The development of gene-editing technologies, such as the clustered regularly interspaced short palindromic repeats and associated Cas9 endonuclease system, coincides with a rapidly expanding knowledge of the role of genes in the human ageing process. This raises the prospect that, in addition to the treatment of genetic diseases and disorders, it may become possible to use gene-editing technologies to alter the ageing process and significantly extend the maximum human lifespan. Germline editing poses distinctive problems due to its implications for individual (...) members of future, unborn generations. In this essay, I wish to home in, narrowly, on a single ethical objection to extending the lifespan of future generations by editing the human germline. The objection suggests that to extend lifespans is to unethically inflict the harm of loneliness on future people. I claim that the argument rests on assumptions that ought to be rejected. (shrink)