By studying ancient residues, scholar finds clues of humanity’s past

Archaeochemist Andrew Koh, the new museum scientist at the Peabody Museum, analyzes carbon residues on artifacts to learn how ancient peoples lived and died.
Andrew Koh

(Portrait by Dan Renzetti, photo illustration by Michael S. Helfenbein)

When archaeological scientist Andrew Koh unearths a dusty artifact, say a clay pot or alabaster jar, the last thing he’ll do is clean it.

Archaeologists routinely wash artifacts soon after excavating them to examine their ornamentation and style. For Koh, the dirt and grime could yield evidence of humanity’s past just as exciting as the objects themselves.

A pioneer of archaeochemistry, a uniquely interdisciplinary field that applies chemical analysis to substances found on artifacts, Koh is keenly interested in ancient vessels’ former contents. The residues he studies offer valuable insight into how ancient peoples lived and died.

Last fall, Koh was appointed Museum Scientist at Yale’s Peabody Museum. He also directs the Yale Ancient Pharmacology Program, an initiative that merges the sciences and humanities in the study of organic residues. His work — which has already yielded an exciting discovery within Yale’s Babylonian Collection — demonstrates the exciting benefits of sifting through Yale’s collections, where new breakthroughs are waiting to be found.

Koh recently spoke to Yale News about his new role, his discoveries — including the remnants of an opiate concoction found in the Yale Babylonian Collection — and what makes Yale the perfect setting for interdisciplinary scholarship. The interview has been edited and condensed.

What does archaeochemistry involve?

Andrew Koh: Throughout history, humans have produced, traded, and consumed organic goods. Think olive oil, wine, medicine… Analyzing the remnants of those commodities provides us a clearer understanding of how people navigated life thousands of years ago. We can learn something about how they conducted commerce, nourished themselves, spent their leisure time, and treated illnesses, among many other things. 

By its nature, archaeochemistry is an interdisciplinary field. To find and analyze evidence requires working across many disciplines: chemistry, geology, botany, history, near eastern languages, anthropology, et cetera. Yale and the Peabody Museum are ideal settings to do this work.

How so?

Koh: First, Yale’s strengths span the sciences, arts, and humanities. There is so much opportunity here to work across disciplines with top-flight scholars and so many great resources at my disposal, including a world-class library and cutting-edge analytical tools. Second, Yale’s collections, both at the Peabody Museum and elsewhere, set the university apart. The Peabody’s collections alone are an incredible resource but there’s so much more. I can consult rare primary sources at the Beinecke Library and Medical Historical Library, artifacts in the Yale Babylonian Collection and the Dura Europos collection at the Yale University Art Gallery.

The university is uniting these collections so that scholars can easily work across them. That’s hugely important. You know how when we gaze at stars, we’re seeing a point of reference that originated thousands or millions of years ago? Yale’s collections are like human starlight. They capture and preserve evidence of how people lived hundreds and thousands of years ago. How they ate, drank, and healed themselves.

Have you captured any of the starlight recently?

Koh: I’ve been analyzing a vessel in the Yale Babylonian Collection, a collection of the Peabody Museum, that was acquired more than a century ago with the support of financier J.P. Morgan. It’s from the Egyptian tradition during the Persian period — about 2,500 years ago — and probably was commissioned by a local governor, or satrap, in Egypt. It’s made of Egyptian alabaster, which is really calcite, and it’s quite beautiful. It is inscribed with the name of Xerxes I, the great king of Persia, in four languages: Old Persian, Elamite, Akkadian, and hieroglyphic Egyptian.

The vessel contained a brown residue, but that’s not why it was collected, so nobody had analyzed it. An initial study in collaboration with Agnete Lassen, the Babylonian Collection’s curator, demonstrated that the residue was from an opiate concoction. And that’s just the start of the inquiry. I’m interested in learning more about it.

How does being at Yale facilitate your study of the vessel?

