The oddest question you have (probably) heard today.

[popeyespappy]

I'm not arguing that we can't do some wonderful things, but what you describe is not nearly enough to do what is suggested in the OP. You say "target cells" and talk about introducing viruses that do not replicate into a host. Therein lies one of countless problems with the premise. He's talking about a mother passing on a virus to a fetus in her body -- a virus that would change the fetus into a different species, after having moved through the mother's body into the womb. Yes, the virus is genetically engineered, but he spoke of no intricate introduction process, though I stand by the fact that intricate introduction into the fetus or no, it is not possible to change a monkey to a whale in the womb. On top of all of this, how do we know that a human body would not reject an inhuman body as a foreign object, if such a change actually took place? Really, just because something could hypothetically work on a cellular level does not mean it will work in the womb, with no fiddling done before insemination -- meaning natural reproduction.

I think one of the points I’m having difficulty trying to make is this. The mother doesn’t have to pass the virus to her children. If an engineered virus was introduced into the mother that targeted the germ cells that are embedded in the substance of the ovaries from which eggs cells are formed, all the genetic changes could be made to the mother. If the genetic changes only affected gestational processes they would have no effect on the well being of the mother. She could then pass the modified DNA as opposed to the virus to any offspring via natural processes.

As far as monkeys to whales goes try thinking more along the lines of lions to tigers. Different species don’t have to be that different. Lions and tigers are separate species. However they are not that different. They are capable of interbreeding. Some ligers are even capable of producing viable offspring.

The main point of my first post in this thread was just that we already have some of the technology required for such an undertaking available to us now. While there are many obstacles remaining they are not insurmountable. The solutions too many of them could possibly be available within our lifetime. The solutions to most of them probably will be available within a few generations. That is if we can manage to keep from sending ourselves back to living in the Stone Age before then.