There used to be a site Nova Notes run by Al Schroeder that contained his Wold Newton-ish "Schroeder's Speculations." It's gone now, but I managed to dig up some gold from its heyday: a timeline combining the Lord of the Rings and Conan. Here's Schroeder's opening paragraph:
There are two major texts, at least, that deal with civilizations that existed in what today's anthropologists call prehistory: one is the Red Book of Westmarch, on which Professor Tolkien based his Lord of the Rings. The other is the Nemedian Chronicles, which deals both with the "Pre-Cataclysmic" age and the Hyborian Age, on which Robert E. Howard based his Kull and Conan stories. Looking into real prehistory, about the only place you can fit the over seven thousand years of Tolkien's history and eight thousand years of Howard's history, and have Cro-Magnon man functioning in a non-glacial environment, is in the relatively warm period of 50,000 to 25,000 years ago. Besides, as you'll see below, there is good reason, taking Tolkien at his word, to date the "awakening of the elves" as when the Big Dipper/Great Bear formed. Certainly, it is one of the few events that can be dated to our timelines...Check out the rest of Schroeder's rationale and his timeline here.