toward, or away from, or relative to, points of light in the sky.
We of European descent are so conditioned to think of reliance on devices that it strikes us as exotic when we’re reminded that most skilled humans over most of history made extensive use of their brains as “technology.” They memorized so much more than we do. A licensed London cab driver must demonstrate memorization of the streets of London to pass the licensure exam. Researchers have shown that the process of memorizing that map alters the brains of the cabbies in observable ways. They are programming themselves. Sailing navigators did the same. To an experienced ocean navigator, the sky-map was as familiar as the wind and the water, and the techniques for setting and adjusting sails to best exploit the wind at a given time.
If you’ve ever been to a planetarium show, you probably know that the subjective experience of the night sky varies drastically from culture to culture. The projector can overlay “our” constellations, derived from those of the Greeks of the first millennium BCE, and it can then show us those of other cultures—including the indigenous cultures of the places we live. There’s no more ancient or clear example I can think of for the human mind’s compulsion to see patterns than “constellations.” The night sky also varies from place to place on Earth. You won’t navigate by Polaris (the North Star) in the southern hemisphere; you’ll use the Southern Cross—as we call it—instead.
The problem with using the stars to find your way is that, while they may seem eternal and fixed in place to us, our planet moves underneath them ceaselessly. Our planet rotates on a tilted axis too, so we have “seasons,” and the stars in the sky change with those. Mariners looked for a star or group of stars that didn’t seem to move even as the “wheel of Heaven” turned around them. Polaris in the Northern Hemisphere “wobbles” only a little from its position directly North, and the Southern Cross is similarly constant in the southern hemisphere.
One can sail with the stars at night, but with only one during the day—the one around which the Earth orbits. Many of us are at least somewhat familiar with the concept of using a hand-held device to find latitude based on the angle of the Sun over the horizon. That is an early-modern and modern European technique, as is the latitude-longitude imaginary grid. Polynesians needed neither. In fact, the best Polynesian navigators memorized not only the night sky; they memorized the relative positions, and bearings (directions from one’s own position) of a group of islands scattered over a vast expanse of ocean, using a spatial concept so foreign to Europeans that it took a long time before any of them were able to make any sense of it—even when a Polynesian navigator drew it out in the sand or modeled it with stones and strings. Polynesian maritime technology—their vessels, their navigational skills, their intimate understanding of their ocean—was the most advanced in the world, which is why they manifested themselves so late in human history; the islands of Polynesia, the easternmost (relative to Europe) in all the Pacific, were not settled until what we call the Late Medieval period of European history, because reaching them required crossing the largest expanses of water on Earth, to find relatively tiny specks of land, many of them upwind.
Sailing the stars reminds us how much we rely on contrivances and contraptions in our world, rather than on the knowledge we program into our own brains. Our brains can figure out how to get computers to do things for us that we cannot do ourselves—but we’re also using them to do things we can do for ourselves, but don’t want to be bothered with. We’re not going to go down either a Luddite rabbit hole here or into some sort of dour reactionary prognostication. It is, though, worth knowing what humans are capable of, without any of this stuff, and asking ourselves how much we want to rely on our stuff to do stuff for us, and how much it might be worth learning how to do for ourselves.
We were going out to dinner with friends a few years ago and I was glancing repeatedly at the nav screen in the car to get to a restaurant I’d never been to before. My friend asked me teasingly if I were one of those people who’d drive straight through a storefront window if the GPS told me to. Clearly, my brain saw fit to remember that.