In a modern oven in Pasadena, Calif., this week, yeast that could be as old as ancient Egypt was used to bake an especially aromatic loaf of sourdough bread.
The baker, Seamus Blackley, was experimenting with yeast he had extracted from a 4,000-year-old Egyptian loaf. He was trying to make his own bread using the same ingredients, and some of the same methods, as the ancients.
It turned out well, and Mr. Blackley — who is also a creator of the Xbox, a physicist and a self-professed “bread nerd” — posted the results on Twitter. “The crumb is light and airy,” he wrote. “The aroma and flavor are incredible. I’m emotional.”
Thousands of people responded in a surge of interest that extended far beyond niche communities of bread nerds and yeast enthusiasts, whose interests traverse science, gastronomy and history.
Mr. Blackley is a thorough hobbyist. He collects wild yeast from medieval forests, is fluent in the language of ancient grains, and takes close-up videos while bread-making so his followers on social media can fully appreciate the texture of good dough.
And he is passionate about ancient Egyptian history.
“It’s deeply cool to me,” he said in an interview. “I think it’s really important, and we owe so much to these ancient people. And often, or maybe always, we tend to think of people living in antiquity as being simple or stupid, and of course that’s insane. They were brilliant.”
Mr. Blackley said he was surprised this week by the enthusiastic reaction to his ancient spores. Something similar happened in April, when he made a loaf of bread using a yeast strain that was said to be 5,200 years old.
He had not extracted that yeast himself and could not be sure of its exact provenance. But tweeting about the experience helped him connect with others who shared his interests, including Richard Bowman, a biologist at the University of Iowa, and Serena Love, an archaeologist, Egyptologist and honorary research fellow at the University of Queensland in Australia.
Dr. Bowman brews beer, and he got in touch with Mr. Blackley to talk about yeast. It was Dr. Bowman who devised a way for Mr. Blackley to extract yeast strains from ancient artifacts without damaging them.
And Dr. Love, who also brews beer, managed to get Mr. Blackley access to the artifacts — including ceramics that were once used to make or store beer and bread — from the Museum of Fine Arts in Boston and the Peabody Museum at Harvard.
“I had to submit all sorts of documentation, detail our methods and show that it’s a nondestructive analysis,” she said. “Once they could see that we weren’t harming the vessels, they gave us permission.”
From there, Mr. Blackley used Dr. Bowman’s method to flush out samples of yeast that had clung to the porous ceramics for millenniums.
Mr. Blackley also had a sample of actual bread from the Middle Kingdom, which came from the site of a mortuary temple for the pharaoh Mentuhotep II and is now at the Museum of Fine Arts. “There were three loaves there, as offerings, and the building was built on top of it,” Dr. Love said.
Mr. Blackley extracted the yeast, took that specimen home and used barley and einkorn flour to awaken the sleeping spores.
Yeast is a living thing — a fungus. It metabolizes carbohydrates, yielding alcohol and carbon dioxide as byproducts. (The alcohol is handy for the creation of beer, and the carbon dioxide is good for bread, as the bubbles help the dough expand.)
Once they run out of food, yeast spores can go dormant — rather than simply dying — and stay quietly viable for thousands of years until they are extracted, Dr. Bowman said.
There is a caveat: It is not yet certain that Mr. Blackley baked with an ancient yeast strain on Monday. His extractions may have been contaminated by modern spores.
So Dr. Bowman is working to verify the samples. “We need to isolate them, sequence them, and compare the genomes to the modern samples and see the genetic divergence,” he said.
Mr. Blackley said that while Monday’s loaf probably did incorporate the ancient strain of yeast, he still considered it a practice round.
“I don’t understand why everyone is so interested in this, but I’m happy that they are,” he said. “It gives us an opportunity to demonstrate good science.”
Once the samples are verified, he hopes to experiment further with baking styles that mimic the methods of ancient Egyptians. He also wants to fine-tune his spore extraction technique.
“It’s a hobby project for all of us,” he said. “This is really in the great tradition of amateur science — people doing something because they think it’s the right thing to do — and I’m very proud of that.”