T. rex was as smart as a crocodile, not an ape, according to study debunking controversial intelligence findings

Since the 1970s, most scientists have agreed that Tyrannosaurus rex was about as smart as modern reptiles.

Then, in 2023, a study by a Brazilian neuroscientist argued that T. rex had a cognitive intelligence closer to that of primates. Could this iconic dinosaur have been as smart as a baboon, or even a human? 

Probably not, finds a new study published in the journal The Anatomical Record. The international team of scientists reaffirmed the older understanding that T. rex intelligence was likely similar to that of a crocodile.

"This traditional view is likely the right one," first author Kai Caspar, a zoologist at Heinrich Heine University Düsseldorf in Germany, told Live Science. Caspar studies how cognition evolves and the different cognitive capacities between animal groups. 

To study brain biology in long-extinct Animals like dinosaurs, scientists use endocasts — or molds of the fossil skull — to estimate relative brain size and the proportion of tissue that it once held. It's not a perfect proxy, but currently it's the best model.

In modern alligators and crocodiles, the brain only occupies about 30% of the cranial cavity. In birds and mammals, it's close to 100%.

Related: Never mind outrunning a T. rex — you could probably outwalk it