Scientists: Biting Insects May Have Killed Off Dinosaurs

Some of the smallest animals on Earth may have been responsible for the extinction of some of the biggest.

A new book argues that the demise of the dinosaurs was due not to an asteroid impact, nor massive volcanic eruptions in India, but instead to tiny biting disease-spreading insects and arachnids — mosquitoes, mites, ticks and biting flies.

"There are serious problems with the sudden-impact theories of dinosaur extinction, not the least of which is that dinosaurs declined and disappeared over a period of hundreds of thousands, or even millions of years," entomologist George O. Poinar, Jr., said in a press release from Oregon State University in Corvallis, Ore., last week.

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Poinar's new book, "What Bugged the Dinosaurs?: Insects, Disease, and Death in the Cretaceous," co-written with his wife Roberta Poinar, explains how DNA from leishmania, a single-celled organism that causes a debilitating disease in humans and other vertebrates, was found in the gut of a biting insect trapped in amber from the Late Cretaceous.

"In another biting insect, we discovered organisms that cause malaria, a type that infects birds and lizards today," Poinar explained, adding that dinosaur feces also showed evidence of infection by parasitic worms and single-celled organisms.

The Poinars are among the world's top experts on ancient insects trapped in amber, and have long argued that DNA extracted from them would still be viable even after tens of millions of years, an idea that was picked up by writer Michael Crichton for his novel "Jurassic Park."

"We don't suggest that the appearance of biting insects and the spread of disease are the only things that relate to dinosaur extinction," Poinar added. "Other geologic and catastrophic events certainly played a role. But by themselves, such events do not explain a process that in reality took a very, very long time, perhaps millions of years. Insects and diseases do provide that explanation."

• Click here to read the full press release from Oregon State University.