There seem to be quite ancient human remains and artifacts that are several to tens of millions of years old, but younger than the Dinosaur Era. Where do humans in this period come from, if the first human creation pre-dated the dinosaurs, and modern human was introduced only 120,000 years or so ago?

There, indeed, was an intermediate cohort and this you are piecing together nicely from the actual physical evidence of its existence, and comparing it to the account from us of the two great creation events for humanity. There was a preliminary build-up to the modern human. This included not only other hominid species, but modern humans built on the previous design with some enhancements were reintroduced as a kind of test run prior to the official launch of modern human on the scene in earnest. The purpose for this was to field test the adaptability and hardiness of the changes designed into modern human, as well as to do some preliminary healing for some of the leftover karmic issues from some individuals who would be instrumental as filling key leadership roles with the rollout of modern human to come later. This was a dual agenda, therefore, to pave the way and capitalize on the enhancements, to not only check them out but reconfigure the karmic foundation for what was to be restarted. This was certainly successful in terms of the numeric consequences, with nearly 8,000,000,000 human souls in residence at the current moment on the earth successfully, and the persistence of the species under the very extreme subjugation and suppression committed by the combined depredations of the spirit meddlers and the Dark Extraterrestrial Alliance. That is a testament to the winning combination of spiritual as well as physical characteristics. This is one reason we have confidence you can triumph in your contest to win out over the evil in the earth plane.