McGonigal's Worm

A sudden, unexplained worldwide loss of fertility afflicts nearly all chordates, discovered gradually by scientists and provoking institutional, legal, and social responses including wagers on the last surviving birth. International institutes search for causes and remedies, and a testing program finds a handful of nonhuman candidates plus two humans with fertility potential. Efforts to preserve the species focus on these discoveries, while the narrative follows the scientific coordination, bureaucratic disputes, and the personal dilemmas of those chosen—notably Musha ibn Scmuel and Cecilia Clutt—as they confront pressure, ethics, and reluctance about becoming humanity's last hope.