In the debate addressing socio-ethical issues related to human enhancement, some have suggested that technological modifications of individuals could vastly increase diversity between them. This article argues the contrary. In this thought experiment, we argue that if—as some have argued—we have a moral obligation to use technology to enhance humans and other species, and if such enhancement is understood as improving particular traits only, it might artificially make all the species in the world converge toward a specific one, which we have named the last universal common descendant. In this reductio ad absurdum, we suggest that this argument could be used to challenge the idea that it would be morally good to enhance humans and other species without considering their species limitations.