|"Space invader" DNA infiltrated mammalian genomes - http://www.newscientist.com/channel/life/dn14992-space-invader-dna-infiltrated-mammalian-genomes.html?feedId=online-news_rss20|
New Scientist article: Parts of mammalian DNA are so alien they have been dubbed space invaders by the researchers that found them.
We normally get our genes vertically -- handed down from our parents and theirs before them. Bacteria get theirs in this way too, but also horizontally -- passed from one, unrelated individual to another.
Now biologists have found the unexpected: horizontal gene transfer has occurred in mammals and amphibians too.
The culprit is a kind of parasitic DNA found in all our cells, known as a transposon that jumped sideways millions of years ago into several species by piggybacking onto a virus.