A arqueóloga Eva Rosenstock nunca foi do tipo potsherd. Ela preferiu o trabalho de estratigrafia: classificando as camadas de artefatos remanescentes onde os humanos viveram, aprendendo sobre as mudanças ao longo do tempo. Com cerâmica, ela diz, "você ama ou não". Essa divisão entre os fragmentos é especialmente notável em Çatalhöyük, uma famosa cidade neolítica na Anatólia, na Turquia. Rosenstock trabalhou como um dos principais investigadores na área de West Mound de Çatalhöyük, onde a população parece ter declinado e depois desaparecido por volta de 5700 a.C. Em comparação com o East Mound - a parte mais famosa da cidade pré-histórica - o West Mound está cheio de cerâmica.

“Você tem um fragmento de terra que você cava [no East Mound]”, diz Rosenstock. A população então mudou para o West Mound "por volta de 6000 a.C." e a quantidade de cerâmica "explode em quilos e dúzias de quilos de cerâmica que você extrai do solo". Bocados quebrados de tigelas e potes permanecem, alguns com decorações como listras vermelhas vibrantes. Mas, na maior parte, Rosenstock permaneceu desinteressada nos vasos quebrados - até que outro pesquisador notou algo estranho. Depósitos calcificados foram encontrados nos vasos cerâmicos, mas em nenhum outro lugar. Se esses depósitos aparecessem em outros objetos, como ossos ou ferramentas feitas pelo homem, eles provavelmente teriam sido um produto do ambiente onde foram enterrados. Mas os depósitos encontrados exclusivamente no interior da cerâmica apontavam para outra explicação.

"Ficou claro que isso deve ter a ver com o material que estava dentro desta tigela", diz Rosenstock. Ela não tinha certeza do que fazer com a estranha descoberta até saber sobre o trabalho de Jessica Hendy. Arqueóloga da Universidade de York, a pesquisa de Hendy envolve a extração de proteínas do cálculo dentário em dentes fossilizados e a análise das moléculas para aprender sobre as dietas de humanos antigos. Quando Rosenstock se aproximou de Hendy para discutir a aplicação do mesmo método ao material escamoso no interior da cerâmica Çatalhöyük, Hendy estava ansioso para mergulhar.
Potsherd Food
Examples of calcified deposits from modern and ancient vessels at Çatalhöyük. a Examples of CaCO3 accretions from a modern tea water pot with extensive calcified deposits used near the research project compound Çatalhöyük, b a close-up of calcified deposits, c a relatively intact vessel (not analyzed in this study) demonstrating bowl shape and extent of calcified deposits and d a selection of four sherds analyzed in this study showing deposits adhering to the inside surface of the ceramic sherds. (Jessica Hendy et al.)
The results of that years-long collaboration are described in a new paper in Nature Communications, revealing just how effective dirty dishes can be in helping archaeologists decode the past.
“This is the oldest successful use of protein analysis to study foods in pottery that I’m aware of,” Hendy says in an email. “What’s particularly significant is the level of detail we were able to see from the culinary practices of this early farming community.”

The potsherds yielded proteins from numerous plants—barley, wheat, peas and bitter vetch—as well as the blood and milk of several species of animal, including cows, sheep and goats. Of even greater interest to the researchers was the precision with which they could identify the proteins. They didn’t just see barley, but could identify the specific signature of endosperms, the edible part of the plant. The material was stored in ceramic containers in a way that suggests it was probably used to make some kind of porridge.

The milk offered even more insight, as the researchers could distinguish whey from other parts of the liquid—and in one jar they found only whey, indicating the ancient Anatolians were actively transforming the milk into something like cheese or yogurt. “Here we have the earliest insight into people doing this kind of milk processing,” Hendy says. “Researchers have found milk in pottery in earlier times, but what’s exciting about this find and this technique is that we can see actually how people are processing their dairy foods, rather than simply detecting its presence or absence.”
Caroline Solazzo, who works on protein analysis in textiles at Smithsonian’s Museum Conservation Institute, was impressed by the study. “The work was done by a very good team of experts in ancient proteomics studies,” Solazzo says. “It seems that proteins can be better extracted from the accumulation of visible residues in the crust than from the ceramic wall, which is an interesting result for future studies of this type.”

To identify the proteins, Hendy and her team took samples from the potsherds and put them through a mass spectrometry machine. This “shotgun” approach is different from past protein analyses, which involved looking for specific proteins rather than doing a catch-all examination. Proteins are made of specific chains of amino acids. Some proteins, like osteocalcin (which is found in bone), are made of only a couple dozen amino acids, while others form chains of thousands of the building blocks. To decipher the protein puzzle left behind in the jars from Çatalhöyük, Hendy and her team compared their results to a database of known proteins.

Reliance on a reference catalogue is one of the hurdles of this type of research, because the analysis is only as good as the database. Such archives tend to contain lots of data on commercially significant species like wheat, Hendy says, whereas less common plants remain underrepresented. Due to gaps in the data, the researchers couldn’t identify everything in the batch—but they still managed to unlock a wealth of information.
Çatalhöyük Map
Map of Çatalhöyük. a Site location and b site plan of Çatalhöyük, adapted from Hodder33. Çatalhöyük consists of two distinct mounds; the East Mound, dating to circa 7100–5900 BC, and the West Mound, dating to circa 6000–5600 BC. (Jessica Hendy et al.)
Hendy and Rosenstock aren’t the first ones to use proteins as windows into ancient life. In 2008, researchers looked at proteins trapped in clay pots that belonged to the Inupiat of Alaska around 1200 A.D. They found signs of seal muscle in the vessel, providing evidence of the Alaskan native’s diet. And bioarchaeologist Peggy Ostrom managed to extract proteins from the 42,000-year-old leg bone of a horse discovered in Juniper Cave, Wyoming.
The question of how long such proteins survive is hard to answer at this point, because the technique is so new. Rosenstock and Hendy speculate that the proteins survived in their potsherds thanks to limescale buildup on the vessels (think of the white buildup around your faucets or tea kettles). But scientists won’t know just how long proteins can survive until they pull samples from many more sites of different ages and different environments.
“We would love to use this technique to identify the diverse cuisines of past societies and how culinary traditions have spread around the world,” Hendy says.
As for Rosenstock, she’d like to learn more about whether certain foods at Çatalhöyük were always eaten together for reasons of nutrition—the way rice and beans create a more nutritious meal together due to the combination of amino acids. She also says that after this exciting discovery, her mind is finally changed about potsherds. “It got me really interested in ceramics, in the end.”