Human occupation of the Americas, unlike that of Africa, Europe, and Asia, is relatively recent. The earliest immigrants reached North America from East Asia more than 12,500 years ago, when sea levels fell during the last major period of continental glaciation and united the two continents via a land bridge across the Bering Strait. Some researchers believe this migration, interrupted by various interglacials during which rising sea levels submerged the crossing, began tens of thousands of years earlier. Nevertheless, by the time the bridge last closed about 10,000 years ago, the entire Western Hemisphere was populated, at least thinly, with hunter-gatherer bands in environments ranging from barren, torrid deserts to sopping rain forests to frigid uplands.

Evidence of Paleo-Indian hunter-gatherers is relatively scarce in Argentina, but one of the continent’s oldest confirmed archaeological sites is at Monte Verde, Chile, just across the Andes from present-day Bariloche. Radiocarbon dating here has given a figure of 13,000 years at a site that, according to University of Kentucky archaeologist Tom Dillehay, has some of the continent’s earliest evidence of architecture, as well as use of wild potatoes and other native tubers. The most geographically proximate early human sites—later than Monte Verde—are 900 kilometers or more to the north.

As important as hunting was, gathering wild foods probably contributed more to the diet. As population gradually reached the saturation point under hunter-gatherer technology, they began to rely on so-called incipient agriculture, one of whose hearths was the Peruvian highlands. In the process of gathering, incipient agriculturalists had acquired knowledge of the annual cycles of seed plants, and they selected, scattered, and harvested them in a lengthy domestication process. In fact, the earliest domesticated plants could have been root crops like manioc in the Amazon lowlands, but as these are perishable tubers rather than durable seeds, there is little archaeological evidence to support this supposition.

In any event, starting about 6000 B.C., beans (Phaseolus spp.), squash (Cucurbita spp.), and potatoes (Solanum spp.) became the staples of an agricultural complex that, as population grew, supported a settled village life and, eventually, the great Andean civilizations. Maize was a later addition, acquired from Mexico. In Argentina, outliers of these civilizations appeared on the eastern Andean slopes as far south as present-day San Juan Province and in the highlands of Córdoba; across the Gran Chaco, in Mesopotamia, semisedentary shifting cultivators raised maize, manioc (cassava), and sweet potatoes.

When the Spaniards finally arrived, according to one scholar, they found “the richest assemblage of food plants in the Western Hemisphere.” Domestic animals were few, however—only the dog (sometimes raised for food), the guinea pig (definitely raised for food), and the llama and alpaca (both raised for food and fiber, with the llama also serving as a pack animal).

Slower to develop than the Andean region, due partly to late demographic saturation, most indigenous societies in what is now Argentina remained nomadic or semisedentary until shortly before the Spanish invasion. In Patagonia, some indigenous peoples sustained a hunter-gatherer lifestyle even into the 20th century.