"De-evolution" or "devolution" is a concept suggesting that species can revert to more primitive forms over time.

Some scientists don't accept this concept at all. They say Evolution is a continuous process of change driven by natural selection, mutation, and genetic drift. It doesn't have a predetermined direction or goal of becoming "better". 

When a species loses a trait, like the eyes of cave-dwelling fish, it's not because the species is devolving. It's because those traits became unnecessary or even detrimental in a specific environment, and natural selection favored individuals who didn't waste energy on them. Some organisms, like viruses, have evolved to become simpler and more parasitic. This is not de-evolution, they say; it's a different evolutionary pathway that can be very successful in specific niches. 

But now we have  a sort of evidence that shows de-evolution can happen.

Tomatoes in the Galápagos are quietly de-evolving

On the younger, black-rock islands of the Galápagos archipelago, wild-growing tomatoes are doing something peculiar. They're shedding millions of years of evolution, reverting to a more primitive genetic state that resurrects ancient chemical defenses.

These tomatoes, which descended from South American ancestors likely brought over by birds, have quietly started making a toxic molecular cocktail that hasn't been seen in millions of years, one that resembles compounds found in eggplant, not the modern tomato.

In a study published recently in Nature Communications, scientists at the University of California, Riverside, describe this unexpected development as a possible case of "reverse evolution," a term that tends to be controversial among evolutionary biologists.

That's because evolution isn't supposed to have a rewind button. It's generally viewed as a one-way march toward adaptation, not a circular path back to traits once lost. While organisms sometimes re-acquire features similar to those of their ancestors, doing so through the exact same genetic pathways is rare and difficult to prove.

However, reversal is what these tomato plants appear to be doing.

The key players in this chemical reversal are alkaloids. Tomatoes, potatoes, eggplants, and other nightshades all make these bitter molecules that act like built-in pesticides, deterring insect predators, fungi, and grazing animals.

De-evolved tomato species from the Galápagos. Credit: Adam Jozwiak/UCR

Tomato plant with more standard alkaloids. Credit: Adam Jozwiak/UCR

While the Galápagos are famous as a place where animals have few predators, the same is not necessarily true for plants. Thus, the need to produce the alkaloids.

What makes these Galápagos tomatoes interesting isn't just that they make alkaloids, but that they're making the wrong ones, or at least, ones that haven't been seen in tomatoes since their early evolutionary days.

The researchers analyzed more than 30 tomato samples collected from distinct geographic locations across the islands. They found that plants on eastern islands produced the same alkaloids found in modern cultivated tomatoes. But on western islands, the tomatoes were churning out a different version with the molecular fingerprint of eggplant relatives from millions of years ago.

That difference comes down to stereochemistry, or how atoms are arranged in three-dimensional space. Two molecules can contain exactly the same atoms but behave entirely differently depending on how those atoms are arranged.

To figure out how the tomatoes made the switch, the researchers examined the enzymes that assemble these alkaloid molecules. They discovered that changing just four amino acids in a single enzyme was enough to flip the molecule's structure from modern to ancestral.
They proved it by synthesizing the genes coding for these enzymes in the lab and inserting them into tobacco plants, which promptly began producing the old compounds.

The pattern wasn't random. It aligned with geography. Tomatoes on the eastern, older islands, which are more stable and biologically diverse, made modern alkaloids. Those on the younger, western islands where the landscape is more barren and the soil is less developed, had adopted the older chemistry.

The researchers suspect the environment on the newer islands may be driving the reversal. It could be that the ancestral molecule provides better defense in the harsher western conditions.
To verify the direction of the change, the team did a kind of evolutionary modeling that uses modern DNA to infer the traits of long-extinct ancestors. The tomatoes on the younger islands matched what those early ancestors likely produced.

Still, calling this "reverse evolution" is bold. While the reappearance of old traits has been documented in snakes, fish, and even bacteria, it's rarely this clear, or this chemically precise.
And this kind of change might not be limited to plants. If it can happen in tomatoes, it could theoretically happen in other species, too.
It wouldn't happen in a year or two, but over time, maybe, if environmental conditions change enough.
And 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.

Adam Jozwiak et al, Enzymatic twists evolved stereo-divergent alkaloids in the Solanaceae family, Nature Communications (2025). DOI: 10.1038/s41467-025-59290-4