One (Wo)man’s Trash
Unearthing valuable data from ancient dumps
Carla Hadden, CAIS’s newest post-doc, gestures to a large, boldly colorful painting of her favorite animal: a lightning whelk. It is the kind of elongated, spiral snail shell that beachgoers covet, and while working on her dissertation, Carla collected hundreds of them, making use of the abundant meat to cook tasty-sounding whelk fritters. She even sent me the recipe.
“I never felt more connected to the people I’m studying than when I was out in this big bay in waste-deep water [collecting shells], and I look around and kids are doing the same thing with their parents. And I imagine this is what life might have been like,” Carla said.
She is referring to the people of the gulf coast who lived in the late Woodland Period about 1000 years ago. At the heart of things, Carla is an archaeologist. She first came to the Center for Applied Isotope Studies (CAIS) as a grad student learning the ins and outs of radiocarbon dating.
“I loved it. So I found every opportunity I could to come back here. They couldn’t shake me after that,” Carla said.
A self-proclaimed coastal girl, Carla strives to debunk the belief that ancient people of the coast were inferior to the agricultural communities of the continent’s interior. To someone who grew up on the Atlantic seaboard, the notion that coastal bands lived a hand-to-mouth backwater existence was absurd. Now a post-doc at CAIS, Carla has the opportunity to expose that theory. Through field research, lab analyses, and method development, her work contributes to a more complete understanding of the relationship between humans of the gulf coast and their environment.
Working primarily in the Weeden Island culture area, Carla sifts through shell middens, which essentially amount to ancient garbage dumps. These rich resources of pottery sherds, fish bones, and oyster shells hold pieces to the puzzle of what life was like for the people who left them there. Although the sheer number of shells contained in middens poses a serious logistical challenge, Carla is up to the task. An important part of her work at CAIS involves engineering more efficient methods to extract data from these shells. With better data, CAIS can build better coastal chronologies, which have significant implications for our understanding of ‘complex’ societies.
“It was previously thought that you only get cultural complexity when you get agriculture,” Carla said.
But geochemcial analyses of shells from the Weeden Island culture area show that people were not aimlessly wandering in search of food. They were in a given place collecting oysters and catching fish every season of the year. The findings contribute to mounting evidence demonstrating that these people were complex hunter-gatherers; that is, they were sedentary, hierarchical societies whose access to rich natural resources rendered agriculture unnecessary.
In addition to exposing the myth of the backwater coastal peoples, coastal chronologies provide a stark contrast between human-environmental interactions now versus 500–1000 years ago.
“What my research has shown is that people were sustainably exploiting the environment until the period of industrial-commercial techniques,” Carla said.
Thousands of years ago, people living on the coast became a critical part of the food web, impacting marine ecosystems, and changing the relative abundance from taxa to taxa. By analyzing fish bones and shells found in shell middens, Carla starts to put together a timeline that compares which species people were catching and in what volumes these species were caught over time.
The comparison is alarming. Although fisheries began declining thousands of years ago, the rate of change was so slow it would have been imperceptible in an individual lifetime. That is no longer the case.
Recall the food chain, which consists of trophic levels. Very simply put, larger, carnivorous consumers are found in upper trophic levels, and the smaller organisms on which they feed make up lower levels. The point at which humans are fishing in the trophic cascade indicates the health of the ecosystem. Initially, people will fish at the top and work their way down the food web as resources are depleted. ‘Fishing down the food-web’ is a warning sign that the fisheries are in decline. In fact, during the past century or so, the rate of decline has accelerated to the point that people are noticing it in their lifetime.
“The oceans are in trouble,” Carla said, “They’re seriously in trouble.”
In the wake of this catastrophe and the scramble to correct it, Carla believes that it is imperative to turn to history for guidance. We may not be able to reset things to the way they were prior to the steepened rate of change, but Carla thinks we can use the data of the past as a baseline to make better decisions on how to manage the fisheries moving forward. Without coastal chronologies, there is not baseline.
Beyond the urgency of the fisheries problem, passion of and love for the coast spurs Carla’s work. In that way, she’s lucky.
“I just want to better understand how people dealt with coastal life. It is a great place for people to live and settle and for populations to grow. Anything to do with the coast, I’m into it,” Carla said.
Currently, Carla and CAIS director Jeff Speakman are working on a project with the Smithsonian. The team seeks to evaluate pollution levels in the Chesapeake Bay by comparing concentrations of heavy metals found in oyster shells.