Something Strange Is Happening to Tomatoes Growing on the Galápagos Islands Scientists say wild tomato plants on the archipelago’s western islands are experiencing “reverse evolution” and reverting back to ancestral traits Sarah Kuta - Daily Correspondent July 9, 2025 4:29 p.m. Scientists are investigating the production of ancestral alkaloids by tomatoes in the Galápagos Islands. Adam Jozwiak / University of California, Riverside Some tomatoes growing on the Galápagos Islands appear to be going back in time by producing the same toxins their ancestors did millions of years ago. Scientists describe this development—a controversial process known as “reverse evolution”—in a June 18 paper published in the journal Nature Communications. Tomatoes are nightshades, a group of plants that also includes eggplants, potatoes and peppers. Nightshades, also known as Solanaceae, produce bitter compounds called alkaloids, which help fend off hungry bugs, animals and fungi. When plants produce alkaloids in high concentrations, they can sicken the humans who eat them. To better understand alkaloid synthesis, researchers traveled to the Galápagos Islands, the volcanic chain roughly 600 miles off the coast of mainland Ecuador made famous by British naturalist Charles Darwin. They gathered and studied more than 30 wild tomato plants growing in different places on various islands. The Galápagos tomatoes are the descendents of plants from South America that were probably carried to the archipelago by birds. The team’s analyses revealed that the tomatoes growing on the eastern islands were behaving as expected, by producing alkaloids that are similar to those found in modern, cultivated varieties. But those growing on the western islands, they found, were creating alkaloids that were more closely related to those produced by eggplants millions of years ago. Tomatoes growing on the western islands (shown here) are producing ancestral alkaloids.  Adam Jozwiak / University of California, Riverside Researchers suspect the environment may be responsible for the plants’ unexpected return to ancestral alkaloids. The western islands are much younger than the eastern islands, so the soil is less developed and the landscape is more barren. To survive in these harsh conditions, perhaps it was advantageous for the tomato plants to revert back to older alkaloids, the researchers posit. “The plants may be responding to an environment that more closely resembles what their ancestors faced,” says lead author Adam Jozwiak, a biochemist at the University of California, Riverside, to BBC Wildlife’s Beki Hooper. However, for now, this is just a theory. Scientists say they need to conduct more research to understand why tomato plants on the western islands have adapted this way. Scientists were able to uncover the underlying molecular mechanisms at play: Four amino acids in a single enzyme appear to be responsible for the reversion back to the ancestral alkaloids, they found. They also used evolutionary modeling to confirm the direction of the adaptation—that is, that the tomatoes on the western islands had indeed returned to an earlier, ancestral state. Among evolutionary biologists, “reverse evolution” is somewhat contentious. The commonly held belief is that evolution marches forward, not backward. It’s also difficult to prove an organism has reverted back to an older trait through the same genetic pathways. But, with the new study, researchers say they’ve done exactly that. “Some people don’t believe in this,” says Jozwiak in a statement. “But the genetic and chemical evidence points to a return to an ancestral state. The mechanism is there. It happened.” So, if “reverse evolution” happened in wild tomatoes, could something similar happen in humans? In theory, yes, but it would take a long time, Jozwiak says. “If environmental conditions shifted dramatically over long timescales, it’s possible that traits from our distant past could re-emerge, but whether that ever happens is highly uncertain,” Jozwiak tells Newsweek’s Daniella Gray. “It’s speculative and would take millions of years, if at all.” Get the latest stories in your inbox every weekday.

Scientists say wild tomato plants on the archipelago's western islands are experiencing "reverse evolution" and reverting back to ancestral traits