Saturday, January 12, 2008

Did mozzies, not a meteor, do for the dinosaurs?

Did mozzies, not a meteor, do for the dinosaurs?
6th January 2008

Disease-carrying mosquitoes could have killed off dinosaurs instead of a cataclysmic comet
The theory goes that dinosaurs were wiped out after an asteroid smashed into the Earth 65million years ago.

But now it has been suggested they were sent into eternity by an equally catastrophic but somewhat smaller threat - biting insects.

Disease spread by mosquitoes, mites and ticks was probably the major factor that finished off the reptiles, say scientists.

The insects could have also made it harder for dinosaurs to survive by changing the nature of plant life.

Bees and other pollinators helped promote the rapid spread of flowering plants, leading to the loss of vegetarian dinosaurs' traditional food sources. As the planteating dinosaurs declined, so would their predators.

The theory helps explain why dinosaurs took so long to die off, say husband-and - wife team George and Roberta Poinar.

According to the most widely accepted explanation, the dinosaurs vanished after an asteroid or comet hit the Earth between the Cretaceous and Tertiary periods.

Another theory is that they were driven to extinction by massive volcanic eruptions in India, which led to extreme climate change.

But George Poinar, a courtesy professor of zoology at Oregon State University, points out that they did not disappear immediately.

Their extinction was drawn out over hundreds of thousands or even millions of years.

An asteroid impact should have led to an abrupt extinction, and climate change would probably also have wiped them out in a relatively short time, he said.

But emerging diseases spread by biting insects, combined with the spread of flowering plants, and competition with insects for plant resources, was "perfectly compatible" with a lengthy process of extinction.

The Poinars outline their theory in What Bugged The Dinosaurs? Insects, Disease And Death In The Cretaceous, published by Princeton University Press.

The professor said examination of insects preserved in amber found organisms which can cause malaria, dysentery "and other abdominal disturbances".

The infections the insects carried would have caused repeated epidemics that slowly wore down dinosaur populations, which had little or no immunity.

Professor 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."

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