Usually, evolution moves forward—organisms adapt and rarely go back to old traits, especially using the same genetic pathways. But researchers have spotted something unusual in Galápagos tomatoes.
It’s almost as if they’re tapping into their ancestral genes and evolving backward, a rare and surprising twist in nature’s playbook.
Long ago, birds likely carried South American tomato seeds to the Galápagos Islands. Now, those island tomatoes are doing something strange—they’ve started producing a toxic chemical mix not seen in modern tomatoes but more like what’s found in eggplants.
In a surprising study, scientists from the University of California, Riverside, say this could be a rare case of reverse evolution, where plants are reviving ancient traits that disappeared millions of years ago.
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It’s unexpected, it’s bizarre—and it’s happening right now, on a volcanic island in the Pacific.
Alkaloids are bitter chemicals found in tomatoes, potatoes, eggplants, and other nightshades. They act like nature’s built-in bug spray—helping protect plants from insects, fungi, and hungry animals.
In the Galápagos, where animals don’t pose much of a threat, you might think plants have it easy. But they don’t—plants still face intense pressure from pests. That’s why Galápagos tomatoes are reviving their chemical defenses.
Scientists began studying this because alkaloids can be harmful to humans in large amounts. By understanding how and why these compounds are produced, researchers hope to keep crops safe from both pests and people.
Researchers studied over 30 Galápagos tomato samples from across the islands and uncovered something surprising. On the eastern islands, the tomatoes produce the same alkaloids as today’s cultivated varieties. But on the western islands? The tomatoes are making a throwback version—alkaloids with a chemical signature closer to ancient eggplant relatives from millions of years ago.
What’s the secret behind this odd split?
It’s all about stereochemistry—how atoms are arranged in 3D space. Even if two molecules have the same atoms, their shapes can give them totally different behaviors.
To uncover how Galápagos tomatoes flipped back to an ancestral state, the team looked at the enzymes behind their bitter alkaloids. They found that just four amino acid changes in a single enzyme were enough to switch the chemistry from modern to ancient.
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To prove it, the team recreated the enzyme genes in the lab and inserted them into tobacco plants—those plants immediately started making the old-school compounds.
Even more intriguingly, the shift wasn’t random—it matched the islands’ geography. Older, eastern islands hosted tomatoes with modern alkaloids, while younger, western islands produced plants with ancient chemistry, perhaps shaped by harsher conditions.
The tough conditions on the younger Galápagos Islands might be pushing tomatoes to tap into ancient chemistry. Scientists suspect these older alkaloids offer better defense in harsh environments.
To test the theory, the team ran evolutionary models using modern DNA to predict what ancient tomatoes were like—and found that the western island plants match those ancient traits remarkably well.
This kind of “reverse evolution” is rare, especially with such precise chemical changes. But the evidence is strong: with just a few tweaks to a single enzyme, these plants rewound their biology by millions of years.
And it raises a provocative idea—if tomatoes can do it, could other species too? Even us?
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While it wouldn’t happen overnight, the study suggests evolution isn’t a one-way street. Lost traits might reappear. Ancient genes might awaken, especially when the environment pushes life to adapt in unexpected ways.
As researcher Jozwiak puts it, “If you change just a few amino acids, you can get a completely different molecule. 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.”
Journal Reference:
- Jozwiak, A., Almaria, M., Cai, J., et al. Enzymatic twists evolved stereo-divergent alkaloids in the Solanaceae family. Nat Commun 16, 5341 (2025). DOI: 10.1038/s41467-025-59290-4
