I though Hobbits were coming from the East of Middle Earth (I think Smeagol/Gollum was a part of a Hobbit community that hadn't migrated and so lived East of the mountains) and were granted the Shire by a king of Arnor, though they still had to fight orcs while there
Politics is a sufficient condition. Perhaps Sauron would not tolerate 'independent' Orcs he can't use as canon fodder?
>Again, the lack of people and trade on Anduin is a shocker for me.
Yeah, it's the humans which are hardest to explain away. Some peasants should have thought 'We're tried of paying taxes to Gondor. We'll just move and no one can or would even bother find us'.
Elves are not only long-lived, but also bound to Arda. When they die, they rest some time in Mandos' halls and then reincarnate. No matter how twisted and shitty the world becomes, they are stuck with it. No matter the traumas they suffer and the wrongs commited by them, they cannot escape it [the consequences]. Because their victims will be around forever too, and they can't forget either.
Also, orcs were twisted elves, so perhaps they also had slow reproduction cycles?
So a drought, cicadas, pest explosion, shorter growing season, fungus/etc, wildfires, on and on, would immediately lend to famine, and perhaps war.
Lots of additional people die during famine, fighting each other for scraps.
Hm.. Orcs are easy to explain. I doubt Sauron or Saruman care at all about their lives. As the animated adaption put it: "When there's a whip there's a way". add in constant external warfare (and possible internal warfare too) and you end up with a low population.
Hobbits are implied to have a very different past from their LOTR circumstance (IIRC they conquered the Shire from the Orcs?), though I recall very few details are given. One may also suspect a low reproduction rate judging by lifespan. Perhaps the Shire started from a low base, and only by LOTR had enough for an industrial revolution?