The Believing Brain - Michael Shermer [151]
Negative Beliefs
Christopher Columbus’s confidence in achieving a successful mission to the Far East by way of sailing west is a prime example of beliefs driving perceptions. His first voyage was premised on Ptolemy’s cartographical coordinates for the length that the Euro-Asian continent extends east, as well as the overall circumference of the world, both of which were miscalculated to a degree perfectly in sync with Columbus’s expectations.
To compute the size of the earth, Ptolemy used an estimate of 500 stadia per one degree of longitude, instead of the more accurate figure of 700 stadia per degree employed by the estimable ancient Greek geographer and mathematician Eratosthenes. A stadium is about 185 meters, so 500 stadia equals 92,500 meters (or 92.5 kilometers) and 700 stadia equals 129,500 meters (or 129.5 kilometers) per degree of longitude. The actual circumference of the earth is 40,075 kilometers at the equator. Ptolemy’s calculations estimated it to be about 33,300 kilometers, or 17 percent too small. Add to this Columbus’s use of Marinus of Tyre’s estimate on the high side of the length that the Euro-Asian land mass stretched eastward (thereby leaving less water to sail across), plus the fact that the land routes from Europe to China and India had become politically unstable after the fall of Constantinople in 1453, and Columbus’s plan to sail west to get to the east was actually quite reasonable. (Sailing down the coast of Africa, around the Cape of Good Hope, and east to India and China had never been successfully completed and was considered potentially problematic at best and disastrous at worst.) Thus, in one of the most prescient coincidences in the history of serendipitous discovery, after sailing a little more than 5,000 kilometers westward across the “Ocean Sea” (the Atlantic) on his maiden voyage, Columbus encountered land in the exact place where he had calculated the Indies would be, and thus he dubbed the people he engaged there “Indians.”2
Why did Columbus not immediately realize he was not in Asia? Surely the flora and fauna and people he discovered were nothing at all like what Marco Polo had reported from his land excursions eastward from Europe where he had met the Great Khan and absorbed Asian culture. The answer can be found in the dual problem of perception and cognition, or data and theory. What threw Columbus off was coarse-grained data coupled with incorrect theory. Marco Polo’s reports of Asia were sketchy at best, allowing ample wiggle room for interpreting New World data as Old World facts. Plus, there was no theory of a New World, so in Columbus’s mind when he made first contact with the New World on that fateful day in October 1492, where else could he be but Asia?
Because of the power of the paradigm to shape perceptions, Columbus’s cognitive map told him what he was seeing. When his men dug up some common garden rhubarb, Rheum rhaponticum (used in pies), for example, the ship’s surgeon determined that it was Rheum officinale, the medicinal Chinese rhubarb. The native American plant gumbo-limbo was mistaken for an Asiatic variety of the mastic evergreen tree that yields resin used to make lacquer, varnish, and adhesives. The South American nogal de pais nut was classified as the Asian coconut, or at least what Marco Polo had described as such. Columbus deemed a plant with the aroma of cinnamon to be that valuable Asian spice. After first touching land in San Salvador, Columbus then sailed to Cuba, bringing with him some San Salvadorian captives to help with communications with the Cuban natives, who told him that there was gold to be found at “Cubanacan”—the middle of Cuba—which Columbus heard as