Thirteenth-century sailors circulated navigational maps known as “portolan charts,” which they supplemented and edited based on their individual knowledge and experiences. These authorless, communal, and evolving charts became increasingly accurate over time. Wiki much?
The map pictured is a “mappa mundi,” or “map of the world.” These maps were generated by medieval Christian scholars from existing evidence and (educated) guesswork. Surprisingly accurate given the time period, they were used for everything from decoration to strategic planning. Over a thousand examples of mappae mundi have been preserved; their origins and sources are in many instances well cataloged.
In contrast, “portolan charts” were practical guides to navigation, showing coastlines and known islands or other objects or phenomenon of interest. Such charts grew organically from the work of sailors. Often these maps were the product of disparate collaborators, and sometimes contained notations in multiple languages. A sea captain in 1290 might ask around for the latest portolan chart prior to an expedition and, following the journey, recirculate an amended version containing his own knowledge or subsequent discoveries.
From Tony Campbell, Map Librarian of the British Map Library: "The medieval mappaemundi (world maps in the Christian tradition) are the cosmographies of thinking landsmen. By contrast, the portolan charts preserve the Mediterranean sailors firsthand experience of their own sea, as well as their expanding knowledge of the Atlantic Ocean." See Tony Campbell, "Portolan Charts from the Late Thirteenth Century to 1500," in The History of Cartography, Volume 1: Cartography in Prehistoric, Ancient, and Medieval Europe and the Mediterranean (1987), 372.
I imagine this observation has been made before, but are not thirteenth-century portolan charts a very early precursor to wikis? The knowledge accumulation these charts facilitated may not have been as “fast” as the word wiki implies, but the organic collaboration and fact-checking appears in full force.
(Thanks to the James Ford Bell Library, University of Minnesota for the background on portolan charts. Click here to learn more.)