This story as I recall it was a short story in a compilation book of the 1980/1990s. The plot has a Martian cruise ship suffering a disaster in space. Only a handful of people get into a lifeboat and it is damaged enough they cannot get to Mars. They crash land somewhere in Europe at the time of the Neanderthals.
Using firearms and weapons they had on the ship they fight off the Neanderthals who in the story are not friendly at all. I do not recall why Mars never comes to the rescue but as the story progresses they have children and one by one the original people die off. And of course their children are the basis for the Cro Magnons.
I have been racking my brain for the title of the story or the title of the book it was in. Guess either my PTSD from Desert Storm is fogging my memory or maybe it's fading due to age. I know sooner or later I'll get the name of it. Thanks for the assist in any case.