Some experts have long believed that the fall of a massive asteroid caused the extinction of the dinosaurs 65 million years ago. However, a new analysis by a professor of psychology at the University of Albany suggests that dinosaurs were in trouble long before the asteroid hit. Professor and evolutionary psychologist Gordon Gallup and his former student Michael Frederick, now at the University of Baltimore, argue that the emergence of toxic plants, combined with the inability of dinosaurs to associate the taste of certain foods with danger, led to their population already being dramatically reduced by the time the asteroid hit. …
Acquired gustatory aversion is an evolutionary defense found in many species, in which the animal learns to associate eating a plant or other food with negative effects, such as feeling sick. To explain the defense mechanism, Gallup uses the example of rats.
“The reason most eradication efforts have been unsuccessful is that, like many other species, they have evolved to deal with plant toxicity,” Gallup says. "When rats come across a new food, they usually only taste a small amount, and if they feel bad, they show a remarkable ability to avoid that food again because they associate the taste and smell from it with an unpleasant reaction."
What made the dinosaurs extinct?
The first flowering plants, called angiosperms, appear in the fossils long before the fall of the asteroid and right before the dinosaurs began to gradually disappear. Gallup and Frederick argue that as plants developed and toxic defenses developed, dinosaurs continued to eat them despite gastrointestinal distress. While there is uncertainty as to when flowering plants became poisonous and how long it took for the trait to spread, Gallup and Frederick note that their appearance coincides with the gradual disappearance of the dinosaurs.
In addition to studying the distribution of toxic plants during the lifetime of dinosaurs, Gallup and Frederick investigated whether birds (which are considered descendants of dinosaurs) and crocodiles (also descendants) can acquire gustatory aversion. It turned out that the birds, instead of getting used to the taste, developed an aversion to the visual features of what made them feel bad. They knew what they shouldn't eat to survive. In a previous study in which 10 crocodiles were fed a variety of meats, some of which were mildly toxic, Gallup found that, like dinosaurs, crocodiles did not learn to understand tastes.
“While the asteroid was certainly important, the psychological deficit that made dinosaurs unable to abstain from certain plants had a major impact on them,” says Gallup. "The common view of the extinction of dinosaurs associated with an asteroid impact implies that the extinction of the dinosaurs should have been sudden, but the opposite is evident: dinosaurs began to disappear long before the asteroid fell and continued to gradually disappear for millions of years after."
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