Kham's first humans

The Liber campaign's first humans came alongside its first para-humans, the Nange. The Nange here see a "Time Memorial" of millennia, when they were slaves to a Spider Queen. Seven hundred years before the present, the Nange (probably) east of what's now Kham rebelled.

This is about the earliest "calendar" we get for this campaign.

Before the Nange revolt, the Spider Queen's foremost servants were intelligent spiders. Lowest in rank were humans like us. Some of her spiders, for whatever reason, elected to transplant their heads onto human bodies. These were the Temple Sentinels. An arthropod race would envy our improved lung-capacity, on a lowish-oxygen planet (although this world's oxygen hadn't dipped so low for the dino detour). That would imply that the Queen wasn't from here.

For a Beyond Countless Doorways tie-in, the Spider Queen hailed from a high-oxygen plane like Dendri. It may be the Zhival who led her to (evil) greatness. She picked up servants as she traversed the Doorways. Along for the ride were vermin: mosquitoes and rats; and the housecats to control them.

Most of this world's mainline d20-rules races descend from the Queen's invasion-force and entourage. Vermin (including cats) did what vermin do, slipping away into the forests and swamps. Most sentient races fled during the revolt. The humans count as "vermin" for this purpose, going cimarrón in bits and batches over the millennia of servitude. Kham's elite descends from them.

Some of the earliest-diverged tribal maroons have adapted to a permanent forest canopy. They trend to fair, freckled skin; dark-red curly hair; wide eyes; flat noses; short stature. The beastlords of Kham descend from in an urban population, albeit also cluttered with artificial pillars as befits a spider civilisation. These are not freckled but tanned, like Amazonians on Earth. Besides these two races I don't think the human founding-population has since enjoyed much time to acquire separate characteristics in tune with the environment.

The races have, however, evolved separate languages, indeed language-families. Also keep in mind that this world is still subject to conjunction with others: the tundra orcs, for one, likely found their own way here. Other continents may host other extraplanar humans. Elves too, given the Faerie link.