Asia is the largest and most populous continent in planet Earth, with over 4.3 billion people and an area of 17,212,000 square miles (44,578,875 km²). The continent of Asia is east of Europe and northeast of Africa. The world's oldest civilizations are in Asia, in countries like India and China. Asia and Europe together form one big continent called Eurasia. Asia is the home to most of the human population (60% of humans live in Asia), and compromises 30% of earth's land area. Around the 1400s-1600s, many European explorers tried to find a safe, trade route to India. A very well known explorer who successfully explored Asia was Marco Polo. Asia is bordered in the east by the Pacific Ocean, in the south by the Indian Ocean and the Southern Ocean, to the north by the Arctic Ocean and to the west by Europe and North Africa.