Thursday, June 14, 2012

Rabbit Bones and Ancient Environments

Where do rabbits go when they die? In the case of ancient rabbits from Pueblo Grande, many ended up in large middens (trash piles) after they found their way into the dinner bowls of pre-Hispanic Hohokam families. In fact, since cows, chickens, or goats didn’t arrive in Arizona until after the 16th century, rabbits were the most common source of protein for Pueblo Grande’s original residents. Thousands of rabbit bones were discovered during decades of archaeological excavations. Each bone has been carefully cleaned, cataloged, and preserved in the collections of Pueblo Grande museum.

Photo of excavations of Trash Mound 1. Taken by Dana Goddu on 13-Jan-1939.
Hundreds of rabbit bones were discovered during excavation of this midden.

Why, you might ask, are thousands of dead rabbits receiving such care and attention? By preserving ancient animal remains, Pueblo Grande Museum is ensuring that future archaeologists will be able to ask and research new questions about ancient societies and environments. Animal bones can provide information about how dietary practices differed between socio-economic classes and cultural groups. Additionally, they can reveal the past environmental conditions of an area. For my dissertation project, in which I investigate the relationship between past societies and their natural environments, I will be using a sample of Pueblo Grande’s rabbits, graciously lent to me by the museum staff, to address just such a question.

Rabbit and Jackrabbit femora

Before they were an ingredient in Hohokam stews, the ancient rabbits of Pueblo Grande lived in the regions around the Salt River, where they fed on a variety of local plants. The elements of oxygen, nitrogen, and carbon from vegetation can tell us many things about environmental conditions. The specific values of oxygen isotope ratios in plants are influenced by the humidity of a region; values of nitrogen isotope ratios are influenced by the quantity of local rainfall; and values of carbon isotope ratios of plants tell us whether they are adapted for hot and dry regions, or for cool and wet ones. Rabbits, and indeed all animals, make bone tissue from the food they eat. Fortunately, the original isotopic signals of the plants they eat are preserved in their bones for thousands of years. Studying the chemicals found in rabbit bones therefore allows researchers to reconstruct the conditions of the environment in which they lived.

Because Pueblo Grande was inhabited for such an extended period of time, and because rabbits were regular menu items throughout its occupation, we can study how isotope ratios of oxygen, nitrogen, and carbon changed in rabbit bones through time, thus allowing us to study how humidity, rainfall, and plant cover in the area changed through time. Working with Collections Curator Holly Young and Collections Aide Lindsey Vogel, I selected a sample of rabbit bones that spans 700 years of Pueblo Grande’s history. These bones provide an excellent opportunity to study long-term interactions between ancient Hohokam society and the local environment.

So, the next time you spot a rabbit as you walk the trail at Pueblo Grande, keep in mind that its ancestors not only fed Hohokam families, but also hold valuable information for scientific studies of ancient environments.

Posted By Andrew Somerville
Ph.D. Candidate in Biological Anthropology
University of California, San Diego

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