Asia is the world's biggest and most populated continent, and it is mainly found in the Eastern and Northern Hemispheres. Asia is also the world's most populous continent. It shares the continent landmass of Eurasia with the continent of Europe, and the continental landmass of Afro-Eurasia with both Europe and Africa. It also shares the continental landmass of Afro-Eurasia with both Europe and Africa. As a continent, Asia has a land area of 44,579,000 square kilometres (17,212,000 square miles), accounting for about 30% of the Earth's total land area and 8.7% of the Earth's total surface area. The continent, which has long been home to the bulk of the world's people, was the location of many of the world's first civilizations, including the Egyptians and the Greeks. In June 2019, it had a population of 4.5 billion people, accounting for approximately 60% of the world's total population.
Generalized speaking, Asia's borders are bordered on its eastern side by the Pacific Ocean, its southern border by the Indian Ocean, and its northern border by the Arctic Ocean. In the absence of a distinct physical and geological barrier between Asia and Europe, the border between the two continents is a historical and cultural construct. It is rather arbitrary and has shifted from its inception in ancient antiquity, when it was originally conceived. East–West cultural, linguistic, and ethnic distinctions are reflected in the split of Eurasia into two continents, some of which vary on a spectrum rather than along a clear dividing line, and the division of Eurasia into two continents reflects this divide. In general, the most widely accepted boundaries divide Asia into two parts: Asia to the east of the Suez Canal, which separates it from Africa; Asia to the east of the Turkish Straits, which separates it from Russia, and Asia to the south of Caucasus Mountains, Caspian and Black Seas, which separate it from Europe.
From the year 1 CE until the year 1800 CE, China and India alternated as the world's two biggest economies. A significant economic power, China drew many people to the east, and for many people, the fabled riches and splendour of ancient Indian civilization embodied Asia, drawing European trade and exploration as well as colonial intrusion into the region. The unexpected discovery of a trans-Atlantic passage from Europe to America by Christopher Columbus while searching for a way to India exemplifies this profound interest. The Silk Road was established as the primary east–west trade route through Asia's hinterlands, while the Straits of Malacca served as a significant maritime connection between the continents. Although Asia has seen economic vitality (especially in East Asia) and strong population expansion throughout the twentieth century, the region's total population growth has declined in recent decades. A large number of major religions, including Hinduism, Zoroastrianism, Judaism, Jainism, Buddhism, Confucianism, Taoism and Christianity, as well as Islam, Sikhism and other faiths, originated in Asia. Asia is also the home of numerous minor religions.