New study shows T. rex wasn’t as smart as primates

In December 2022, neuroscientist Susanna Herculano-Houzel of Vanderbilt University published a paper Due to which there was an uproar in the world of dinosaurs.

After analyzing previous research on the brain cavities of fossil dinosaurs and the neuron counts of birds and other related living animals, Herculano-Houzel concluded that scary Tyrannosaurus Rex There may have been more than 3 billion neurons – more than a baboon.

As a result, he argued, hunters could have become smart enough to make and use tools and create the social cultures seen in present-day primates.

The original “Jurassic Park” movie shocked audiences with its pretty smart reimagining of Velociraptors to open doors, Herculano-Howell’s paper described t rex Essentially smart enough to sharpen his own shivs. The bold claims made headlines, and almost immediately attracted scrutiny and skepticism from paleontologists.

one in paper Published in “The Anatomical Record” on Monday, an international team of paleontologists, neuroscientists and behavioral scientists argue that Herculano-Houzel’s assumptions about the size of the brain cavity and the associated neuron count were baseless.

Truth t rex Scientists say the intelligence was probably much closer to the intelligence of modern crocodiles than that of primates – that’s a perfectly respectable amount of intelligence for a theropod.

“It needs to be emphasized that reptiles are certainly not as dim-witted as is commonly believed,” said Kai Kasper, a biologist at Heinrich Heine University Düsseldorf and co-author of the paper. “So while there is no reason to believe that t rex It had the habits of primates, it was certainly a behaviorally sophisticated animal.”

Brain tissue does not fossilize, and so researchers examine the shape and size of the brain cavity in fossilized dinosaur skulls to find out what their brains might have been like.

In their analysis, the authors objected to Herculano-Houzel’s assumption that dinosaur brains filled their skull cavities in the same proportions as bird brains. Herculano-Howzel analysis revealed that t rex The brain occupied most of their brain cavity, similar to that of modern ostriches.

But dinosaur brain cases more closely resemble those of modern reptiles such as crocodiles, Kasper said. For animals such as crocodiles, brain matter occupies only 30% to 50% of the brain cavity. Although brain size is not an accurate predictor of neuron number, a very small organ would have many fewer than the 3 billion neurons estimated by Herculano–Houzel.

“T. rex It turns out to be the largest dinosaur with the largest brain that we’ve studied, and it’s the largest dinosaur not closely related to modern birds, but even under our most generous estimates we’ve found 2 Couldn’t find 3 billion neurons,” Co said. Author Thomas R. Holtz, Jr. is a vertebrate paleontologist at the University of Maryland, College Park.

Furthermore, the research team argued that neuron count is not an ideal indicator of an animal’s intelligence.

Holtz explained that giraffes have about the same number of neurons as crows and baboons, but they do not use tools or display complex social behavior like those species.

“Clearly in broader strokes you need more neurons to form more thoughts and memories and to solve problems,” Holtz said, “but the sheer number of neurons an animal has doesn’t tell us what the animal is doing.” How to use it?

“Neuronal count is really equivalent to the storage capacity and active memory on your laptop, but cognition and behavior is more like an operating system,” he said. “Not all animals’ brains run the same software.”

Based on CT scan reconstruction, t rex The paleontologist said the brain was probably “a long tube with much less cortical extension than you see in a primate or a modern bird.” louis chiappeDirector of Dinosaur Institute At the Natural History Museum of Los Angeles County.

“The argument is that a t rex Would be as intelligent as a leader – no. It doesn’t make sense to me,” said Chiappe, who was not involved in the study.

Like many paleontologists, Chiappe and his colleagues at the Dinosaur Institute were skeptical of Herculano-Houzel’s original findings. The new paper is consistent with previous understanding of dinosaur anatomy and intelligence, he said.

“I’m pleased to see that my simple study has opened the way to new studies using solid data published by paleontologists,” Herculano-Houzel said in an email. “Readers must analyze the evidence and draw their own conclusions. That’s what science is all about!”

When thinking about the inner life of t rexThe most important finding, the scientists said, is that reptilian intelligence is actually more sophisticated than that of our species.

“These animals engage in play, are able to be trained and even show excitement when they see their owners,” Holtz said. “What we found does not mean t rex There was a mindless automaton; But neither was it going to organize any triceratops Tell stories of the rodeo or the duckbill that was so big but ran away.”