Did the Dinosaurs Bug Out?

Most people say that an asteroid wiped out the dinosaurs. But what if the culprit was actually something that, though much smaller, had a more lasting...sting.

Husband-and-wife entomologists George and Roberta Poinar believe that insects took down the (arguably) most ferocious species of Earth's history. As they explain in the new book, What Bugged the Dinosaurs? Insects, Disease and Death in the Cretaceous, an asteroid or volcanic eruption would not explain why the dinosaurs died off over hundreds of thousands of years. Though these catastrophic events undoubtedly had some effect on population numbers, the authors say, they don't by themselves explain the mass extinction.

The Poinars study ancient plant and insect species that were trapped in drops of amber thousands or millions of years ago. (Think Jurassic Park.) In the gut of one amber-preserved bug, they found a pathogen that causes leishmania, a parasitic disease that can take root in reptiles. In another, they found pathogens for malaria. They also studied dino feces, and found the roots of dysentery and yet more intestinal parasites, most of which are transmitted by insects.​

The tropical climate of the Late Cretaceous would have provided the perfect conditions for these bugs to thrive. Their rising numbers not only affected the dinosaurs' health, but their food supply. Thanks to the insects' pollinating abilities, the dinosaurs' traditional food sources—like ferns, cycads, and gingkoes—were slowly replaced by flowering plants. Insects and dinosaurs, the Poinars wrote, "were locked in a life-or-death struggle" for survival—and the little guys won.