There are humans in this ruin, and it couldn't help but shock me; the intelligence did not mention anything about this ruin having a human stock.
Though, it shouldn't be surprising considering this is a resource site and sometimes Grimms use humans, there are some things that only we could do, or it is easier to use the human stock rather than their own people, and they also eat them, if they felt too hungry.
The Grimms have cities of humans deep in their territory; most of the humans are used as livestock, but some are trained to infiltrate; there are even some that Grimms treat equally as a human tribe. It is one of their newest experiment that started a few millennia ago.
They treat humans of few cities are equal as to human tribes, whose ancestors have redeemed themselves.
Though these Grimms are inwardly distrustful after the tragic fate, they have suffered three and a half millennia ago, that now they did not let humans reach above Emperor class.
Creation is hard, cheer me up!