“Only Human” by Gareth Roberts (2005) — Doctor Who
Synopsis
A “dirty” rip in time and a Neanderthal in 21st Century London. That’s enough to draw the Doctor’s attention. However, whenever and wherever he came from, the Doctor can’t get Das the Neanderthal back to his own time without the effects of time travel killing him, so the Doctor enlists Captain Jack Harkness to mind him for a month to acclimate him to the 21st Century while the Doctor and Rose investigate the past, only to find a party of scientists from the future experimenting on humanity’s ancestors.
