This Month in Archeology

2007 March 28
The origins of agriculture and a bushel basket full of dirt

If you visited Kampsville in the summer of 1963 you might have noticed students in the archeology field school standing waist-deep in the Illinois River, holding bushel baskets of soil halfway underwater. Other students would have been holding kitchen strainers, scooping up bits of charcoal and other material floating to the surface. As odd as it sounds, this was the first large-scale use of an archeological recovery method that is now standard practice throughout the world.

The method is called flotation, and is responsible for many advances in our understanding of how people lived in the past. Flotation involves immersing soil samples from archeological sites in water, gently washing away the sand, silt, and clay, leaving behind organic material like charcoal, seeds, and tiny bones. Our methods of flotation are more advanced these days (we have special machines to process the samples, and we don't have to stand in rivers to do it), but the basic idea is the same.

Without flotation a lot of important material is lost or destroyed during excavation. Fish scales, for example, are fragile and difficult to see while digging through the soil, and are rarely recovered by trowels or shovels alone. By comparing fish scales at ancient sites to modern ones, we can learn what types of fish people were eating and how big the fish were. Fish scales grow from the inside out like tree rings, and by studying them closely we can sometimes even tell what time of year a fish was caught.

The greatest contribution of flotation, though, has been to our understanding of paleoethnobotany: the study of how people harvested and used plants in the past. For most of human history we gathered plants from the wild. The shift from gathering plants to farming took place over a few thousand years – which is fairly quick on archeological time scales.

Several types of artifacts demonstrate how and when people began to rely on tended crops: stone hoes to cultivate fields, mortars and pestles to grind the grain, large ceramic pots to cook and store the harvest. The best evidence, though, comes from the plants themselves. Seeds from wild plants are very different from those that have experienced generations of cultivation and plant husbandry, allowing us to learn which plants were farmed in different regions of the world.

Plant remains recovered from as early as 8,000 B.C. in this area show that people were eating lots of different foods. Archeological sites of this age often have nuts and nutshells, especially from hickory and walnuts. Knotweed, maygrass, lotus, and other plants considered weeds today are also common at these early sites. (All of these plants are edible, if you just know how to cook them right!)

The number and variety of plant remains and seeds increased slowly through time, as people began to help the plants along instead of just gathering them from wild plots. People took the first steps toward agriculture at this time, clearing and weeding fields and saving seeds from one year for planting the next.

By about 1,000 B.C. several plants had been truly domesticated. Squash seeds recovered from this time, for example, are much larger than their wild counterparts, and the rinds of squash plants are much thicker – indicating that over many generations people had been selecting plants for these specific traits.

Domesticated plants begin to dominate at archeological sites around 100 B.C., meaning that people were relying on what they grew themselves more than what they gathered from the wild. Plants with large edible seeds were common, including chenopod (a type of goosefoot) and sunflower.

Corn appears at archeological sites in western Illinois around this time too. Corn was first domesticated in Mexico and spread slowly throughout the continent. Prehistoric corn was much smaller than most kinds we grow today (the cobs were only a few inches long), but it was still a useful crop and became more important through time.

By A.D. 1,000 people in this area had become true farmers, and most of their diet consisted of food they grew themselves. They farmed many different varieties of corn, sunflower, squash, beans, and other crops. Their villages were larger and more permanent than before, many of them close to rivers where they farmed the floodplains. The river bottomlands where prehistoric agriculture first developed are still prized today for their rich soils, and the farming tradition in this region continues from thousands of years ago.

We have come almost full-circle in using farm implements to study early agriculture: the wood-slat bushel baskets used by archeology students in 1963 came from Calhoun County apple orchards. Easily available at the time, the baskets are artifacts themselves these days. It won't be long, on archeological time scales anyway, until our current agricultural practices are considered ancient history. Imagine archeologists of the future studying the remains of modern farm machinery to learn about life in the early 21st Century. I bet they won't be standing in a river to do it.

Dr. Gregory Vogel is Director of Research at the Center for American Archeology in Kampsville, Illinois. He may be contacted at: gvogel@caa-archeology.org, or P.O. Box 366, Kampsville, IL, 62053.