Ancient settlers in the Americas adapted to and adapted diverse environments ranging from the high plateau of the Andes and central plateau of Mesoamerica to the tropical rain forest and river systems of the Amazon and Caribbean, as well as the prairies of North and South America. But, given the isolation of these societies, where did the first peoples to settle the continent come from?

The first settlers migrated from Asia, though their timing and their route are debated. One possibility is that the first settlers migrated across the Bering Strait from what is now Russia to Alaska and gradually migrated southward sometime between 15,000 and 13,000 B.C.E. But archaeological excavations have identified much earlier settlements along the Andes in South America, perhaps dating to over 40,000 years ago, than they have for Mesoamerica or North America. These findings suggest that the original settlers in the Americas arrived instead (or also) as fishermen circulating the Pacific Ocean.

Like early settlers elsewhere in the world, populations of the Americas could be divided into three categories: nomadic peoples, semi-sedentary farming communities, and dense agricultural communities capable of sustaining cities. Urban settlement and empire formation centered around two major regions. The first area, Lake Titicaca, located at the present-day border between Peru and Bolivia, is the highest lake in the world (12,500 feet high) and the largest lake in South America (3,200 square miles). The second area was in the Valley of Mexico on the central plateau of Mesoamerica, where empires emerged from the cities around Lake Texcoco. Access to these large freshwater lakes allowed settlers to expand agriculture through irrigation, which in turn supported growing urban populations.

The earliest farming settlements emerged around 5000 B.C.E. These farming communities began the long process of domesticating and modifying plants, including maize (corn) and potatoes. Farmers also domesticated other crops native to the Americas such as peppers, beans, squash, and avocados.

The origins of maize in Mesoamerica are unclear, though it became a centerpiece of the Mesoamerican diet and spread across North and South America. Unlike other grains such as wheat and rice, the kernels of maize — which are the seeds as well as the part that is eaten for food — are wrapped in a husk, so the plant cannot propagate itself easily, meaning that farmers had to intervene to cultivate the crop. In addition, no direct ancestor of maize has been found. Biologists believe that Mesoamerican farmers identified a mutant form of a related grass called teosinte and gradually adapted it through selection and hybridization. Eaten together with beans, maize provided Mesoamerican peoples with a diet sufficient in protein despite the scarcity of meat. Mesoamericans processed kernels through nixtamalization, boiling the maize in a solution of water and mineral lime. The process broke down compounds in the kernels, increasing their nutritional value, while enriching the resulting masa, or paste, with dietary minerals including calcium, potassium, and iron.

The masa could then be cooked with beans, meat, or other ingredients to make tamales. It could also be rolled flat on a stone called a metate and baked into tortillas. Tortillas played roles similar to bread in wheat-producing cultures: they could be stored, they were light and easy to transport, and they were used as the basic building block of meals. Aztec armies of the fifteenth century could travel long distances because they carried tortillas for sustenance. Along their route, communities were obligated to provide tribute in tortillas. The rapid military expansion of the Aztec Empire was sustained in part by the versatility of the tortilla, which gave soldiers the ability to fight far from home.

Andean peoples cultivated another staple of the Americas, the potato. Potatoes first grew wild, but selective breeding produced many different varieties. For Andean peoples, potatoes became an integral part of a complex system of cultivation at varying altitudes. Communities created a system of “vertical archipelagos” through which they took advantage of the changes of climate along the steep escarpments of the Andes. Different crops could be cultivated at different altitudes, allowing communities to engage in intense and varied farming in what would otherwise have been inhospitable territory.

The settlement of communities, including what would become the largest cities, often took place at an altitude of nearly two miles (about 10,000 feet), in a temperate region at the boundary between ecological zones for growing maize and potatoes. The notable exception was the Lake Titicaca basin, at an elevation of 12,500 feet, where the abundance of fresh water tempered the climate and made irrigation possible. Communities raised multiple crops and engaged in year-round farming by working at different altitudes located within a day’s journey from home. Some of these zones of cultivation were so distant — sometimes over a week’s journey — that they were tended by temporary or permanent colonies, called mitmaq, of the main settlement.

At higher elevations, members of these communities cultivated potatoes. Arid conditions across much of the altiplano, or high-plains plateau, meant that crops of potatoes could sometimes be planted only every few years. But the climate — dry with daily extremes of heat and cold — could be used to freeze-dry potatoes that could be stored indefinitely. Above the potato-growing zone, shepherds tended animals such as llamas and alpacas, which provided wool and dried meat, or ch’arki (the origin of the word jerky). They also served as pack animals that helped farmers bring in the crops from their high- and low-altitude plots. The animals’ manure served as fertilizer for farming at lower altitudes.

At middle altitudes, communities used terraces edged by stone walls to extend cultivation along steep mountainsides to grow corn. In the lowlands, they cultivated the high-protein grain quinoa, as well as beans, peppers, and coca. Farmers chewed coca (the dried leaves of a plant native to the Andes from which cocaine is derived) to alleviate the symptoms of strenuous labor at extremely high altitudes. Coca also added nutrients such as calcium to the Andean diet and played an important role in religious rituals. In the lowlands communities also grew cotton, and in coastal areas they harvested fish and mussels. Fishermen built inflatable rafts made of sealskin.