Evolution of the Placenta

[Patrick]

@Ashwin_s

Let me give you an example. One big novelty in mammalian evolution is the placenta. Many modern papers hypothesise that key changes required for placenta were incorporated through viral infections.
Now how does common ancestry explain anything about the development of the placenta? The true mystery is in how a viral genome turned out to be such a beneficial fit.
Hence my statement that the faster the change, the more trivial common ancestry becomes as an explanation.
Would you agree?

Can we have someone who knows something about evolution explain this? I am not an expert but I do know enough to know that you are mashing up the science. Dr. Swamidass, please help us.