Reverse evolution? These wild tomatoes are turning back time

Evolution is taking an unexpected turn on the volcanic islands of the western Galápagos. Wild tomato plants are producing a toxic blend of chemicals that hasn’t existed in their species for millions of years.

Somehow, these plants have started making molecules more like eggplants than the modern tomato. This bizarre twist in evolution is being studied by scientists at the University of California, Riverside.

The research team describes this phenomenon as a rare case of “reverse evolution.” That term raises eyebrows in the world of biology, where evolution is typically seen as a one-way street – not a boomerang.

Tomato evolution in reverse

Normally, evolution moves forward, adapting organisms to current conditions. The idea that it can loop back and restore long-lost traits isn’t just controversial – it’s considered highly unlikely.

Even when organisms regain something similar to an ancestral trait, they almost never do it through the exact same genetic route. But that’s what these Galápagos tomatoes seem to be doing.

“It’s not something we usually expect,” said Adam Jozwiak, a molecular biochemist at UC Riverside and lead author of the study. “But here it is, happening in real time, on a volcanic island.”

The tomatoes aren’t just making alkaloids – bitter chemicals that many nightshade plants, like potatoes and eggplants, produce for defense – they’re making an ancient version of them. And these aren’t the same ones found in cultivated tomatoes today.

A chemical clue from the past

The team collected over 30 tomato samples from across the Galápagos. On the eastern, older islands, tomatoes made the expected modern alkaloids.

But on the younger, rockier western islands, something had changed. Those plants were producing a different form of the molecule – one with a structure seen only in distant tomato ancestors and still present in eggplant relatives.

The reason? A small tweak in enzyme chemistry. Specifically, four amino acid changes in one enzyme flipped the way the plant built its alkaloid molecule.

Two molecules can have the same atoms but act completely differently depending on how those atoms are arranged. In this case, that small change meant the difference between modern and ancient chemistry.

To test the idea, the researchers re-created the enzyme genes in the lab and inserted them into tobacco plants. As a result, the tobacco plants started making the ancestral alkaloids, just like the western island tomatoes.

“Our group has been working hard to characterize the steps involved in alkaloid synthesis, so that we can try and control it,” Jozwiak said.

Nature’s harsh conditions may be the trigger

Why is this happening? The researchers think the backward direction of tomato evolution has to do with the islands themselves.

The eastern islands are older, more stable, and have richer ecosystems. The western ones are newer, harsher, and less developed. The plants there may be responding to tougher conditions by falling back on an older, stronger chemical defense.

“It could be that the ancestral molecule provides better defense in the harsher western conditions,” Jozwiak said.

To make sure this was a true throwback, the team ran evolutionary modeling using modern DNA to reconstruct what ancient tomato ancestors might have looked like. The chemistry of today’s western island tomatoes matched those early models.

Is reverse evolution real?

Referring to this phenomenon in Galápagos tomatoes as “reverse evolution” is a bold claim. There are other examples in nature – snakes regaining limbs, bacteria flipping traits – but they’re rare. This case stands out because the genetic and chemical steps are so precise and clearly documented.

“Some people don’t believe in this,” Jozwiak said. “But the genetic and chemical evidence points to a return to an ancestral state. The mechanism is there. It happened.”

And this shift isn’t just interesting for botanists. It has wider implications for other species – possibly even humans.

“I think it could happen to humans,” noted Jozwiak. “It wouldn’t happen in a year or two, but over time, maybe, if environmental conditions change enough.”

Reverse evolution as a survival strategy

The study opens a window into how flexible evolution might be. Traits we thought were gone forever may just be dormant, waiting for the right conditions to reappear.

“If you change just a few amino acids, you can get a completely different molecule,” Jozwiak said. “That knowledge could help us engineer new medicines, design better pest resistance, or even make less toxic produce. But first, we have to understand how nature does it. This study is one step toward that.”

What’s growing on the rocky edges of the Galápagos isn’t just wild tomato – it might be a preview of how life, under pressure, rewrites its own rules.

The full study was published in the journal Nature Communications.

—–

Like what you read? Subscribe to our newsletter for engaging articles, exclusive content, and the latest updates. 

Check us out on EarthSnap, a free app brought to you by Eric Ralls and Earth.com.

—–