Wild tomatoes on the Galápagos Islands are using chemical defences reminiscent of their ancestors, according to a study published in the journal Nature Communications. The flowering plants have "started making a toxic molecular cocktail that hasn't been seen in millions of years", said the researchers from the University of California and Weizmann Institute of Science in Israel.
Tomatoes are nightshades, like potatoes and eggplants, that produce alkaloids, or "bitter toxins that protect the plants against predation", said the BBC Wildlife Magazine. The 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" largely produced by ancestral tomatoes.
Evolution usually "moves forward, adapting organisms to current conditions", said Earth.com. The "idea that it can loop back and restore long-lost traits" is "considered highly unlikely".
But these tomatoes developed the trait using the same genetic route the ancestral plants did. Researchers identified a specific enzyme responsible for the tomatoes' alkaloid production and "confirmed its ancient roots", said ScienceAlert.
The plants may be "responding to an environment that more closely resembles what their ancestors faced", said Adam Jozwiak, the lead author of the study. The eastern islands are "biologically diverse and more stable", said IFLScience. But the western islands, where the plants are producing the ancient alkaloids, are "younger, the landscape is more barren, and the soil less developed".
This looks like evolution is "going backwards", said the BBC Wildlife Magazine. But what it really shows is the "amazing flexibility of evolutionary processes". | 
