Fossil teeth show T. rex maintained a human-like body temperature
Chemical analysis of fossilized T. rex teeth indicates the dinosaur's body temperature was about 97°F, nearly identical to humans. This direct evidence supports a warm-blooded metabolism and helps explain how tyrannosaurs thrived in cold regions like Alaska.
The UCLA team's method examines chemical bonds preserved within tooth enamel, which form at body temperature and remain stable for millions of years. Perfecting the technique took a decade, shrinking the required sample size by roughly 90 percent before museum curators agreed to part with tiny fragments from two teeth belonging to "Thomas," the most complete T. rex skeleton in the Natural History Museum's collection.
At 97°F, the predator ran warmer than modern reptiles, which typically sit near 82–86°F, but cooler than most birds—its evolutionary descendants—which often reach 104–109°F. The measurement aligns with fossil evidence of tyrannosaurs living in Alaska, suggesting internal heat generation helped them endure environments where many reptiles could not survive.
This finding could reshape public understanding of dinosaur biology, moving beyond the sluggish, cold-blooded stereotype toward a more active, bird-like image. For paleontologists, the technique may open doors to measuring temperatures in other extinct species, potentially revising theories about ancient ecosystems and migration patterns. Museums and educators could use this concrete number to make prehistoric life feel more tangible to visitors, while researchers studying modern climate change might draw parallels between warm-blooded dinosaurs and animals currently adapting to shifting habitats.