I wondered what can be the plausibility level of enhancing human abilities not through implants, but biological modifications? My story involves Mars where the church dislike more advanced AIs, and they seek to upgrade humans. While i speculate growing up in low gravity already changes humans, but what about further changes, for example cats sight, dogs smell? Could it be possible to alter a certain group of cells and avoid that the own immune system of the body destroys them? Or alter the whole body? While it were probably easier to alter the embryo, but also it is very questionable, since it cant make any decisions.