A new study suggests tyrannosaurus rex had the intelligence to match his muscles.
According to neuroanatomist Suzana Herculano-Houzel, the tiny-armed predatory dinosaurs that are often described as dumb dopes might have been as smart as modern apes — or at least had a comparable number of brain cells.
But there’s nothing like scientific controversy to ponder some big questions about intelligent beings and the electrochemical constellations inside our own heads that we still don’t fully understand.
Herculano-Houzel, the paper’s sole author, used data from living birds and modern reptiles to infer how the number of neurons changes with increasing brain mass.
She then extrapolated to predict how many brain cells T. rex could have had in his telencephalon – the most developed part of the brain, also known as the cerebrum. Comprised of two hemispheres, this piece of neural anatomy is responsible for the animal’s cognition (among other things).
Herculano-Houzel felt that T. rex had about 3 billion brain neurons packed into his 343-gram (12-ounce) brain; more than the number found in baboons. According to his calculations, another theropod dinosaur, Alioramusnicked about 1 billion brain neurons in its 73-gram (2.5-ounce) brain, which is comparable to that of a capuchin monkey.
If these numbers reflected intelligence, it “would make these animals not only giants, but also long-lived animals with flexible cognition, and thus even more magnificent predators than previously thought,” writes Herculano-Houzel, of Vanderbilt University in Nashville. published paper.
“An elephant-sized but agile carnivorous biped with macaque- or baboon-like cognition must indeed have been an extremely competent predator,” she adds.
It’s officially news: T. rex had a brain neuron count comparable to that of a baboon, meaning it had what it takes to build tools, solve problems, and live to 40 years, enough to build a culture! The paper has just been released by J Comp Neurol. The reality was actually MORE terrifying than the movies! pic.twitter.com/6HafJVHQlk
— Suzana Herculano-Houzel (@suzanahh) January 5, 2023
It’s pretty wild, to suggest Tyrannosaurus and other theropod dinosaurs were “the primates of their time”, and that involves making some assumptions to get there. But it’s where Herculano-Houzel goes next that has arguably caused even more uproar among paleontologists, biologists and neuroscientists.
Based on his findings and previous studies, Herculano-Houzel predicts T. rex would have matured quickly, lived quite a long time – more than 40 years – and had a brain capable of using tools and transmitting this knowledge to those close to him.
Their number of neurons Tyrannosaurus and possibly other theropod dinosaurs “in the cognitive domain of modern tool-using, culture-creating birds and primates,” writes Herculano-Houzel.
Cue a lot of skepticism. “Intelligence itself is already a difficult thing to study, let alone the intelligence of an extinct taxon that is unable to have its behavior observed,” said Tess Gallagher, a paleobiologist at the University of Bristol. wrote on Twitter.
“Do not mistake yourself. T. rex was probably smarter than we think, but tool-using capabilities? It’s a very big claim to make.”
Another criticism among biologists is that the size of the skull does not necessarily correspond to the volume or mass of the brain. Herculano-Houzel used estimates of brain size based on CT scans of fossilized skulls.
While Herculano-Houzel argue theropod brains filled their cranial cavity, other studies suggested that the brain of T. rex occupied only between a third and a half of its endocranial space.
Either way, brain folds, wrinkles, and synaptic connections are often considered better predictors of intelligence than the total size of the brain or even the number of cells in it.
Crows, for example, are remarkably intelligent animals with relatively small brains; they have fewer brain neurons than baboons but outperform them in cognitive tasks, said Kai Caspar, zoologist at the University of Duisburg-Essen in Germany.
“Maybe the number of neurons doesn’t make an animal’s mind and the connectome matters too?” caspar tweetedreferring to the network of connections in a given brain.
But the bony skulls are preserved, and the slimy brains aren’t, so that’s all scientists really need to do to try to imagine what the dinosaurs looked like.
Herculano-Houzel argues that estimating the number of neurons from brain mass is a method that has been applied to hundreds of species of mammals, birds, and non-avian dinosaurs, so it is robust.
But she also notes that it turns animals’ brains “into a seamless soup” of floating brain cells that, in reality, are structured in layers of tissue.
Tyrannosaurus continues to surprise us, with recent findings painting them as social animals with sleek, rustling tails that tended to hunt in packs, not alone, and compete for love. Regardless of the number of neurons in their brains, tyrant lizards love to make us think.
The study was published in the Journal of Comparative Neurology.