Retro tomatoes: a species of the plant is evolving backward
Environmental factors may play a role


Some tomatoes have evolved to possess the characteristics of their ancestors. While it is rare, there have been instances of species displaying traits from further back in evolution. But for the first time, scientists have now been able to prove it through genetic evidence. And there's potential for similar evolutionary changes in the future as the environment changes, even in humans.
Blast from the past
Wild tomatoes on the Galápagos Islands are using chemical defenses that are reminiscent of their ancestors, according to a study published in the journal Nature Communications. The flowering plants 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," said a statement about the study.
Tomatoes are nightshades, like potatoes and eggplants, and nightshades produce alkaloids, which are "bitter toxins that protect the plants against predation," said the BBC. Researchers discovered that tomatoes "on the older eastern islands produced alkaloids found in modern cultivated tomatoes," while tomato plants "on the younger western isles were making unique alkaloids." And the latter alkaloids were largely produced by ancestral tomatoes.
Subscribe to The Week
Escape your echo chamber. Get the facts behind the news, plus analysis from multiple perspectives.

Sign up for The Week's Free Newsletters
From our morning news briefing to a weekly Good News Newsletter, get the best of The Week delivered directly to your inbox.
From our morning news briefing to a weekly Good News Newsletter, get the best of The Week delivered directly to your inbox.
"Some people don't believe in this," Adam Jozwiak, a molecular biochemist at the University of California, Riverside, and the lead author of the study, said in the statement. But the "genetic and chemical evidence points to a return to an ancestral state. The mechanism is there. It happened."
Researchers deemed the phenomenon a possible case of "reverse evolution." Usually, evolution "moves forward, adapting organisms to current conditions," said Earth.com. The "idea that it can loop back and restore long-lost traits isn't just controversial — it's considered highly unlikely."
The case of the tomatoes is especially interesting, as the plants developed the ancestral trait using the same genetic route the ancestral plants did. The researchers pinpointed a specific enzyme responsible for the tomatoes' alkaloid production and "confirmed its ancient roots," said ScienceAlert. Species can sometimes "re-acquire features similar to those of their ancestors," said the statement, but "doing so through the exact same genetic pathways is rare and difficult to prove."
Back to the future
Reverting to an ancestral genetic trait could be a response to the harsh Galápagos environment. "The plants may be responding to an environment that more closely resembles what their ancestors faced," Jozwiak said to the BBC. The geography supports that claim. The eastern islands are "biologically diverse and more stable. Here, the tomatoes "produced modern alkaloids," said IFLScience. On the other hand, the western islands, where the plants are producing the ancient alkaloids, are "younger, the landscape is more barren, and the soil less developed."
This phenomenon may not be exclusive to tomatoes. It has also been seen in snakes, fish and bacteria, though it's "rarely this clear or this chemically precise," said the statement.
This looks like evolution is "going backward." But what it really shows is the "amazing flexibility of evolutionary processes," said the BBC. And given the reality of climate change, other species may eventually go through similar processes. "I think it could happen to humans," said Jozwiak. "It wouldn't happen in a year or two but over time, maybe, if environmental conditions change enough."
A free daily email with the biggest news stories of the day – and the best features from TheWeek.com
Devika Rao has worked as a staff writer at The Week since 2022, covering science, the environment, climate and business. She previously worked as a policy associate for a nonprofit organization advocating for environmental action from a business perspective.
-
Scientists are the latest 'refugees'
In the spotlight Brain drain to brain gain
-
Bacteria can turn plastic waste into a painkiller
Under the radar The process could be a solution to plastic pollution
-
Scientists want to regrow human limbs. Salamanders could lead the way.
Under the radar Humans may already have the genetic mechanism necessary
-
A potentially mutating bat virus has some scientists worried about the next pandemic
Under the Radar One subgroup of bat merbecovirus has scientists concerned
-
The treasure trove of platinum on the moon
Under the radar This kind of bounty could lead to commercial exploitation
-
Possible dwarf planet found at edge of solar system
Under the radar The celestial body has an unusual orbit
-
Is the world losing scientific innovation?
Today's big question New research seems to be less exciting
-
Full moon calendar: dates and times for every full moon this year
In depth When to see the lunar phenomenon every month