A Taste of Andean History
The particles beneath your couch cushions, the dirt in your vacuum cleaner, and the crumbs on your kitchen floor say much more about you than you might want to know. From the type of grain used to make your toast, to the way you cooked your popcorn, food remains can offer a wealth of information about your culture, customs, and habits. Christine Hastorf, a Berkeley professor of anthropology, studies similar remains in ancient settlements to gain insights into early cultures. "We can address identity and cultural construction questions as well as economic questions about what was grown where and how much."
Just as some researchers extract sherds of pottery and human bone from archeological sites, Hastorf, an archeobotanist, extracts plant remains. She immerses bags of soil collected from representative areas across an archaeological settlement in water, collecting charred macroremains such as seeds, wood splinters, and tuber chunks that float to the surface.
Tinier evidence such as phytoliths, grains of silica or other minerals produced by plants for structural support and other uses such as starch granules are also extracted from soils with organic solvents. Often unique to a particular type of plant, these microscopic remains can help identify the presence of potatoes, onions, and other plants that decompose faster than dried corn kernels. "When you peel an onion, you'll pick up the big pieces of skin, but the little pieces that land on the floor will stay there and be discovered by their starch grains," Hastorf says.
After identifying, counting, and weighing the remains, Hastorf and her group plot their data on a map of the site. The technique can provide an overview of activities in each part of the settlement. The absence of plant remains can be just as informative as their presence, Hastorf says. "Finding plant remains everywhere except one spot means that area could be special-they do not burn things there or keep it especially clean."
While Hastorf has worked on sites from the highlands of Peru to Turkey, her longest-running project is based along the southern shore of Lake Titicaca in Bolivia. Hastorf's research focuses on the early settlement period of the Taraco Peninsula, from 2000 BC, when people first began building structures with stone foundations, to AD 500, when an urban center called Tiwanaku gained regional influence.
With evidence from two peninsular sites, Hastorf is tracing the domestication and use of plant foods in the Titicaca basin. These include indigenous crops such as quinoa and potato, but also maize, which originated in Mexico. With a scanning electron microscope, she and her research team can measure changes in the characteristics of quinoa and potatoes as they evolve from wild to cultivated forms, and an increasing dependence on domesticated varieties.
Maize, by contrast, Hastorf finds concentrated in ceremonial areas in early times, but becomes increasingly common in later centuries. She attributes this change to the fact that it was initially imported to the highlands via llama caravans; only after local farmers develop a local strain capable of growing at the 13,000-foot elevation of the altiplano does maize become widespread.
Plant remains are also helping to explain a curious finding in analyses of human remains from the sites. The bones of these early settlers are enriched with a nitrogen isotope typically associated with a diet rich in meat. To Hastorf, the evidence didn't add up. "They didn't have enough land to eat a llama a night-they were most probably eating them once a month or every two months on a feast day," Hastorf says. Then Hastorf learned that animal fertilizer affects the nitrogen levels in plants. She realized that early settlers might have been using llama dung to fertilize their crops. This finding, says Hastorf, "not only helps us interpret the human diet, but helps us understand their level of farming intensity and its sophistication."
Hastorf has worked in the Titicaca basin since 1989. Over the ensuing decades, she has become part of the local community. When residents asked her to help them build museums to teach their children about their past and keep artifacts from the peninsula locally accessible, Hastorf agreed. Community members contributed adobe bricks, while Hastorf hired the contractors, bought cement, with the help of U.S. government grants. She has also mentored a number of Bolivian and other Latin American students, helping them enter graduate school to become professional archeologists in their own right.
"They're teaching me about their world, and they've been gracious to me. I owe them for sharing with me their ancestry and their world, and for letting me excavate, study, and bring students in. It should go both ways," Hastorf says.
As originally published in Science Matters, Volume 7, Issue 54 (June 2010).