A new amber theory

Jan 4, 2008 09:12 GMT  ·  By

We talk about asteroid impacts or massive volcanic eruptions, but in fact the largest beasts that roamed the Earth could have been wiped out by one of the tiniest: insects. More precisely, biting, disease-carrying insects. And this proof could emerge from amber.

"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. But competition with insects, emerging new diseases and the spread of flowering plants over very long periods of time is perfectly compatible with everything we know about dinosaur extinction", said George Poinar Jr., a courtesy professor of zoology at Oregon State University, who details his theory in his new book "What Bugged the Dinosaurs? Insects, Disease and Death in the Cretaceous", written together with his wife, Roberta Poinar.

Poinar is famous for his idea of extracting DNA from insects fossilized in amber and translated by Michael Crichton for the book and movie "Jurassic Park". He is one of the most known specialists in amber fossils.

He now shows that even if catastrophic events did occur 65 million years ago, when dinosaurs disappeared, insect-carrying diseases could have finished the giant reptiles off.

"We don't suggest that the appearance of biting insects and the spread of disease are the only things that relate to dinosaur extinction. 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", said Poinar.

Amber is fossilized tree sap acting like a natural embalming agent on trapped very small animals or plant materials, keeping them in a nearly perfect 3-D form, for millions of years.

"During the late Cretaceous Period, the associations between insects, microbes and disease transmission were just emerging. We found in the gut of one biting insect, preserved in amber from that era, the pathogen that causes leishmania - a serious disease still today, one that can infect both reptiles and humans. In another biting insect, we discovered organisms that cause malaria, a type that infects birds and lizards today. In dinosaur feces, we found nematodes, trematodes and even protozoa that could have caused dysentery and other abdominal disturbances. The infective stages of these intestinal parasites are carried by filth-visiting insects", said Poinar.

"In the Late Cretaceous, the world was covered with warm-temperate to tropical areas that swarmed with blood-sucking insects carrying leishmania, malaria, intestinal parasites, arboviruses and other pathogens, and caused repeated epidemics that slowly-but-surely wore down dinosaur populations. Ticks, mites, lice and biting flies would have tormented and weakened them. Smaller and separated populations of dinosaurs could have been repeatedly wiped out, just like when bird malaria was introduced into Hawaii, it killed off many of the honeycreepers. After many millions of years of evolution, mammals, birds and reptiles have evolved some resistance to these diseases. But back in the Cretaceous, these diseases were new and invasive, and vertebrates had little or no natural or acquired immunity to them. Massive outbreaks causing death and localized extinctions would have occurred", he explained.

The insects would have also changed plant life on our planet, shifting the food basis for all dinosaurs, no matter if herbivore or carnivore. Dinosaur's plant food items, represented by seed ferns, cycads, gingkoes and other types of gymnosperms, were replaced by modern flowering plants, spread by pollinating insects. Insects can also spread plant diseases that wipe out big patches of vegetation, and can have outbreaks, erasing available vegetation.

"Insects have exerted a tremendous impact on the entire ecology of the Earth, certainly shaping the evolution and causing the extinction of terrestrial organisms. The confluence of new insect-spread diseases, loss of traditional food sources, and competition for plants by insect pests could all have provided a lingering, debilitating condition that dinosaurs were ultimately unable to overcome", wrote the Poinars.