All the cells in your body, aside from somatic mutation and immunity, carry the same DNA as the fertilized egg. Species, however, have distinct DNA, and there is no plausible natural mechanism for such alteration outside of conventional biology. Biotech angels cannot be ruled out of course, but they could not just prep stem animals and leave these to abruptly differentiate later on; so they would have to continuously engineer the gene pool, which would look a lot like regular evolution, except perhaps neater.