READ: Gallery — Agriculture

Scientists are still not sure why humans abandoned foraging and took up farming in several places around the world at about the same time. This gallery highlights where agriculture emerged and what was grown.

Glaciers continued to advance until about 18,000 years ago. At this point temperatures began to even out and then to gradually increase. Sea levels began to rise. With ice caps at both poles, the Earth is currently in what is called an interglacial period and, technically speaking, still within the "Pliocene-Quaternary glaciation," or ice age.

As temperatures increased and sea levels rose, two important things happened. Land bridges such as the one connecting Asia and North America were submerged and climates throughout most of the world became more moderate, enabling certain species of plants and animals to prosper.

The Bering Land Bridge once connected the eastern-most edge of Siberia with what is now the western coast of the Seward Peninsula in Alaska. Until about 11,000 years ago, the bridge was a treeless tundra with shrubs and shallow ponds that served as a corridor between Asia and the Americas, a route used by wildlife and by early humans. Today, the Bering Land Bridge National Preserve in Alaska (shown here looking west) is an impassable wetlands that ends at the 58 mile wide Bering Strait.

Agriculture emerged in the Fertile Crescent, a wide swathe of river valleys and rich soils in the Middle East, about 10,000 years ago when humans first cultivated cereal grasses like emmer wheat. The first "farming" was thought to have occurred near Jericho in the West Bank region of present-day Israel and Jordan by a group of people called the Natufians, but full-scale agriculture really took off a bit later in Mesopotamia – a region between the Tigris and Euphrates rivers in present-day Iraq. Agriculture emerged in the Nile River Valley of Egypt shortly thereafter.

By about 7,000 to 8,000 years ago, agriculture had emerged in other regions of Asia. The soils deposited from large rivers were extremely fertile and proved ideal for the cultivation of cereal crops. Domestication of wheat and barley occurred in the Indus Valley in what is now Pakistan and India. East, in present-day China, millet and wheat (and later rice) was grown in the Huang He (Yellow) River Valley.

Agriculture came later to the Americas but it's important to note that it emerged completely independent of the farming that had already begun on the Asian continent. The rising seas had covered the Bering Land Bridge thousands of years before and humans in the Americas developed agriculture on their own, without contact with humans living in Afro-Eurasia. At about this same time or earlier, agriculture also emerged in the highlands of Papua New Guinea in the Pacific region. Farmers in the Americas cultivated a wild cereal grass called teosinte in Mesoamerica and grew potatoes in the Andes Mountains while farmers in Papua New Guinea grew sugar cane and tubers like taro and yam.

The first Mesoamerican farmers cultivated a wild grain called teosinte and transformed it into maize, an ancestor of modern corn, using artificial selection. In this picture of a recently grown strain of teosinte, the "cob" that we are familiar with is barely present but the telltale  "corn silk" is very prominent.

Once maize was cultivated, it became an extremely important part of life in Mesoamerica. It was the primary source of food energy and early communities like the Olmec, Maya and Aztecs considered the prolific grain to be a divine source of life. Modern agriculture transformed maize even further, cultivating innumerable strains of plump, sweet corn for use as food for humans and livestock.

Humans don't exactly have a monopoly on farming. Some types of ants "farm" aphids, protecting them on the plants that the smaller insects eat and then themselves consuming the sugary "honeydew" that the well-fed aphids secrete. Symbiotic (interdependent) relationships like this are not unlike those that we have with our livestock and crops.