雅思阅读 136: Proteins from the Age of Dinosaurs（恐龙时代幸存的蛋白质）

改编自 University of Liverpool / ScienceDaily（2026年5月）。雅思阅读 Section 3 难度，约 1050 词。 素材来源：https://www.sciencedaily.com/releases/2026/05/260514084421.htm

Reading Passage

A. For most of the twentieth century, a fossil was understood to be a stone. Minerals dissolved in groundwater gradually replaced the original bone, cell by cell, until the structure turned to rock while retaining its shape. By the time a specimen reached a museum drawer, every trace of the animal's own chemistry was supposed to have vanished into the surrounding sediment. That comfortable picture was shaken in 2005, when a researcher studying a seventy-million-year-old Tyrannosaurus rex noticed flexible, vessel-like fragments inside a broken bone. The finding was greeted with deep suspicion. Organic molecules of that age, critics pointed out, simply could not survive; what looked like tissue must be modern bacterial contamination, or residue from the glue and preservatives used in preparation. Two decades later, a study of an Edmontosaurus hip bone has tipped the balance firmly toward the controversial reading. The researchers believe they have shown that collagen — the main structural protein of bone — genuinely survives inside some dinosaur fossils, sixty-six million years after the animal died. The implication, if correct, is that fossils are not always the inert stones museums have treated them as; some may still carry faint chemical traces of the living animal.

B. The specimen at the centre of the new work is unglamorous to look at. It is a 22-kilogram section of the Edmontosaurus sacrum, the fused vertebrae that anchor the hips, recovered from the famous Hell Creek Formation of South Dakota. Edmontosaurus was a large, duck-billed plant-eater that browsed beside T. rex in the final marshy decades of the Cretaceous. What elevates this particular bone is the battery of techniques brought to bear on it. The Liverpool team did not rely on a single measurement. They examined fragments under cross-polarised light, where collagen's regular microscopic banding reveals itself as a characteristic shimmer. They digested samples in acid and analysed them by tandem mass spectrometry. Colleagues at UCLA identified hydroxyproline — an amino acid found almost exclusively in collagen — and, crucially, quantified it. When protein sequences were read out, the recovered fragments matched sequences already reported in another duck-billed dinosaur and in T. rex. Multiple independent lines of evidence, pointing the same way, are what converts a curiosity into a claim. The study was published in Analytical Chemistry, a journal whose reviewers are practised in the analytical techniques at issue, which is part of why it has been taken more seriously than earlier, contested reports. The Edmontosaurus sacrum was recovered from the Hell Creek Formation, the same fossil-rich rock unit that has yielded so many T. rex specimens over the last century.

C. The team's conclusion is deliberately provocative. One of the study's senior authors states that the results show, beyond reasonable doubt, that original organic molecules such as collagen occur inside some fossils, and that they refute the long-held hypothesis that any organic material found in a fossil must be contamination. This is a strong claim, and it addresses a worry that has dogged the field since the 2005 announcement. Critics had argued that soft, vessel-like structures could be made by bacteria living in the bone, or that protein fragments could have washed in from the soil. Hydroxyproline is awkward to dismiss on those grounds: it is a signature of collagen, not of generic decay. Matched sequences across three distantly related dinosaurs make contamination from a single modern source still less plausible. The researchers are, in effect, asking paleontology to take its own controversial evidence seriously at last. They are not, they are careful to say, claiming that complete proteins survive; the molecules they detect are fragments, chemically degraded but still recognisably collagen.

D. The biological prize, if the claim holds up, is considerable. Bones alone can sort dinosaurs into family trees, but they are silent on growth, ageing, physiology and disease. Traces of original protein could, in principle, reveal evolutionary relationships too subtle for bone shape to capture, and even suggest how individual animals lived and died. The researchers go further: they suggest that museums may already hold a library of overlooked material. Cross-polarised light photographs taken decades ago, on specimens never touched by modern proteomics, could show patches of collagen that were photographed but not recognised. Re-examining those collections, with mass spectrometers in hand, might turn a century of accumulated fossils into a ready-made archive of molecular data. It is a prospect that would have seemed fanciful a generation ago. If even a fraction of the specimens in storerooms around the world yield such traces, the data could resolve disputes about relationships that bone shape alone has left open.

E. A puzzle remains, and it is the one that kept sceptics sceptical all these years. Proteins are fragile; in the laboratory, they break down on scales of years to centuries, not millions of years. Why, then, did these fragments survive? The leading answer points to the mineral matrix of bone itself. Collagen fibres are wrapped in a cage of mineral crystals that may shield them from water, oxygen and microbes, slowing chemical decay to a near halt. Burial conditions matter too: rapid, deep burial in fine, anoxic sediment can outrun decomposition before it begins. Edmontosaurus fossils are already famous for exceptional preservation, some specimens retaining skin impressions so vivid that they are known as "dinosaur mummies". If mineral shielding and lucky burial really do the work, the search for original proteins should widen beyond the most spectacular specimens to the ordinary bones in ordinary drawers. The stone replica, it turns out, may still whisper of the animal itself. Recent work on non-enzymatic cross-linking — chemical reactions that lock protein fragments together without biological help — is beginning to explain how that whisper can survive so long. If those reactions do the shielding, then the search for original molecules should extend to a much wider range of fossil sites than the most celebrated "mummies".

Questions 1-4

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

List of Headings i. Why a single hip bone became the focus of a multi-method study ii. How dinosaur fossils are prepared in museums iii. A deliberately provocative conclusion iv. What collagen reveals about dinosaur diet v. The scientific prize on offer vi. How proteins could possibly survive millions of years vii. Why T. rex became extinct

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 did critics dismiss Mary Schweitzer's 2005 claim? A. They believed the tissue was likely contamination or bacterial material. B. They had never seen a T. rex bone. C. The fossil was too young to contain proteins. D. They thought dinosaurs had no soft tissue.

6. Why is hydroxyproline important? A. It is found only in modern glue. B. It is an amino acid strongly associated with collagen. C. It is a mineral used in radiometric dating. D. It indicates the bone was exposed to fire.

7. What does the study suggest about museum collections? A. Most fossils should be discarded. B. Old specimens may contain overlooked collagen that modern techniques could detect. C. Museums have hidden away all their best fossils. D. Cross-polarised photographs are unreliable.

8. According to the final paragraph, why might proteins survive so long? A. Because dinosaurs lived in cold climates. B. Because the mineral matrix of bone may shield collagen from decay. C. Because proteins never decompose. D. Because fossils are kept in air-conditioned rooms.

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 Edmontosaurus fossil studied came from South Dakota.
10. Hydroxyproline was found for the first time in any vertebrate fossil.
11. The researchers concluded that organic material in fossils is always contamination.
12. Some Edmontosaurus specimens are known for preserving skin impressions.
13. The Edmontosaurus was a carnivorous dinosaur related to T. rex.

Questions 14-15

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

The researchers propose that collagen fragments may be shielded by the mineral (14) __________ of bone, and that rapid, deep (15) __________ in fine sediment can outrun decomposition.

答案与解析

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