I'm interested in horizontal gene transfer in bacteria, viruses, and organisms such as Bdelloid Rotifers. I've just read in Carl Zimmer's 'A Planet of Viruses' the following passage:
As a host cell manufactures new viruses, it sometimes accidentally adds some of its own genes to them. The new viruses carry the genes of their hosts as they swim through the ocean, and they insert them, along with their own, into the genomes of their new hosts. By one estimate, viruses transfer a trillion trillion genes between host genomes in the ocean every year.
It's interesting to consider the scale of DNA-swapping that has occurred given the frequency by which it happens and the evolutionary timescale.
Are there any examples of genes in the human genome that we know were deposited by viruses that would have given an evolving human a physical/mental advantage? Where did they come from? What benefit did they provide?
I'm interested in genetic additions from non-human-ancestor species, rather than the transfer of genes that occurred as mutations from other humans.