Located primarily in the Northern and Eastern Hemispheres, Eurasia stretches from the Atlantic Ocean in the west to the Pacific Ocean in the east. In the north, Russia and Scandinavia abut the Arctic Ocean; its southern boundaries are Africa, the Mediterranean Sea, and the Indian Ocean. The division between Europe and Asia as two different continents is a historical and cultural construct, with no clear physical separation between them; thus, in some parts of the world, Eurasia is considered the largest of five or six continents.
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, with the Ural and Caucasus ranges being the main delimiters between the two. Eurasia is connected to Africa at the Suez Canal, and Eurasia is sometimes combined with Africa as the supercontinent Afro-Eurasia.
Jared Diamond, in his book Guns, Germs and Steel, credits Eurasia's dominance in world history to the unique east-west extent of Eurasia and the availability of Eurasian animals and plants suitable for domestication. He included North Africa in his definition of Eurasia, due to it having a similar climate and peoples.
The Silk Road symbolizes trade and cultural exchange linking Eurasian cultures through history and has been an increasingly popular topic. Over recent decades the idea of a greater Eurasian history has developed with the aim of investigating the genetic, cultural and linguistic relationships between European and Asian cultures of antiquity. These had long been considered distinct.