AnotherQuark t1_j6p3iu5 wrote

I read once that our mammalian ancestors originally took the dna coding needed to evolve a placenta from a virus.

Apparently there's a phenomenon of dna swapping between viruses and their hosts. I realize that viruses work a lot differently than bacteria when it comes to doing what they do, and how they do it. But, i imagine it at least wouldn't be impossible for similar things to happen with other organisms.