Have movies and most conventional paleontologists got it all wrong? T. rex and other theropod dinosaurs (the meat-eaters) are often portrayed as intelligent predators that can outmuscle and outsmart their opponents. But is that really supported by science?

A recent study found no compelling evidence that the relative brain size of large theropods, like Tyrannosaurus rex, was any different from that of modern reptiles, like crocodiles and alligators.¹ The new study published in The Anatomical Record found their brains were just bigger because their body size was bigger.¹

Possibly even more importantly, the study also found that brain endocasts of dinosaur skulls likely overestimate the size of their brains because the brains of extant reptiles do not completely fill their skull cavities. Doug Wylie, one of the co-authors of the paper, said, “The first time I dissected an alligator brain, I took the top of the skull off and I went, ‘Where is the brain?’ Because there is this big space in there.”² Instead, cerebrospinal fluid takes up some of the cavity. This has likely caused an overestimation of the size of many theropod brains, suggesting the need for reevaluation.

Furthermore, this same study disputed a 2023 report that T. rex brains had more neurons than an extant primate, like a baboon. Instead, they found that reptile brains are packed more loosely with neurons compared to both birds and mammals. Reptiles, like T. rex, had fewer connections and circuits in their brains, likely making them less intelligent.²

Darren Naish, another co-author of the study, said, “The possibility that T. rex might have been as intelligent as a baboon is fascinating and terrifying, with the potential to reinvent our view of the past. But our study shows how all the data we have is against this idea. They were more like smart giant crocodiles, and that’s just as fascinating.”²

This study confirms that dinosaurs were not birds or even bird-like. The brains of theropods were shaped and sized more like today’s reptiles. And many of their measured sizes are likely overestimated since much of the brain cavity was likely filled with fluid.

Current data on T. rex brain size and shape indicate their intelligence, thought processing, and senses were probably very similar to alligators and crocodiles.^3,4 Some dinosaurs may have been able to smell really well, but they could not perform complex tasks.

God designed dinosaur brains that were perfectly suited for their lifestyles and body size when He created dinosaurs on Day 6 of the creation week (Genesis 1:25).

References

1. Caspar, K. R. et al. 2024. How smart was T. rex? Testing claims of exceptional cognition in dinosaurs and the application of neuron count estimates in palaeontological research. The Anatomical Record. Published on anatomypubs.onlinelibrary.wiley.com April 26, 2024, accessed April 29, 2024.
2. Baisas, L. 2024. T. rex was probably about as intelligent as a crocodile. Popular Science. Posted on popsci.com April 29, 2024, accessed April 29, 2024.
3. Clarey, T. 2015. Tyrannosaurus rex Was No Birdbrain. Acts & Facts. 44 (8): 15.
4. Clarey, T. 2015. Dinosaurs: Marvels of God’s Design. Green Forest, AK: Master Books, 130.

Stage image: Picture of T. rex brain endocast from Tim Clarey
Stage image credit: Copyright © Institute for Creation Research

* Dr. Clarey is the director of research at the Institute for Creation Research and earned his doctorate in geology from Western Michigan University.