Late Sunday night, Seamus Blackley — physicist, amateur baker, Egyptology hobbyist, and father of the Xbox — set out to bake a loaf of sourdough using 4,500-year-old yeast collected from ancient Egyptian pottery.

Two weeks ago, with the help of Egyptologist @drserenalove and Microbiologist @rbowman1234, I went to Boston’s MFA and @Harvard’s @peabodymuseum to attempt collecting 4,500 year old yeast from Ancient Egyptian pottery. Today, I baked with some of it... pic.twitter.com/143aKe6M3b — Seamus Blackley (@SeamusBlackley) August 5, 2019

By the time the bread had cooled and Blackley had tweeted about the experience and his process, it was early Monday morning. Within a day, Blackley’s tweets had gone viral, attracting both the incredulity and the awe of people wondering: a) if the yeast was really 4,500 years old, b) how this intersects with issues of colonialism and appropriation, and, most basically, c) how/why/what?

Inspired by these questions and curious about the process, Eater reached out to Blackley and his collaborators, Serena Love, Ph.D., an archeologist who worked at Brisbane’s University of Queensland, and Richard Bowman, a microbiologist and graduate student at the University of Iowa.

The conversation, which has been edited for length and clarity, is below.

Eater: How did you decide to start baking with “ancient Egyptian” yeast?

Seamus Blackley: I received a sample of yeast that was supposedly ancient Egyptian from a brewer friend of mine in April. I put a couple pictures on Twitter, and for some reason, it really took off. I started to get questions: “How do you really know this is ancient Egyptian yeast?” It drove me crazy, because I didn’t know. It became clear to me that I better get my shit straight if only because I don’t want to be a liar. We owe ancient Egyptians such a debt to our modern world — they deserve better than that, too. Serena and Richard agreed and wanted to help get the real thing.

Serena Love: I asked Seamus, “Could you give me the source of this yeast?” And he said, “It doesn’t exactly have the most secure provenance.” So I threw out, “Well, what do we have to do to get really secure provenance?” And he said, “Get me into a museum.”

How did you convince museums to give you access to their millennia-old collections?

SL: I’m an archeologist by trade. I’ve been in the industry for over 25 years. I know a lot of people who know people. So, I did a scattershot of emails. It was a bit of just relying on reputation; I was trying to contact people that I knew personally, who could vouch for me and say that, I just want to sample your yeast, and no, I’m not completely out of my mind.

I got ignored by lots of people; some never even bothered to respond to me. So I’m actually loving this Twitter stuff now, because all the people who blew me off — take that!

First was Boston’s venerable Museum of Fine arts, home to one of the finest collections of Ancient Egyptian antiquities in the US. I set up my equipment and cameras, and the process went very smoothly. Then I got an amazing surprise... pic.twitter.com/8Uel7VEyDH — Seamus Blackley (@SeamusBlackley) July 29, 2019

How do you even word that kind of request in an email?

SL: I basically said, “This is what we’re interested in, we’re interested in a non-destructive technique, these are our methods, would you allow us in?” I spent hours crawling through their online collections to find out exactly which vessels they had, so I then I started quoting the object numbers. I was looking for a beer jug, a bread mold, or a loaf of bread.

Can you explain your theory that yeast could still be hibernating beneath the surface of these vessels?

SB: One aspect that’s important to the survival of anything in the microscopic world is the ability to hibernate when there’s no water present. Almost every microbe can do this, including the yeast in the bacteria that we have in our cultures. Yeast can survive literally indefinitely. There’ve been experiments putting yeast spores in a vacuum, in space, and then feeding them, and they come back.

So, we reasoned, if some of these things were driven into the porous ceramic matrix of these vessels that were used for brewing, raising bread, molding bread, or in the bread itself if it wasn’t completely baked — the Egyptian baking technique didn’t involve an oven, so it’s likely that some of the dough remained slightly raw — then those microbes will still be around, and we can revive them. This was the thesis.

What was your method for extracting the yeast without damaging the pottery?

