Koalas Are Enduring a Pandemic Like Those Our Ancestors Faced
Stopping the world's scariest diseases Dec. 6 2012 7:19 AM  Past
Pandemics Are in Our Genes  What koalas can teach us about human
evolution and disease.  (Continued from Page 1)  This ongoing
merging makes the koala retrovirus different than just about any
other virus on Earth today known to science. But it is hardly
unique in the history of life. When scientists look at the
genomes of humans and other animals, they see stretches of DNA
that bear indisputable hallmarks of viruses. In many cases, two
closely related species will share the same viral DNA at the
same spot in their genomes. That shared remnant of an ancient
parasite tells scientists that the virus infected the common
ancestor of both species. We share viral DNA with other
primates, indicating that our common ancestors were invaded by
viruses starting some 60 million years ago.  Aris Katzourakis of
the University of Oxford has tallied up all of the invasions of
retroviruses into the ge