By Bruce Bower, Science News
Prehistoric communities in one part of Peru’s Andes Mountains may have gone from maize to amazingly complex. Bioarchaeologist Brian Finucane’s analyses of human skeletons excavated in this region indicate that people living there 2,800 years ago regularly ate maize. This is the earliest evidence for maize as a staple food in the rugged terrain of highland Peru, he says.
Maize agriculture stimulated ancient population growth in the Andes and allowed a complex society, the Wari, to develop, Finucane contends in the August Current Anthropology. Wari society included a central government and other elements of modern states. It lasted from around 1,300 to 950 years ago and predated other Andes civilizations, including the Inca.
Scientists disagree about when and how civilizations formed in the Andes. One theory holds that complex societies, which perhaps fell short of states with centralized bureaucracies, first appeared at least 3,600 years ago in fishing villages along Peru’s coast and then spread inland. Based on remains of various wild and domesticated plants found at inland sites, other researchers suspect that agriculture had an especially big impact on the establishment of highland societies, beginning roughly 2,500 years ago. Questions also remain about whether prehistoric Andean civilizations depended primarily on maize or on a suite of crops including potatoes and beans.
Previous work has shown that prehistoric societies in the lowland areas of Central and North America depended on maize to grow large enough in numbers to develop state institutions, a pattern that Finucane sees paralleled in the Andes Mountains.
“These new findings indicate that intensive maize agriculture was the economic foundation for the development of the Wari state,” says Finucane, currently a law student at Yale University.
The new data convincingly demonstrate that highland residents relied on maize shortly before the rise of the Wari state, comments archaeologist Daniel Sandweiss of the University of Maine in Orono. A warmer, wetter climate during the Wari period and the spread of terraced cultivation areas may also have spurred maize farming, he suggests.
Not directly addressed by Finucane’s findings is whether ancient fishing villages provided the basis for later Andean civilizations, such as the Wari, says Sandweiss, a proponent of that hypothesis.
Finucane analyzed the chemical composition of bones from 103 individuals excavated by other researchers at six prehistoric sites in Peru’s Ayacucho Valley, one of several Andean regions where early civilizations arose. Ratios of certain chemical isotopes that collect in bone reflect the types of foods that an individual consistently consumed over at least the last decade of life.
Radiocarbon measurements of human bones at each site yielded age estimates that ranged from 2,800 years to 900 years. This time span encompasses three eras of Ayacucho prehistory: the Formative period of small farming villages, the Huarpa period of expanded settlements and irrigated fields, and the Wari period of centralized bureaucracy and state government.
Chemical signatures of substantial maize consumption appeared in the bones of individuals from every Ayacucho site, including three from Formative period sites, Finucane says.
Only a relatively small part of the Andean valley contains soil suitable for maize cultivation. Competition for cropland, he speculates, may account for evidence of considerable warfare during the Huarpa and Wari periods.
Finucane “makes a strong case” for maize as a key food in the Ayacucho Valley by about 1,800 years ago, but not 2,800 years ago as argued in his new paper, remarks Yale University anthropologist Richard Burger, who was not involved in the study. Only one skeleton in Finucane’s sample can be definitively dated to the Formative period, and signs of maize consumption in that specimen remain preliminary, in Burger’s view.
Finucane’s proposal is not out of the question, though. Another recent study of bone isotopes suggests that maize was regularly eaten at highland Andes sites in Argentina beginning around 4,000 years ago, says anthropologist Robert Tykot of the University of South Florida in Tampa. Tykot co-authored that investigation.
Chemical analyses are needed of other human skeletons that have been found at Formative period sites, Burger adds. Investigations of prehistoric diets in Andes valleys located at higher altitudes than Ayacucho will offer additional insights.