We tend to think of evolution as a very linear thing that does not regress to past markers, but it turns out that might not actually be the case when life is presented with obstacles that were overcome once before. Of course, this is not easy to prove, especially when it comes to animals, but there is one species of tomatoes that might make us rethink a lot of what we know about our genetics.
For those who think that tomatoes have nothing to do with humans or animals, they would be right, and the evolution of plants has been severely influenced by farmers and scientists trying to create the perfect varieties, so the comparison is a bit unfair to begin with. But still, in the harsh volcanic terrain of the western Galapagos, wild tomatoes have managed to surprise scientists when instead of adapting to the conditions in the expected way they reactivated old traits long thought extinct, bringing ancient biochemistry back to life.
The evolution of tomatoes, an unprecedented discovery
The study broke in the Nature Communications journal, where researchers from the University of California, Riverside, and Israel’s Weizmann Institute explained that they had uncovered what they were calling “reverse evolution” in these wild tomatoes. This reversal has been chemically and genetically confirmed, which is something evolutionary biologists have rarely seen and never this clearly and clearly something that impacts the way we will now see crops.
Since the Galapagos are a hostile environment, the fact that tomatoes grew there in the first place is already quite impressive. But how they grew is even more fascinating. They have managed to call on their genetic past and revive an ancient defense mechanism, producing toxic alkaloids, bitter, defensive compounds, of a kind that have not been seen in tomatoes for millions of years.
The study focused on two types of wild tomatoe species, Solanum cheesmaniae and Solanum galapagense, which likely came to the islands from mainland South America. Scientists gathered samples from over 50 locations across the Galapagos, but the really interesting data came from the youngest, most volcanically active islands, like Fernandina and Isabela as on these newer islands, the tomatoes were making not just modern alkaloids but an older version, one that looks chemically similar to the compounds found in eggplants.
On the older, more stable eastern islands, the tomatoes were sticking to the newer forms of these chemicals, which matters because even though both versions of the alkaloid are made of the same atoms, their structures are not the same.
To test their findings, the researchers inserted these modified genes into tobacco plants, which then began making the same ancient compounds. That confirmed it was not some random mutation and that it was a deliberate genetic reactivation of an old pathway that was happening specifically in rough, younger islands, meaning the cause of the mutation is likely an environmental cause.
“Reverse evolution” is a concept that has always been met with a healthy dose of doubt from scientists. Traditional evolutionary theory says that once a trait disappears, it should be pretty much gone for good, but this study proves that under the right conditions, lost traits can come back. There have been some examples previously, like some snakes developing tiny limbs again or bacteria reactivating ancient genes, but this is the first time it has been documented with this level of chemical and genetic precision in a plant species as important as the tomatoe.
It is also the first time that it has not felt like a coincidence or an aberration from nature, but a conscious “choice” made by the plants to stay alive in an environment that is so hostile.