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Was the Tyrannosaur as Smart as a Monkey? Assessing a New Claim

One researcher argues that, based on bird studies, the huge predators may have had many more brain cells than we have supposed

Vanderbilt University neuroscientist Suzana Herculano-Houzel tells us, in a recent paper, that tyrannosaurs had similar numbers of brain neurons as “primates.”

But how would we know? Herculano-Houzel stats with the assumption that dinosaurs are descended from birds and makes a distinction between the theropod dinosaurs like the tyrannosaur and others:

From that assumption, Herculano-Houzel realized that theropods in particular had a similar correlation between body mass and brain size to pre-impact birds, or basal birds. From there, she used the neuron count of modern birds like emus and ostritches and applied the same rules of scaling to figure out how many neurons theropods like the T-Rex may have had.

Frank Landymore, “In terrifying news, big brained T-rex may have been as smart as primates” at Futurism (January 9, 2023) The paper is open access.

Here’s her case, in her own words:

Here are a few thoughts from other research:

First, we tend to think of the extinct vertebrate order of dinosaurs as very much like reptiles today and that reptiles cannot be smart. But reptiles today may be smarter than is generally believed. The limits may be practical rather than intrinsic.

Here’s an example: The anole lizard was found to be as capable as the tit (a small bird) in a problem-solving test for a food reward (a grub). But because anoles are exothermic (cold-blooded), they didn’t need many grubs. Not compared to the birds, anyway. Birds are endothermic (warm-blooded). So the anoles had the same problem-solving ability but didn’t need it nearly as often because they can simply shut down their metabolism instead. Of course, dinosaurs may have been endotherms like birds rather than exotherms like reptiles but the difference may not always play out as a difference in intelligence.

Intelligence tests for life forms should probably factor in issues like: How important is it for this life form to solve this problem soon?

Crocodilians (alligators, caymans, crocodiles) have been reported to use sticks as decoysplay, and work in teams.

All it really means is that endothermy and problem-solving intelligence are not the same thing.

And then there is the, by now famous, octopus: The invertebrate controls eight limbs and consequently has a huge amount of brain tissue. Perhaps that allows it to rival mammals in intelligence.

None of this shows that Herculano-Houzel’s hypothesis is correct; only that it is plausible. Predators tend to be smarter than prey, after all, and exotherms can definitely be smart. In any event, the most widely accepted thesis as to why the entire order Dinosauria went extinct is not that they were all stupid but that the planet was hit by an asteroid:

NASA keeps track of possible asteroid hits today. We aren’t immune though we do have a greater chance of creating defences than the dinosaurs did. Whether or not dinosaurs ever used tools.

You may also wish to read: Even lizards can be smart — if you catch them at the right time. But can we give machines what the lizard has by nature? What is it that we want machines to be and do under our guidance that these—often seemingly strange—life forms are and do spontaneously? The life forms do those things to stay alive. Does it matter then that machines are not alive?

Denyse O'Leary

Denyse O'Leary is a freelance journalist based in Victoria, Canada. Specializing in faith and science issues, she is co-author, with neuroscientist Mario Beauregard, of The Spiritual Brain: A Neuroscientist's Case for the Existence of the Soul; and with neurosurgeon Michael Egnor of the forthcoming The Human Soul: What Neuroscience Shows Us about the Brain, the Mind, and the Difference Between the Two (Worthy, 2025). She received her degree in honors English language and literature.

Was the Tyrannosaur as Smart as a Monkey? Assessing a New Claim