The Sun

IT’S the question that has plagued scientists for years – why did dinosaurs die out?

In new book My Beloved Brontosaurus, US fossil expert Brian Switek documents the weirdest explanations for the extinction of the prehistoric beasts.

Here Amy Jones runs through some of the top theories.

CATERPILLARS: The creepy crawlies are thought to have evolved at the time of the dinosaurs. They could have stripped plants of their leaves, a valuable food to the plant-eating monsters. The plant eaters would have gone hungry and eventually died out. If the plant eaters died, then the meat eaters would die from lack of food.

STRESS: German scientist Heinrich K Erben discovered that the shell thickness of a certain type of dinosaur had decreased over time. He suggested the warm climate 65million years ago could have caused overpopulation of dinosaurs, leading to stress, which causes hormonal imbalances, making females lay eggs with thin shells.

STUPIDITY: There is evidence that many of the large dinosaurs had very small brains compared to their body size. With such a small brain capacity, it’s possible they wouldn’t have been able to compete with faster-thinking animals.

ASTEROID IMPACT: The most accepted extinction theory is that an asteroid between four and nine miles wide struck the earth on the tip of Mexico’s Yucatan Peninsula. The comet would have sent clouds of dust and steam into the atmosphere and caused huge forest fires, tidal waves, severe storms and eliminated all sunlight. The dinosaurs stood no chance without sunlight and plant life.

This idea was first postulated in 1980 by father and son Luis and Walter Alvarez of the University of California at Berkeley.

DISEASE: A deadly and contagious disease may have circulated among the dinosaurs. Every population of dinosaurs had its own parasites and diseases which they developed immunity to. But the lowering of sea levels meant the beasts could migrate and share diseases.

VOLCANIC ACTIVITY: A huge increase in volcanic activity 65million years ago could have poisoned the Earth’s atmosphere, making the climate unsuitable for the creatures. And immense clouds of dust could have blocked sunlight, leading the atmosphere to cool to an inhospitable level.