Re: It's intriguing to speculate
"A worthy question, one which is addressed by Harry Turtledove in A Different Flesh, although Homo erectus, not Homo neanderthalis, were used in the story."
Also in "Anonymous Rex" by Eric Garcia, but in that case dinosaurs have evolved into roughly human shapes.
https://en.wikipedia.org/wiki/Anonymous_Rex_%28novel%29
And: ugh, I've read more Turtledove books than I'd like to admit. The author has some intriguing ideas but his writing leaves something to be desired.