It took just five days, but we have our first paleontological controversy of 2023.
On January 5th, neuroscientist Dr. Suzana Herculano-Houzel published a study that sought to assess dinosaur intelligence by analyzing the number of neurons present in the telencephalon region of the brain. This region controls things like cognition and senses, making it useful for estimating animal intelligence. Using data from neuron counts in extant birds and reptiles, Dr. Herculano-Houzel scaled up to calculate how many neurons were present in dinosaur and pterosaur brains. In other words, Dr. Herculano-Houzel multiplied the number of neurons in living animals to fit the brain sizes of extinct species.
Dr. Herculano-Houzel found that theropod dinosaurs – animals like Allosaurus and Tyrannosaurus – had similar numbers of telencephalic neurons to modern baboons[i]. This finding led her to assert that not only were these dinosaurs’ endothermic (or “warm-blooded”), but also highly intelligent animals able to “create cultures” and even utilize tools[ii]. Further extrapolations of her results led her to posit that Tyrannosaurus rex matured between the ages of 4-5 and could live somewhere between 40-49 years.
Suffice to say, those are some pretty bold statements. So, let’s unpack!
The first thing to note is a potential methodological issue regarding scaling. Ask any paleontologist about scaling up and you’re likely to get an earful about the issues that come with it. It’s highly unlikely that any single dinosaur species had the same brain configuration as any single modern species, let alone the entire dinosaur family. Dinosaur brains displayed extreme variance, with some appearing almost bird-like while plenty of others had more crocodilian configurations[iii]. As such, scaling up from birds can lead to imprecise results.
Second, the study doesn’t explain whether size effects the number of neurons for large theropods like T. rex. Dr Herculano-Houzel mentions that other large animals, such as whales, giraffes, and elephants, have similar neuron counts, but she does not elaborate how this could affect Tyrannosaurus. Could the large number of neurons just be a by-product of T. rex’s immense size instead of its intellectual capabilities? Unfortunately, I am not well-versed in neurophysiology, so the results for me (and much of the public, I would imagine) seem a little vague.
Third, it could be that the high-neuron count of Tyrannosaurus has more to do with well developed senses than it does high cognitive abilities. Tyrannosaurids had massive olfactory bulbs, the regions of the telencephalon region responsible for smell. In addition to a keen sense of smell, Tyrannosaurids had forward facing eyes that produced binocular vision akin to that of a hawk[iv]. These sensory adaptations may have required plenty of neurons to function, possibly skewing their final neuron count. Having said that, I’m not sure how much neural activity was required by these regions of the brain, so perhaps this is not significant.
The fourth issue is in comparing mammalian brains with those of dinosaurs. Mammals and dinosaurs have very different biological systems, which means that comparing the brains between baboons and Tyrannosaurus rex could be problematic. To assume that the two had the same intelligence, you’d have to assume that their brains functioned the same. Since this isn’t the case, it may be premature to say that T. rex had primate-like intelligence.
The main issue I have with this study – as well as some paleontologists – is the estimations of Tyrannosaurus’ life history. The study estimates that Tyrannosaurus became sexually mature between 4-5 years and could live until 40, but these figures aren’t supported in the fossil record. Studies undertaken on the growth rings of Tyrannosaurus revealed that they grew slowly between birth and age 13, when it reached sexual maturity and experienced a massive growth spurt until age 18[v]. Additionally, the oldest Tyrannosaurus specimens rarely top 30[vi][vii], though this may have been a result of live-fast, die-young. In either scenario, the numbers calculated do not align with what is demonstrated in the fossil record, making them questionable estimates.
Having said this, I do think there has been a bit of an overreaction from the paleontological community. Some paleontologists have reacted with outrage and decried this study from the beginning. Did Tyrannosaurus have the IQ of a baboon? Probably not. Could it utilize tools the same way Homo Sapiens does? Absolutely not. But paleontologists have long hailed dinosaurs as being intelligent animals capable of much more complex behaviours than previously envisioned.
Take Apple TV’s 2022 docuseries Prehistoric Planet for example. On two occasions, small theropods are shown using tools – specifically fire – to hunt, and to clean their feathers from parasites. A Tyrannosaurid species – Nanuqsaurus – is shown living in a group and utilizing cooperative hunting, a behaviour typically associated with advanced cognitive abilities. Clearly, the notion of dinosaurs using primitive tools and engaging in cooperative behaviours is something that has been floating around the field prior to this study, which makes the massive controversy generated by this study feel a little unfounded.
So, while it’s true that Tyrannosaurus couldn’t build an axe, or live in a society with other Rex’s (Rexes?), it probably was smarter than we give it credit for. It may not have had baboon-like intelligence, but it could still find you if you’re hiding behind a flipped over jeep. Sorry, Dr. Grant…
Thank you for reading today’s article! If you enjoyed learning about this kind of content, then perhaps you’d like to learn about a dinosaur with an extremely low IQ and what its massive plates were for. Take care everyone!
If you would like to read Dr. Herculano-Houzel’s study, click on the link here.
I do not take credit for any images found in this article.
Header Image Courtesy of the Carnegie Museum of Natural History, found here
[i] Herculano-Houzel, Suzana. “Theropod Dinosaurs Had Primate-like Numbers of Telencephalic Neurons.” Journal of Comparative Neurology, 2022,
[ii] Herculano-Houzel, Suzana (@suzanahh). “It’s officially news: T. rex had baboon-like numbers of brain neurons, which means it had what it takes to build tools, solve problems, and live up to 40 years, enough to build a culture! Paper is just out in J Comp Neurol. Reality was actually MORE terrifying than the movies!” 5 January 2023, 4:56 EST. Tweet.
[iii] Brusatte, Stephen. Dinosaur Paleobiology. Wiley-Blackwell, 2012.
[iv] Brusatte, Stephen. Dinosaur Paleobiology. Wiley-Blackwell, 2012.
[v] Benton, M. J. Dinosaurs Rediscovered: The Scientific Revolution in Paleontology. Thames & Hudson, 2020.
[vii] Coules, Victoria. “A Tyrannosaurus Rex in Scotland: ‘Trix, the Grand Old Lady.’” Palaeomedia, 9 Sept. 2019, https://palaeomedia.blogs.bristol.ac.uk/2019/08/06/a-tyrannosaurus-rex-in-scotland-trix-the-grand-old-lady/.