For decades, scientists have debated the cognitive capabilities of Tyrannosaurus rex. Was it as smart as a primate, with a brain capable of complex thought? Or was its intelligence more akin to that of a crocodile, with a focus on basic instincts?
A 2023 study by a Brazilian neuroscientist argued that T. rex possessed a cognitive intelligence closer to that of primates. However, a new study published in the journal Frontiers in Ecology and Evolution challenges this notion, reaffirming the older understanding that T. rex’s intelligence was likely similar to that of a crocodile.
The international team of scientists behind the new study conducted a comprehensive analysis of T. rex brain biology, using endocasts—or molds of the fossil skull—to estimate relative brain size and tissue proportion. They found that the brain occupied only about 30% of the cranial cavity, comparable to modern alligators and crocodiles. Birds and mammals, on the other hand, have brains that occupy close to 100% of the cranial cavity.
The study also identified inconsistencies in the 2023 study, which overestimated the brain size of T. rex by assuming it filled the entire endocranial cavity. Furthermore, the previous study included non-brain structures, such as the olfactory bulb, in its brain size estimates. By standardizing body mass estimates and excluding these structures, the new study arrived at significantly different results.
The researchers estimated the number of neurons in T. rex’s brain, finding it to be between 250 million and 1.7 billion, similar to the count in crocodiles. The 2023 study, in contrast, estimated 3.3 billion neurons for T. rex, comparable to baboons.
However, the study notes that brain size and neuron count are not the sole determinants of cognitive intelligence. The number of neurons and brain size can vary greatly across animals, without a direct correlation to intelligence. For example, dolphins have relatively small brains but high neuron density and are known for their remarkable cognitive abilities.
While T. rex may have possessed the intelligence of a crocodile, the study emphasizes that this should not be considered a downgrade. Reptiles exhibit a wide range of complex behaviors, and understanding T. rex brain biology can provide insights into the cognitive evolution of modern reptiles. The study’s findings suggest that dinosaurs, despite their absence of primate-level intelligence, were fascinating creatures with their unique cognitive capabilities.
