Chile pepper history has been rewritten by fossils found in Colorado

Features writer

One afternoon in 2021, a postdoctoral researcher and undergraduate at the University of Colorado at Boulder walked into the campus museum not knowing they were about to change the history of the chile pepper.

It was to be a simple introduction to the collections, recalled the researcher, Rocío Deanna. "I wanted to show him the procedures to work with fossils," she said.

The undergrad, Abel Campos, spotted something peculiar amid the rocks in the drawers. The mark was unmistakable: The bulbous cap and stem looked very much like the logo of a certain chain restaurant.

"This looks similar to the nightshades," Deanna recalled him saying, referring to the chile pepper's family of plants. Also known as the Solanaceae and including tomatoes and potatoes, that's the family Deanna has spent her career studying, specifically their evolution.

The chile pepper fossil, it turned out, was from a geologic formation spanning northwest Colorado that rose during the Eocene era, a time between 30 million and 60 million years ago.

"I was shocked," Deanna said. "A chile pepper fossil from Colorado? How is that possible?"

Like every serious "solanologist," she understood the long-held understanding: that the chile pepper evolved close to 15 million years ago in South America.

But here was this fossil suggesting the chile pepper was in North America many, many millions of years before. This was during a wet, tropical time suited for the fruit to grow.

Deanna texted a picture to a Boulder colleague and fellow solanologist, Stacey Smith.

"I was like, ‘Are you kidding me right now?’" Smith said. "I was just astonished. It was not what anyone expected. It's the wrong place, it's the wrong time. All of it seemed impossible. But yet it's so obvious that that's what that was."

The shape, indeed, was unmistakable. That was a chile pepper in present-day Colorado all right — likely the small, berrylike ones growing around South and Central Americas still today, color uncertain but likely quite spicy, and likely growing around here 50 million years ago.

Deanna went on to find a matching fossil in the Boulder collections and another at the Denver Museum of Nature and Science.

"We knew it was time to get ready to publish this thing," Smith said.

Hers, Deanna's and Campos's name were on a paper recently published by the journal New Phytologist. The findings not only blow the lid off the history of the chile pepper, but also beg the question: What do we really know about the origins of our most beloved produce?

If the chile pepper grew in such a vastly different time and place than what was previously known, what of other nightshades? These fossils take the chile pepper back about 50 million years. But could other fossils out there take it back even further? To other eras and lands?

Goes the first line of the New Phytologist paper: "Fossil discoveries can transform our understanding of plant diversification over time and space."

In this niche world of research, Deanna and Smith have seen fossils as the missing piece.

"I think everybody who works in any group of plants hopes that someone else finds fossils for them," Smith said. "It became clear that no one else was really looking for these fossils."

The reason, she said: No one has known where to look.

"They’re very unlikely to be stumbled across," Smith said.

For years, Deanna has gone stumbling. She's gone to museums and archives all around the world, from Argentina, to London, to Berlin and parts of Russia. She's sifted through rocks with vague labels and no labels at all, taking magnifying glasses and microscopes to crevices in search of any subtle hint of any nightshade, any seed or pollen.

"I planned my visit to Gainesville (University of Florida) to (view) the only fossils of nightshades from the U.S.," Deanna said, "but never imagined finding new fossils next to the University of Colorado, Boulder, where I was based."

No magnifying glass or microscope needed for this one. That was a chile pepper. "That's what was so lucky about this fossil," Smith said.

With more luck, more discoveries could be made.

Deanna has been studying this stuff for more than a decade. "I currently have more questions than when I started," she said.

A common question from the common outsider: Why should we care?

More knowledge "will translate into predictions of the future of these plants, including important crops like tomatoes, eggplants, peppers, etc.," Deanna answered. "If we know their preference between moving or evolving in the past, we can predict what is going to happen to these species in the face of climate change."

Why should we care?

Smith pondered for a moment, quiet in deep thought.

"I think it's easy to think of ourselves as a big part of evolutionary history, and the truth is we’re not. We’re this very recent arrival that's kind of made a big mess of things. But all these amazing things we use to eat and make clothes with and build with, a lot of it comes from plants that have been here a very long time."

She went on: "We’re sort of taking advantage of millions of years of evolution working without us. So everybody should thank 50 million years of evolutionary history when they eat their hot sauce."

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Features writer

Seth is a features writer at The Gazette, covering the outdoors and the people and places making Colorado colorful.

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