雅思阅读 166: Taking the Temperature of a T. rex（给霸王龙量体温）

改编自 Scientific American / UCLA / Science Advances（2026年9月）。雅思阅读 Section 3 难度，约 1050 词。 素材来源：https://www.scientificamerican.com/article/t-rex-was-as-warm-blooded-as-humans-new-study-finds/

Reading Passage

A. For more than a century, the Tyrannosaurus rex of popular imagination was a giant overgrown lizard: a cold-blooded relic, lumbering slowly through the Cretaceous sun until an asteroid ended its reign. That picture has steadily dissolved. Dinosaurs are now understood as closer to birds than to modern reptiles, and many researchers suspect they generated much of their own body heat rather than basking like snakes. The obstacle has always been measurement. No living specimen of Tyrannosaurus has been available since 66 million years ago; one cannot place it on a treadmill, slip a thermometer into its mouth, or watch it shiver. Paleophysiology, therefore, has had to infer an extinct animal's inner life from the fragments it left behind — bone microstructure, growth rings, the chemistry of fossilised tissue — and each proxy brings its own uncertainties. Until recently, the best one could say was that dinosaurs were probably not the slow, cold creatures of old illustrations; pinning an actual internal temperature to one of them remained out of reach. The temptation is strong to project modern reptiles onto fossils, and for good reason: the first dinosaur skeletons, unearthed in the nineteenth century, were naturally compared to lizards, and the label "terrible lizard" stuck. A new study, published in Science Advances, claims to have crossed that threshold, recovering a body temperature for T. rex accurate enough to compare with living mammals.

B. The method behind the claim exploits a remarkable property of tooth enamel. Enamel is the hardest tissue in the body, and as it forms around a growing tooth it locks into its crystal structure the ratio of two oxygen isotopes in the fluid from which it grew. That ratio, in turn, depends on temperature: the warmer the fluid, the greater the proportion of the heavier isotope that becomes trapped. Read today on a mass spectrometer, the chemistry of fossil enamel acts as a chemical thermometer, recording the animal's body temperature at the moment the tooth mineralised. The technique, known as clumped-isotope thermometry, was pioneered by Robert Eagle, a geobiologist at the University of California, Los Angeles, who spent roughly fifteen years refining it. Its appeal lies in what it is not sensitive to: unlike estimates based on surrounding rock, the enamel thermometer is comparatively unaffected by the temperature of the environment the carcass ended up in, because the signal was fixed while the animal was still alive. "The enamel chemistry is truly recording the temperature at which it formed," says Aradhna Tripati, a UCLA geoscientist and co-author, "and 66 million years later we can read it."

C. The sample that made the calculation possible was not a complete skeleton but a scatter of tiny enamel fragments eroded from T. rex teeth in modern-day Montana. From these microscopic remains the team extracted the isotope ratios and converted them into a number: the dinosaur ran at roughly 36 degrees Celsius. That figure lands strikingly close to the normal internal temperature of a healthy human being, and far above the cool, fluctuating body temperatures of lizards sunning themselves on a rock. A predator that maintained mammalian-style warmth would have been capable of sustained activity — of pursuit, digestion and rapid growth — that a truly cold reptile of the same size could not match. The team is careful to note, however, that a single temperature is not a single metabolism: a large animal can stay warm simply by its bulk, an effect known as gigantothermy, so the result constrains the question without closing it.

D. The finding does not arrive in isolation. A 2022 study led by Jasmina Wiemann, a paleobiologist at Johns Hopkins University, had already suggested that dinosaurs spanned a range of metabolic styles, placing T. rex toward the lower end of warm-bloodedness rather than at the fevered extreme. The new temperature estimate fits neatly alongside that picture. Whereas small, active birds are extremely warm-blooded, and large dinosaurs may have relied partly on their size to retain heat, T. rex appears to have resembled a large mammal more than a small, hot bird. Wiemann, who was not part of the new work, calls it "impressively precise" and says it complements rather than overturns the earlier metabolism ranking. The picture emerging is not a simple choice between "reptile" and "machine" but a spectrum, on which different dinosaurs sat at different points. Birds, the surviving descendants of one branch of the dinosaur family, sit at the warm end, having evolved the fastest metabolisms of any back-boned animal; giant sauropods may have sat near the middle, kept warm partly by their sheer bulk. T. rex, on this map, belongs closer to a large mammal than to either extreme.

E. The broader implication is ecological. A predator holding a mammalian body temperature could, in principle, have lived almost anywhere on Earth, including polar regions that once looked too cold for reptilian beasts; Wiemann notes the result suggests T. rex could even have inhabited the ancient Arctic. The accumulating isotope evidence from several research groups is now converging on the same conclusion — that most non-avian dinosaurs were probably warm-blooded — rather than pointing in conflicting directions. Eagle intends to apply the same enamel thermometer to avian dinosaurs and to early mammalian ancestors next, using a tool that began as a roundabout substitute for a thermometer and has become, in effect, a way of listening to the metabolism of creatures that have been silent for tens of millions of years. Paleontology, it turns out, can now ask the same questions that a physiologist might ask of a living cheetah: how warm was it, and how did it keep warm? The answer, for T. rex at least, looks decidedly mammalian, and it is hard to look at a 36-degree tyrannosaur without picturing it on the move.

Questions 1-4

Choose the correct heading for paragraphs B, C, D and E from the list of headings below.

List of Headings i. A chemical thermometer locked in fossil enamel ii. How dinosaurs hunted prey in Montana iii. The recovered temperature — and what it does not yet prove iv. The anatomy of a T. rex tooth v. How the result fits earlier metabolism rankings vi. Why birds are warmer than mammals vii. An ecological picture that extends to the poles

1. Paragraph B: ____
2. Paragraph C: ____
3. Paragraph D: ____
4. Paragraph E: ____

Questions 5-8

Choose the correct letter, A, B, C or D.

5. Why must scientists use indirect methods to study dinosaur metabolism? A. Fossil bones always dissolve too quickly. B. No living dinosaur can be measured directly. C. Museums forbid testing real specimens. D. Dinosaurs were all cold-blooded.

6. What does the clumped-isotope technique measure? A. The thickness of fossilised tooth enamel. B. The ratio of oxygen isotopes in enamel that records formation temperature. C. The age of the rock surrounding a fossil. D. The speed at which a dinosaur grew.

7. What body temperature did the T. rex estimate yield? A. Roughly 36 degrees Celsius. B. Around 10 degrees Celsius. C. Exactly equal to a modern bird. D. It could not be estimated.

8. How does the new result relate to Wiemann's 2022 work? A. It directly contradicts it. B. It fits alongside it, placing T. rex at the lower end of warm-bloodedness. C. It proves Wiemann wrong about birds. D. It replaces it with a reptilian conclusion.

Questions 9-13

Do the following statements agree with the claims of the writer?

Write:

• TRUE if the statement agrees with the information
• FALSE if the statement contradicts the information
• NOT GIVEN if there is no information on this

9. The enamel thermometer is relatively unaffected by the surrounding environmental temperature.
10. T. rex is estimated to have been about as warm as a healthy human.
11. A single temperature reading by itself proves exactly how T. rex produced its heat.
12. T. rex fossils have been found in the modern Arctic.
13. Eagle spent about fifteen years developing the isotope technique.

Questions 14-15

Complete the summary below using NO MORE THAN TWO WORDS from the passage.

Fossil tooth enamel traps an isotope ratio that records the temperature at which it formed. The new estimate places T. rex near (14) __________ degrees Celsius, closer to a large mammal than to a small, hot (15) __________.

答案与解析

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