Noticed in Legends that while I was playing a fortress recently, two local tribal monkey-people had stolen some books while I wasn't watching.
That's great (from a modding point of view). Except wait, tribal monkey-people are baby-snatchers, not item thieves. I dug a bit further to find out what's going on.
It seems that these guys came from the nearby minotaur civ, The Impunity of Liberation (thankfully they're still in 'thieving' stage right now - steel-clad minotaurs slice through poorly defended fortresses like hot axes through unicorn butter).
The Impunity of Liberation is quite a cosmopolitan civ. Population around 23,000, there's an established community of tribal monkey-people which make up about 23% of the population. In fact for the past 260 years, the civ has been ruled by them. I guess they're just better at writing law or something.
Determined to find the roots of tribal monkey-people in the Impunity of Liberation, I searched back through their 530 years of history. However I reached a dead-end at Agine Lacylustful, 1st recorded tribal monkey-person civ member and tavern-keeper at the Oats of Fruit in Matchintense from the year 67-68. In 68 she joined the ill-fated expedition to found Wildnesshields and was killed by a roc along with everyone else in 79.
Nowadays Matchintense is 99% monkey-person, so it makes sense that this is where they started, but it wasn't always so. And Agine has a minotaur name, so presumably her parents (sadly unknown) were also part of the civ.
The Impunity of Liberation has never been to war with monkeypeople (despite a history of kidnappings) so the first monkey-people probably weren't part of a site takeover. Their only wars are the systematic annihilation of the Elves of the Romantic Oak as part of their warleader's plans to bring peace to the world (Elf, former member of the Romantic Oak, warleader of the Impunity of Liberation since the year 92, rides a cave dragon).