SB: You want to get the old stuff without the contamination of all the modern yeast that’s floating around. If you dig a pot up out of the ground, it’s immediately contaminated by the stuff that was in the dirt, the air in the museum, the sandwiches that employees bring in, etc. If you scrape the surface of a pot, you’re just going to get that stuff, so a) you’re damaging an invaluable artifact, and b) you’re not getting what you want.

You want to get to the microbe that has been embedded and gone to sleep inside these little protective cocoons in the ceramics. So we developed a technique that is not unlike fracking, in which we inject — under pressure, using a sterile syringe and and basically a cotton ball — a special nutrient bath into the ceramic matrix. And let it sit for a bit to wake up and unbind the organisms that are dormant. We then vacuum them up in the same syringe. You can get almost all of the fluid back out of the ceramic. In the course of doing that, you’re going to get the stuff that’s deep inside.

So that’s what we did, very gently, with the sample that Serena got us access to. I went in, put on basically a full-body condom, gloves, face mask, everything sterile. We saved those samples, and I sent them off to Richard.

How can you be sure that the yeast you ended up with is really thousands of years old and hasn’t been overly contaminated by modern yeast?

SB: So we know they’re contaminated because we’re sampling them from vessels that have dirt and yeast that have settled on them over time. If we have a ton of samples — and this why Serena is trying to set more meetings, and we’re trying to improve the technique — and we keep on seeing the same organisms, then we have a pretty good bet that those are the ones that were actually driven in by the Egyptians into the ceramic.

Richard Bowman: Artificial selection [ed. note: the selective breeding of plants and animals to produce desirable traits] really messes with the molecular block method of figuring out the actual age of the yeast. But we can do a whole genome sequencing on the yeast for only about $300. That’s like magic to me. Then we can compare the genomes of these samples that we’ve obtained to current modern yeast. Even wild yeast will still have these same markers. The sequences will have significant differences the older the yeast is, compared to the newer yeast, as bakers and brewers have selected the yeast they found easier to work with.

At the bio lab, we will characterize and separate out the various organisms we harvested from the vessels and breads. We can then see what’s modern, and likely a contaminant, and what’s old. We will then make a guess, using all the samples, of what the actual Egyptian mix was. pic.twitter.com/g3WWkV8byE — Seamus Blackley (@SeamusBlackley) July 29, 2019

So most samples went to Richard, and then, Seamus, you kept a sample for yourself?

SB: I kept one in my kitchen, where I’ve taught myself how to be 1 percent as good as an ancient Egyptian baker with ancient grain. Under sterile conditions, I gave these little guys their first meal of grain in a very, very, very long time. They were in this stuff called YPD, which is the kind of universal growth medium used in biology. I poured them out into sterilized Einkorn flour, which is the most primitive grain we have around. It was a universal grain throughout Egyptian history. The cool thing is that we have verified that the Einkorn we can get is genetically identical to the Einkorn that we find in ancient sites, so it’s really like feeding these organisms Chicken McNuggets. It’s the food they like.

The yeast woke up right away. I was totally surprised. Usually, when you collect a wild yeast sample, you get a horrible, black, gross muck for a few days, and then you start to get the yeast taking over and amplifying, when you get a higher statistical percentage of yeast than other stuff you don’t want. In this case, a lot of stuff grew — some stinky stuff — but I could tell there was a ton of yeast growing right away. It was kind of remarkable. On the second day it was bubbling like a real starter. I kept feeding it for the rest of the week because I wanted to be sure that we were only seeing stuff that ate Einkorn. It was a huge pain in the ass. You have to sterilize the flour for a couple of days, make sure that no modern yeast gets into the samples while you’re feeding them. Even then, there is a bunch of modern stuff in that sample.

The thing I baked with on Sunday is for sure contaminated with modern yeast, but I’ll tell you what: it smells really different than any other sample I’ve ever had. It acted differently than any other starter I’ve ever used. And it produced a soft, super high, fluffy loaf of Einkorn and barley bread. Which, as any baker will tell you, is really impossible. Baking with ancient grains produces pucks. I’ve worked for years to be able to bake with Einkorn. That’s how hard it is. And this made it easy.

