Wild Tomatoes in Galápagos Challenge Evolution’s Forward Path

Researchers have made a groundbreaking discovery in the Galápagos Islands that suggests the phenomenon of “reverse evolution” may be occurring in a wild tomato species. The plant, scientifically known as Solanum pennellii, was first studied in detail in 2024 during an investigation into alkaloids—natural compounds that can serve as pesticides. The findings challenge traditional views of evolutionary processes, which typically suggest that species only move forward in their development.

During the study, scientists observed that Solanum pennellii from the younger western islands of the archipelago were producing alkaloid compounds that modern tomatoes have not exhibited for millions of years. In contrast, samples taken from the eastern, older islands displayed a more advanced defense system. This led researchers to conclude that rather than being left behind in the evolutionary timeline, the younger plants may have reverted to ancestral traits.

Adam Jozwiak, a molecular biochemist at the University of California, Riverside and a contributor to the study, emphasized the rarity of observing reverse evolution. “It’s not very common to see reverse evolution,” he commented. The research, published in the journal Nature Communications in June, indicates that environmental pressures may have prompted these tomatoes to revert to an earlier evolutionary state.

Uncovering Ancient Traits

The physical appearance of the western Solanum pennellii differs from that of its eastern counterparts, featuring a purplish hue and darker vines. However, the most significant differences lie at the molecular level. Analysis of over 30 tomato samples revealed that the western specimens shared a molecular fingerprint with eggplants, another member of the nightshade family. While modern tomatoes have lost the ability to produce eggplant alkaloids, the wild tomatoes from the Galápagos appear to have re-evolved these ancestral traits.

Jozwiak noted that understanding these molecular changes could potentially lead to advancements in crop development, stronger pesticides, and even medical applications. He stated, “By studying these molecules, we can design better crops for eating and explore how evolution may be more flexible than previously thought.”

The Solanum pennellii species is believed to have arrived in the Galápagos Islands between one and two million years ago, likely transported by birds. Evolutionary changes among these plants must have occurred within the last half million years, which correlates with the emergence of the younger islands due to volcanic activity. The environmental conditions on the younger islands, characterized by less developed soil and a more barren landscape, may have influenced this intriguing evolutionary reversal.

Evolutionary Implications

The discovery raises important questions about evolutionary biology, particularly regarding the concept of reverse evolution. While it is well-documented that species can exhibit island-specific traits—such as the finches observed by Charles Darwin in 1835—the term “reverse evolution” remains controversial among biologists. Jozwiak pointed out that evolution is not a linear process, asserting, “Change is change,” and that adaptations can occur in various directions.

Eric Haag, a professor of biology at the University of Maryland, highlighted that the findings challenge Dollo’s Law, which posits that once a trait has been lost in evolution, it cannot be regained in the exact form. He noted that the specific amino acid changes observed in the Galápagos tomatoes are some of the same ones found in much more distant ancestors, suggesting a complex interplay in evolutionary processes.

The implications of this research extend beyond tomatoes. Jozwiak remarked on the potential to study other species and consider whether similar evolutionary reversals could be occurring more widely, including in human biology. For instance, there are rare cases of humans born with rudimentary tails—traits that were present in primate ancestors millions of years ago.

As research continues, scientists hope to uncover more about the evolutionary mechanisms at work. Jozwiak expressed his intention to return to the Galápagos Islands to investigate further the traits influenced by these ancestral molecules, including the plants’ interactions with insects and their decomposition rates.

The findings surrounding Solanum pennellii not only provide a unique perspective on evolutionary biology but also emphasize the adaptability of nature. As scientists delve deeper into the complexities of evolution, the Galápagos Islands continue to serve as a rich field for exploration and discovery.