And elves aren't even drastically more powerful than humans in LotR.
I mean Elrond, Galadriel, Glorfindel are. Rest not so much, and growing weaker with each era as corruption of the world wages heavily on their shoulders.
Those that shall not escape to Aman, are doomed to become not more than Wraiths - and that's how Tolkien linked his elves to medieval faeries.
Which is also why we are subservient to our reptilian overlords with their many eggs. Research into our past is not gonna get 100% precise results but im pretty sure there where more differences between us and neanderthals then pure birth rate.
Human birthrates are pretty piddly comparison to almost every other species on the planet (slower gestation, smaller litters). But we beat them out with our special powers. WE are the Elves of the world.
True but it's all kinda relative.
We compare ourselves to other in our weight category, and even then it's possible some vermin could sucker punch us with some extreme breeding speed. Happens from time to time with locusts.
Unfortunately our information is limited in that regard, and we may never know for sure, since many factors could affect population decline. But findings suggest that Denisovans may have figured out craftsmanship and drilling technology before we did (and I also heard they may also have the oldest flutes found, meaning they may have figured out music as well, but couldn't find articles confirming that). So not only where they larger and stronger, but likely smarter as well. They were the actual Eves of our world.
Hard to say. We know preciously little about Denisovians, though most Denisovian-blooded population in the world New Guinea Papuans does not seems to be extremely blessed by this inheritance. They were more thick boned, so yeah stronger in terms of encumberance, but probably less agile (based on Neanderthals their closest kin, as I think we lack much bones of Denisovians aside of teeth) and slower. So while neanderthal could survive some harsh beating better than modern man, well when more modern weapons comes into play - would it matter much? And neanderthals were not-numerous really and living in smaller tribes than modern men.
In terms of technology let's remember in cold climate there are better chances for fossils and archeological remains. As modern men left Africa after common ancestor of Ns and Ds, lot's of his achievements probably rotted away faster in African climate.
And yes Denisovians definitely existed, as sister branch to Neanderthals. Both early split of Homo sapiens compared to like 95% of our other ancestry.