And, look, there may not be any ancient yeast in this. This could all be crazy, because we haven’t done all the science, and we’re going to. But it definitely acted different. It was really exciting.

Here is a large batch of starter, carefully made from the Old Kingdom sample, added to water and some unfiltered olive oil. The idea is to make a dough with identical ingredients to what the yeast ate 4,500 years ago. The aroma of this yeast is unlike anything I’ve experienced. pic.twitter.com/vf6QwKZmFi — Seamus Blackley (@SeamusBlackley) August 5, 2019

Was your baking process much different from modern bread making?

SB: I basically used a Greek or Roman baking process, with a basket. That has nothing to do with the way the Egyptians baked. My goal was to start getting a feel for this dough and the way the yeast acts.

How did ancient Egyptians bake bread?

SL: The way that the Egyptians actually cooked was by heating pots stacked over an open flame. In bakeries, there’s a pattern in the floor that Mark Lehner at Harvard called “egg cartons”; it’s these holes in the ground where the earth is very scorched. What the Egyptians are doing is taking those preheated bread molds — they’re kind of bell-shaped — and putting it inside the ground. They then put the bread dough into the heated pot, put a second pot on top, and cover it with ash and charcoal. The dough then gets cooked by the heated pot, rising into the second one, and you end up with this giant loaf of bread.

SB: I literally want to build that in my backyard. That’s our goal.

Tell me more about the bread that you baked.

SB: It was pungent and had an overtone of brown sugar. It was a richer, more comforting, sweeter smell than I’m used to baking with sourdough. And I’ve done a lot of sourdough baking with whole grain. The texture was incredibly soft, almost cake-like. Really beautiful, fine-grained, well-risen bread.

Whatever was in that sample made a really satisfying and rich bread. It’s super comfort food. You would not have to be a sourdough enthusiast to tell the difference. It’s very obvious. That smell of brown sugar, the way it triggers something in your brain that’s just really good — it was pretty exciting. I was very emotional late Sunday night, when that thing came out of the oven.

Can you explain the “T” you scored into the top of the loaf?

SL: The Egyptian language is gendered, a lot like French, and so the demarcation for the female is the letter T. But the letter T is actually a bread loaf, so it’s also used in the word for bread, so it’s a bit of a double entendre here.

SB: You’re the first person who got that! Fucking hell!

And here is the result. The scoring is the Hieroglyph representing the “T” sound (Gardiner X1) which is a loaf of bread. The aroma is AMAZING and NEW. It’s much sweeter and more rich than the sourdough we are used to. It’s a big difference. After this cools we will taste! pic.twitter.com/sYCJ8uP1oj — Seamus Blackley (@SeamusBlackley) August 5, 2019

Have you faced backlash from people concerned about cultural appropriation or theft?

SL: Yeah. I appreciate the sentiment they’re coming from.

SB: It comes from their anger at the fact that these artifacts have been taken out [of Egypt]. We’re trying to glorify all of this. But I understand why they’re angry. Yeah, I get it.

What’s next for this “GastroEgyptology” project?

SL: The next museum that we’re headed to is Berkeley. That’s really exciting because they actually have the collection from the Old Kingdom, the oldest we can get ahold of, whereas the collection that Seamus has been talking about is actually from the Middle Kingdom [ed. note: Blackley mistakenly wrote on Twitter that the sample dates back to the Old Kingdom of Egypt].

SB: The cool thing about this is if we can pull this off, then we’ll be baking in a way that nobody’s seen in a very long time and making a type of bread with a character and a flavor that’s going to be completely new. I have fantasies of shipping this all over the country in bags with English and hieroglyphs. We want to share it with people. We want to preserve it. And we want to bake with it. We want to teach people how to bake like Egyptians.

Lastly, a colleague and a lot of people online want to know: were any of you afraid that you would unleash some kind of pharaoh’s curse with the baking of this bread?

RB: I did have a professor look at the initial samples received and say, “Sew it up and get rid of it.”

SB: I was hoping to at least get, like, nuked out of it. The ancient Egyptian gods were pretty badass.