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Mammal Brains Got Smaller During First 10 Million Years After Asteroid

By Egleze Editorial Desk · Published July 3, 2026 · Big Think · The mass extinction that accidentally created the dinosaurs | Steve Brusatte
Mammal Brains Got Smaller During First 10 Million Years After Asteroid
Big Think
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The mass extinction that accidentally created the dinosaurs | Steve Brusatte

What was said

"During the first 10 million years or so after the asteroid, the mammal brains actually got smaller relative to their bodies. So to put it very glibly, mammals were actually getting a bit dumber during the time after the asteroid. Now I know intelligence is a lot more than just brain to body size. But to be very glib about it, mammals were decreasing the size of their brain relative to their body. So what was going on? Well, it seems like what's really underwriting all of that is that the bodies of these mammals were getting so huge."

Research from Brusatte's lab using CT scans of fossil mammal skulls reveals an unexpected finding: mammals' brains got relatively smaller in the 10 million years after the asteroid as their bodies rapidly ballooned to fill ecological niches left by dinosaurs. Within 200,000 years, mammals went from cat-sized to pig-sized; within a million years, to cow-sized, with brain size lagging behind body growth.

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Attributed speaker claim

Egleze verified who said this and where. The underlying claim has not been independently established by Egleze.

Source and context

Egleze verified who said this and where. The underlying claim has not been independently established by Egleze.

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Big Think
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The mass extinction that accidentally created the dinosaurs | Steve Brusatte
Clip time
46:12
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Big Think
Big Think

The mass extinction that accidentally created the dinosaurs | Steve Brusatte

July 3, 2026 · 1h 44m · 8 Egleze moments
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