Were the dinosaurs wiped out by insects?

The Guardian, 7 January 2008

http://www.guardian.co.uk/science/2008/jan/07/dinosaurs

James Randerson, science correspondent

They were the most imposing and terrifying creatures
that have ever walked on the surface of the Earth, but
according to a new theory the dinosaurs may have been
pushed towards extinction 65m years ago by humble
insects.

During the later part of the dinosaurs’ dominion over the
land, insects underwent an explosion in diversity and in
the process dealt a double whammy to the lumbering
giants - they spread disease and contributed to a
transformation of vegetation which the plant-eating
reptiles failed to adapt to.

The hypothesis is laid out in a new book by entomologists
George and Roberta Poinar. George Poinar is a professor
of zoology at Oregon State University.

“We can’t say for certain that insects are the smoking gun,
but we believe they were an extremely significant force in
the decline of the dinosaurs,” said Poinar. “Our research
with amber shows that there were evolving, disease-carrying
vectors in the Cretaceous [period], and that at least some of
the pathogens they carried infected reptiles. This clearly fills
in some gaps regarding dinosaur extinctions.”

In the gut of one biting insect preserved in amber - fossilised
tree sap - from that era, the team has found the pathogen
that causes the parasitic disease leishmaniasis, and in another
they found a type of malaria parasite that infects birds and
lizards. By inspecting fossilised dinosaur faeces, the team
also found parasitic microbes that are carried by insects.

Apart from spreading disease, the insects were busy
pollinating flowering plants.

These gradually took over from seed ferns, cycads and
gingkoes. If herbivorous dinosaurs could not adapt to this
new diet they would have gone hungry.

Poinar believes that the most popular theory for the
dinosaurs’ demise - that a meteorite impact changed the
global climate - falls short because the extinction took
too long.

“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.”