The human genome contains fragments of viruses that our species tangled with in our distant evolutionary past. Now new scientific research has isolated some of the viruses that still haunt our genomes, even after millions of years of evolution. In today's Scientific American, Katherine Harmon has a great roundup of new studies of the retrovirus genes that lurks in our own genome, as well as in the genomes of other life forms.

Harmon writes:

Genetic code from retroviruses has been found to compose some 8 percent of the human genome, having been copied in during replication and left to be inherited by us and our progeny. But non-retroviral RNA viruses do not use their host's DNA to replicate-and some do not even enter the host cell's nucleus. Nevertheless, new research has turned up surprising evidence that some of these viruses are enmeshed in the genomes of vertebrates-including humans and other mammals.

One of these new studies, published online July 29 in PLoS Pathogens, has uncovered some 80 examples of viral genetic data circulating in the genomes of vertebrate species for the past 40 million years.

To discover these connections, the group ran computer analyses of 5,666 genes from all known non-retroviral, single-stranded RNA virus families against the genomes of 48 vertebrate species. The strongest matches belonged to just two virus groups: Bornaviruses and filoviruses, the latter of which includes the deadly Ebola and Marburg hemorrhagic fever pathogens.

There's a lot more to it than this, and it's well worth reading her whole article, via Scientific American