Anyway, I'd like to import two relevant posts from different discussions, one by me and one by the inestimable DaleCoz:
Right about the open country part of this, but Neanderthal extinction supposedly came when the coldest part of the last Ice Age compressed forests against the Mediterranean, to the point where there wasn't enough forested habitat to sustain a viable Neanderthal population.
Piecing together various extinction theories, the picture I get is that Neanderthals could kick our ancestors' butts in a forested habitat because they were specialized for ambush-hunting and considerably more powerful--probably two or three times as strong on a pound for pound basis. Our ancestors specialized in open country and endurance hunting--nowhere close to as strong but much better at distance running and moving over long distances to follow game herds.
Our ancestors were adapted to move a lot, not just on the hunt but also because they had to in order to survive in open country. They lost strength compared to their ancestors but gained endurance. Since they were moving so much, they also had to pare down the weight of their tools compared to what the less mobile Neanderthals could get away with carrying. That's significant in terms of developing civilization, as we'll see later.
Neanderthal versus modern humans: Think football (American version) linebackers versus marathoners, only the Neanderthals were far more massive and stronger than even an NFL linebacker. The disadvantage: those massive bodies wore out their joints fast when Neanderthals had to move a lot to follow migratory game in open country. When you find Neanderthal skeletons in what had been open country, they're usually crippled with arthritis.
Neanderthals probably used open country only when they were forced to. It was sub-optimum habitat for them. At the same time, a residual ability to operate in open country may have saved them at the height of various glacial advances, as long as there wasn't competition in the open country.
When modern humans spread to the open country to the north of Neanderthals, they took away the ability of Neanderthals to use that habitat in emergencies, because modern humans were better in open country. At that point, it was just a matter of time until a glacial advance reduced the forests to the point where they couldn't support a viable Neanderthal population.
Implications if that's all true:
- Neanderthals generally used heavier, less specialized tools than moderns, because those tools took less effort to make and since they moved around less the extra weight didn't matter enough to justify the extra effort to develop lighter tools. When Neanderthals were forced into open country they developed lighter-weight tools.
If Neanderthals won out over our ancestors, there had to be a reason. Possible reasons: either forests pushed north and into the Middle East to create a continuous forested belt that let Neanderthals spread back into Northern Europe and south into North Africa or a branch of Neanderthals adapted to open country.
If Neanderthal adapted to open country and beat our ancestors there, then they would probably do so by adapting in a lot of the same ways we did, and would probably end up looking and acting more like us than their Neanderthal ancestors, which kind of defeats the purpose of this exercise.
If Neanderthals won because their forest habitat spread, I'm not sure you end up with civilization. If you did, that civilization would probably have less trade because Neanderthals weren't good at long-distance travel and because their tools didn't require specialized material (good quality flint, among other things) to the same extent.
I suspect that a Neanderthal civilization would have more trouble than our ancestors did in using aquatic resources and would be less likely to develop sea-faring. Those big, muscular bodies wouldn't float at all well, which means that swimming would be mostly shear power, and exhausting. That doesn't mean they would completely avoid aquatic resources, just that using them would be more dangerous to Neanderthals than to moderns.
There could also be subtle differences in the way Neanderthal minds worked. Modern humans can barely, sometimes, create complex political structures that last a few hundred years before they fall apart. Tweak the balance between selfishness and altruism or planning ahead versus short-term thinking even a little and you might end up with Neanderthals never being able to go beyond a tribal society. Or on the other hand, you might end up with them able to establish their equivalent of Egypt and have the same dynasty ruling three thousand years later.
Would Neanderthals be able to read? Ability to read couldn't have been selected for directly until civilizations developed, so there had to be some other use for the mechanisms that later let us read. Would Neanderthals have selected for those pre-reading mechanisms? Would Neanderthals be better or worse at math and physics? What about spatial relationships? Would they be master architects and engineers or would they stink at those things? Neanderthal lawyers? Accountants? Would some of them be good at those things?
What about social structure? Would they be monogamous, polygamous, as flexible as human societies are? Would they easily form hierarchies with kingdoms and empires or would they be too independent?
Would Neanderthals develop religions? Modern humans as far as I know, pretty much universally develop religions of some sort, and substitute ideologies with strong elements of belief when those religions are discredited. Is developing religions a universal aspect of becoming intelligent or is it unique to modern humans? If Neanderthals didn't develop obsessions with the afterlife and forces beyond them, how would that influence how their societies developed?
And this is getting long even for me.
Perhaps a shift in perception? Rather than viewing Homo Florensis as small, stupid humans, consider them super-chimps.
And those giant rats from that island of theirs. Domesticable? Rats are ominvores, you could breed a pig-equivalent foodbeast, and an agressive hunting beast. Rats are also very good at transferring diseases to humans...Consider a specific culture of Homo Florensis...they were already tool and fire users, and cooperative hunters.
Cannibals, chimp-strong, with fire and communication and thrown rocks, with their gigantic rats, bred for agression to strangers over thousands of years, howling thought the black forests and mountains of Borneo and Sumatra. Complete with the occasinoal lethal disease...might discourage humans from moving down there.