A colorfully illustrated episode of the animated series After Skool explained the concept of Neanderthals. Specifically, when and where they lived, how they communicated and how these archaic humans might have gone extinct but for the genome that lives on through the DNA of modern humans.
There was roughly a 5000 year period where both Neanderthals and Humans lived in the same place at the same time. During this period there was inbreeding between the 2 species. The proof is in our DNA. 1.5 to 2.6 percent of the DNA of anyone outside Africa is of Neanderthal origin. Interestingly enough, this DNA can have an affect on your personality!