Afro-Eurasia-America is a continuous landmass that exists during periods of low sea level induced by ice ages, and comprises about 85% of the Earth's land area when present in the current era. It consists of the supercontinents of Afro-Eurasia, and the Americas, which are in turn comprise Africa and Eurasia, and North and South America, respectively. These are joined by the Bering land bridge, or Beringia, during an ice age's glacial maximum, when the sea level is low enough for the area to become dry land. When this happens, some wildlife is exchanged.

The Bering Strait, the Chukchi Sea to the north and the Bering Sea to the south, are all shallow seas (see maps). During cycles of global cooling, such as the most recent ice age, enough sea water became concentrated in the ice caps of the Arctic and Antarctic, so that the subsequent drop in eustatic sea levels exposed shallow sea-floors that have subsequently re-flooded. Other land bridges around the world have emerged and disappeared in the same way. Approximately 14,000 years ago, mainland Australia was linked to both New Guinea and Tasmania; the British Isles formed an extension of continental Europe via the dry beds of the English Channel and North Sea; and the dry basin of the South China Sea linked Sumatra, Java and Borneo to the Asian mainland.

The Columbian Exchange was a dramatically widespread exchange of animals, plants, culture, human populations (including slaves), communicable disease, and ideas between the Western and Eastern Hemispheres. The contact between the two areas circulated a wide variety of new crops and livestock which supported increases in population in both hemispheres. Explorers returned to Europe with maize, potatoes, and tomatoes, which became very important crops in Eurasia by the 18th century. Similarly, Europeans introduced manioc and the peanut to tropical Southeast Asia and West Africa, where they flourished and supported growth in populations on soils that otherwise would not produce large yields.

In the biological and ecological exchange that took place following Spanish establishment of colonies in New World, people of Europe and Africa settled in the New World, and animals, plants and diseases of Eurasia and the Western Hemisphere were introduced to each area in an interchange.

This exchange of plants and animals transformed European, American, African, and Asian ways of life. New foods became staples of human diets, and new growing regions opened up for crops. For example, before AD 1000, potatoes were not grown outside of South America. By the 1840s, Ireland was so dependent on the potato that a diseased crop led to the devastating Irish Potato Famine. Since being introduced by 16th-century Portuguese traders, who brought them from the Americas,maize and manioc replaced traditional African crops as the continent’s most important staple food crops. New staple crops that were introduced to Asia from the Americas via Spanish colonizers in the 16th century, including maize and sweet potatoes, contributed to the population growth in Asia.