Re: Reverse evolution in Galápagos tomato

On 6/25/2025 11:48 PM, Pro Plyd wrote:

 https://phys.org/news/2025-06-tomatoes-galpagos-quietly-de-evolving.html
 On the younger, black-rock islands of the
Galápagos archipelago, wild-growing tomatoes
are doing something peculiar. They're shedding
millions of years of evolution, reverting to a
more primitive genetic state that resurrects
ancient chemical defenses.
 These tomatoes, which descended from South
American ancestors likely brought over by birds,
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.
 In a study published recently in Nature
Communications, scientists at the University of
California, Riverside, describe this unexpected
development as a possible case of "reverse
evolution," a term that tends to be controversial
among evolutionary biologists.
 That's because evolution isn't supposed to have
a rewind button. It's generally viewed as a
one-way march toward adaptation, not a circular
path back to traits once lost. While organisms
sometimes re-acquire features similar to those
of their ancestors, doing so through the exact
same genetic pathways is rare and difficult to
prove.
 However, reversal is what these tomato plants
appear to be doing.
...
 

Solanaceae (tomatoes, potatoes, egg plant, deadly night shade) produce a toxin.  It is why peeling potatoes was so popular, and why people that that eat a lot of potatoes can exhibit some of the neurological effects of the toxin.  Cooking reduces the effectiveness of the toxin, but not a whole lot.  I was on a panel discussion on GMO agricultural products when I was a post doc at Michigan State, and we explained why things like putting an extra copy of growth hormone in a fish was not toxic or Round up resistant plants just had a naturally occurring enzyme put in them.  One member of the panel pointed out that natural breeding of crop plants had produced killer crops in the past.  Insect resistant celery and potatoes had been bred by just selecting the most insect resistant plants, and it turned out that they had selected for toxic levels of psoralen in celery that peeled the skin off the farm workers harvesting it in the first test crops, and the potatoes were found to have lethal levels of Solanaceae toxin.  The two examples were relevant because there are no regulations for testing naturally bred crops and both products almost made it out for public consumption.  The celery was abandoned because they could not harvest it.  A commercial product for the potatoes was being created and about to be marketed, but one of the researchers involved in the development of the product had kept working on trying to figure out why it was so insect resistant, and he found out that the potato had toxic levels of the toxin.  They could have poisoned millions because there are no food safety regulations for naturally occurring fruits and vegetables.  The public was worried about one additional possible antigen in soybeans, but they had no qualms about having Kiwi and Star fruit in the supermarkets with thousands of new potential antigens.
All that is happening with this tomato toxin is that one of the enzymes involved in making the toxin is reverting back to using and producing different stereo isomers of the toxin.  The ancestors had enzymes that produced one stereo isomer (had a specific physical structure), but the enzyme evolved to produce the other stereo isomer, so the toxin had a different shape.  There is no reason why this could not happen because the original enzyme had that activity.
It is just a reversion of the specific enzymatic activity.
We discussed chirality in a recent thread, and enzymes choose the chirality.  It isn't any miracle or supernatural phenomena.  Only a molecule of a specific physical structure can fit into a lot of enzymatic active sites, and stereo isomers have different physical shapes even though they have the same elemental composition.
Ron Okimoto