England as well as Spain, Central Asia and Constantinople, was employed to create the book from this mass of data. Utilizing the information inherited from the classical geographers, he created one of the most accurate maps of the world to date, the Tabula Rogeriana (1154). The map, written in Arabic, shows the Eurasian continent in its entirety and the northern part of Africa. An adherent of environmental determinism was the medieval Afro-Arab writer al-Jahiz (776–869), who explained how the environment can determine the physical characteristics of the inhabitants of a certain community. He used his early theory of evolution to explain the origins of different human skin colors, particularly black skin, which he believed to be the result of the environment. He cited a stony region of black basalt in the northern Najd as evidence for his theory. Medieval Europe During the Early Middle Ages, geographical knowledge in Europe regressed (though it is a popular misconception that they thought the world was flat), and the simple T and O map became the standard depiction of the world. The trips of Venetian explorer Marco Polo throughout Mongol Empire in the 13th century, the Christian Crusades of the 12th and 13th centuries, and the Portuguese and Spanish voyages of exploration during the 15th and 16th centuries opened up new horizons and stimulated geographic writings. The Mongols also had wide-ranging knowledge of the geography of Europe and Asia, based in their governance and ruling of much of this area and used this information for the undertaking of large military expeditions. The evidence for this is found in historical resources such as The Secret History of Mongols and other Persian chronicles written in 13th and 14th centuries. For example, during the rule of the Great Yuan Dynasty a world map was created and is currently kept in South Korea. See also: Maps of the Yuan Dynasty During the 15th century, Henry the Navigator of Portugal supported explorations of the African coast and became a leader in the promotion of geographic studies. Among the most notable accounts of voyages and discoveries published during the 16th century were those by Giambattista Ramusio in Venice, by Richard Hakluyt in England, and by Theodore de Bry in what is now Belgium. Early modern period Following the journeys of Marco Polo, interest in geography spread throughout Europe. From around c. 1400, the writings of Ptolemy and his successors provided