Dinosaurs, such as the iconic Tyrannosaurus rex – popularly known as T-Rex – were as intelligent as reptiles, but not as intelligent as apes, as research last year suggested. An international team of paleontologists, behavioral scientists and neurologists has reexamined the size and brain structure of dinosaurs and concluded that they behaved more like crocodiles and lizards than primates.
This is explained in a study published in the journal The Anatomical Record. Hady George, from the University of Bristol, and Darren Naish, from the University of Southampton (United Kingdom) participated in the work; Kai Caspar, from Heinrich Heine University (Germany), and Cristian Gutiérrez-Ibáñez, from the University of Alberta, and Grant Hurlburt, from the Royal Ontario Museum (Canada).
In a study published last year, it was claimed that dinosaurs like the T-Rex had an exceptionally high number of neurons and were substantially more intelligent than previously assumed. The research highlighted that these high neuron counts could directly inform intelligence, metabolism and life history, and that the T-Rex was more ape-like in some of its habits. Cultural transmission of knowledge and use of tools were cited as examples of cognitive traits he might have possessed.
However, the new study takes a closer look at the techniques used to predict both brain size and the number of neurons in dinosaur brains. The team found that previous assumptions about the size of dinosaur brains and the number of neurons they contained were unreliable.
The new research follows decades of analysis in which paleontologists and biologists examined the size and anatomy of dinosaur brains and used this data to infer behavior and lifestyle. Information about dinosaur brains comes from the mineral fillings of the brain cavity, called endocasts, as well as the shapes of the cavities themselves.
The team discovered that the size of his brain, and therefore also the number of neurons, had been overestimated. Furthermore, they show that neuron count estimates are not a reliable guide to intelligence.
To reliably reconstruct the biology of long-extinct species, researchers would need to look at multiple lines of evidence, including skeletal anatomy, bone histology, the behavior of living relatives, and trace fossils. “The best way to determine the intelligence of dinosaurs and other extinct animals is to use many lines of evidence ranging from gross anatomy to fossil footprints, rather than relying solely on estimates of the number of neurons,” says Hady. Kai Caspar adds: “We maintain that it is not good practice to predict intelligence in extinct species when all we have to go on is neuron counts reconstructed from endocasts.”
“The neuron count is not a good predictor of cognitive performance, and its use to predict intelligence in long-extinct species can lead to very misleading interpretations,” adds Ornella Bertrand, from the Miquel Crusafont Catalan Institute of Paleontology.
Naish concludes: “The possibility that the ‘T-Rex’ was as intelligent as a baboon is fascinating and terrifying, and has the potential to reinvent our view of the past. But our study shows that all the data we have goes against it.” “They were more like intelligent giant crocodiles, and that’s equally fascinating.”
