As a fan of both Tolkien and Antediluvian lost civilization speculations, a recent article from
Nature made my day. Modern humans seem to not only have bred with Neanderthals and Denisovians, but it seems we also are related to another 'mystery' species of early humans. It seems like ancient Eurasia had many species of ancient humans, so much so that it looked like the multi-hominid world of Tolkien's Middle Earth with its Hobbits, Dwarves, Elves and men. Follow the link below to the article:
http://www.nature.com/news/mystery-humans-spiced-up-ancients-sex-lives-1.14196