T. rex is at the heart of the debate over dinosaur intelligence

WASHINGTON — Simply guessing the physical appearance of a dinosaur — or any extinct animal — based on its fossils is a difficult proposition, with many uncertainties. Assessing dinosaur intelligence, taking into account the countless factors that contribute to that trait, is significantly more difficult.

A study published last year by Vanderbilt University neuroscientist Susana Herculano-Hozel, which evaluated the intelligence of Tyrannosaurus rex, focusing on estimated brain size and the number of neurons in the brain, similar to those found in primates — especially baboons — caused a stir in scientific circles. .

Now, an interdisciplinary scientific team has published a rebuttal study, calling into question Herculano-Hozel's methodology and challenging her assessment of the intelligence of Tyrannosaurus rex and other large predatory dinosaurs in the branch of dinosaurs called theropods.

Instead they proposed a more holistic approach to assessing the intelligence of a T. rex or any extinct animal, taking into account brain size and number of neurons along with other factors such as the animal's anatomy and environment, data from living relatives, and fossil evidence about how it moved and navigated. A feed that offers insight into her life.

“Our main findings are that the brains of most dinosaurs, including T. rex, were similar in relative size to those of living reptiles, such as crocodiles and crocodiles. Furthermore, it is likely that their numbers of neurons were not exceptional, especially For animals in their bodies. Zoologist Kai Kaspar of Heinrich-Heine University in Germany, who studies the behavior of living animals and is lead author of the study published this week in the journal The Anatomical Record, said:

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“What needs to be emphasized is that reptiles are certainly not as stupid as commonly thought,” Kaspar added. “Their behaviors can be very complex, and the experimental data we have point to many cognitive similarities between them and mammals and birds. So, while there is no reason to assume that Tyrannosaurus had primate-like habits, it certainly had complex behaviour.” animal.”

Herculano-Hozel said she stood by her findings and called the new analysis flawed.

“The only thing in dispute is what already existed at the time of my study: what the actual size of dinosaur brains was. Even then, we're talking about the difference between a tyrannosaur brain and a baboon or ape.” “Size,” Herculano-Hozel said.

“Their conclusion hinges on one very important point: whether theropods like T. rex shared a relationship (brain-to-body size) with their warm-blooded cousins, the ostriches and chickens, or with their more distant living relatives, the crocodiles.” The former said because I compared theropods to ostriches and chickens; They now say the last,” added Herculano-Houzel.

Comparison to modern birds was also integral to the new study, Kaspar said.

A 67-million-year-old T. rex skeleton has been named "TRX-293 Trinity Dinosaur" Seen during a preview at Kohler Auctions in Zurich, Switzerland, on March 29, 2023.
A 67-million-year-old T. rex skeleton called “TRX-293 TRINITY Tyrannosaurus” is seen during a preview at Koller Auctions in Zurich, Switzerland, March 29, 2023. (Photo: Dennis Palebous, Reuters)

“It's not a trivial question.”

Caspar said there are problems with trying to measure intelligence by the number of neurons in the brain.

“The first hurdle is to estimate the actual size of the brain of the extinct animal in question. This is not a trivial question in dinosaurs. While the brain fills almost the entire cranial cavity in birds and in mammals, this is not the case for dinosaurs.” “It is a species of reptile whose brain fills only about 30-50% of the cranial cavity,” Kaspar said.

“The 2023 study assumed the existence of 100% complete dinosaurs like T. rex, and this was certainly not the case,” Kaspar added.

Caspar said it is not known how dense neurons were in dinosaur brains.

“However, when looking at living animals, we see that the number of neurons is not actually a good indicator of intelligence in the first place, intuitive though that may seem at first glance,” Kaspar added.

Dinosaurs, except for their bird descendants, disappeared 66 million years ago after an asteroid hit Earth. Over two centuries of scientific study, dinosaurs have come into better focus, although there are many doubts about Tyrannosaurus and others.

“Given the size of the brain we found, T. rex likely occupied a level of intelligence not seen in the modern world: more intelligent than crocodiles, but less intelligent than birds and typical living mammals,” said Thomas Holtz, a paleontologist at the University of Maryland. , co-author of the new study.

“Intelligence is one of the hardest things to measure even in modern animals, and many of our common assumptions don't really hold up when you actually examine what real animals do in the real world,” Holtz said.

“So when we try to estimate intelligence and cognition in ancient animals, we will encounter some difficulties. It would be nice if we could estimate just one number and reveal the full complexity of an animal's biology and lifestyle, but nature is not like that.” I do not like it.”

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