T. Rex may have been terrifyingly smart with a baboon-like brain capacity

The age of dumb dinosaurs is over, according to new research that claims theropods like the ‘tyrant’s key’ Tyrannosaurus rex actually had the same number of brain neurons as modern primates. By comparing the brains of these animals to modern birds, the study mathematically calculated how many neurons could possibly be crammed into theropod brains, and the results point to them being capable of problem solving, tool use and even culture. So much for the stupid reptilian brain.

Soft tissue is quite difficult to find when dealing with prehistoric remains, so how can researchers assess organs such as the brain of an animal preserved in the fossil record? Neuroscientist and study author Suzana Herculano-Houzel decided to turn to the dinosaurs still living today for insight: modern birds.

In recent years, we’ve learned that the old “bird brain” insult isn’t really valid, as modern birds have densely packed neurons that mean that even though their brains are tiny, they’re actually quite cognitively capable. Given that they are descendants of dinosaurs, it assumes you can look for commonalities through something known as phylogenetic bracketing, which uses the evolutionary tree to infer the likelihood of unknown traits in extinct organisms.

If we follow this line of thinking, it would be possible to assume how many neurons a bird like an emu has and then scale up the size of the brain and the number of neurons to fit the skull cavity of a behemoth like T. rex. But, as Herculano-Houzel explained in a video shared with Twitterthis implies assuming proportionality.

“First, you must have good reason to believe that the same proportionality that applies to birds already applied to dinosaurs as T. rexwhich is what I just did.”

In her paper, Herculano-Houzel explains how the key to making reasonable assumptions about proportionality depends on considering dinosaurs as separate groups. It was once the case that different groups such as sauropods and theropods were lumped together, but as time has passed and discoveries have been made, it is becoming increasingly clear that there are few rules that can be applied to the Dinosaurs as a whole.

However, when Herculano-Houzel looked at theropods, it became clear that these animals had brain sizes similar to those you would expect to find in a bird of the same size. As such, she says it’s reasonable to expect the same scaling rules to apply to T. rex as with today’s emus and ostriches.

Using math, Herculano-Houzel was then able to estimate how many neurons theropods like T. rex had, which turned out to be similar to modern primates. This implies that they were not stupid, and may have lived to be around 40 years old, as Herculano-Houzel’s previous research has found that neuron number is associated with life history.

Living for decades with billions of neurons could therefore have given these animals the time and thinking power to solve problems, use tools and even have culture. The theory would certainly be in line with the recent makeover T. rex got in Apple TV+ Prehistoric planetwhich showed its softer side as a male and female engaged in a touching mating display.

Herculano-Houzel’s estimates set T. rex in line with the brain capacity of baboons, only they were massive with giant, skull-crushing teeth. It wouldn’t quite do it Jurassic Park Update?

“I have a whole new respect for dinosaurs,” concluded Herculano-Houzel. “Also: you can be thankful for that asteroid now – otherwise life would be much different, perhaps led over these days by T-rexes who had figured out how to cook their food and afford as many neurons as we humans have now.”

“Yes, that’s a movie I’d like to see.”

The study was published in The Journal Of Comparative Neurology.

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