Eurasia covers around 55,000,000 square kilometres (21,000,000 sq mi), or around 36.2% of the Earth's total land area. The landmass contains well over 5 billion people, equating to approximately 70% of the human population. Humans first settled in Eurasia between 60,000 and 125,000 years ago. Some major islands, including Great Britain, Iceland, and Ireland, and those of Japan, the Philippines and Indonesia, are often included under the popular definition of Eurasia, in spite of being separate from the contiguous landmass.
Physiographically, Eurasia is a single continent. The concepts of Europe and Asia as distinct continents date back to antiquity and their borders are geologically arbitrary. In ancient times the Black Sea and the Sea of Marmara, along with their associated straits, were seen as separating the continents, but today the Ural and Caucasus ranges are more seen as the main delimiters between the two. Eurasia is connected to Africa at the Suez Canal, and Eurasia is sometimes combined with Africa to make the largest contiguous landmass on Earth called Afro-Eurasia. Due to the vast landmass and differences in latitude, Eurasia exhibits all types of climate under the Köppen classification, including the harshest types of hot and cold temperatures, high and low precipitation and various types of ecosystems.