The possibility of performing germline modifications on currently living individuals targets future generations’ health and well-being by reducing the diversity of the human gene pool. This can have two negative repercussions: (1) reduction of heterozygosity, the latter being associated with a health or performance advantage; (2) uniformization of the genes involved in reproductive recombination, which may lead to the health risks involved in asexual reproduction. I argue that germline interventions aimed at modifying the genomes of future people cannot be ethically justifiable if there is no possibility of controlling the intervention either by reversing or altering it, whenever need demands it. This argument is challenged on six different grounds: safety, population versus individual focus, spontaneous mutations, exceptionalism, the intentional pursuit of genetic diversity through germline interventions, and harm reduction potential.