Smart Dinosaur? T. Rex Had Crocodile-Like Intelligence and Not Ape-Like Brains, Study Claims

A new study debunks controversial claims that the intelligence of the T. rex was similar to that of apes. Instead, the study finds that these creatures had an intelligence equivalent to that of crocodiles today.

T. Rex Intelligence

Ever since the 1970s, the majority of scientists have agreed that the intelligence of the Tyrannosaurus rex was equivalent to that of modern reptiles. However, a 2023 study argued that this dinosaur's intelligence was more similar to that of primates, sparking questions about whether these dinosaurs could have been as smart as baboons or even humans.

However, a new study supports the older claim that the intelligence of a T. rex was similar to that of a crocodile.

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Crocodile-Like Intelligence

Kai Caspar, the study's first author and a zoologist from Heinrich Heine University Düsseldorf, says that it is likely that the traditional view is correct. Caspar also studies the evolution of cognition and the various cognitive abilities across different groups of animals.

To examine the biology of the brains of long-extinct animals, such as dinosaurs, scientists make use of endocasts, or fossil skull molds, to predict the relative tissue proportion and brain size. While this proxy is imperfect, it remains the best model.

For modern crocodiles and alligators, the brain occupies only roughly 30% of the cranial cavity. Among mammals and birds, however, this figure is near 100%.

Casap and his colleagues claim this was one of the main issues with the 2023 study. They note that this study overestimated the T. rex's brain size by assuming its brain covered the entire cavity. However, considering the form and shape of the available dinosaur endocasts for study, Caspar says that the ratio of brain to fluids may have been closer to reptiles than modern birds.

Another issue was the inconsistency of the data. In this 2023 study, the brain size estimates covered other structures in the head of the T. rex within the brain cavity. However, these structures were not actually part of the brain itself. The data also used a mix of adult and juvenile samples of T. rex dinosaurs.

For the new study, the researchers tidied the data by standardizing the estimates of body mass. They also excluded structures within the skull that do not play any role in neural activity.

Doing this did not lead them to replicate the 2023 study's results. Caspar shares that they reached significantly different findings.

The researchers estimated the neuron count in the brain of the T. rex using their new estimates for brain volume. They found that the neurons of the T. rex ranged between 250 million and 1.7 billion, which is similar to the number in crocodiles. In contrast, the 2023 study estimated that T. rex had 3.3 billion neurons, similar to baboons.

However, the study also notes that neuron count and brain count are not the best cognitive intelligence predictors. Such figures vary across animals but do not always imply better competence.

Caspa explains that though the T. rex likely had crocodile-like intelligence, this should not be considered a downgrade.