Geographical exploration, sometimes considered the default meaning for the more general term exploration, refers to the practice of discovering remote lands and regions of the planet Earth. It is studied by geographers and historians. Two major eras of exploration occurred in human history: one of convergence, and one of divergence. The first, covering most of Homo sapiens history, saw humans moving out of Africa, settling in new lands, and developing distinct cultures in relative isolation. Early explorers settled in Europe and Asia; 14,000 years ago, some crossed the Ice Age land bridge from Siberia to Alaska, and moved southbound to settle in the Americas. For the most part, these cultures were ignorant of each other's existence. The second period of exploration, occurring over the last 10,000 years, saw increased cross-cultural exchange through trade and exploration, and marked a new era of cultural intermingling, and more recently, convergence. Early writings about exploration date back to the 4th millennium B.C. in ancient Egypt. One of the earliest and most impactful thinkers of exploration was Ptolemy in the 2nd century AD. Between the 5th century and 15th century AD, most exploration was done by Chinese and Arab explorers. This was followed by the Age of Discovery after European scholars rediscovered the works of early Latin and Greek geographers. While the Age of Discovery was partly driven by European land routes becoming unsafe, and a desire for conquest, the 17th century saw exploration driven by nobler motives, including scientific discovery and the expansion of knowledge about the world. This broader knowledge of the world's geography meant that people were able to make world maps, depicting all land known. The first modern atlas was the Theatrum Orbis Terrarum, published by Abraham Ortelius, which included a world map that depicted all of Earth's continents.: 32  Source: Wikipedia (en)