migration and population movements: The Americas had by then been found in Texas and as far east as the Mississippi, these roughly 11,000-year-old hunting artifacts were attributed to a general “Clovis culture,” suggesting the primacy of Clovis as the oldest site FROM THE ROCKIES TO THE ANDES It is unlikely that the Clovis culture was a “mother culture” to all the Americas The first settlers who came through the break in the Canadian ice barrier may not all have settled first in New Mexico or even in the western part of North America Some may have immediately started migrating southeast, going all the way to the Gulf of Mexico Some may have gone directly south, right past New Mexico, to settle in Central America Others may have followed opportunity or comfortable weather all the way to present-day Colombia and Venezuela or to Peru and Bolivia This would explain the apparent antiquity of some South American sites, many of which seem to have arisen at the same time as the Clovis culture or even before While controversy surrounds many of the Paleo-Indian sites in Latin America (for excavations there have often been done by Europeans and Latin Americans using techniques not always accepted by North American scientists), the site at Monte Verde in Chile seems to be older than Clovis Several layers, or strata, of artifacts at Monte Verde contain wood and stone tools; the remains of hutlike dwellings; and the fruits, plants, and meat that were eaten in them In the archaeological practice of stratigraphy, excavation proceeds from the upper strata, or layers, of soil to the lower, with the assumption that objects buried deeper in the soil are older Radiocarbon testing often bears this assumption out, but sometimes earth movements and water or wind erosion can jumble the contents of the soil deposits These shift s can complicate the stratigraphic record and corrupt the carbon content of the site, rendering radiocarbon dating unreliable or useless Monte Verde’s location near both a river and a damp bog casts doubts on the carbon test results, which state that the upper level of artifacts is 12,500 years old and that an even lower stratum of artifacts is some 33,000 years old While the age of the lower strata (which may have been corrupted by water action or other agents) is in doubt, the artifacts dated to 12,500 years ago are probably that old If this theory is correct, then Monte Verde is 1,000 years older than Clovis Sites such as Pikimachay in Peru and Taimataima in Venezuela and many other South American sites have also yielded stone tools and butchered animal bones From their technology and materials these sites seem to be of the same approximate age as Clovis and Monte Verde, but like the latter site, they suffer from dubious stratigraphic evidence whereby doubt is cast on their radiocarbon dates It is noteworthy that a great many South American sites, excavated by unaffi liated archaeologists in the past 30 years, tend to yield radiocarbon dates between 13,400 and 14,200 years ago If the age of any of these sites proves to be incon- 721 testable, then South America will have the oldest proven Paleo-Indian site Older South American dates could establish that Paleo-Indians emerging from Canada’s ice-free corridor headed straight for the south If this were the case, communities in South America could have emerged virtually simultaneously with their Clovis counterparts up north, or even earlier Far from the controversy of South America’s radiocarbon dates are archaeologists who see that hunter-gatherers from just south of the Canadian ice sheets could indeed have settled the entire length of the Americas in a single millennium Computer models and comparisons to the movements of historic marooned populations indicate that with opportunistic migration (say, in the pursuit of food sources) and even conservative population growth, Indians could have expanded from Canada to Chile within 100 generations It seems that once ancient Siberians crossed into the Americas, their settlement of the new landmasses, even with any delay caused by the gradually receding Canadian ice sheets, was remarkably fast FROM THE AMAZON TO THE CARIBBEAN The vast majority of early Paleo-Indian sites are concentrated along the Pacific side of the Americas This may be more than circumstantial evidence Paleo-Indians seemed to have migrated along the base of the North American Rockies and then the Mexican Sierras and the Andes, hunting on the wide-open plains but within sight of the sheltering mountains Their eastward expansion into the North American Woodlands and the South American Amazon may be obscured by the environment itself, tangling the stratigraphic evidence in vegetal undergrowth However, it may simply be that Paleo-Indians spent much of their early prehistory nearer the western longitudes and open spaces to which they had grown accustomed in their early migration Either way, most Paleo-Indians seem to have kept the rising sun to their left during their early expansion In South America a change in the overall southward migration pattern also marked a change in lifestyle from almost exclusively hunting and gathering to partial and then full agricultural settlement This agrarian phase, which commenced in different regions between 5,000 and 10,000 years ago, was an important shift in Native American culture Some anthropologists cease referring to these agrarians as Paleo-Indians, choosing instead to describe them as archaic cultures Three patterns of migration signal the archaic shift: the exploration of the coastlines in search of diversified food sources (for example, the addition of fish and shellfish to the regular diet), the absolute cessation of migration after phased adaptations to agriculture, and finally a movement into the Amazon forests after developing a certain familiarity with its environment Prearchaic Paleo-Indians would have had little incentive to settle in the Amazon forests, since their quarries as hunters were large, migratory animals that favored open landscapes