In a study recently published in the journal Antiquity, researchers successfully sequenced DNA from fish remains found in a Roman-era fish-salting vat at a cetaria in northwest Spain. The discovery sheds new light on the species used in the production of garum, the fermented fish sauce that was immensely popular throughout the Roman Empire. According to Phys.org, the effort identified the fish remains as European sardines, revealing that this species was a key ingredient in Roman condiments.
The multidisciplinary team, which included archaeologists and geneticists, developed a method to identify animal remains even when they are damaged beyond recognition. By comparing multiple overlapping DNA sequences and matching them to a full fish genome, they were able to genetically identify the species from samples that traditional visual identification methods could not decipher. This advancement addresses a challenge in archaeology, as the intense processing involved in making garum—crushing and fermenting fish—often leaves remains that are fragmented and degraded.
"Fish bones are a frequent find in the archaeological record of the Roman period, yet their use in archaeogenomic studies is residual, probably due to the fragmentary nature of remains, which makes identification to species or even genus difficult," said Dr. Paula F. Campos from CIIMAR, Universidade do Porto, according to Phys.org. She added, "Despite enduring conditions that promote the degradation of DNA, the methods we outline allow for the identification of species from these processed bones."
Garum was more than just a condiment; it was a staple in Roman cuisine, prized for its salty and umami flavors. Made by crushing and fermenting small fish like sardines in coastal fish-salting plants known as cetariae, garum had a long shelf life that facilitated commerce across the Roman Empire. The Atlantic coasts of Hispania (modern-day Spain and Portugal) and Tingitana (modern-day Morocco) were particularly famous for their production of the sauce.
The research team did not stop at identifying the ancient sardines. They also compared the DNA sequences from the ancient samples with those of modern European sardines. Co-author Campos and her colleagues discovered that Roman-era sardines were closely related to those found in the same area today. "This finding aligns with previous visual identification of sardine remains in other Roman-era fish-salting plants," Campos noted. This genetic continuity is notable, especially considering the mobility and dispersal capabilities of the sardine species.
These findings have implications for future studies. By demonstrating that usable DNA can survive in fermentation environments like the brines used by the Romans to make garum, the door is opened for similar analyses of other archaeological fish remains. "Analysis of these data has the potential to open a new research avenue into the subsistence economies, cultures, and diets of past human populations and provide information on fish populations that cannot be obtained from fishery catch data or modern specimens alone," the researchers wrote, as reported by Gizmodo.
The ability to genetically identify fish species from archaeological contexts allows for a deeper understanding of ancient economies and trade networks. It also offers insight into how historical human activities have impacted marine species over time. "That insight could help assess the effects of human-environment interaction over the centuries," said Annalisa Marzano at the University of Bologna in Italy, who was not involved in the study, according to New Scientist. "This might help identify with more precision some regional variations in the main ingredients of the ancient fish sauces and pastes."
The study also underscores the importance of sardines in the Roman diet and economy. Fish was a source of protein for the Romans, and processing it into products like garum helped sustain populations and armies across the empire. Other garum production sites have contained remnants of additional fish species such as herring, whiting, mackerel, and anchovy, indicating a diverse use of marine resources.
Looking ahead, Campos and her team plan to expand their research to include other fish species from additional Roman-era garum production sites. "We are expanding the sampling locations to see if the results are consistent across the entire Roman Empire," she said.
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