A new tooth test suggests T. rex was not cold-blooded like modern reptiles; the giant predator’s body temperature was estimated at a human-like 97°F

For years, scientists have debated one basic question: was T. rex warm-blooded, as we are, or cold-blooded, as lizards are? A new study adds direct physical evidence to that debate. The study, ‘The body temperature of Tyrannosaurus rex,’ published in Science Advances on September 16, 2026, found that T. rex had a body temperature of about 36°C (97°F), roughly the same as a human being. The research, conducted by geobiologists at UCLA, provides this figure from direct evidence in T. rex tooth fossils rather than from guesswork or growth models. This appears to be the first direct temperature estimate from a T. rex tooth, according to the study.

How scientists read a temperature from a tooth