Was a 100 million year old virus the why of human pregnancy

[Carolynn]

http://www.slate.com/articles/health_an ... ?gt1=38001

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.

I had a thought -- What if it wasn't 100 million years ago, but @65 million years ago, and brought to earth on a large astroid that wiped out many living species and made a safter develpmental environment for the virus' hosts to become better and better at safely replicating it?

And part of that process was that some of the species came out on top of the food chain, also guaranteeing safer and better replication

Twilight Zone stuff then, eh? Chariots of the Gods? Destiny? Man's fascination with the stars is because part of us wants to go back? WOO WOO WOO, WOO WOO WOO.........