The Tyrannosaurus Rex was an imposing predator: four meters tall by 12 meters long, eight tons in weight and a mouth full of enormous sharp teeth, making this dinosaur one of the deadliest carnivores that have ever inhabited our planet. But what about his mental abilities? In this regard, there is actually an ongoing heated debate in the scientific community: just last year, in fact, a study by the neuroscientist Suzana Herculano-Houzel, of Vanderbilt University, had suggested the possibility that dinosaurs like T. Rex had an exceptional density of neurons in their brain, sufficient to guarantee them intellectual abilities at least equal to those of a primate such as the baboon. A statement, however, greeted with a strong dose of skepticism by many paleontologists, and which today is contradicted by the results of new research, just published in the journal The Anatomical Record.
Suzana Herculano-Houzel's study was based on the analysis of the brains of the closest relatives of dinosaurs that still inhabit our planet: birds. Starting from the assumption that the relationship between the size of neurons and the size of the brain of dinosaurs was the same as that observed today in large birds such as ostriches, the neuroscientist calculated the quantity of neurons that could be contained in the brain of a dinosaur like the T. Rex, arriving at the conclusion that the number was extremely high. Enough, as we said, to guarantee a high intelligence to these dinosaurs, comparable to that of primates such as baboons, intelligent monkeys, capable of using tools and creating, and transmitting, cultural traditions.
A very different image from the classic one of dinosaurs all muscles and little brains. Certainly intriguing, but also strongly opposed by many paleontologists and experts in the field. “There were many of us who thought that it was necessary to clarify the question,” explains Cristian Gutierrez-Ibanez, a biologist at the University of Alberta who participated in the new study that disproves the exceptional intelligence of dinosaurs. “Because the news had appeared in the press, and it is easy to be bewitched by this pop idea of a super smart T. Rex, who knows how to use tools and has a culture”.
The biologist then joined forces with a handful of colleagues from around the world, and searched for Heculano-Houzel, finding several errors in the neuroscientist's hypotheses and conclusions. Starting from the assumption that the brain of dinosaurs was similar to that of modern birds. Dinosaurs – write the authors of the new study – were in fact reptiles, and the brains of reptiles are very different from those of birds. For example, it does not fill the entire cranial cavity as happens in birds, but is surrounded by a considerable amount of cerebrospinal fluid, which takes up space and reduces the space available for the neurons.
Another important aspect concerns the relationship between brain size and body size of animals. “We don't know why – explains Gutierrez-Ibanez – but larger animals also need more neurons”. A T. Rex, therefore, likely employed a large portion of its brain to control its enormous body, leaving little gray matter available to develop higher cognitive functions, such as using tools. A baboon, which weighs between 14 and 40 kilos, however, only needs a minimal fraction of the same neurons to control its vital functions and movements, and with a decidedly smaller brain it still has many extra neural cells to dedicate to cognitive functions more refined.
For these and other reasons, the authors of the new study believe that comparing the intelligence of a T. Rex to that of a baboon is incorrect. According to them, it is more plausible that the king of dinosaurs had an intelligence comparable to what we see in crocodiles today. Absolutely sufficient for the needs of the most fearsome predator that has ever lived on Earth, but qualitatively inferior to that of the animals that survived it, such as mammals and birds.