Early Americans: southern exposure.

Regardless of when people first migrated to the Americas, archaeologists have established that humans lived at sites from Alaska to Tierra del Fuego between 11,500 and 10,000 years ago. Ongoing research in southern Argentina, described in the August-October Current Anthropology, supports the view that prehistoric hunter-gatherers adapted in sophisticated ways to the southernmost reaches of the New World.

Since 1990, 10 promising rock shelters and a number of open-air occupation sites have been located in a survey of Argentina's Rio Chico Basin, according to Hugo G. Nami of the Smithsonian Institution in Washington, D.C. The area contains an abundant supply of plants and animals that prehistoric folks could have exploited, Nami says.

Excavations have proceeded farthest in Don Ariel Cave, the largest of the identified rock shelters. People inhabited both a main chamber at the front of the cave and a small "annex" in the rear, Nami contends. Both parts of the cave have yielded numerous stone tools, including scrapers, knives, and spear points. Microscopic analysis indicates that many scrapers were used in the preparation of leather, Nami holds.

Investigators also found a large assembly of guanaco bones in the cave. The guanaco is a humpless, South American relative of the camel.

Radiocarbon dates place occupation of the cave's main chamber at about 4,000 years ago. Remains in the cave's annex are probably older than that, Nami argues. He suspects people lived there on a regular basis beginning around 11,000 years ago, as previously indicated for nearby sites in Chile.