Ancient DNA Analysis Proves Roman Fish Sauce Was Made of Fish

The retrieval and analysis of ancient DNA has changed everything we thought about ourselves and our pets. We aren't some purebred superior species, we are mutts. If god made Adam out of dust, when exactly did he do that – before or after our ancestors intermixed with Neanderthals and Denisovans, and in the case of West Africans, possibly an archaic hominin as well?

We also learn from ancient DNA, also known as aDNA, that mammoths had become unsustainably inbred before going extinct, that horseshoe crabs once thronged Greenland's shores, that dogs did originate from wolves, and that cats really are perfect. We also learn from aDNA that Phoenicians may have founded Carthage, but they sure didn't live there.

Now this powerful technology has been unleashed on that famed condiment, the ancient Roman fish sauce garum, and has revealed: It was made of fish. European sardines, in the case of the fish sauce makers at Adro Vello, Galicia – Sardina pilchardus, Gonçalo Espregueira Themudo and colleagues reported in Antiquity in July.

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A shock it was not, because an ancient Roman recipe for garum calls for fish, but it is good to know that the ancient authors of cooking instructions were reliable sources.

Further proof that the Galician garum was made of sardine derived from the fish bones and scales at the bottom of the vats. Elsewhere, other fish could be used to make garum too, such as sprats and anchovies or even mackerel.

Let us be clear that the Antiquity team investigating the fish exploited at the Adro Vello salting facility isn't the first to extract and analyze ancient DNA from fish. The technique is most famously wielded on the remains of humans and terrestrial animals we care about but work has been done on fish, including salmon (in the context of early Americans exploiting the fish) and sturgeon. Ancient DNA indicates that of the multiple species of salmon, paleo-Canadians in prehistoric British Columbia 11,000 years ago sniffed at the pink, but ate of the Chinook, sockeye and coho.

Now, the breakthrough is to unleash ancient DNA technology on fermentation brine vats in Roman Spain.

"Despite the prevalence of such remains in the European archaeological record, to our knowledge, genomic studies have yet to take advantage of the vast potential of this data source for elucidating past fish consumption and the population dynamics of commercially relevant fish species," the team explains the rationale of their research.

My cousin Finny

"Ancient DNA" usually refers to genetic material retrieved from a being that had been dead for more than 100 years, yet was preserved thanks to extraordinary conditions. The older the creature, the more degraded its DNA will be under all circumstances, but one can get lucky. In the case of the fish sauce vats, the genetic material was retrieved from the fish bones, despite their being in a parlous state.

Technically, the article published in Antiquity in July aimed to demonstrate that usable genetic material can be extracted from the gook at the bottom of a fish-sauce fermentation vat, despite the sea creatures being crushed and then subject to acid and salt trauma. They have duly shown it can be.

The fish salting and fermentation facility at Adro Vello came into use possibly as early as the first century, but certainly from the third. In general, big fish like tuna would be gutted and salted for preservation, and small or otherwise inferior fish would be relegated to fermentation vats. The archaeologists identified four vats at Adro Vello that, based on residue analysis, had been used to make fish sauce and/or pastes.

They add that fish paste could contain other animals.

Residential ruins at the site date to later times, not to the era of the fish sauce factory. That fits with the site's identification. One does not want to live near a fish sauce factory, which involves fermenting raw fish and their offal. This would be in keeping with archaeological investigations of another ancient garum manufacturing facility in Israel, which was built suitably far from Ashkelon.

Another insight of the new paper, armed with the ancient DNA, is to shed light on the family tree of the sardines used in the Spanish garum factory at Adro Vello.

As sardines go, the Adro Vello population seems to have been quite the thoroughbreds compared with the sardines today in the Mediterranean and Atlantic Ocean off Europe and North Africa. They have admixed.

What are we to learn from that? Apparently, that like us, today's sardines are also mutts. The fish populations in Roman times may have been more discrete, and the admixture evident today may have resulted from forced connectivity, caused by the intense modern fishing and shipping activities in the Mediterranean and Atlantic.

The bottom line is that despite the obnoxiousness of its manufacture, fish sauce was a popular condiment throughout the Roman Empire and beyond. Fish as a food has been popular since we figured out how to catch them and were so in the Empire. Salting big ones to extend their shelf life could enable their consumption in the Empire interior, and reducing the inferior specimens to essence of sardine not only improved the taste of dishes but concentrated nutritive elements as well. It was a win-win-win – except for the sardines and anybody living in the vicinity of the fish sauce factory.