Koh: It does so in many ways. First, we extracted the residues at Yale’s Institute for the Preservation of Cultural Heritage and analyzed them at the West Campus Analytical Core. Then I consulted an exquisite modern facsimile of the De materia medica — a five-volume pharmacopeia of medicinal plants and medications originally written by a Greek physician in the first century C.E. — at the Medical Historical Library to serve as an ethnographic guide. The original codex was produced around 515 C.E. in what is now northwest Turkey at Constantinople, capital of the Byzantine Empire, and served as a medical reference for a millennium at its imperial hospital.

The facsimile contains at least five medical recipes that used opiates, derived from centuries of previous knowledge. They describe very specific processes for making these medicines with copious notes by medical personnel in Greek, Hebrew, Arabic, Persian, and Turkish. I can go to the Peabody’s herbarium and reference specimens of plants I’ve studied in De materia medica after identifying phytochemical fingerprints in vessels.

I also spoke with a colleague in Yale’s Department of Near Eastern Languages & Civilizations, who teaches a class on ancient Egyptian medical texts. We discussed a 3,600-year-old papyrus that contains opiate recipes. I can consider how that might relate to what I found in De materia medica and the residues I analyzed. Lastly, we are working with a student from “Collections of the Peabody Museum,” a first-year seminar class, and Ellery Frahm, the director of the Yale Initiative for the Study of Ancient Pyrotechnology, to study the calcite itself, rewriting the history of these vessels.

In 2013, you were part of a team that discovered an ancient wine cellar in modern-day Israel. What was the significance of that discovery?

Koh: In that case, I was working as a standard archaeologist and scholar of ancient cultures and texts. As associate director of the dig, I was using the excavation of a 4,000-year-old Canaanite palace in Tel Kabri in the Upper Galilee, which was ancient Phoenicia, as a field school for students. The wine cellar was a once-in-a-lifetime discovery. What made this find particularly extraordinary is that it’s by far the most intact ancient palatial wine cellar ever discovered. Many vessels remained in situ, which is rare because people tended to take their valuables with them or resettle the site. This site was probably destroyed by an earthquake or other violent event that made the people flee and leave behind thousands of liters of wine, never to return.

We first found one enormous, three-foot-tall jar that held dozens of liters of wine. It’s extremely rare to find a jar like this intact but there is only so much I can learn from studying a single vessel. Then another popped up, and another, and another until we had about 40 of them. At that point, I could start asking much more interesting questions.

What did you discover?

Koh: We already knew that people in that period made wine, so that’s not that interesting. But once we had recovered enough intact vessels, we could start detailing the process by which they made the wine. For example, our analysis showed that there was liquidambar, or sweetgum, inside some of the jars, which is a valuable resin imported from the north that would have kept the wine from becoming vinegar, but likely served additional purposes we are only starting to understand. Today, liquidambar is used for cancer research. We also found evidence that the wines were spiked with things such as juniper berries, honey, cedar oil, and even ingredients we would classify today as psychoactive. These ingredients weren’t for preservation, so perhaps they masked the taste of the preservatives or were even the centerpiece of specific rituals.

Where are you doing fieldwork this summer?

Koh: In June, I’m taking a team of students to central Greece to co-direct an archaeological and botanical survey. We’ll be collecting ancient pottery and specimens of plants used in ancient pharmacology as part of the Southern Phokis Regional Project [SPRP], a collaboration that strives to be international, inclusive, and interdisciplinary.

The tradition in archaeology, naturally, is to dig. That means that studying plants used in ancient organics almost becomes an extra-curricular activity. But this summer, collecting botanical specimens is a primary driving force, which is unprecedented for a major dig. If a plant from the region is mentioned in a recipe in an ancient text, then we’ll collect it as an ethnobotanical reference specimen in partnership with our collaborators in Greece.

This spring, I’m taking the team to Horse Island — a 17-acre island the Peabody owns just off the coast of Branford, Connecticut — for a two-day training session. It’s a perfect location to simulate the conditions we’ll encounter in Greece in a convenient and controlled setting. It’ll give us a chance to test our equipment and for the students to learn how to conduct a field survey with interdisciplinary nuances tailored to the Yale Ancient Pharmacology Program. This way, we can hit the ground running when we go overseas. It’s another example of how the resources at the Peabody and Yale uniquely support this work.

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