Posted: Fri Sep 30, 2011 5:14 pm Post subject: Was a 100 million year old virus the why of human pregnancy

http://www.slate.com/articles/health_and_science/doublex/201...

The above article claims that about 100 million years ago, a virus infected the DNA and made it possible for placental mammals to exist. As the scientist claim, the virus was able to worm its way into mammal DNA as a place it would be able to replicate itself rapidly and relatively safely.