Bornaviruses and Human Evolution

Wired has an article on a startling discovery in virology—that viruses other than retroviruses can attach themselves to their host DNA. Tina Hesman writes:

Bornaviruses, a type of RNA virus that causes disease in horses and sheep, can insert their genetic material into human DNA and first did so at least 40 million years ago, the study shows. The findings, published January 7 in Nature, provide the first evidence that RNA viruses other than retroviruses (such as HIV) can stably integrate genes into host DNA. The new work may help reveal more about the evolution of RNA viruses as well as their mammalian hosts.

“Our whole notion of ourselves as a species is slightly misconceived,” says Robert Gifford, a paleovirologist at the Aaron Diamond AIDS Research Center, affiliated with Rockefeller University in New York City. Human DNA includes genetic contributions from bacteria and other organisms, and humans have even come to rely on some of these genes for basic functions like fighting infections.

Retroviral segmants have been found to be involved in placental development as well and make up a sizable percentage of our DNA. I have posted about ERVs before, here and here. This just shows how "mutt"-like our DNA is and will certainly rattle some cages.