When I first began writing Nightsong about 10 years ago, there were many theories about why our ancient cousins went extinct. As a novelist, I chose my own theories, based on what might work in the story and my own gut feelings.
For example, one theory intrigued me. Is it possible that the partnership of humans with wolf-dogs may have given Homo sapiens an advantage over the Neanderthals? With the help of these dogs, early modern humans may have outhunted Neanderthals. Pat Shipman advances this theory in her book The Invaders: How Humans and Their Dogs Drove Neanderthals to Extinction. These wolf dogs (not hybrids of wolves and dogs but rather a distinctive group of ancient wolves) could track animals from their scent, run much faster than humans, and were pack animals. If the hunters killed a mammoth, the wolf dogs could chase off scavengers (cave hyenas, etc.) that competed with the modern humans.
The wolf dogs would have been able to track Neanderthals to their caves or wherever they lived. This is the scenario I envisioned in my novel. Imagine you are a Neanderthal and you see these strange humans, who are slighter than you and have baby faces (as compared to the Neanderthal face) but they are accompanied by huge wolf-dogs barking and baring their teeth, dogs that seem to be partners with and obey the strange humans. A very scary vision indeed.....
I am the author of NIGHTSONG: A Neanderthal mystery. I hope you may want to dip into my blog after you've read my novel (or even if you haven't) to learn a bit more about the Neanderthals and to hear some of the music described in the novel. I may go off topic sometimes...